Artificial crowns and their types. Types of artificial crowns

Installation of artificial crowns is one of the most popular procedures in modern dentistry. If there are significant defects in the tooth tissues, the elimination of which by filling or installing an inlay is impossible, you simply cannot do without an artificial crown. Loss of a tooth due to trauma or due to the incapacity of a diseased tooth is a condition that requires dental correction, since both the appearance and functional abilities of the jaw are impaired. Installing an artificial crown is a fairly quick, painless and affordable procedure that is provided today by almost every dental clinic.

What are the types of artificial tooth crowns?

The patient is provided with a huge selection of different types of artificial crowns. A competent dentist will definitely help the patient in choosing, taking into account the individual needs and capabilities of each patient. According to their purpose, all artificial crowns are divided into restorative crowns, that is, those that restore the damaged anatomical shape of a natural tooth, as well as supporting crowns, which provide fixation of bridges. Depending on the material from which the artificial crown is made, the following types of crowns are distinguished:

• metal - made from alloys of noble and base metals:

• cast - made by pouring a metal crown into a pre-prepared mold;
• stamped - crowns that are made by stamping them from special discs or sleeves;

• non-metallic - crowns that are made of porcelain or plastic;
• combined - crowns, the base of which is metal, and the lining is porcelain or plastic.

Basic requirements that artificial crowns must meet

Artificial crowns must meet specific requirements, as they can negatively affect the periodontal tissue of supporting teeth and the patient’s body as a whole. These requirements are the following mandatory conditions:

• the crown should not overestimate the bite and limit the movements of the lower jaw;
• It is strictly forbidden for the crown to fit tightly to the tissues of the tooth, especially in the area of ​​its neck;
• the crown should not violate aesthetic standards;
• the length of the crown should not exceed the depth of the periodontal sulcus;
• the thickness of the edge of the artificial crown should not exceed the volume of the periodontal sulcus;
• The width of the edge of the crown should be the same as the width of the ledge formed in the tooth.

Indications and contraindications for installing an artificial crown

The following conditions are direct indications for the installation of an artificial crown:

• destruction of hard tooth tissues as a result of a pathological process such as caries, fluorosis and others;
• anomalies in the color, structure and shape of the tooth;
• the need to restore the shape of teeth and the height of the lower third of the face in case of pathological wear;
• fixation of some types of prostheses;
• the need to splint teeth for periodontal diseases;
• temporary fixation of orthopedic and orthodontic devices;
• convergence, protrusion or divergence of teeth.

Contraindications to the installation of an artificial crown are the presence of chronic periodontal inflammation, acute periodontal inflammatory process, the presence of significant pathological mobility of teeth, as well as the presence of dental plaque.

Crown manufacturing procedure: main steps

The procedure for making an artificial crown can take a period of time from a week to a month, and consists of several stages:

1. At the first stage, odontopreparation of the tooth is carried out and the necessary impressions are taken, a model of the artificial crown is cast and it is plastermed into the occluder. Next, the teeth are modeled, stamps are obtained, and stamping is performed.
2. At the second stage, the artificial crown is tried on and its color is determined, the crown is grinded and polished.
3. The last stage is the installation and fixation of the artificial crown.

The tooth should not remain exposed for the time required to make an artificial crown. Therefore, temporary crowns are manufactured and installed, which help protect teeth from mechanical trauma and the negative influence of pathological microorganisms. In addition, a temporary crown allows you to restore the functionality of the tooth before installing a permanent artificial crown.

Solid crowns are made from medical alloys and metals in dental laboratories using casting technology. They are designed to get rid of obvious dental defects. These devices are used in dentistry to restore the natural shape of teeth, as well as supporting and fixing elements for dentures.

Solid dental crowns can be installed on a patient if the following indications exist:

1. Damage to the crown parts of the teeth.
2. The presence of unconscious contractions of the masticatory muscles.
3. Abnormal size, location and shape of teeth.
4. Pathological bite.
5. Pathologies of occlusion.
6. The need to place supporting and fixing clasps on the teeth.
7. Bruxism.
8. Abnormal wear of teeth.

Important! In the presence of carious pathologies and other causes of destruction of dental tissues, crowns are installed only in those clinical situations where it is impossible to eliminate the defects using fillings or installing an inlay.

The cost of installations depends on the specific dental clinic and the materials used in the manufacture of structures. The final price includes the costs of a panoramic x-ray, installation of a temporary prosthesis, and directly for the manufacture of an all-metal product and its installation.

zirconium crowns.

What alloys are they made of?

The list of materials that are suitable for the manufacture of such structures includes:

• alloy of chromium and cobalt
• chromium-nickel alloy
• high titanium alloys
• alloys containing precious metals (precious alloys)

Interesting fact! Titanium is resistant to aggressive factors, does not darken and does not provoke the development of allergic reactions, therefore it is often included in alloys for the manufacture of cast dentures. And alloys containing gold in their composition are characterized by ductility, which ensures an accurate fit to the gum.

Solid crowns are also divided into the following types:

• metal coated
• metal without coating
• metal with ceramic lining
• combined bridges

Designs without coating are usually made of polished metal, are low in cost, but are often not suitable for patients due to their unaesthetic appearance. Metal structures coated with gold look more attractive. However, spraying can negatively affect the mucous lining of the oral cavity.

Solid crowns with veneer are covered with ceramic material and look the most aesthetically pleasing. For longevity, recommended care instructions must be followed. A combined prosthesis is made from several metal-ceramic prostheses (which cover the smile area) and from solid crowns.

Contraindications

Solid crowns have many contraindications - for example, inflammatory diseases of the oral cavity or sensitivity to the alloys used.

Advantages and disadvantages

The list of advantages of solid cast structures should include:

1. High precision of fit of the inner surface of the cast crown to the tooth stump. This is important to prevent saliva, pathogens, and food debris from getting between the crown and the tooth.
2. The ability to take into account the individual characteristics of the patient’s dental structure when making crowns.
3. Possibility of spraying to improve the aesthetic properties of the crown.
4. Excellent wear resistance and strength of the finished product, due to which solid cast structures are considered very reliable and can last for quite a long time - their period of use can exceed 10 years, subject to the doctor’s recommendations.
5. The ability to restore the natural structure of the chewing surface of the teeth, which ensures the return of their full chewing function.
6. Recreation of acceptable interdental contacts.
7. No need for deep preparation. When installing cast crowns, the teeth need to be ground down by 0.8 millimeters.
8. Inertness to body tissues, lack of negative impact on them.
9. Affordable cost of manufacturing and installation of solid cast structures.

The list of disadvantages of using cast structures includes:

• the need to grind down the surface of the teeth
• high level of thermal conductivity of structures (if the pulp of the supporting tooth is located close, the patient may feel discomfort)
• excessive wear of teeth on the opposite jaw with constant contact
• possibility of an allergic reaction to alloy components: chromium, nickel, beryllium

The appearance of solid structures can also be classified as a disadvantage: due to the shade that does not match the natural color of the enamel, such a dental substitute is often installed on chewing teeth. However, this disadvantage can be overcome by using cast prostheses with ceramic lining.

Differences from metal ceramics and stamped crowns

Metal ones can be made by casting or stamping. Stamping involves obtaining a finished structure from special sleeves, processed in a special way and coated with spraying. If it is necessary to make a bridge, stamped microprostheses are connected to each other by soldering. This technology is now somewhat outdated, but is still used in some medical institutions.
Cast ones differ from stamped ones in a more advanced manufacturing method, which allows for optimal fit of the structure to the tooth, preventing excess pressure on the gums. When manufactured by casting, a pre-prepared cast is used, and when stamping, the desired shape of the structure is achieved by extrusion. Cast crowns provide better chewing of food, and when installed, the likelihood of periodontal inflammation is minimized.
The service life of cast products significantly exceeds that of stamped structures. This is because the stamping material is softer and thinner, so it is more susceptible to deformation and abrasion.
The advantage of cast metal crowns over metal-ceramic structures is their affordable price. Solid products are a fairly budget option, so they are most often chosen by various categories of patients.

Thus, solid crowns are a priority when it is necessary to correct a number of dental problems.

Installation steps

If it is necessary to install solid crowns, the following steps are followed:

1. Preparation: sanitation of the patient’s oral cavity, correction of pulpitis and caries if necessary, filling of root canals
2. Grinding the surface of the abutment tooth
3. Taking an impression of the tooth and the entire dentition using silicone masses
4. Preparation of impressions (wax crowns) and their transfer to the dental laboratory for the possibility of making a mold for casting the structure
5. Product casting
6. Fitting
7. Fixation of the structure in the patient’s oral cavity. If there is no need for modification, the patient does not experience discomfort when the dental substitutes meet the antagonist teeth, then the structure is fixed with permanent cement

Note! While permanent tooth replacements are being manufactured, the patient may be prescribed temporary products necessary to speed up the adaptation of the gums to prosthetic structures.

When choosing cast microprostheses with veneer, the manufacturing process of the structure also includes applying ceramic material to a metal base, as well as glazing the structure.

Fact! Solid-cast structures are most often used for prosthetics of lower second and third molars, upper third molars, and upper second molars.

What can be the basis for installing a solid crown?

There are several options, namely:

1. Grinding the tooth and putting a finished crown on it. This option is used if tooth depulpation has not been performed. Before installing the structure, the surface dental tissues are ground down (3-4 mm on all sides). This reduction is necessary so that the denture thickness can be used to withstand pressure during the chewing process.
2. Installation of stump inlays. A very popular technique. The installed structure includes a pin and a prosthesis. In preparation, the doctor removes part of the tooth and creates a depression in the dental tissue one-third deep. A specialist installs a tab into this recess, made from a model that is cast from special plastic. The inlay is fixed with cement. This technique allows you to restore teeth that have been destroyed by 70%. Materials for making the inlay are metal alloys, metal ceramics.
3. Installation of a microprosthesis on a pin with an already extracted tooth. In this case, a puncture is made to the mucous membrane, after which the doctor makes a depression in the bone and installs a pin. An adapter (abutment) is placed on the pin. A cast crown is installed on this adapter.

Features of oral care after installation of cast crowns

Installation of solid structures does not require specific care for the oral cavity. It is important to brush your teeth regularly and watch your gums. In cases of gingivitis or periodontal disease, cast products are sometimes decemented. Under conditions of proper manufacturing, correct installation and oral hygiene, all-metal crowns can last up to 15-20 years.

Reliability, safety, durability and functionality allow these products to be widely used in dental practice. The undoubted advantage of these microprostheses is their reasonable cost, which in some cases is a priority criterion for patients. Of course, prices in different medical institutions may differ, but they still remain quite affordable everywhere.

Installing solid crowns can significantly improve the quality of life of patients with certain dental problems.

The article is for informational purposes only. This is an outdated method of prosthetics that is not used in the Zub.ru network of clinics. Our network uses only modern materials and technologies.
We recommend that you familiarize yourself with information about more modern and safer analogues - for example,

Destruction or traumatic fracture of a significant part of the crowns of the front teeth and premolars, when it is impossible to restore them with fillings or inlays;

Anomalies in the development and position of the anterior teeth in adults, which for any reason cannot be eliminated by orthodontic methods; - pathological abrasion of hard dental tissues;

Fluorosis, wedge-shaped defects;

Anomalies in the development of hard dental tissues (impaired amelogenesis);

Aesthetic defect in the crowns of natural teeth (discoloration, loss of shape, loss of shine, etc.);

Inconsistency of existing artificial crowns (metal, plastic, combined) and bridges with aesthetic and other requirements;

Included dentition defects.

Metal-ceramic crowns and bridges can also be used as a splinting structure for mild to moderate periodontitis. Each of these indications should be linked to a specific situation.

For example, in case of significant carious destruction or traumatic fracture of most of the crowns of natural teeth, before using metal-ceramic prostheses, it is necessary to make cast stump pin inlays.

This is due to the fact that with significant carious destruction of the anterior teeth and premolars, the hard tissues of their crowns are very weakened and, under the influence of occlusal load, can break off along with the metal-ceramic structure fixed on them.

The danger of such a complication increases sharply in patients with anomalies of teeth and bite, parafunctions of the masticatory muscles (bruxism). In case of traumatic fracture of a significant part of the tooth crown, a cast stump pin insert is necessary to improve the fixation of metal-ceramic crowns and bridges.

