FR2550705A1 - Dental prosthesis and process for producing it - Google Patents

Abstract

The invention relates to orthopaedic stomatology. The dental prosthesis which is the subject of the invention is of the type consisting of a metal alloy possessing anticorrosive properties and mechanical resistance, and of at least one aesthetic or decorative vestibular coating, and is characterised in that the said decorative vestibular coating is made from a material which is stronger than the base plate and consists of nitrides, oxynitrides, carboxynitrides, cyanonitrides and/or monoxides of group IVB metals in the periodic table of elements, the ratio of the thickness of the said decorative vestibular coating to the thickness of the base plate being within a range of 1:10 to 1:200. The invention permits, in particular, the production of dental prostheses not containing noble metals and with greater durability than monolithic prostheses made from noble metals.

Description

 The present invention relates to medicine, in particular orthopedic stomatology, and in particular relates to a dental prosthesis and a method of manufacturing the same.

 We already know monolithic metallic dental prostheses which are generally made either from precious metal alloys such as gold, platinum, palladium, or from various anticorrosive steels or alloys.

 In the first case, metallic dental prostheses have a high biological indifference (neutrality) and excellent aesthetic qualities. However, given the low wear resistance of the precious metal alloys, these prostheses have an insufficient longevity.

 In the second case, we save precious metals and ensure the longevity of dental prostheses.

However, dental prostheses made of anti-corrosive steels or alloys are inferior to the previous ones from the point of view of their biological indifference (neutrality) and their aesthetic characteristics.

Depending on the construction materials used, the following varieties of fixed dentures can be distinguished
- porcelain and "cermet" prostheses (metal-ceramic materials);
- prostheses made of metal alloys with a low content of precious metals;
- layered structures of dental prostheses in which the precious metal is used only as a vestibular layer (covering) of the dental prosthesis.

 The manufacture of ceramic-metallic structures is complicated; as for porcelain crowns, which have good aesthetic-decorative qualities, they are mainly used for the restoration of frontal teeth.

They lack mechanical strength due to the fragility of porcelain.

 In alloys with a lower precious metal content, it is not possible to reduce their precious metal content below 40-600 without seriously compromising their biological neutrality.

 Solid dentures with high medico-biological characteristics and high aesthetic-decorative properties can only be obtained by considerably reducing (from 80 to 95%) the consumption of precious metals used for their manufacture. However, at present, dental prostheses of this kind cannot find wide applications, their high medico-biological characteristics and their aesthetic-decorative properties being preserved only for 2 to 3 months of use.

 We already know a layered dental prosthesis design (Great Britain patent application NO 1215485, class A 61 C 13/02) obtained by a galvanic process by first depositing a layer of metal compatible with the tissues of the human body (gold, rhodium or chromium), in swite a second layer of non-precious anticorrosive metal (such as nickel), more resistant than the first, and a third layer of metal (such as gold, rhodium or chromium) compatible with living human tissue.

 There is also known a design of dental prosthesis (USSR author's certificate NO 212 442, class A61 C 5/08). This prosthesis is made up of a metal base plate made of a resistant metal anticorrosive alloy (silver and palladium alloy) and a decorative vestibular layer. The vestibular layer is a gold alloy having a hardness lower than that of the base plate.

 These dentures reduce the consumption of precious metals by 90 to 95%. However, since the thickness of the precious metal layer of said prostheses does not exceed 10 to 20 micrometers (when the thickness is greater, the layered design of the dental prosthesis loses its raison d'être because of the increased consumption of precious metal), the masticatory surfaces of the prosthesis, subject to wear and tear by intense attrition, wear out quickly (after 2 to 3 months) and the decorative and aesthetic effect of the dental prosthesis found to be compromised. In addition, in the event of damage to the decorative vestibular coating of the dental prosthesis, there is an accentuated electrochemical "clearing up" (that is to say a variation of the difference of electrical potentials from 20 to 60 mV) of the prosthesis structure, we are witnessing the formation and active effects of microgalvanic couples. This may cause local and general harmful actions on the human body.

Simultaneously, under the effect of the microgalvanic couples, there is an intense degradation of the base plate of the prosthesis and, as a consequence, an accelerated process of the disintegration of the decorative vestibular covering.

 It was therefore proposed to create a dental prosthesis not containing precious metals and durable (longer service life than that of monolithic prostheses in precious metals), retaining throughout its duration of use medical and biological characteristics as well as decorative and aesthetic properties, while being simple from the point of view of manufacture and therefore inexpensive.

