DENTURES (fr. prothese, from grech, prosthesis addition, accession) — means for substitution of defects of dentitions or alveolar shoots of jaws. The denture is a part of orthopedic treatment and the prophylactic providing normalization of functions of chewing and the speech and preventing further destruction and loss of teeth; it promotes elimination of dysfunction of masseters, temporal and mandibular joints, and also eliminates the cosmetic defects caused by loss or defects of teeth.
The denture was applied still in the ancient time. So, at excavation of the ancient Phoenician city of Sidon (4 — 3 centuries BC) false teeth from a bone, and also teeth of people which were attached to the next teeth by means of a gold or silver wire (fig. 1) were found. The prostheses consisting of false teeth and a number of the gold rings strengthening on the next healthy teeth (fig. 2) were found in tombs of Etruscans (9 — 6 centuries BC) at excavation of the city of Tarkviniya. In Ancient Rome barbers, jewelers and other handicraftsmen were engaged in production of dentures. Only in 11 century AD the Arab, the surgeon Abul-Kasim, being engaged in a zubovrachevaniye, laid the foundation for prosthetic dentistry as the section of medicine. The fr. surgeon A. Paré offered a prosthesis (obturator) for closing of a palate defect, having used a gold plate for this purpose. Improvement of a denture is connected with a name of P. Foshar who applied bayonet teeth, the full removable prostheses strengthening on toothless jaws by means of a spring (fig. 3), etc.
The denture is carried out after careful inspection of dentoalveolar system taking into account the general condition of the patient. By preparation of an oral cavity for prosthetics the size and topography of defect of dentitions, a condition of solid tissues of the remained teeth and a parodonta, a type of a bite, existence of deformation of an occlusal surface of dentitions, a form of an alveolar shoot of an upper jaw and an alveolar part of a mandible, especially on toothless jaws, a condition of a temporal and mandibular joint is defined.
Distinguish three types of a denture: direct, the next and remote. In the first case the prosthesis is prepared to an exodontia (or jaws) and imposed directly on a wound not later than in 24 hours after operation (a so-called immediat-prosthesis). The next prosthetics is performed within two weeks after operation when epithelization of a wound comes to the end. Start the remote prosthetics after there is a full wound repair and the reorganization of a bone tissue of an alveolar shoot connected with an exodontia, most often in 4 — 6 months after operation and use of a temporary prosthesis. Dentures are rather full until there is a mobility of basic teeth or other changes causing need of production of a new prosthesis.
Sanitation of an oral cavity (treatment of caries, diseases of a mucous membrane, etc.), elimination of deformations of dentitions, excision tyazhy and hems, if necessary — correction of bridles of lips and language, keen edges of alveoluses after an exodontia, plastics of an alveolar crest, deepening of a threshold of an oral cavity, etc. == Vida of dentures == shall precede prosthetics
According to kinds of defects of teeth and dentitions distinguish the following prostheses (fig. 4). 1. Dentures for substitution of defects of crowns of teeth; tabs from porcelain (fig. 4, 1) and various alloys concern to them (see. Tabs tooth ). 2. Dentures for recovery of the destroyed crowns of teeth — artificial crowns and bayonet teeth (fig. 4, 2 and 3). 3. Dentures for substitution of separate teeth or groups of teeth; fixed bridge-like prostheses and removable — concern to them small saddle, byugelny and partial plastinochny (fig. 4, 4—8). 4. Dentures for substitution of dentition — full plastinochny removable prostheses (fig. 4, 9). 5. The dentures for substitution of defects of dentition supplied with devices for splintage of mobile teeth. 6. Zubo-chelyustno-litsevye the prostheses applied to substitution of defects of dentitions and sites of jaws and the person. The post-resection hollow prosthesis for an upper jaw offered by H. Pichler in 1923 concerns to the same group. Along with it produce also front ektoproteza for substitution of an ear, a nose, defects of firm and soft tissues of maxillofacial area (fig. 5).
The choice of a design of a prosthesis depends on the size of defect of dentitions, a condition of fabrics of a parodont and a prosthetic bed. Fixed prostheses are usually applied to recovery of the separate destroyed teeth and substitution of small defects of dentitions (a tab, a crown, bayonet teeth, bridge-like prostheses). At a combination of defect of dentition to a disease of a parodont (see. Periodontosis ) byugelny (arc) prostheses which use gives the chance along with substitution of defects to shinirovat mobile teeth are shown. In the absence of a significant amount of teeth when fixing of byugelny prostheses can cause an overload of a parodont of basic teeth, partial plastinochny prostheses are shown. After loss of all teeth prostheses for toothless jaws (so-called full removable prostheses) are recommended.