Anomalies in the development of anterior teeth (size and shape) in adults are undoubtedly an indication for the use of metal-ceramic crowns, since plastic crowns do not meet the increased functional, preventive and aesthetic requirements.

Porcelain crowns best meet aesthetic standards, surpassing even metal-ceramic structures in this regard. However, porcelain is brittle and they break under bending forces caused by occlusal loads.

This is especially true for patients with a deep bite, prognathic and progenic relationship of dentition with deep incisive overlap, parafunctions of the masticatory muscles (bruxism) and pathological abrasion of hard dental tissues.

In these cases, preference should be given to metal-ceramic crowns, which have not only the high aesthetic qualities of porcelain crowns, but also the advantages of durable solid dentures. As for anomalies in the position of the anterior teeth in adults, orthodontic treatment is indicated.

However, due to age-related changes in the bone tissue of the jaws, hardware correction of the position of the teeth takes longer than in children and does not always give positive results; relapses and other complications are observed more often than in childhood.

All this makes many adult patients refuse such treatment. In these cases, after depulping the teeth, metal-ceramic crowns and bridges and cast stump pin inlays with a modified axis of inclination of these teeth are used.

In case of pathological abrasion of hard dental tissues, porcelain is not the only material for lining solid dentures. Along with ceramics, high-strength plastic (isosite, etc.) is used in such cases.

Due to the fact that with this pathology there is a danger of ceramic chipping, to achieve a high aesthetic effect it is enough to veneer only those crowns and facets that are visible in a given patient when talking and smiling. Most often these are prostheses in the area of ​​incisors, canines and first premolars, less often second premolars, and even less often - first molars.

Therefore, when deciding which crowns and facets of a solid-cast metal-ceramic prosthesis in a given patient should be veneered with ceramics, you need to talk to him and determine the teeth that will be visible. It is advisable to line these crowns and facets with porcelain, and it is better to leave the remaining parts of the prosthesis in the area of ​​​​the molars of the upper and lower jaws completely metal.

Occlusal contact on metal crowns and facets in the area of ​​the indicated teeth of the upper and lower jaws ensures the stability of the interalveolar distance (bite height) and favorable conditions for the construction of metal-ceramic prostheses in the area of ​​the anterior teeth and premolars. In addition, to prevent porcelain from chipping, we recommend that the closure surfaces of crowns and facets in the area of ​​molars and second premolars be left metal.

It is advisable to veneer the vestibular and chewing surfaces of the first and sometimes second premolars and all front teeth with ceramics. Such prostheses, while fully satisfying aesthetic requirements, can withstand increased occlusal load and abrasion for a long time.

For the same purpose, it is better to first make removable, fixed or a combination of them (as indicated) in the area of ​​the lateral teeth, restore the height of the bite, and then make and strengthen metal-ceramic crowns or bridges in the area of ​​the front teeth.

As for fluorosis, wedge-shaped defects and impaired amelogenesis, for these types of pathology the indications for the use of metal-ceramic crowns and bridges are quite wide.

If with wedge-shaped defects it is still possible to restore the integrity of the crowns of natural teeth with various filling and composite materials, then with fluorosis and impaired amelogenesis this is not possible. For these types of pathologies, metal-ceramic crowns are indicated.

Porcelain crowns are less durable and more likely to break. Aesthetic defects in the crowns of natural teeth, especially the anterior ones (discoloration, loss of shape, loss of shine, etc.), are currently one of the most common indications for the use of metal-ceramic crowns and bridges.

Old designs of artificial crowns (metal, plastic, combined) and soldered bridges must be replaced not only for aesthetic reasons, but also because they do not meet functional and preventive requirements.

Regarding the indications for the use of metal-ceramic prostheses for dentition defects, it must be remembered that it is advisable to use them only when dentition defects are included (Kennedy class III and IV) and the absence of 1-2 teeth.

For large defects in the dentition, the use of metal-ceramic dentures is associated with the risk of chipping of the ceramic veneer. In patients with intact periodontium in the area of ​​the anterior teeth, such prostheses can be used even in the absence of three teeth, since in this part of the dental arch the occlusal load is less than in the area of ​​premolars and molars.

The use of cantilever metal-ceramic prostheses is inappropriate, especially for terminal defects in the lateral parts of the dental arches. The risk of using such dentures is less when the antagonists are artificial teeth of removable dentures.

We cannot agree with the authors who consider periodontitis a contraindication to the use of metal-ceramic prostheses and are convinced that for mild to moderate periodontitis, metal-ceramic crowns and bridges can be used.

Clinical, radiological and functional studies conducted at our department have shown that metal-ceramic dentures provide reliable immobilization of moving teeth, do not have a negative effect on marginal periodontal tissue and meet aesthetic requirements.

In 96.8% of patients with mild and moderate periodontitis, the use of metal-ceramic structures leads to stabilization of the pathological process, as evidenced by the results of X-ray and functional studies.

Resorption of bone tissue of the alveolar process slows down or stops. The results of rheoparodontography indicate an improvement in regional blood circulation in the marginal periodontal tissues.

Oral hygiene also improves significantly, since virtually no plaque (plaque) forms on the glazed surface of metal-ceramic dentures.

This is evidenced by the change after orthopedic treatment in the average values ​​of the plaque index PI, which characterizes the hygienic state of the oral cavity.

However, it should be remembered that, firstly, the indication for the use of such prostheses is mild to moderate periodontitis in remission, after anti-inflammatory therapy and appropriate orthopedic preparation of the dental system.

Secondly, metal-ceramic prostheses must meet certain design requirements.

The edges of metal-ceramic crowns should be located on a 135° circular shoulder formed at the gum level. The body of the bridge should not be adjacent to the cervical part of the abutment teeth in order to avoid injury to the marginal periodontal tissues.

Before glazing, it is necessary to carefully check the closure of crowns and facets with antagonists in the central, anterior and transversal occlusions and in different phases of articulation.

Finished metal-ceramic dentures should first be strengthened temporarily for 2-3 months. to identify and eliminate their shortcomings and possible complications. Patients with periodontitis with metal-ceramic dentures should be under medical supervision; if necessary, anti-inflammatory periodontal treatment and occlusion correction should be carried out.

The use of metal-ceramic crowns and bridges in accordance with the listed indications is possible only in cases where, in the process of preparing teeth or restoring bite height, an interocclusal space of 1.8 mm can be created.

The use of metal-ceramic dentures is contraindicated: in the presence of teeth with living pulp in patients under 18-20 years of age; with severe periodontitis.

The first contraindication is associated with the need for deep preparation (up to 1.8 mm) of hard dental tissues and the danger of damage and death of the pulp due to the large size of the tooth cavity with thin walls, its proximity to the tooth surface and wide dentinal tubules in children, adolescents and young adults.

The second contraindication is explained by the high hardness of the ceramics, its indestructibility, as well as the rigidity of the metal-ceramic structure, which can cause functional traumatic overload of the periodontium of the supporting teeth or their antagonists and aggravate its condition.

Relative contraindications to the use of metal-ceramic fixed prostheses are: malocclusion with deep incisal overlap; small size of the lower jaw incisors; pathological abrasion of teeth; parafunction of masticatory muscles (bruxism); insufficient height of the crowns of natural teeth, especially in the presence of defects in the dentition.

In the presence of the listed factors, the manufacture and use of metal-ceramic prostheses is difficult or even impossible due to the danger of damage to the dental pulp and the development of all kinds of complications at different times after strengthening the structure.

In patients with a deep interlocking bite, the lower incisors completely overlap the upper ones.

The latter have an oral slope and fit tightly to the antagonists, covering them from the vestibular side. The crowns of the upper jaw incisors on the oral surface are often worn and thinned, so it is impossible to grind them to the required depth without damaging the pulp and create a gap between the upper and lower front teeth to construct a metal-ceramic crown.

Certain difficulties also arise with prognathic and progenic occlusion with deep incisal overlap.

With these types of occlusion, there is also a danger of functional traumatic overload of the supporting teeth and their antagonists, which can lead to pathological changes in periodontal tissue, loosening of teeth and chipping of the ceramic veneer.

The incisors of the lower jaw have thin, fragile crowns, as a result of which during their preparation, especially when creating a ledge in the cervical area, there is a real danger of damage to the pulp.

With pathological abrasion of teeth, bruxism and other parafunctions of the masticatory muscles, accompanied by displacement of the lower jaw, there is high excitability and increased muscle tone and, as a result, strong compression of the dentition.

The use of metal-ceramic crowns and bridges under these conditions can lead to overload of the supporting teeth and chipping of the ceramic veneer. In addition, with pathological abrasion of teeth, a decrease in the interalveolar distance (bite height) and crowns is observed.

Without preliminary orthopedic treatment and the creation of an interocclusal gap, the construction of metal-ceramic prostheses is impossible.

We consider these contraindications to be relative, since with appropriate orthopedic (orthodontic) preparation of the dental system and restoration of the interalveolar distance, more favorable conditions for prosthetics can be created and metal-ceramic crowns or bridges can be used.

In this case, one should strictly monitor the correct execution of all clinical stages and the technology for manufacturing prostheses.

It is necessary to approach with special care the preparation of mandibular incisors with living pulp: you should not create a deep ledge - you can limit yourself to the ledge symbol or prepare without a ledge.

Often, an attempt to create a circular ledge on these teeth leads to damage to the pulp.

It must be remembered that metal-ceramic bridges are used mainly for small defects in the dentition (1-2 teeth). With large defects (3-4 teeth), the slightest deformation of the intermediate part of the bridge can lead to cracking and chipping of the ceramic veneer. At the same time, the use of cantilever metal-ceramic prostheses should also be sharply limited or completely eliminated.

The most common prostheses used to restore a damaged tooth crown are full artificial crowns. Due to the fact that they have different designs and are intended for different purposes, they are systematized according to certain criteria:

By design or by size and method of covering the tooth:

complete, that is, covering all surfaces of the tooth;

equatorial, that is, reaching the equator of the tooth;

crowns with a pin;

telescopic crowns;

fenestrated or fenster crowns.

By manufacturing method:

• stamped;

• soldered (suture) - are now practically not used.

Depending on the material:

metal (gold alloys, stainless steel, cobalt-chrome alloys (CHS), silver-palladium, titanium);

non-metallic (plastic, porcelain);

combined, that is, lined with plastic, porcelain or other ceramic masses (metal-plastic and metal-ceramic).

By purpose:

restorative;

supporting (in bridges or other types of prostheses);

fixing (for holding medications, orthodontic or maxillofacial devices);

splinting;

temporary and permanent.

Clinical rationale for orthopedic treatment with stamped crowns

Indications:

An absolute indication for the use of artificial crowns is significant tooth destruction due to caries, its complications or other reasons that cannot be eliminated with a filling or inlay.

For covering teeth that serve as supports for clasps, especially if their clinical shape needs to be changed.

For fixation during treatment with bridges, i.e. abutment crowns.

Pathological abrasion.

Anomalies of shape.

For attaching various orthodontic or maxillofacial appliances.

For splinting in case of periodontal diseases and jaw fractures.

Contraindications:

Covering intact teeth with crowns, unless this is caused by the design features of dentures.

Untreated foci of chronic inflammation in the region of the marginal or apical periodontium.

Pathological mobility (III degree according to Entin).

General poor health condition.

Clinical and laboratory stages of manufacturing stamped crowns. Preparation of teeth in the manufacture of a stamped crown. Requirements for a correctly prepared tooth for a stamped crown

1st clinical stage – examination, diagnosis, choice of treatment method, psychotherapeutic preparation of the patient, premedication (if necessary), tooth preparation, taking impressions.

1st laboratory stage – Obtaining dismountable plaster models of jaws. Making wax bases with bite ridges (if necessary).

2nd clinical stage – determination of the central relationship of the jaws.

2nd laboratory stage – production of a stamped crown.

3rd clinical stage – checking the quality of the manufactured crown (fitting) in the oral cavity.

3rd laboratory stage – grinding and polishing of artificial crowns.

4th clinical stage – fixation of the crown with cement.

1st clinical stage

After examining the oral cavity and making a diagnosis, the doctor should issue an order and administer anesthesia, since odontopreparation is accompanied by significant trauma to dental tissues. Preparing a tooth for a stamped crown involves giving it a certain shape, most often resembling a cylinder and ensuring a free application of the crown, the edge of which, entering the gingival groove, should tightly cover the neck of the tooth.