 This problem is solved by means of a dental prosthesis composed of a solid base plate made of an anticorrosive metal alloy and at least one decorative vestibular coating, in which, according to the invention, said decorative vestibular coating is made of a more lasts as the base plate and is in the form of nitrides, oxynitrides, carboxynitrides, cyanonitrides and / or monoxides of metals from the secondary family of Group IV of the periodic table, with the understanding that the ratio of the thickness of the decorative vestibular covering with the thickness of the base plate is from 1/200 to 1/20.

 The base plate of the prosthesis is made of a resistant anticorrosive material such as stainless steel, a chromium-cobalt metal alloy, chromium-cobaltmolybdenum, or any other traditional metal alloy.

Such a base plate gives the dental prosthesis a high mechanical resistance under the alternating loads of contrary signs which take place during the crushing of food. The base plate of the dental prosthesis can be massive (monobloc) or composed of separate elements joined in a stationary manner by welding or brazing.

 The nitrides, oxynitrides, carboxynitrides, cyanonitrides and / or monoxides of metals of the secondary family of group IV of the Periodic Table of the Elements, which are used for the manufacture of the decorative vestibular coating of the claimed dental prostheses, are characterized by their high chemical resistance in acidic, alkaline or neutral environments of the oral cavity, by their absence of toxicity and by their compatibility with the living tissues of the organism. For this reason, dental prostheses are stable in the environments of the oral cavity and are indifferent (neutral) from the biological point of view.

 It is recommended to use as decorative vestibular coating materials nitrides, oxynitrides, carboxynitrides, cyanonitrides and / or titanium and / or zirconium monoxides.

 Since nitrides, oxynitrides, carboxynitrides, cyanonitrides and / or titanium and / or zirconium monoxides have a wide range of yellow-golden, red-golden and silver tints and shades (depending on the type of chemical compound and the parameters of its preparation process) when applied to metal parts, they provide the required decorative and aesthetic effect. This is how zirconium nitride, depending on its nitrogen content, has a hue ranging from silver to old gold, that is to say that it imitates platinum or gold alloys. titanium, mixtures of titanium nitrides and zirconium nitrides, titanium and / or zirconium monoxides and their oxynitrides can be of goldpale, yellow-golden and red-golden hue, or have a large number of shades imitating the gold of various titles and extending the range of shades obtained.

 The hardness of the materials from which the decorative vestibular coating of the dental prostheses claimed 4 3 2 is formed is 10 104 MPa at 28.4.103 MPa (220 to 2900 kg / mm), which is much higher than the hardness of the known metal alloys used in stomatology. This is why the decorative vestibular layer of such a prosthesis is distinguished by a very high resistance to wear (from 180 to 220 times greater than that of a layer of galvanic gold) and allows the dental prosthesis to resist attrition wear.

 The increased fragility of the materials used for the decorative vestibular layer imposes boundary conditions on the ratio of the thickness of the base plate and the vestibular layer. The thinner the decorative vestibular layer, the higher its plasticity. However, an excessive thickness of this layer reduces the longevity of the prosthesis as a result of its wear by rapid attrition.

 It has been established experimentally that the ratio of the thickness of the decorative vestibular layer to that of the base plate should preferably be chosen in the range of 1/10 to 1/200. In the case of dental bridge prostheses or skeleton prostheses, the thickness of the decorative layer is calculated so as to obtain a prosthesis with the thinnest cross section.

 The decorative vestibular layer of the proposed dental prosthesis depends on the objectives to be achieved and can be either single layer, two layers, or multiple layers. In a decorative vestibular layer with several layers, alternating layers of titanium and zerconium compounds may alternate. The multilayer compositions of the decorative vestibular layer make it possible to vary their adhesion properties to the substrate in different materials, to improve the plasticity and wear resistance characteristics of the decorative layer and to extend the range of shades of said layer.

 The claimed dental prostheses can be extended to the following parts: unitary, stamped and cast crowns (total, necklaces, semi-crowns, three-quarter crowns, tenon crowns), cast monolithic dental bridge prostheses, brazed dental bridge prostheses with artificial teeth castings and veneers, cast inserts, attachments for fixing dental prostheses in case of periodontosis, as well as skeleton prosthesis aprons and arches, bent and cast crampons.