Artificial crowns are applied to recovery of a form of crowns of teeth, and also to fixing of fixed prostheses and orthodontic devices. As material for production of crowns serve gold and silver-palladium alloys, chrome stainless steel, plastic, porcelain and a combination of metal to plastic or porcelain. Crowns are shown in the absence of inflammatory process at a top of a fang.
Bayonet teeth apply to recovery of completely destroyed crowns of teeth at well remained and steady root with the channel, available to treatment. Despite a big variety of designs, bayonet teeth always consist of two details: root metal pin and actually tooth (crown). The pin is entered into the canal of a fang (after sealing of an apical part of the canal) and strengthened cement. The crown of bayonet tooth can be metal, plastic, porcelain or revetted, i.e. metal with facing from plastic or porcelain. Logan crowns — standard bayonet teeth with a porcelain crown belong to bayonet teeth.
Bridge-like prostheses consist of basic elements (a crown, font teeth, tabs) and to an intermediate part (body). They can be all-metal or revetted with plastic or porcelain; they are applied at loss of 3 teeth if parodont basic teeth it is not changed. The support of a bridge-like prosthesis usually shall be bilateral, especially on molars. The bridge-like prosthesis with a unilateral support is applied to substitution of defect of one foretooth, usually in the cosmetic purposes. Prosthetics of one molar is not shown.
Removable prostheses for substitution of defect of dentition have basis, the holding elements (clasps) and false teeth. Basis is the plate from plastic or metal which is precisely repeating a relief of a prosthetic bed, i.e. a mucous membrane, an alveolar shoot, a hard palate on which the prosthesis leans and necks of teeth from a palatal or lingual surface, to the Crimea it touches. On basis false teeth and the holding devices — clasps are strengthened. Chewing pressure is transferred to basis, and from it to a prosthetic bed. Chewing pressure and on prostheses is in the same way transferred at total absence of teeth.
Small removable saddle prostheses are located within defect of dentition and the site of an alveolar crest corresponding to it. Byugelny prostheses are the most rational design of partial removable prostheses. The Byugelny (arc) prosthesis has, except false teeth and basis, an arch and its branches; the basis covers only toothless sites of an alveolar shoot, leaving free the sky or that part of an alveolar crest where there are teeth. The parts of basis called by saddles connect among themselves an arch — a clasp. The basis of a byugelny prosthesis is made by a metal framework (an arch, clasps, occlusal slips, fastenings for plastic, etc.).
Plastinochny partial prostheses are applied usually to substitution of extensive defects of dentitions. Full prostheses in which the basic plate covers all prosthetic bed and which have no basic teeth produce for prosthetics of toothless jaws.
Fixing of removable prostheses during chewing, a conversation is reached in various ways. The most widespread means of fixing partial removable 3. items are clasps (fig. 6). To destination they are divided into the holding and basic holding. The holding clasps counteract the shift of a prosthesis in the vertical and horizontal directions, pressure from a prosthesis at the same time is transferred to a prosthetic bed. The design of the basic holding clasps is more perfect; they consist of a rigid basic element — an occlusal slip and two shoulders. The occlusal slip is located between chewing hillocks of tooth or in the bed which is specially created for it; by means of occlusal slips vertical pressure is distributed also on basic teeth.
Also castle fastenings (fig. 7) which consist of the matrix having a bed for in a masonry part (patritsa) are applied to fixing; matrix have in a crown of natural tooth or solder to an artificial crown, in a masonry part connect to a prosthesis.
Teeth which serve as a support for the fixing elements of a prosthesis (crowns, tabs, clasps) call basic. At the choice of basic teeth consider their arrangement, height and a form of crowns, a condition of a parodont, etc. Mistakes in the choice of basic teeth lead to their functional overload and, as a result of it, to patol, mobility of these teeth.
Fixing of full removable prostheses is based on use of anatomic points of a retention, adhesion and the vacuum which is formed under basis of a prosthesis. Points of an anatomic retention are served by the anatomic educations interfering shift of a prosthesis during chewing: arch of a hard palate, alveolar crest of a mandible, alveolar shoot, hillocks of an upper jaw, etc.