Position of the patient and the doctor during odontopreparation

When grinding, a certain sequence must be followed. Most appropriate start with preparing the contact surfaces. A thin one-sided separation disc is inserted into the straight tip, with the abrasive surface facing the mesial or distal surface of the tooth. The disc is installed above the contact point parallel to the tooth axis. The treatment is carried out intermittently at minimum speed, without strong pressure of the cutting tool on the tooth in order to avoid jamming of the disc and injury to soft tissues. By briefly touching the tooth, hard tissue is removed until a visible gap appears between the teeth. Keeping the disk parallel to the long axis of the tooth, grind the contact surface until the cutting tool touches the neck of the tooth. You should be wary of excessive removal of tooth tissue with the formation of a ledge. You can also use a thin fissure bur (diamond or carbide) on a turbine unit.

If the teeth are very dense, preliminary mechanical separation is possible. To do this, a loop of bronze-aluminum ligature wire is placed around the interdental contact, the ends of which are twisted until a slight pressure is felt on the teeth. After a day, the teeth move away from each other, and the resulting gap allows for easy preparation of the contact surface with a separating disc.

Grinding of the contact surfaces is considered complete if all overhanging edges in the cervical area from the contact sides are removed. The accuracy of the preparation is controlled by the probe. The smoothness of its movement under the gum indicates a smooth surface. The ground surfaces must be parallel to the long axis of the tooth. For a novice doctor, it is difficult to determine the parallelism of the sides of the tooth, so the shape of a truncated cone with the apex facing the antagonist teeth may be recommended. The contact walls of the tooth will converge towards each other, but their inclination should be barely noticeable (1-3°). The thickness of the layer of hard tissue removed from the contact surfaces will be minimal at the neck and more significant at the equator, chewing or cutting surface of the tooth.

Grinding vestibular and oral surfaces carried out approximately according to the same rules. The thickness of the layer of tissue removed depends on the severity of the equator, anatomical shape, size and position of the crown in the dentition.

First, use large heads to remove the most protruding areas of the tooth in the equator area. And then, using diamond, cylindrical or wheel-shaped heads, the vestibular and oral surfaces are leveled, achieving a smooth transition between them, without sharp edges: In the front teeth, the labial surface can be ground with a separation disc. Having given the patient's head a more horizontal position, the separation disc is installed parallel to the long axis of the crown and the required layer of tissue is gradually removed with intermittent movements. Particular attention should be paid when processing the pre-gingival roller.

To prevent injury to the gingival margin when grinding the gingival ridge, use a diamond head of a conical shape or in the form of an inverse truncated cone. Control of the preparation is carried out visually or using an angular probe. After grinding the side walls of the front teeth, a cylindrical shape is obtained only in the cervical area. In other areas, the anatomical shape inherent to the tooth is preserved. The oral surface of the front teeth is ground down to the thickness of a stamped crown. The preparation of the side walls is completed by grinding down the edges of the tooth in the places where the labial and oral surfaces transition to the contact ones. The smoothness of the transition should correspond to the curvature of the cervical part of the tooth in the corresponding areas.

When grinding the chewing surface or cutting edge, it is necessary to preserve their inherent anatomical shape. To do this, the layer of hard tissue in the area of ​​the cusps and fissures is alternately removed from the premolars and molars, and the cutting edge of the incisor and canines is ground off and, additionally, the vestibular and oral sides. The amount of tissue removed is controlled using carbon paper folded into 16 layers. This roughly corresponds to a crown thickness of 0.25-0.3 mm. Being placed between the tooth being prepared and the antagonists, it stains areas of the chewing surfaces that are not sufficiently separated from each other when the dentitions are closed. Grinding is carried out until the carbon paper can easily pass between the teeth.

Sanding hard fabrics chewing surfaces molars and premolars leads to separation from antagonists. In the anterior teeth, separation from antagonists in the position of central occlusion is achieved only with direct or orthognathic bites with minimal overlap. With deeper overlap, separation can be achieved by grinding the palatal surface from the cusps to the incisal edge of the upper anterior teeth, as well as the labial surface and the incisal edge of the lower anterior teeth.

Having shortened and separated the tooth prepared for the crown from the antagonists, the cutting edge on the vestibular side of the upper teeth and on the lingual side of the lower teeth, as well as the transition of the chewing surface to the lateral ones, are additionally subjected to grinding. Otherwise, the volume of the artificial cow will be too large, and it will protrude from the dentition.

When preparing a tooth for a crown, you should pay attention to its position in the dentition. For example, when turning along the axis, you can correct the position of the tooth by grinding the most protruding areas - mesio-vestibular and oral-distal.

Complications during preparation:

patient refusal due to fear of pain - it is necessary to find contact and administer pain relief if there are no contraindications.

Anesthesia requires more careful adherence to the preparation regimen due to the risk of pulp overheating;

damage to the soft tissues of the cheek and tongue, especially when working with separation discs (the gums and tongue are often cut).

• Prevention: hand rest in any position, protection with a mirror, special metal protection

  If soft tissue is injured, you must immediately stop the drill and carefully remove the cutting instrument from the oral cavity. The wound must be pressed with a sterile napkin and the patient must be provided with surgical care.

  Injury to the soft tissues of the oral cavity rarely occurs without mental trauma for the patient and the doctor. In the future, after the injury, the doctor will need to make every effort to convince the patient of the overall favorable outcome of orthopedic treatment;

grinding during separation not to the neck of the tooth, but higher, penetrating into the thickness of the dentin

• Prevention: the separation disc must be directed strictly along the longitudinal axis of the tooth being prepared and during rotation it must be pressed more tightly against the wall of the tooth being prepared;

insufficient removal of hard tooth tissues from the occlusal surface - when fitting the crown there will be an increase in the interalveolar height;

insufficient removal of tooth tissue from the vestibular, lingual or proximal (contact) surfaces - the manufactured crown will not tightly cover the clinical neck and food debris will get in and the gingival margin will be injured;

pulp burn

compliance with the rules of preparation, taking into account safety zones according to Abolmasov

fainting, collapse.

Prevention of complications:

Psychological preparation of patients.

The operation of preparing teeth with living pulp must be carried out under anesthesia, and in some cases, with the use of anesthesia.

The tool must be highly abrasive and well centered.

It is necessary to protect soft tissues.

The drill should be turned on after inserting the handpiece into the oral cavity and securely fixing the hand holding it. It is necessary to remove the cutting tool only after the drill has completely stopped.

Compliance with the rules of tooth preparation.

Taking impressions. Characteristics of alginate impression materials.

After preparing the tooth for a stamped metal crown, it is necessary to take an impression that gives an exact impression of the prepared tooth. Impressions are taken from both jaws. Usually an impression is taken with alginate masses; their use allows you to get a fairly accurate impression, but requires certain skills. You can also use gypsum (extremely rarely); double impressions made using silicone, polysulfide, and polyester masses are especially accurate. When taking an impression, you must follow the correct sequence of actions.

Selection of impression tray.

To obtain anatomical impressions, special metal or plastic spoons are used for the upper and lower jaws. A spoon consists of a body and a handle. In the body of the upper tray, there is a bed for the imprint of teeth or alveolar processes, a bed for the imprint of the palatine vault, and an outer side. The lower tray differs from the upper one in that instead of a bed for the imprint of the palatine vault, it has a notch for the tongue, limited by the inner edge. The sides of the tray serve to hold the impression mass, and the handle helps to properly fix the tray in the oral cavity. Impression trays come in various shapes and sizes. If elastic masses are used for impressions, the tray must be perforated.

Preparing the impression mass and placing it on the tray.

Inserting a spoon with the mass into the oral cavity.

Formation of the edges of the print.

Removing the impression from the oral cavity.

Requirements for an anatomical impression:

1. The anatomical impression should convey a clear impression of the mucous membrane up to the transitional fold and the remaining teeth.

   The edges of the print should be smooth, rounded, but not thick.

Provisional crowns

The prepared tooth becomes sensitive to thermal, chemical and infectious irritants. To avoid this, cover the tooth with a temporary crown or cap made of celluloid.

Methodology: before preparation, impressions are taken from the teeth with alginate material, into which self-polymerizing (cold polymerization) plastic is applied, and after treating the teeth, it is introduced into the oral cavity until final hardening. Then the provisional crown is processed. It is fixed on the tooth immediately after preparation using temporary cement.

1st laboratory stage

Alginate mass impressions are immersed for 5 minutes in a solution of potassium permanganate. Plaster impressions are glued together with boiling wax, immersed in cold water for 5-10 minutes and plaster models are cast. In order to fix them in the position of central occlusion in the occluder, wax bases with bite ridges are used. On plaster models, along the boundaries outlined with a chemical pencil, templates or bases are made from dental wax. In the area of ​​dentition defects, rollers are installed, the width of which in the lateral sections is no more than 1-1.2 cm, and in the area of ​​the front teeth - 0.6-0.8 cm, the height of the rollers in the lateral sections is 1-2 mm above the chewing surface natural teeth, and in front of them the occlusal plane should be located at the level of the cutting edges.

Obtaining a plaster model.

The impression taken out of the water is shaken off, placed on the table with a spoon up so that all the remaining water drips off, and they begin to stir the plaster, adhering to the rules. Pour as much water into the rubber cup as is required to saturate the plaster. This is approximately one part water to two parts plaster. Gypsum is poured into water in small portions until there is no free water left on top. Only after this the plaster is vigorously stirred with a special spatula to obtain a homogeneous thick mass without lumps.

A model cast from too liquid gypsum will be brittle, since the gypsum will bind only the amount of water that is required, according to the chemical formula, the rest of the water will evaporate, and the model will become porous and loose. Excessively thick plaster will not give an accurate impression, since it will not display the relief of the mucous membrane (when taking an impression) or all the indentations in the impression (when receiving the model). Pores may appear in such plaster, since air bubbles will not have time to escape through its thickness before it hardens.

It is necessary to strictly observe the rules for storing gypsum, resulting from its properties described above. It is necessary to protect the plaster from moisture and contamination. Gypsum is stored in thick paper bags or in sealed barrels in a dry room. Before use, it is recommended to sift the gypsum through a sieve to remove lumps and random impurities.

To better fill all the depressions in the impression and to eliminate air bubbles, it is recommended to pour plaster in small portions onto the protruding parts of the impression and shake it at the same time. There are special vibrators for this purpose, but good results can be achieved without a vibrator by tapping the impression tray on the edge of a rubber cup.

The impression is filled with plaster slightly above its edges; pour a little plaster onto a table covered with oilcloth and, turning the print upside down with a spoon, place it on the plaster in a horizontal position. The height of the model should be 1.5-2cm at its thinnest part. The edges of the model are smoothed with a spatula and wait until the plaster has completely hardened.

Separating the model from the plaster impression. When the plaster hardens, remove the impression tray with light blows of a hammer or spatula.

The finished model is trimmed, giving it more accurate contours, and they try to keep all its anatomical details intact. The lower model does not have a recess on the lingual side, so as not to weaken it.

Any damage, such as a fracture of the model, a break in the alveolar ridge, scratches in the area of ​​the working part, etc., make the model unsuitable for further work. In some cases, gluing a broken plaster tooth or part of it is acceptable. The broken tooth must be accurately attached to the model and strengthened with cement or waterproof glue (a solution of celluloid in acetone).

2nd clinical stage

To compare models in the occluder, it is necessary to determine the central occlusion or central relationship of the jaws in the clinic.

Depending on the presence of antagonizing pairs of teeth and their location, the establishment of dentition in central occlusion is carried out differently.

With existing antagonist teeth, the height of the bite is fixed by natural teeth - this is a fixed bite, the anatomical and physiological norm for a given patient. With an unfixed bite, wax templates are fitted in the oral cavity and the mesiodistal position of the lower jaw is fixed so that the height of the bite obtained using occlusal ridges is 2-4 mm less than the height of relative physiological rest.

Determination of the central relationship of the jaws.

According to the degree of difficulty in determining the central relationship of the jaws, four groups of dentition defects are distinguished:

When making 1-2 crowns, the central occlusion is determined by its characteristics, based on which the models are plastered into the occluder, that is, most often they deal with the 1st group.

Models compiled in central occlusion are fixed in the articulator. Having gained an idea of ​​the nature of the closure of the dentition and the relationship of the jaws, they proceed directly to the manufacture of the prosthesis.

2nd laboratory stage

Methods stamping of metal crowns.