 In case of moderate continuity solutions of the decorative vestibular coating (presence of micropores or microcracks, local wear by attrition) which do not deteriorate the decorative and aesthetic qualities of dental prostheses, between the base plate and the decorative vestibular coating it may form microgalvanic couples by filling said defects with the liquid of the oral cavity.

 One consequence of the operation of the microgalvanic couples (without adequate measures being taken) lies in the appearance and development of corrosion foci of the most electro-negative metal of the couple, that is to say of the plate- base of the dental prosthesis. This leads to a local disintegration of the base plate under the covering and to an accelerated degradation of the weakened decorative vestibular covering (because there is a lack of base plate), due to mechanical effects, and, ultimately, to loss decorative and aesthetic properties of the dental prosthesis.

 To improve the anticorrosive protection of the material of the base plate of the claimed dental prosthesis, between the base plate of the claimed dental prosthesis and the decorative vestibular coating, it is recommended to make a protective layer of a more electronegative metal than the material of the decorative vestibular covering and capable of passivating in the liquid media of the oral cavity, it being understood that the ratio of the thickness of the protective layer to the thickness of the decorative vestibular covering is from 0.3 / 1 to 1/1 .

 In the presence of the aforementioned protective layer in the event of a solution of continuity of the decorative vestibular covering, the liquid medium of the oral cavity does not access the base plate of the prosthesis, but the material of the protective layer. A microgalvanic couple is formed between the metals of the protective layer and the vestibular decorative coating. The role of the anode in this couple belongs to the metal which is more electronegative, that is to say to the metal of the protective layer. However, the metal of the protective layer was chosen so that, under the conditions of the anodic polarization, it lends itself sufficiently well to passivation. In the area of the defect of the decorative vestibular coating, given the difference in the electrical potentials of the metals come into contact, there is always an anodic polarization, that is to say that the protective layer lends itself entirely to passivation (to the formation of passive layers). The protective layer having passive films does not allow the metal of said layer to disintegrate further (to dissolve), thereby preventing the advancement of corrosion phenomena. Thereby, the corrosion resistance of the claimed prosthesis is obtained.

 As the metal of the protective layer, it is recommended to use titanium, tantalum or chromium.

These metals lend themselves easily to passivation in the media of the oral cavity by preventing the disintegration by corrosion of the protective layer and, consequently, of the base plate of the dental prosthesis.

 To ensure safe protection of the metal alloy of the dental prosthesis base plate against corrosion, the protective layer must be continuous (free of open pores). Given that as the thickness of the layer increases the probability of the presence in said layer of through pores decreases, the thickest protective layer should be produced.

However, as the thickness of the protective layer increases, the work required for its deposition also increases. From this point of view, the thinnest protective layer should be produced.

 It has been experimentally established that the ratio of the thickness of the protective layer to the thickness of the decorative vestibular covering must be within the range of 0.3 / 1 to 1/1. The lower values are chosen for tantalum and titanium, and the higher values are chosen for chromium.

 The physico-mechanical characteristics (the coefficient of thermal expansion, plasticity, micro-hardness, etc.) of the base plate and the decorative vestibular coating or the protective and decorative layers differ significantly (in a ratio of the unit to several units).

 In the event of a change in the temperature regime, or else in the event of the application of mechanical loads, in particular when using the dental prosthesis, it appears at the separation faces of said coatings of concentrations of mechanical stresses. In some cases, this leads to separation (flaking) of the decorative vestibular covering.

 To avoid this phenomenon in the claimed dental prosthesis, it is recommended to spare between the base plate and the decorative vestibular coating or between the decorative vestibular coating and the protective layer, an intermediate layer composed of titanium, tantalum or chromium mixed to a corresponding metal nitride. The content of said nitrides increases according to the thickness of the intermediate layer in the direction of the vestibular covering in the range of 0.01% by mass to 90-99% by mass, and the ratio of the thickness of the intermediate layer to the thickness of the decorative vestibular covering is in the range from 0.3 / 1 to 1/1.

 In the intermediate layer, the aforementioned distribution of the contents of metals and their nitrides ensures a gradual variation of the physico-mechanical characteristics of said layer. The values of the characteristics of the intermediate layer vary according to its thickness in the range of the values of the characteristics of the base plate up to the value of the characteristics of the decorative vestibular covering.

 In stomatological practice, when making dental prostheses of the dental bridge type, brazed structures of the base plate of the dental prosthesis are used quite frequently. The elements of this structure (crowns, veneers, artificial teeth) are produced separately and then joined together by brazing into a single structure.