The great value at prosthetics of toothless jaws is attached to a pliability of fabrics of a prosthetic bed; a pliability call the vertical or horizontal displacement of a mucous membrane under pressure of basis of a prosthesis. At prosthetics it is important to find out a vertical pliability as hypodispersion of chewing pressure on all prosthetic bed depends on it. The mechanism of a vertical pliability is connected with emptying of vessels of a mucous membrane under pressure of a prosthesis. Sites of a mucous membrane of a hard palate where there is a rich network of vessels, represent so-called buffer zones, as if shock-absorbing a prosthesis. Buffer properties of a mucous membrane of a hard palate are not identical at different people and change during life in connection with change of vessels under the influence of age factors, and also at various diseases. The change of secretion of mucous and small sialadens leading to dryness of a mucous membrane worsens fixing of a prosthesis.
Adhesion (sticking) arises between a prosthetic bed and basis of a prosthesis in the presence of a thin coat of saliva. Vacuum under a prosthesis is created at its shifts when the space between it and a mucous membrane increases, and penetration of air is interfered by the mucous membrane adjacent to edges of a prosthesis — the so-called regional valve.
The manufacturing techniques depend on a design 3. item. Metal crowns stamp or cast. Bridge-like prostheses can be produced in parts (at first crowns, then a body of a prosthesis) which then accustom to drinking, or they are cast at the same time on fire-resistant model (tselnolity bridge-like prostheses). The framework of byugelny prostheses is usually cast entirely or on details which then accustom to drinking.
False teeth for fixed prostheses can be metal tselnolity, but they meet the cosmetic requirements a little. More often in a metal bed strengthen porcelain or plastic facets. Porcelain facing it is possible to arrange on a vestibular surface of a cast crown or to cover a crown completely (ceramic-metal crowns).
Teeth from plastic (see. Polymeric materials, in stomatology ) or porcelain (see) produce in the industrial way (fig. 8) in a large number of sets. They have various sizes, the form, shades of color that allows to select the teeth corresponding to specific features of the person.
Plastic teeth during polymerization of plastic of basis of a prosthesis connect to it monolitno; porcelain teeth become stronger in basis by means of crampons or canals into which plastic gets. Crampons represent wire pins from gold alloy, platinum or stainless steel; they are fixed by one end in porcelain of tooth, to others — in plastic of basis.
Exact prints from jaws (negatively representing a prosthetic bed) for the subsequent production of a prosthesis (any form) receive using special Impression materials (see) or gypsum (see); at the same time are necessary the main print (from the fitted a prosthesis jaw) and auxiliary (from an opposite jaw). Prints divide on anatomic (approximate, without functional mobility of a mucous membrane) and functional (final) which reflect mobility of fabrics of a prosthetic bed that is especially necessary for production of a full removable prosthesis. On a print cast plaster model, on it model basis of a prosthesis from wax and establish false teeth; correctness of statement of teeth, height of a bite, etc. are checked by the doctor directly in an oral cavity of fitted a prosthesis. The subsequent stages — a gipsovka of the prepared prosthesis in a press form, smelting of wax, preparation of the plastic test, molding of basis, pressing and polymerization of plastic, finishing of a prosthesis, etc. — are carried out In dentoprosthetic laboratory (see) the dental technician (see. Dental technician ).
By-effects during the use of dentures
At bridge-like prostheses there can be a functional overload of basic teeth, and also changes in a pulp during the processing of these teeth under crowns. Pressure from a removable prosthesis can accelerate an atrophy of an alveolar crest and a mucous membrane of a prosthetic bed. Prostheses can cause an injury of a mucous membrane of an oral cavity, allergic reactions and have the toxic effect connected with features of material from to-rogo they are made. Use of a removable prosthesis, basis to-rogo badly corresponds to a relief of a prosthetic bed, leads not only to injuries of a mucous membrane, but also to shaking of the remained teeth and other disturbances in dentoalveolar system.
Subjectively in the beginning 3. the item is perceived as a foreign body, salivation amplifies, some people have desires on vomiting, especially during the imposing of a full removable prosthesis. Also the pronunciation of some sounds is broken. Gradually these phenomena pass, the habit to a prosthesis is created. However in some cases correction of a prosthesis is necessary.
Bibliography: Alshits A. A. Sealing of carious cavities tabs, M., 1969; Gavrilov E. I. Theory and clinic of prosthetics by partial removable prostheses, M., 1973; Kurland V. Yu. Orthopedic stomatology, Atlas, t. 1 — 2, M., 1963 — 1970; Complete denture prosthodontics, ed. by J. J. Sharry, N. Y., 1974.
E. I. Gavrilov.