Plaster models fixed in the articulator are examined and the degree of separation of the prepared tooth from the antagonists is checked. An eye scalpel is used to remove the plaster that disrupts the clarity of the contours of the neck of the tooth. Engraving is carried out carefully to avoid damage to the cervical part of the tooth. If excess plaster is removed inaccurately, its perimeter is reduced or expanded. You cannot deepen the gingival groove, only mark its exact contours. If the interdental spaces are not filled with impression material and are filled with plaster, it is carefully removed with a thin file or an ophthalmic scalpel. The contours of the gingival margin should be clearly defined along the entire perimeter of the tooth neck. Using a sharply sharpened chemical pencil, outline the clinical neck of the tooth. The resulting line serves as a guide for determining the length and width of the edge of the crown, as well as the degree of its immersion in the gingival groove.

The anatomical shape of the artificial crown is restored using special modeling wax and a modeling spatula. The sharp edge of the spatula is used to trim the wax, and the rounded edge is used to melt it over the fire of the burner.

To obtain the first layer, boiling wax is poured onto the stump of a gypsum tooth, holding the model with the base up, the tip of a spatula with boiling wax is applied to the surface of the tooth from the neck to the cutting edge or chewing surface, preventing the melted wax from getting on the neck area and maintaining the accuracy of its contours. By layering molten wax on the surface of a plaster tooth, we achieve an increase in volume necessary to restore the anatomical shape. To obtain an imprint of antagonist teeth on a modeled tooth, their occlusal surface is lubricated with a thin layer of oil, petroleum jelly, or simply moistened with water. Having received an imprint of the antagonists on warm wax, they proceed to modeling the artificial crown. The wax is cooled and the excess is scraped off. The volume of the modeled tooth is reduced by the thickness of the metal of the stamped crown - 0.25-0.3 mm.

The relief of the chewing surface is modeled taking into account the age-related characteristics of natural teeth. After modeling, the surface of the wax should be smooth. All surfaces in contact with antagonists are separated by the thickness of the metal.

The modeled tooth is cut out from a plaster model. The crown part of the tooth in the direction of the longitudinal axis should be continued approximately to the height of two more crowns. The thickness of the so-called root part of the plaster stamp must exactly correspond to the cross-sectional profile in the neck area; violation will lead to the production of an artificial crown with an inlet hole of inaccurate size.

Marking a plaster stamp is carried out in several ways:

Having retreated approximately 1 mm from the line of the clinical neck of the tooth, marked with a chemical pencil, a groove 0.5 mm deep is made parallel to it. – it serves as a guide for determining the length of the edge of the metal crown.

First, mark the second line with a chemical pencil, located at a distance of 1 mm from the first, and then engrave the groove, retreating another 1 mm from the second line. The advantage is that preliminary shortening of the crown along the groove allows you to subsequently clarify its length along the second line drawn with a chemical pencil. A pre-created length reserve significantly reduces the likelihood of excessive shortening of the crown and thus ensures the greatest accuracy in the manufacture of the prosthesis.

Using a spatula, remove excess gypsum from the entire cervical part and give it a cross-sectional profile equal to the contour of the cervix.

Metal stamps are prepared using plaster stamps.

To obtain an exact copy of a plaster stamp from metal, it is soaked in water or in a solution of office glue. Liquid plaster is poured into a rubber ring with a diameter of 3-4 cm and a height of 4-5 cm. The wet plaster stamp is pre-coated with a thin layer of plaster, removed and re-immersed in it, and then completely placed in the liquid plaster so that the stamp is positioned strictly vertically and is in the very center of the rubber ring. This makes it easier to release the plaster stamp from the mold and ensures that the mold remains accurate.

The hardened gypsum block is pushed out of the rubber ring, the block is shaped into a rectangle, and wedge-shaped longitudinal grooves with a depth of 3-4 mm are made on two opposite sides, leaving a layer up to the gypsum stamp of at least 3-5 mm. The longitudinal recesses must be oriented towards the plaster stamp so that the fracture line passes strictly through its middle. To split a plaster mold, it is placed on the palm of the left hand, and the blade of a plaster knife is inserted into a longitudinal wedge-shaped groove. If the fracture line is misaligned, it may be difficult to remove the plaster stamp from the mold. In this case, on the half of the mold where the gypsum stamp remains, an additional wedge-shaped groove is made strictly in the direction of the stamp and the remaining part of the gypsum block is split along it. After releasing the plaster stamp, all parts of the plaster mold are folded, placed in a rubber ring and a molten low-melting alloy is poured into it, melted in a special spoon on the flame of a gas or alcohol burner at a temperature of 65-95 ° C. In our country, the Melott alloy is used: tin, lead, bismuth (5: 3: 8), melting point - 65 ° C.

For each tooth, 2 stamps are cast: the first is used for final stamping, the second for preliminary stamping. Defects that appear on the surface of the stamp are removed with a file carefully in the neck area. Excess metal on the chewing surface is removed with burs or circles without disturbing its relief. In this form, the metal stamp is ready for stamping the crown.

When making several crowns, the following technique is used: liquid plaster is poured into a manufactured metal frame 5-6 cm wide, sides 2 cm high and 15-20 cm long, into which the previously prepared teeth are lowered in a horizontal position to half their thickness and at a distance of 1 cm apart from each other

After the plaster has hardened, “locks” are made in the form of indentations at both ends of the block and lowered into cold water to soak, then the second half of the mold is cast. After the plaster of the second half has hardened, they are separated from each other with light blows of a hammer and the plaster teeth are removed. Then the two halves of the mold are connected, the entrance hole of each plaster tooth is slightly expanded and the mold is filled with molten low-melting alloy.

For preliminary stamping, a metal stamp No. 2 is used.

For the manufacture of stainless steel crowns, standard sleeves of various diameters and thicknesses (0.20-0.28 mm), produced by industry, are used.

For stamping crowns made of gold or platinum alloy, discs with a diameter of 23-30 mm and a thickness of 0.25-0.28 mm are used.

Preparing sleeves for stamping: select a sleeve according to the diameter of the tooth crown in such a way that it can be pulled onto the metal stamp with some difficulty.

If there are no sleeves of a suitable diameter and they are larger than the diameter of the metal tooth, then they are pulled through the Samson or Sharp apparatus.

The same method is used to produce sleeves from discs (gold, platinum).

To obtain a sleeve of the appropriate diameter, a standard blank or disk is installed against a given die hole and pulled through using a punch. By moving the sleeve from one hole to another, the required diameter is achieved so that the sleeve is put on the metal stamp with some effort.

Repeated pulling of the sleeve through the holes leads to a change in the structure of the metal and its properties, therefore, in order to restore the previous structure of the metal and its properties, the sleeve must be repeatedly subjected to heat treatment after drawing and during operation.

A gold sleeve is calcined until red in the flame of a gas burner or alcohol lamp.

The steel sleeve is calcined in a furnace or in the flame of a soldering apparatus to a temperature of 1100 ° C (straw-yellow color) and quickly cooled in water or air. This achieves fixation of the most stable structure of the steel sleeve, the so-called austenitic one, which is a solid solution of carbon in iron.

Pre-stamping. An anvil, a lead base and hammers are used: copper - for steel, horn - for gold alloy. The approximate shape is first given on an anvil. Having put the sleeve on a stamp made of low-melting alloy No. 2, it is beaten with a hammer, bringing it closer to the shape of the stamp; the blows of the hammer must be directed to the most convex areas of the sleeve, driving them towards the neck of the tooth. You can create a bed in a lead block and hammer a stamp into the sleeve with a hammer until the first imprints of the chewing surface or cutting edge of the tooth appear on the bottom of the sleeve. If the advancement of the sleeve encounters an obstacle from the protrusion on the stamp near the neck of the tooth, then the sleeve is removed and trimmed. Instead of lead, a low-melting alloy is used to form the occlusal surface, pouring it into a mold as shown. Using a hammer, the sleeve is given the approximate shape of the future crown, achieving a tighter fit to the entire surface of the metal stamp.

Before final stamping, the previously made crown is removed by melting the stamp and again subjected to heat treatment according to the same regime.

After preliminary stamping, a gold sleeve must be boiled in a 40-50% solution of hydrochloric or nitric acid before heat treatment to remove traces of lead, which makes gold brittle and contributes to the formation of cracks during stamping.

After preliminary stamping, they begin final stamping: internal, external, combined.

External stamping.

A metal stamp of a tooth with a pre-stamped crown placed on it is wrapped in linen or thick paper (to prevent the mold from getting between the crown and the stamp) and after placing it strictly in the center with the chewing surface downwards, it is hammered into the mass with blows of a hammer or by pressing in a special press.

The press is untwisted by the handle and sharply released, while the cylinder, entering the base, hits the stamping die, and the moldin or rubber acts as a counter-stamp, uniformly transmitting pressure in all directions and facilitating a tight fit of the crown to the surface of the metal stamp.

After stamping, if there are folds on the surface of the crown, they are broken with a hammer, and the crown is removed from the stamp by melting it, holding the crown with tweezers. This ends the laboratory stage.

Before being sent to the clinic, single crowns are bleached, boiled, and wiped; if the crown is intended for anchoring a bridge, then it is not bleached due to the risk of thinning. Such crowns are bleached after the final production of the bridge.

Thus, in external stamping, the stamp is a tooth prepared by us from a low-melting alloy, and the counter-die is a mold or unvulcanized rubber. The combined stamping method combines elements of external and internal stamping - it is not used,

Method combined stamping of crowns. The method of making a metal stamp is borrowed from external stamping, and the method of making a metal counter-stamp is borrowed from internal stamping. It is also called stamping using the MMSI (Moscow Medical Dental Institute) method.

The device consists of a steel cuvette, the internal surfaces of which are conical and have two protrusions along the middle line that facilitate splitting the counter-die.

The metal tooth stamp is prepared in exactly the same way as for external stamping. After this, the surface of the metal stamp is wrapped with one layer of adhesive tape, leaving the occlusal surface or cutting edge free. This corresponds to the thickness of the metal crown. To do this, you can lubricate the surface of the stamp with oil and sprinkle it with talcum powder.

Having installed a holder with a stamp in the center of the cuvette, a molten low-melting alloy is poured into it, after solidification of which the cuvette is placed on a stand upside down, the cotton wool is removed from the hole in the bottom of the cuvette and, by inserting a pestle into the hole, the counter-stamp is removed with hammer blows. The splitting of the counter-stamp and the release of the metal stamp from it is carried out using a chisel or a plaster knife, which is inserted into the resulting recess on the side surface of the stamp. When using a rod with triangular teeth, splitting of the counter die occurs at the moment of its release from the cuvette.

The adhesive plaster is removed from the surface of the metal tooth, a pre-stamped crown is put on and, having installed a counter-stamp in the recess, the latter is inserted into the cuvette by lightly tapping with a hammer so that it takes its previous position. To do this, you can use a pestle with the hollow side. After this, stamping is done by striking the stamp and pestle with a hammer. The stamp with the crown is released from the counter-stamp in the manner described above, that is, by knocking out the counter-stamp, melting it and releasing the crown.

Whitening, grinding and polishing of the crown. The crown, tested in the patient’s oral cavity, is again transferred to the dental laboratory for bleaching, grinding and polishing.

During the manufacturing process of dentures, metal parts are heat treated, which increases and accelerates their chemical interaction with atmospheric oxygen. As a result of such exposure, an oxide film (scale) is formed on the metal surface, which worsens the appearance of the metal and complicates the processes of processing, grinding and polishing the surface.

Removal of the oxide film from the entire surface of metal parts is carried out using bleach. Aqueous solutions of many acids (hydrochloric, sulfuric, nitric, etc.) and their mixtures are used as chills.

To whiten dentures made from gold and silver-palladium alloys, use a 40% aqueous solution of hydrochloric acid. The product is heated red-hot, and then lowered into a vessel with a solution of hydrochloric acid and closed with a lid. After 1-2 minutes, the product is removed from the solution and washed in running water.

All work with hydrochloric acid should be carried out in a fume hood, since its vapors have a harmful effect on the mucous membrane of the respiratory tract. Do not allow it to come into contact with clothing, skin or tools. After stamping crowns from gold alloys in molds made of low-melting metals, their particles remain on the crowns in the form of plaque, which is removed by immersing the crown in hydrochloric acid for 2-3 minutes. Then it is thoroughly washed with water and wiped. A mixture most often consisting of 6 parts nitric acid, 47 parts hydrochloric acid, 47 parts water is used as a whitening agent for treating crowns made of stainless steel. In this solution, steel products are boiled for 1-2 minutes.