 Inexpensive silver solders are effectively used for brazing structural elements made of stainless steel, chromium-cobalt alloys and other anticorrosive metal alloys. Most often, silver and cadminum solders (composition, mass%: Ag 45, Cu 25, Cd 15 and Mn 15) are used with a melting temperature of 620-6600C, or silver solders and zinc (in the USSR, its composition is,% by mass: Ag 63, Cu 27, Zn 10, and in FRG its composition is,% by mass: Ag 37, Cu 38, Zn 15, Cd 0.5 , Mn 5.2, Ni 4, Mg 0.3) at a melting temperature of 800 to 8500C.

 At the places of brazing, the decorative vestibular coating generally deposited at temperatures of 400 to 5000C and above has reduced adhesion due to the evaporation of the individual constituents of the brazing.

This quite often leads to the separation of the decorative vestibular covering or the formation, in said covering, of cracks, pores and other defects at the location of the brazed assemblies.

 For this reason, when the base plate of the dental prosthesis is a structure assembled by brazing elements of anticorrosive metal alloy, it is recommended to make between the vestibular decorative coating and the base plate of the dental prosthesis, or between the intermediate layer and the base plate of the dental prosthesis, an intermediate complementary layer. In the first case, it is useful to make it in cobalt, nickel, chromium, molybdenum or zirconium, or in chromium or molybdenum nitrides. In the second case, it is recommended to make the additional layer of cobalt, nickel, chromium, molybdenum or zirconium. In both cases, the ratio of the thickness of the complementary layer to the thickness of the decorative vestibular covering is in the range of 0.5 / 1 to 1/1, respectively. additional layer to the thickness of the decorative vestibular covering is included in this range, the additional layer does not have through pores. The additional layer without pores constitutes a sufficiently safe barrier not only against the liquid phase, but also against the vapor phase of the evaporated constituents of the solder. A greater thickness of the additional layer would be unjustified because of the increased cost of the operation for obtaining said layer.

 The presence, on the brazed structure of the base plate of the prosthesis, of an additional layer ensures continuity of the brazed assembly, the absence of visible pores in the brazed places and, as a result, high resistance mechanics of such dental prostheses and a high quality of their decorative vestibular coating, including in the area of the brazed assembly.

 In the method of manufacturing such a dental prosthesis, comprising manufacturing its base plate by brazing the elements of said dental prosthesis from an anticorrosive and resistant metal alloy into a single structure, and depositing a coating vestibular decorative by a vacuum method, according to the invention, the area of the brazed assembly of said structure, or the entire structure, is coated before the application of the decorative vestibular coating by a galvanic process or by a vacuum method, d '' an additional layer of cobalt, nickel, chromium, molybdenum or zirconium, or chromium nitrides, molybdenum, the ratio between the thickness of said layer and the thickness of the decorative vestibular coating being within the range from 0.5 / 1 to 1/1.

 As indicated in the foregoing, the additional layer excludes the appearance of defects in the decorative vestibular covering in line with the brazed assemblies and increases the mechanical strength of the brazed assembly.

 The dental prostheses claimed in no way yield it, from the point of view of their decorative and aesthetic characteristics, their biological neutrality, their resistance to chemical agents and to corrosion, to monolithic dental prostheses, executed in alloys of gold or platinum, and even outperform these by their mechanical resistance and their resistance to wear. Furthermore, the claimed dental prostheses are advantageous from the technological and economic point of view. These prostheses are 10 to 15 times cheaper than dental prostheses made of gold alloys, porcelain and ceramic metallics.

 The dental prostheses provided with the claimed vestibular coatings resist the effects of cooking salt and saliva, they are neutral with respect to cultures of pyocyanic bacteria, staphylococcus aureus, colibacillus, cultures of trypsinized cells primarily of fibroplasts of the human embryo, of the grafted line of HEP-2 cells on cells of the human oral epithelium.

 The decorative vestibular coating of the claimed dental prostheses does not cause chromosomal aberrations.

 The process for manufacturing the claimed dental prostheses is technologically simple, it is based on known technological procedures and is carried out as follows.

 First of all, according to methods generally adopted in stomatology (precision casting, stamping), the base plate of the dental prosthesis is made from anticorrosive alloys of non-precious metals (stainless steels, cobalt and chromium alloys, or cobalt, chromium and molybdenum) in the form of blanks of the required shape. The accuracy of the adjustment of said blanks in the mouth of the patient is checked.