To avoid damage to the crown, you must strictly adhere to the whitening regimen.

3rd clinical stage

Checking the quality of production of a stamped crown and the requirements for it.

The quality of a stamped crown made in the laboratory is carefully checked in the oral cavity on a prepared natural tooth, which is greatly facilitated by a preliminary assessment of the artificial crown on a plaster stamp.

The smooth, even surface of the crown indicates the high quality of the stamped prosthesis. Folds and dents on the metal surface, poor coverage of the neck of the plaster stamp by the edge of the crown indicate poor quality of stamping. A gap between the crown edge and the plaster die will result in poor crown retention. Several crowns, which are easily removed from the plaster stamp due to poor quality stamping, can easily be mixed up in the oral cavity before testing.

Checking the length of the crown. On the plaster stamp, the edge of the crown should minimally overlap the line of the clinical neck of the tooth, that is, by 0.3-0.5 mm. The issue is resolved individually according to clinical indications:

If the edge of the crown overlaps the line of the clinical neck more than is required for a given patient, the crown is carefully shortened with a carborundum stone or shaped head.

a crown that turns out to be deliberately short on a plaster stamp and a prepared tooth must be remade.

The finished crown must have an anatomical shape with a well-defined equator, corresponding to the given tooth. The cutting edge and chewing surface are carefully stamped, their relief corresponds to the age of the patient.

Checking the stamped crown on a prepared tooth in the oral cavity.

The artificial stamped crown is removed from the plaster stamp, washed with hydrogen peroxide, disinfected with alcohol and placed on the supporting tooth. If the crown is not applied, it is necessary to check the quality of the tooth preparation. The stump of a ground tooth, expanded in comparison with the perimeter of the neck, can be an obstacle, requiring additional grinding of the hard tissues of the tooth and bringing the stump to the required shape. A narrow crown does not fit on a properly prepared natural tooth due to:

inaccurate print;

inaccurate engraving of the tooth neck on the plaster working model;

narrowing the neck of a gypsum die or removing part of a low-melting alloy when processing a metal die.

Regardless of the reason, the crown is sent to a dental laboratory for re-stamping.

A correctly made crown:

moves along the natural tooth prepared for it;

when the crown is fully applied, it is minimally immersed in the periodontal sulcus.

The depth of immersion is checked with an angled probe, feeling the edge of the crown under the gum along the entire perimeter of the neck of the tooth. Carefully examine the position of the crown edge in the area of ​​the interdental gingival papillae. Excessive immersion of the crown in this place is caused by:

inconvenience when engraving the neck of a tooth on a plaster model;

shortening the metal crown on a metal or plaster stamp due to the sharp bend of the edge of the crown in this place.

Chronic inflammation of the interdental papillae is a common reaction of the marginal periodontium to crown lengthening.

The depth of the crown edge under the gum is checked on the impression. Having inserted the crown into the impression, determine the degree of immersion of its edge into the gum pocket along the entire perimeter of the tooth neck. It will correspond to the width of the cervical part of the crown protruding above the gum imprint.

After specifying the length of the crown, it is necessary to check the density of coverage of the neck of the natural tooth. A wide crown will not fit well, and a slightly narrowed one may not fit completely, which will manifest itself in the occurrence of premature occlusal contact, preventing the closure of the dentition.

Restoring the anatomical shape of the prosthetic tooth involves maintaining the continuity of the dental arch by recreating interdental contact points. An artificial crown that does not have tight contacts with adjacent teeth is considered inferior. Only in patients with sparsely spaced teeth in the form of a diastema or three, such a position of the artificial crown in relation to the adjacent teeth can be considered appropriate. In most patients, the artificial crown should have tight contact with adjacent teeth.

A crown is a permanent prosthesis that restores the shape of a tooth and prevents its further destruction. It is also a foreign body, having a harmful effect on the marginal periodontal tissue. The harmful effects of a crown, like any other prosthesis, can be enhanced by non-compliance with manufacturing rules.

Requirements for making a crown:

Anatomical shape characteristic of a given tooth. Correctly modeled cusps and equator ensure a normal relationship with the teeth of the opposite jaw and neighboring ones. Crown equator:

creates interdental contacts that protect the interdental papilla;

protects the vestibular and oral edges of the gums from damage by food. One of the main conditions for the existence of the dental arch is its continuity, restored by interdental contacts.

Dense coverage of the neck of the tooth with immersion in the gum pocket of no more than 0.3-0.5 mm. A crown wider than the neck of the tooth irritates and pushes back the gum, causing its atrophy - between such a crown and the tooth there is a gap, initially filled with cement, but later saliva dissolves it and food penetrates into the resulting gap, the decomposition products of which cause necrosis of the tooth tissue, this is favored by a violation of the integrity enamel during preparation. Deep immersion of the crown under the gum traumatizes the marginal periodontium.

An artificial crown should not increase the interalveolar height. If not, then with central occlusion, the entire force of the contracting muscles falls only on the tooth covered with the crown and its antagonists. Such occlusion will be traumatic, manifesting itself in the form of pain in the tooth when biting and its mobility.

When modeling the mounds of chewing teeth, it is necessary to take into account age characteristics. In young people, the tubercles are well defined; in older people, on the contrary, due to physiological abrasion they are poorly represented and for this reason the lateral movements of the lower jaw become smoother.

Crown fitting

The crown is placed on the tooth without much effort, gradually reaching the gingival margin. When the edge of the crown tightly covers the neck of the tooth and corresponds to the edge of the gum, it is advanced into the gingival groove. Afterwards, the depth of the crown edges is checked with a probe: in case of deep penetration into the pocket, corrections are made. The edges of the crown cannot be bent wider than the neck of the tooth - the crown is re-stamped. A narrow crown should not be shortened - this may make it inconsistent with the neck of the tooth.

It is also necessary to ensure that there are no premature contacts during lateral occlusions, for which the patient is asked to move the lower jaw to the right and left while maintaining tooth contact - the crown should not interfere with the occlusal relationship during movements of the lower jaw. Identification of possible premature contacts is based on the nature of the closure of the lateral teeth before prosthetics.

If an artificial crown disrupts the usual closure pattern, it should be corrected or redone. Premature contacts should also be avoided with anterior occlusion.

3rd laboratory stage

The crown is polished with an elastic wheel, then a polishing paste is applied to a hard brush or felt (fixed in a grinder), depending on the material from which the crown is made, and polishing is completed with a soft thread “fluff” brush. The following are used as polishing compounds: iron oxide, or crocus (PerOz), Chromium oxide - fine-grained green powder. Pastes developed by the State Optical Institute (GOI) are widely used. The latter are used for polishing stainless steel dentures.

GOI pastes

4th clinical stage

Before committing the crown is thoroughly treated with hydrogen peroxide, degreased with alcohol and dried. The supporting tooth is covered with cotton swabs and subjected to medicinal treatment: cleaned of plaque, washed with antiseptics, disinfected with alcohol, dried with ether or warm air. Cement of a liquid consistency is mixed on a sterile glass plate. The rules for preparing cement and its consistency depend on the brand and the goal that needs to be achieved when strengthening the crown. The prepared cement is introduced into the crown with a spatula, filling it approximately two-thirds. The inner walls are coated to the edge of the crown. Narrow crowns for incisors are filled using a trowel. The crown is placed on the tooth, making sure that the cotton swabs do not get under the edge of the crown. After placing a crown with cement, it is necessary to immediately check the occlusal relationship for central occlusion. If the crown is in close contact with the opposing teeth, the patient is asked to keep the teeth closed for 10-15 minutes until the cement hardens. When using restorative crowns, it is necessary to control their position on the tooth. To do this, in the final phase of application, approximately 3-4 mm from the edge of the crown to the gum, the patient is asked to close his teeth.

When fixing a stamped crown, do not you should immediately check the nature of occlusal contacts in lateral occlusions. This can cause crown displacement and malocclusion. Only after the cement has completely hardened is it necessary to verify the accuracy of restoration of the occlusal relationship. The remaining cement is carefully removed from the surface of the crown and adjacent teeth. Particular care must be taken to remove the cement that fills the interdental space; the movement of the instrument should be directed from the gum to the cutting edge or chewing surface. Do not apply too much force, which could cause the crown to move. Remains of cement on the surface of the polished crown can be easily removed with a cotton swab soaked in liquid phosphate cement; only after this is it necessary to rinse the mouth with a soda solution or a solution of potassium permanganate. After removing the remaining cement, the patient is advised not to eat for 1-2 hours until the fixing material has completely hardened.

Cements for permanent fixation of fixed dentures;

Zinc phosphate cements: “Uniface”, “Adgezor” (Czech Republic), “Phosphacap”, “Poscal” (Germany), “Septocell” (France).

Polycarboxylate cements: “Carboco”, “Aqualox” (Germany), “Selfast” (France).

Glass ionomer cement: “Meron”, “Aqua Meron”. "ChemPhil Superior", "BaseLine", (Germany), "Ionocell" (France), "Fuji ionomer" (Japan).

Polymer cements: “Resiment” (France), “Bifix”, “Dualcement”, “Vario-link”, “F-21” (Germany), etc.

Light and chemically curing cements: “Bifix”, “Avanto” (Germany).

Materials for temporary fixation of artificial crowns

Materials based on zinc oxide and eugenol (guaiacol): Dentol, Temporo-M, Zinoment (Germany), etc.

Cement with calcium superhydroxide: “Provicol” (Germany).

Literature.

1. Markov B.P., Lebedenko I.Yu., Erichev V.V. Guide to practical training in orthopedic dentistry. Part 1. – M.: GOU VUNMC Ministry of Health of the Russian Federation, 2001. – 662 p.

2.Markov B.P., Lebedenko I.Yu., Erichev V.V. Guide to practical training in orthopedic dentistry. Part 2 – M.: GOU VUNMC Ministry of Health of the Russian Federation, 2001. – 235 p.

3. Orthopedic dentistry: Textbook for dental students. fak. honey. universities / Ed. V.N. Kopeikina, M.Z. Mirgazizova. – 2nd ed. add. – M.: Medicine, 2001. – 621 p.

4. Trezubov V.N., Shteyngart M.Z., Mishnev L.M. Orthopedic dentistry: Applied materials science: Textbook for honey. universities – St. Petersburg: SpetsLit, 2001. – 480 p.

5. Trezubov V.N., Shcherbakov A.S., Mishnev L.M. Orthopedic dentistry: Propaedeutics and the basics of a private course: Textbook for honey. universities – St. Petersburg: SpetsLit, 2001. – 480 p.

6.Guide to orthopedic dentistry. / Ed. V.N. Kopeikina. – M.: Triada-X, 1998. – 495 p.

Topic No. 6. Orthopedic treatment of defects in hard dental tissues with plastic crowns. Contraindications and indications for their use. Pain relief during prosthetics with plastic crowns. Principles and methods of preparation. Obtaining an impression. Color selection. Independent work of students: fitting a plastic crown, fixing it with cement.

Purpose of the lesson: Familiarize yourself with the indications and contraindications for making a plastic crown. Study the features of preparing a tooth for a plastic crown. To study the clinical and laboratory stages of manufacturing a plastic crown.

Lesson duration: 3 hours.

Practical lesson plan: Time

1. Organizational moment 5 minutes

2 . Assessment of student knowledge:

questions to the initial level of knowledge: 10 min

1.Safety zones when preparing hard dental tissues

2.Methods of pain relief

3.Types of artificial crowns

test questions on the topic 30 min

1 Indications and contraindications for making a plastic crown.

2. Characteristics of materials used for the manufacture of plastic crowns.

3.Methods of preparing teeth for a plastic crown.

4. Clinical and laboratory stages of manufacturing a plastic crown.

5. Indications for making a crown from self-hardening plastic, manufacturing sequence.

6.Method of fitting and fixing a plastic crown.

7. Errors and complications when using prosthetics with a plastic crown.

3. Examination of the case patient by an assistant 30 min

4 . Classroom independent work of students: 60 min

fitting a plastic crown,

fixation of a plastic crown with cement.

5 . Discussion of students' independent work 20 minutes

6. Assignment for the next lesson 5 minutes

The main indications for the use of crowns are:

1. Destruction or traumatic fracture of a significant part of the tooth, when it is impossible to restore it using a filling or composite material, as well as an inlay.

2. Developmental anomalies and non-carious lesions of hard dental tissues.

3. Anomalies in the development and position of the front teeth, when orthodontic treatment is impossible.

4. Aesthetic defect in the crown of a natural tooth (discoloration, loss of shine, etc.).

5. The presence of artificial crowns that do not meet the aesthetic requirements.

Making porcelain crowns requires certain conditions, and sometimes lengthy preliminary preparation. There may be situations where there are absolute and relative contraindications for the use of porcelain crowns:

Absolute contraindications to the use of porcelain crowns:

1. Teeth with living pulp in children and adolescents.

2. The presence of severe periodontitis in supporting teeth or antagonist teeth.

An absolute contraindication to the use of porcelain crowns in children and adolescents on teeth with living pulp is based on the need for a large volume of preparation (about 1.5 mm) of hard dental tissues and thus the possibility of injury or even opening of the tooth pulp. This is due to the large size of the tooth cavity at this age and its corresponding close location to the tooth surface. The second contraindication is due to the fact that porcelain has great hardness and practically does not wear out, which can cause functional overload of the periodontium of supporting teeth or their antagonists and aggravate the course of the pathological process. Relative contraindications to the use of porcelain crowns

1. Pathological abrasion of hard dental tissues.

2. Parafunctions of the masticatory muscles (bruxism).

3. Malocclusion with deep incisal overlap.

4. Mandibular incisors with living pulp.

The above contraindications are relative, since after appropriate orthopedic (orthodontic) preparation of the dental system and restoration (according to indications) of the interocclusal height, favorable conditions can be created for prosthetics using porcelain crowns.

Thus, the determination of indications for the manufacture of porcelain crowns should be based on a thorough preliminary study of the dentofacial system using general and special research methods and, in some cases, preliminary preparation of the dentofacial system.

^ CLINICAL STAGES OF MANUFACTURING PORCELAIN CROWNS

Clinical steps for making porcelain crowns include:

Patient examination;

Preparation of the dental system for prosthetics (according to

Indications);

Preparation of the abutment tooth;

Taking impressions;

Fitting the porcelain crown before glazing;

Fitting and fixing the finished porcelain crown with cement.

Patient examination

The examination of the patient is carried out according to generally accepted methods and consists of collecting complaints and anamnesis, external examination, examination of the teeth and oral mucosa using general and special research methods.

Studying plaster models of jaws when examining a patient who is planning to have porcelain crowns made will help further clarify the characteristics of the bite, as well as the sagittal, transversal and vertical relationships of the dentition and individual groups of teeth. On diagnostic models, preliminary preparation of abutment teeth can be carried out to determine the optimal amount of preparation for each tooth surface. In some cases (abnormal arrangement of individual teeth), this makes it possible to resolve the issue of the advisability of preliminary depulpation of the abutment tooth. Plastic crowns can be pre-made on plaster models, which, after appropriate correction in the oral cavity, are used as temporary prostheses while the porcelain crowns are being manufactured. To determine the condition of periapical tissues and marginal periodontium in the area of ​​individual teeth, intraoral targeted radiography is used, through which the size and shape of the tooth cavity, the size and topography of tooth roots, and the patency of root canals are studied.

If signs of bruxism or other dysfunctions of the masticatory muscles are detected, it is necessary to apply an electromyographic study of the biopotential of the tone of these muscles and carry out appropriate treatment before prosthetics

To make a porcelain crown, it is necessary to prepare a large volume of hard tooth tissue, as a result of which, in some cases, the pulpless abutment tooth is not able to withstand the corresponding functional load. In this case, it is necessary to clearly define the indications for the manufacture of cast pin inlays. Such preliminary preparation of the abutment tooth is carried out if there are large fillings on it or defects in the crown part of one third And more. To make a porcelain crown for an abnormally located tooth (when orthodontic treatment is impossible), it is necessary to first remove the pulp, followed by modeling and manufacturing a cast pin inlay in the desired projection. A cast pin insert can also be made in case of complete destruction (even subgingival) of the crown of the abutment tooth. However, in this case, the root must be filled to the apex and must not have periapical changes in the bone tissue.

Preparation of the dental system

to prosthetics

Indicated for patients who have relative contraindications to the use of porcelain crowns.

In case of pathological abrasion of teeth, preparation consists of restoring the normal interalveolar distance and height of the lower third of the face. RUkvdi^p, 3 Solid cast non-removable or removable components

4and this "KZZANNIYAM) in °° the region of the lateral 3 U boB > restoring stabilization * g" 7 BITE D ° the required level. In this case, a normal interocclusal distance and

anterior teeth 8" 51 for the use of porcelain crowns on

WASHING, USE OF F and RF°R° crowns in case of pathological bridge of hard dental tissues, the need for preliminary orthopedic treatment in the area of ​​chewing teeth and stabilization of the interocclusal distance is dictated by the possibility of splitting of porcelain crowns even with ideal execution of all stages of prosthetics.

With bruxism and other parafunctions of the masticatory muscles, accompanied by frequent and strong displacements of the lower jaw, high excitability and increased tone of the masticatory muscles are observed. The latter leads to strong compression of the dentition, and the use of porcelain crowns under these conditions can lead to their splitting. Therefore, in the presence of bruxism, appropriate preparation of the dental system is necessary and only then orthopedic treatment with porcelain crowns. In this case, it is important to carefully check the displacement of the dentition in the central, middle, transversal occlusions and at different phases of articulation.

In case of deep bite, as well as prognathic and progenic relationships of the dentition with deep incisal overlap, it is necessary to carry out orthodontic treatment, due to which the depth of the incisal overlap can be reduced and more favorable conditions for the construction of porcelain crowns can be created. If there are defects in the dentition, before making porcelain crowns for the front teeth, dental prosthetics in the area of ​​molars and premolars is necessary.

The incisors of the lower jaw have small crowns, as a result of which during their preparation, especially when creating a ledge in the cervical zone, there is a danger of injury or opening of the tooth cavity. Therefore, if possible, it is better not to use porcelain crowns on this group of teeth (with living pulp). If it is necessary to make the latter in the cervical area, only a symbol of a ledge should be created (especially on the proximal surfaces) with minimal immersion in hard tissue, placing the ledge at the level of the gingival margin.

Carrying out full (orthopedic or orthodontic) preparation in the presence of relative contraindications to the use of porcelain crowns will significantly reduce the occurrence of various complications after the manufacture of crowns.

Preparation of the abutment tooth

Preparation of an abutment tooth for the manufacture of a porcelain crown requires certain conditions and differs significantly from preparation for conventional (stamped, plastic and combined) crowns.

Porcelain is a fragile material, which forces us to increase the volume of preparation of hard dental tissues to a depth of up to 2.0 mm, i.e. 4-5 times more than for a stamped crown. Thickening the porcelain crown is necessary to give it strength and the ability to withstand functional load. In addition, such a deep immersion of the porcelain crown into the hard tissues of the tooth is necessary for its aesthetic fit into the dental arch and to avoid injury to the soft tissues of the marginal periodontium.

To make a porcelain crown, the initially healthy state of the periodontal tissues is necessary. In the presence of periodontitis, the pathological process should be in remission. In cases where the indication for the manufacture of a porcelain crown is an artificial crown that does not meet the requirements, you cannot begin preparing teeth and taking an impression on the day the crown is removed. Studies show that in most cases, in the cervical part of such crowns, signs of inflammation are detected, expressed to varying degrees. Therefore, in patients after removal of defective crowns, it is necessary to carry out drug treatment until the acute or subacute inflammatory process completely disappears. If the remade crown is used as a temporary prosthesis while the porcelain crown is being made, it should be shortened to the gum.

Preparing a tooth for a porcelain or metal-ceramic crown has some features. Preparation should be carried out with a turbine and mechanical drill, well-centered abrasives, under full lighting. Teeth with living pulp must be prepared intermittently, with mandatory water cooling and under local anesthesia. Even if the above conditions are met, the possibility of traumatic damage to the dental pulp as a result of preparation cannot be ruled out. Therefore, it is necessary to know the safety zones of the hard tissues of the anterior group of teeth and the optimal depth of preparation of each tooth.

The results of studies on the safety of the depth of immersion in the hard tissues of abutment teeth are quite fully reflected in the works of N.G. Abolmasova. When preparing a tooth to make a porcelain crown, you must follow a certain sequence:

1. Separation of proximal surfaces.

2. Shortening the tooth crown by a third of its length.

3. Preparation of the oral and vestibular surfaces.

4. Final preparation.

To separate the proximal surfaces, a one-sided diamond separation disc is used, which separates the abutment tooth from the adjacent one and at the same time creates a ledge, not bringing it to the cheap edge by 0.5-1.0 mm (Fig. 4, a). Next, the tooth is shortened by Vs the height of the coronal part. To work at these stages, a mechanical drill is used (Fig. 4.6).

The preparation of the oral and vestibular surfaces is carried out as follows. Using a diamond bur - a reverse cone - a groove up to 1.0 mm deep is formed in the hard tissues along the gingival margin, which does not reach the gum by 0.5-1.0 mm. Next, hard tissues are ground off over the entire surface of the tooth from the cutting edge to the bottom of the formed groove. The preparation of the vestibular surface of the tooth can be done in another way. Using a cylindrical diamond bur, a groove up to 1.0 mm deep is made in the middle of the vestibular surface of the tooth along its axis, departing from the gingival margin by 0.5-1.0 mm (Fig. 4b). Then the hard tissues of the tooth are ground down over the entire surface to the bottom of the groove.

Having carried out the preliminary preparation of the abutment tooth in the above sequence, they proceed to the final preparation and final formation of the ledge at an angle of 90°. This is done with a turbine drill using a cylindrical bur with a diamond coating. The transitional surfaces are smoothed (from proximal to vestibular and oral), and undercut areas are removed. At the same time, the ledge is refined, bringing it to a given level (Fig. 4, d). "A ledge of this shape allows you to accurately restore the anatomical shape of the tooth in the cervical zone, which accordingly improves its aesthetic properties and eliminates trauma to the mucous membrane of the gums (cases of subgingival edge location are not uncommon porcelain crowns). The rectangular shape of the ledge best facilitates the transfer of functional load through the crown and the supporting tooth, which reduces the number of complications in the form of splitting of the porcelain crown. Therefore, in the process of completing the preparation, it is necessary to pay special attention to the final preparation of the ledge. A cylindrical diamond bur is used to smooth out all roughness on the ledge and, if necessary, expand it. Then achieve a uniform location of the ledge along the entire perimeter of the abutment tooth at the required level. Finish processing the ledge using an end bur for a straight or angled handpiece (Fig. 4, d). Select a bur of the appropriate size (according to the width of the ledge) and , working at low speeds alternately in both directions (clockwise and counterclockwise) over the entire surface of the ledge, smooth it out, removing all roughness and irregularities. It is recommended to place the ledge and, accordingly, the edge of the porcelain crown at the gum level. In some cases, for aesthetic reasons, a subgingival location of the vestibular surface and areas of transition from the vestibular surface to the proximal ones is possible, but not more than X depth of the gingival groove (pocket).

Thus, after preparation, the abutment tooth should, if possible, retain its anatomical shape, only in a correspondingly reduced size. It is necessary to take into account that the lateral surfaces of the tooth must convert slightly (4-6°) in relation to the cutting edge.

Some authors suggest using vestibular porcelain half-crowns in a certain group of patients (in the presence of a deep bite, deep wedge-shaped defects, vertical wear of the oral or vestibular surface of the teeth). Structurally, they are almost identical to metal ones, but have only been transferred from the oral surface to the vestibular one. The preparation of the vestibular surface is carried out traditionally with the creation of an appropriate shoulder (at an angle of 90°), as in the manufacture of full porcelain crowns. A distinctive feature of the porcelain half-crown is that when preparing the proximal surfaces, each of them must make angles of PO-115° with the vestibular surface, open orally. The incisal edge is prepared within 1.0 mm with a slight bevel in the vestibular direction. The authors believe that vestibular porcelain crowns are indicated for use only in patients with the pathology listed above, and I do not recommend their use instead of full porcelain crowns. 36

Taking an impression

Taking an impression is one of the important stages of manufacturing

4 °o VO th crowns. The need to have an accurate impression of the dictation

possible subsequent distortion of the finished prosthesis

is subject to perfect execution of all other stages

orthopedic treatment.

When receiving an impression, copper rings filled with thermoplastic mass are used to make a porcelain crown. Copper rings can be standard or made in a dental laboratory. The orthopedic dentistry clinic uses a lot of thermoplastic masses, but only a few of them can be used to make porcelain crowns:

acrodent, dentaform - Ukraine,

Reprodent - Slovakia,

Xantigen - Germany, etc.

Obtaining an impression using a copper ring and thermoplastic mass begins with selecting a ring of the appropriate size. The perimeter of the tooth in the cervical part is preliminarily determined using standard measuring rings or a dentimeter. The ring should fit snugly to the neck of the tooth and accurately follow the contour of the gingival margin. Then, on the back side of the ring from the intended vestibular surface, a triangular-shaped petal is cut out to release excess mass and orientation, after which they begin to design the working edge of the copper ring. To do this, the ring is put on the prepared tooth and, noting the areas of initial contact with the gum, they are cut out. This is done repeatedly until the edge of the copper ring exactly corresponds in relief to the configuration of the gingival sulcus. Subsequently, in order to avoid injury to the soft tissues of the marginal periodontium, the edge of the copper ring is processed and polished until a smooth surface is obtained. The preparation of the thermoplastic mass is carried out in a water bath at a temperature of 60-65°C until it is completely softened. Then the mass without excess is placed in a ring, which is immersed in heated water for several minutes. It is undesirable to heat the thermoplastic mass over a flame, since this will cause some components to evaporate, thereby deteriorating its properties (the thermoplastic mass is reused many times). A ring prepared in this way with a thermoplastic mass to obtain an impression is pushed onto the prepared tooth along its axis so that, blocking the ledge, it plunges into the gingival groove

(pocket), but no more than 100 degrees of its depth. Deeper advancement of the copper ring can lead to injury to the gum mucosa, and in the worst case, damage to the circular ligament of the tooth. After receiving the impression, it is necessary to carefully examine it, especially the display of the ledge. The resulting impression also serves as a control for the preparation, therefore, if any inaccuracies are detected on the tooth, it must be further prepared and the impression taken again. If there are braces on the impression, it must be re-taken until an accurate image of the tooth stump with a circular shoulder is obtained. To make two or more crowns, an impression of each abutment tooth is taken

in the same way.

The above describes the generally accepted method of obtaining an impression using a copper ring and thermoplastic mass. Let's look at some of its modifications. There are recommendations to create retention petals on the back side of the copper ring to prevent injury to the soft tissues of the marginal periodontium. After fitting and determining the depth of immersion of the ring into the gingival groove (pocket), notches are made on its proximal surfaces at the level of the cutting edge of adjacent teeth. Then the copper ring is cut longitudinally from the back to the marked areas (notches) and the resulting petals are bent so that they lie on the cutting edges of adjacent teeth. The bent petals are retention points that prevent the ring from sinking deeper into the gingival tissue.

groove (pocket).

Using this method, a copper ring is prepared, which is filled with the first layer of impression material and an indicative impression is removed. Next, a correction layer is applied and the final impression is obtained. The use of silicone masses is also possible with another method of obtaining an impression. Place the fitted copper ring on the prepared tooth and fill the back side with the first layer of silicone mass. The ring is removed after the mass has hardened, filled with a corrective layer (already on the working side) and an impression of the abutment tooth is obtained. However, in these cases the copper ring must have retention tabs.

The resulting impression is sent to a dental laboratory to make a model (stamp) of the prepared tooth. 3S

The next clinical stage includes obtaining an impression of the combined model using a prepared die. To do this, using an alginate or silicone mass, a complete impression of the dentition is taken, in which a stamp (gatampics) is then placed in the impression of the corresponding tooth. To prevent the die from moving during casting of the model, it is strengthened in the impression using pins and a few drops of hot wax. The combined model is a plaster model of the dentition with the inclusion of a removable model (stamp) of the prepared tooth. The stamp(s) must be freely removed from the general model, installed in it and always be in only one specified position. Work with the patient is completed only when there is convincing evidence of the usefulness of the combined model.

There are recommendations to prepare one porcelain crown or several separate ones, i.e., not standing next to each other, taking an impression to make a combined model immediately after receiving the impression using a copper ring filled with thermoplastic mass. This shortens one clinical stage. After making sure that the impression obtained with the ring is complete, it is reinstalled on the prepared tooth and a complete impression of the dentition is taken. In the laboratory, a die is first obtained, which, without being separated from the copper ring and thermoplastic mass, is installed again in the general cast (after having previously lubricated the shank and the plaster part of the die with petroleum jelly) and the complete model is cast. After opening the model, the stamp along with the ring is pulled out of it. After heating, the copper ring with the thermoplastic mass is removed from the die and then reinstalled into the model.

To make porcelain crowns, two-layer impressions can also be used, which will be discussed in more detail in Chapter. 3.

At the same clinical stage, the color of the future porcelain crown is determined. This must be done together with the dental technician, taking into account the wishes of the patient. It is better to determine the color in the first half of the day in natural light, comparing nearby natural teeth or antagonist teeth with the color scale.

After taking impressions, the prepared teeth must be covered with temporary plastic crowns (caps) to prevent displacement of the supporting teeth (deprived of contact with the zontal teeth), as well as to prevent chemical or

thermal irritation and infection (teeth with living pulp).

Fitting the porcelain crown before glazing

Fitting the porcelain crown before glazing is a crucial moment in prosthetics, since at the last stage (after glazing) it is not recommended to carry out any interventions on the porcelain crown, i.e., violating the integrity of the glaze coating.

Before fitting, you must carefully inspect the porcelain crown and make sure it is complete (no defects, cracks, pores, etc.). The first stage of fitting is to check the compliance of the porcelain crown with the tissues of the prosthetic field, especially carefully in the area of ​​the ledge. The edge of the porcelain crown must fit snugly against the ledge along the entire perimeter of the abutment tooth, otherwise the dental technician will make additional corrections or redo the crown. The outer edge of the porcelain crown should be in the same plane as

Rice. 5. The relationship between the edge of the porcelain crown and the cervical

th shoulder of the abutment tooth:

A- the crown restores the anatomical shape of the tooth

cervical zone; b - the edge of the crown overlaps the ledge; V-

the edge of the crown is less than the width of the ledge

hard tissues of the tooth (Fig. 5,a), i.e. it is in the cervical zone

GV should completely restore the anatomical shape of the tooth.

Under no circumstances should a porcelain crown be used

do not cover (there should be no canopies) the ledge (Fig.

5^ otherwise, injury to the soft tissues of the marginal periodontium is possible

"increasing the likelihood of chipping. The edge of the porcelain crown along

the thickness should not be less than the width of the ledge (Fig. 5,c). WITH

the occlusal surface of the headlights is verified with special care

(Bora crown in all phases of articulation. Then carry out

correction of the shape and size of the crown, as well as checking

matches the color of natural teeth. These last moments

It is better to carry out fittings in the presence of a dental technician.

Thus, the porcelain crown in the cervical and coronal parts should completely restore the anatomical shape of the tooth and have the color and shine of natural teeth.

Fitting and fixing a porcelain crown with cement

Fitting and fixing the porcelain crown with cement is the last stage of orthopedic treatment, which consists of a thorough examination of the porcelain crown (absence of swellings, cracks and pores), determining whether its color matches the specified one and fixing it with permanent cement.

^ LABORATORY STEPS IN THE MANUFACTURE OF PORCELAIN CROWNS

The laboratory stages of making a porcelain crown are carried out in a certain sequence:

making a cap from platinum foil; applying and firing the ground layer of porcelain mass;

application and firing of dentin and transparent layers of porcelain mass;

glazing.

Making a cap from platinum foil

The platinum cap accurately follows the contour of the prepared tooth on its model (stamp) and bears the thermal load during the stages of firing the porcelain mass, while maintaining the specified shape of the porcelain crown.

Platinum foil was proposed as a matrix for firing porcelain crowns about 100 years ago. However, even today this is the only material that does not distort the shape and does not change the color of the porcelain crown at large

temperature conditions, since platinum does not form colored oxides, is quite hard and has a high melting point (1773.5 °C). In addition, the coefficient of thermal expansion of platinum and porcelain is almost identical. The platinum foil for making the cap has a thickness of 0.025 mm.

Depending on the size of the tooth, a diamond-shaped plate is cut out of platinum foil and annealed at a temperature of 1000-1100°C. To obtain the cap, the stamp of the abutment tooth of one of the proximal sides is pressed into the middle of the platinum plate, which, bent in half, is held by the index finger and thumb. In this case, the ends of the plate are joined on the opposite proximal surface and at the cutting edge of the die. Next, the platinum foil fits as tightly as possible over the entire surface of the tooth model, especially in the area of ​​the ledge. This is done using a metal spatula or smoother. Then, using tweezers, bring the ends of the platinum foil together along the cutting and proximal edges and, stepping back from the tooth surface by 1.5-2.0 mm, cut them off. To create a tight seam in the area of ​​the cutting edge, the oral petal of platinum foil is cut at a distance of 0.5-1.0 mm from the surface of the die and pressed tightly against the surface of the cutting edge, and the vestibular petal is folded over the oral one. On the proximal surface, to obtain a seam (like a roofing one), the oral lobe is cut at a distance of 0.5-1.0 mm from the lateral surface of the tooth model. Next, the oral petal is bent with the vestibular petal and then both petals are pressed to the surface of the stamp.

The seam along the incisal and proximal edges, as well as the entire cap, are smoothed again with a smoothing iron, achieving a tight fit over the entire surface of the die with an overlap of the shoulder. The platinum cap is removed from the die, cut off in the cervical part, leaving an overlap of the ledge of 1.5-2.0 mm, and for cleaning it is subjected to heat treatment (calcination) and boiling in a 10% solution of nitric acid. The cap should be removed without tension and placed on the die of the prepared tooth. In this way, the base (matrix) is prepared for applying and firing the porcelain mass.

Applying and firing the ground layer of porcelain mass

The first layer of porcelain mass is the ground layer (core). It is applied to a platinum cap, which, after thermal and chemical treatment, is placed on a model of the prepared tooth (stamp) with tweezers. The porcelain mass is prepared

sewing porcelain powder with a special liquid (not using distilled water) until the MOYAS has an egg-like consistency that does not flow off the glass, placing it on the edge. The resulting mass is applied in small quantities onto a platinum cap. Each portion is mixed with movements of a grooved tool according to the model for compacting the porcelain mass, while removing excess moisture using a paper napkin or other hygroscopic material. This is done repeatedly until the platinum cap is completely and uniformly covered with the primer layer. After applying the primer layer, part of the ledge must be freed from the porcelain mass. The porcelain mass shrinks during firing, as a result of which the platinum cap is deformed in the area of ​​the ledge. Freeing part of the ledge from the porcelain mass before firing allows you to give the platinum cap its original shape after firing. The platinum cap prepared in this way with a ground layer of porcelain mass is removed from the die and placed on a ceramic stand, which is transferred to a muffle furnace for firing. The firing of the soil layer is carried out in a vacuum. After firing, the platinum cap with the primer layer is cooled at room temperature, and then installed again on the die, where it is necessary to carefully adapt the cap to the ledge along the entire perimeter of the tooth. Often, after the first firing of the ground layer, cracks and pores are revealed on it, which must be filled with a new portion of porcelain mass and fired again under the same conditions. The thickness of the soil layer after firing should be 0.5-0.6 mm. Porcelain should have a slightly shiny surface after firing.

Application and firing of the dentin layer of porcelain mass

This stage is the most labor-intensive and complex and includes modeling, firing and correction by grinding. Dentine porcelain mass is prepared in the same way as primer, by diluting the porcelain powder with an appropriate solution. The application of the prepared porcelain mass is carried out on a combined model in small portions. Each new portion is condensed with a grooved tool, achieving maximum Compaction while removing excess moisture (same as when applying a primer layer).

Application of the porcelain mass begins from the oral side,

thus modeling the proximal and vestibular surfaces,

giving the crown the necessary contours. In the area of ​​the tooth neck

° the funnel is modeled so that the porcelain mass reaches

Na pm to correct the applied mass of the ledge, but did not overlap e™-^*™™ pYAK prepared Zh* ledge must be extracted ^ t P ^

z U bk from the combined model^ If < ^ proximal

adjacent crowns tsih^JggJ needle th. „.

areas of thin and flexible<^P*J™ груН товоЙ слой штампик После нанесения дентиннои массы m It is necessary to re-install the complete model^ / applied enamel

on the modeled ^^^^ layers are necessary for mass and glass melt, ^f^™^^ in the area of ​​the cutting edge giving a natural p0L U p ^^ ssu N and the middle of the thickness of the front teeth. y "^^f ™tooth ator so that applied from the cutting edge obliquely to the equator"At the vestibular

tail coat layer smoothly ^^^^7cce^ dentinal surface. On °P^ bH0 « ^оя^а several millimeters for the mass, retreating from the cutting edge by

applying glass melt. large volumetric shrinkage,

Since the porcelain mass is ™ e f ° ™ 1, the porcelain crown is increased in volume (up to 25% depending on the used U ^^^ m0 „ mass). Therefore, the vestibular ID ^ edges are also degraded in a large J""^"^ modeling is carried out increased by 1.5-2.0 mm. Whether the design of the proximal on the combined mo "^" dIM o speak from the model and then the surfaces ** tampzh Jf™ "-" porcelain crown, restore these U "" and ^SaT UD-Xia in time, then If the process m0 ^^ y Ш DO the dried porcelain ^ I and D ^ are also moistened with several "^"^nG surfaces porcelain crowns necessary for modeling according to Ryshssy.

before applying additional portion"<Ц*^ коронки все ее После окончания «»»2£К* Зат?м коронку снимают со поверхности ^a ^G^G2 ^shsh,skaya stand for the die and placed on the ground, carried out in firing. Firing Dentin in ™^£ 0 g ane cracks or under vacuum conditions. When vyya^™ 0 p ^ zhiYa1YUG, as well as when on a porcelain to °P°" to |^Ta r a fora crown, periodically * the previous P^^atY "J r Separated) tooth ", setting it on ^Za™v #from abrasives to giving a combined M „°« e ™" K f C 1 "volume take into account the ratio of its corresponding shape "P and ^ U. After giving** adjacent teeth and ^^hSZJmh platinum colnacho to a porcelain crown ~Ј%Ј+2Z transferred to the clinic, incised to the level of the ledge, ^v for fitting.

Glazing

The last laboratory stage in the manufacture of porcelain col- 1 __ g lazing. After this, it is not recommended to carry out R&D corrections on the porcelain crown, since it is impossible to damage the integrity of the glaze. Therefore, the presence of Na is necessary<=>go technique when fitting a porcelain crown before 3 Hope to determine the areas required for G-dropping. Before glazing, the surface of the porcelain is treated with fine-grained abrasives, brushed with K° powder, washed in running water and dried. According to indications, some areas of the porcelain crown are tinted with dyes (usually in the cervical area on the vestibular surface of the crown). Glazing must be carried out under atmospheric conditions. In this case, gloss (glaze) is formed due to the melting of fluxes over the entire surface of the porcelain crown. After firing, the porcelain crown is cooled at room temperature, carefully examined and, after removing the platinum foil, transferred to the clinic.

For the manufacture of porcelain crowns, porcelain masses “Gamma” (Tables 5, 6), Vitadur, etc. are used.

^T a b l i c a 5. Combination of powders in the Gamma porcelain mass

Example. The color of the future porcelain crown was determined for the patient - 4. Therefore, the ground layer G9, dentine - D4, transparent - Pr will be used.

^ Table 6. Temperature conditions and regional conditions V vacuum porcelain oven "Gamma"

WITH porcelain paste

Ground

Dentin

Jlp^3rjajH4biit

Temperature, C

Vacuum Vacuum Atmosphere

O In recent years, experts have been trying to improve the “Technology for the manufacture of porcelain crowns (manufacturing

porcelain crowns on fire-resistant models, all-porcelain bridges, etc.), excluding the laboratory stage of manufacturing a platinum cap. The technique for producing porcelain crowns by pressing, proposed by Ivoclar (Germany), deserves attention.

The technology proposed by Ivoclar IPS Empress consists of the following components:

pressing furnace EP-500 from IPS Empress, leucite-strengthened ceramic material, a new type of colored dentin masses and paints, light-curing core material with a special color.

The proposed technology is carried out by melting wax. The work is modeled in wax and packed in investment material. After preheating in the muffle, the leucite-reinforced ceramic material is pressed into the muffle under pressure in the EP-500 furnace. After unpacking the pressed objects, the manufacturing process is completed using the dyeing or layering method (depending on aesthetic or anatomical indications).

The basis of a new type of leucite-reinforced ceramic is glass containing latent particles that stimulate crystal growth. During the technology process, leucite crystals several micrometers in size are formed through controlled crystallization in a glass matrix.

Crowns pressed from dentine-colored blanks are reduced to the shape of a dentine base, after which they are restored with a transparent (enamel) layer of porcelain mass to the final shape and fired in a kiln (like all ceramic or metal-ceramic structures).

^ ERRORS AND COMPLICATIONS WHEN USING PORCELAIN CROWNS

It has been established that the use of porcelain crowns requires a special approach, and in some cases, special preparation of the dental system. This complicates the process of their manufacture compared to other types of fixed prostheses. A poet? It is necessary to know about possible errors and complications during and after the manufacture of porcelain crowns, which may be caused by both clinical techniques and manufacturing technology, and the state of the dental system.

A common mistake is* expanding the indications for the manufacture of porcelain crowns, which may be due to insufficient examination of the patient without taking into account the indications and contraindications. It is necessary to clearly distinguish between absolute and positive contraindications, and in cases where it is necessary to carry out any preparation of the dental system (if there are relative contraindications), this should be done with a complete examination, diagnosis and treatment of the patient. Otherwise, after the manufacture of porcelain crowns, complications are inevitable in most patients.

Complications are possible during the manufacturing stages of porcelain crowns. It is unacceptable to start preparing teeth and taking impressions if there is an acute inflammatory process in the periodontal tissues. In the presence of gingivitis, treatment must be carried out until it completely disappears (the process is reversible); in case of periodontitis, the pathological process must be in remission (at this stage the gums are close to the concept of “healthy gums”), otherwise the inflammatory process may deepen with its transition to the underlying sections periodontal

When preparing teeth with living pulp, it is necessary to know the safety zones of hard tissues for each tooth and observe the necessary conditions and regime (under anesthesia, with continuous water cooling, intermittently, etc.). This will greatly reduce trauma and burns to the pulp of the abutment tooth.

Chip is one of the most common complications when using porcelain crowns. As a rule, this complication in the presence of supporting teeth with living pulp occurs in the cervical area on the oral surface. This is due to the fact that when preparing the oral surface of the abutment tooth, sufficient interocclusal space is not created (in order to avoid pulp trauma). At the stage of fitting the porcelain crown, when calibrating the occlusal relationship with antagonists, the porcelain is ground off to eliminate supracontact (sometimes up to half the thickness of the crown). The strength qualities of a porcelain crown depend on the uniformity and completeness of the thickness of the layers of porcelain mass. Therefore, when preparing the abutment teeth, the necessary interocclusal space should be created for the thickness of the future crown (even if the abutment tooth is Ulpated).

natural anatomical shape in a correspondingly reduced

0m size, and the side surfaces are slightly (4-6°)

plunge towards the cutting edge. Greater angle increase

convergence will weaken the fixation of the porcelain crown and lead to

to its disintegration.

It is necessary to correctly determine the indications for depulpation of individual teeth (especially abnormally located ones), without trying to finally resolve the issue during the preparation process or after. Studying x-rays and approximate preparation on a plaster model will allow you to correctly decide

It is necessary to take into account the large volume of hard tissue preparation when making porcelain crowns for pulpless teeth and, in some cases, to pre-make cast pin inlays. Thus, it is possible to exclude chipping of the crown of a natural tooth with a covering structure under functional load.

When preparing (preparing) a tooth for a porcelain crown, it is necessary to form a rectangular ledge in the cervical part and be aware that the use of other types and variants is unacceptable. In addition, the ledge should be around the entire perimeter of the abutment tooth (circular). Only in these cases will the porcelain crown meet the aesthetic requirements and not cause mechanical irritation to the

marginal periodontium.

An error may occur when selecting a copper ring to obtain an impression. A discrepancy between the diameter of the ring and the perimeter of the tooth can result in an inaccurate representation of the supporting tooth on the impression (smaller ring) or injure the soft tissue of the marginal periodontium (larger ring). Soft tissue injury is inevitable when the ring is pushed deeply under the gum, even if its size is appropriate. Therefore, when taking an impression using thermoplastic mass and a copper ring, you need to immerse it in the gingival groove (pocket) no more than Vi

its depths.

When obtaining a combined model, it is important to accurately place the dies in the impressions of the corresponding teeth (do not mix them up!) and firmly fix them to prevent displacement during casting. It is necessary to know that the patient must wait until the model is opened and verified as to its accuracy.

You should very carefully, taking into account the patient’s opinion, determine the color of the future porcelain crown(s). In this case, the presence of a dental technician is necessary. If the color of a porcelain crown does not match the adjacent natural teeth or antagonist teeth, it should be redone without attempting to overcome the situation by repeated multiple firings using dyes. 48

GG adjusted the porcelain crown to the penultimate one

/ l0 glazing) it is necessary to inspect it carefully.

3X3116 No pores, bubbles or cracks indicate a problem

^*a<£Г аторной технологии. Такая коронка должна быть переделана.

laboratory asovka of a porcelain crown needs that its edge is tightly

And he went to the ledge along its entire length, without blocking it without visors). There should be no areas where the thickness of the porcelain crown is less than the width of the ledge. The edge of the porcelain crown and the edge of the ledge must exactly match each other (SM- Fig. 5). Otherwise, a laboratory correction of the porcelain crown is carried out or it is redone. When fitting a porcelain crown, you need to carefully verify the relationship of the crown with the antagonist teeth in the central, anterior and transversal occlusions in order to avoid traumatic overload of the periodontal tissues of the supporting teeth or antagonist teeth, as well as its split.

Laboratory errors relate to the modeling of porcelain crowns, the thickness of the porcelain layers in the crown, and the firing mode in a vacuum oven.

The finished porcelain crown needs to be fixed only with cement. Before this, it is necessary to fit it and determine the color match to the adjacent teeth and antagonists. To fix a porcelain crown, the cement should be mixed slightly thinner than for a conventional metal crown and applied to the abutment tooth without pressure.

Various complications are possible after strengthening porcelain crowns. The most common of them are splitting of the porcelain crown, functional overload of periodontal tissues, etc. Therefore, in order to avoid these complications, patients with porcelain crowns should be monitored at the dispensary. If necessary, they correct the occlusion by selective grinding. This is especially true for those patients who had relative contraindications and received preliminary preparation.

^ ORTHOPEDIC TREATMENT

PATIENTS USING SOLID CAST

METAL-CERAMIC

AND METAL-PLASTIC PROSTHESES

Currently, for the manufacture of fixed prostheses, various types of solid prostheses are widely used: all-metal, metal-ceramic and metal-plastic.

high designs.

The use of various alloys to make a metal frame on which porcelain or plastic is applied has greatly expanded the indications for the use of denture structures called metal-ceramics or metal-plastic.

Metal-ceramic structures combine the advantages of solid dentures and porcelain crowns. They are distinguished by the following advantages: high strength; tightly cover the neck of the tooth, located at a given level; accurately reproduce the relief of the chewing surface; have high aesthetic properties; more indifferent to tissues

oral cavity, etc.

The first alloys for metal ceramics were alloys based on platinum, gold and palladium. Currently, about 300 alloys are used in dental laboratories around the world, which can be divided into three groups: alloys based on precious metals, semi-precious and base metals.

Metal-plastic structures have a certain perfection both aesthetically and functionally. For cladding solid frames in metal-plastic prostheses, you can use various veneering dental plastics, both conventional (sinma, sinma M, etc.) and high-strength (aerodent, pyroplast, isosite, etc.). These advantages are available only to metal-plastic structures lined with high-strength plastic, which in color and strength properties is close to natural teeth, which allows it to be used for lining the oral and chewing surface of a solid-cast frame.

Solid-cast fixed dentures are the most modern

non-removable denture designs. However

Bb preparing them presents certain difficulties and requires

FROM both approaches, a special set of tools, equipment

with me and materials. Solid-cast fixed dentures are used

In I aesthetic, functional and anatomical inferiority

awns to the crown of the teeth, as well as in the presence of dental defects