After adjustment and retouching, the surfaces (the oxides) are removed from the surfaces of the blank and polished until the roughness of its surface R z is 0.1 to 0.4 micrometer. Then, according to the technology adopted, the base plate of the dental prosthesis is subjected to a careful washing and to a thorough degreasing in an ultrasonic bath.

 The decorative vestibular coating of the required thickness and consisting of a material which ensures adhesion and resistance to wear, as well as the required shade and shade of the coating, is applied by a known vacuum method. As already indicated in the foregoing, the decorative vestibular covering may be monolayer, double layer or multiple layers. When two or more layers are applied, the compositions and the pressure of the reaction gas, the evaporated material and the technological parameters of deposition of the layers are varied according to the problems to be solved.

 Then, if necessary, the decorative vestibular surface of the dental prosthesis is subjected to a finishing polishing, and then, if necessary, the missing plastic elements are formed on the prosthesis.

 In the event that the dental prosthesis needs a protective layer, a layer of titanium, tantalum or chromium of required thickness is applied by one of the known methods (galvanic or plasma under vacuum) before depositing the coating. decorative vestibular.

 As indicated in the above, to reduce the concentration of mechanical stresses at the limit of separation of the base plate and the decorative vestibular coating, or between the vestibular decorative coating and the protective layer, an intermediate layer is deposited. Said intermediate layer is also deposited by a known method, for example by a vacuum plasma method by increasing the nitrogen pressure in the chamber during the deposition of the layer.

 If the base plate of the dental prosthesis is a brazed structure, the layers (intermediate protective layer, decorative vestibular coating) are applied to said prosthesis, before the plasma deposition operations under vacuum, a calculated layer of cobalt thickness , nickel, chromium, molybdenum, zirconium, chromium nitrides or molybdenum.

 Other characteristics and advantages of the present invention will be better understood on reading the description which follows of several concrete but non-limiting examples of embodiment.

 Example 1.

 A dental prosthesis is manufactured in the form of a monolithic bridge structure, constituted by a base plate of chromium-cobalt alloy with a decorative vestibular coating of titanium nitride.

 The base plate of the required dental prosthesis is poured into a mold in a wax model, from a chromium-cobalt alloy. The accuracy of its adjustment is checked in the patient's oral cavity and the necessary retouching is carried out. The base plate of the adjusted dental prosthesis is polished using fine abrasives (0.5 to 1 micrometer). After polishing, the prosthesis base plate is carefully washed in an ultrasonic bath of hot water (70-800C) containing 2 to 3% by mass of synthetic detergents.

Then the washing is carried out under running water, in a gasoline bath, and a degreasing is carried out with ethyl alcohol.

 Then the base plate of the dental prosthesis is placed in the chamber of a vacuum device provided with a swiveling device, and the base plate of the prosthesis is installed on the drum of said device. The chamber is also provided with three sources of titanium plasma oriented towards the drum of the pivoting device. The material evaporated in the three plasma sources is chemically pure titanium.

Vacuum is applied in the vacuum chamber to a residual pressure of 1.333 mPa or 1.10 5 mm Hg, the pivoting device is started (speed of rotation 9 rpm), a negative voltage of 1.1 kV, we set
action one of the plasma sources and a current is established
arc 80 A. For 3 minutes complete cleaning is carried out
of the base plate by bombardment of its surface with ions
titanium. Then a voltage is applied to the base plate
180 V negative and the second and three are activated
5th source of plasma. The current: arc in each of
three sources is 90 A. Under these conditions, we send
in the nitrogen chamber by adjusting its pressure in said chamber to 666.5 mPa or 5.10 3 mm of Hg. It then settles
on the base plate a decorative vestibular covering of
titanium nitride. When the thickness of said coating reaches
8 micrometers, we deactivate the plasma sources,
the nitrogen intake is interrupted, the device is stopped
pivoting, we remove the negative tension on the prosthesis and,
10 minutes later, the prosthesis is removed from the chamber.

Decorative vestibular coating has micro-hardness
from 24.5.103- 25.5.103 MPa or 2500 - 2600 kgf / mm2, one shade
corresponding to that of a high titer gold alloy, and a
good adhesion to the base plate.

The prosthesis obtained is sealed in the oral cavity of the
patient with bisphate cement. Observations made
for four years did not reveal any local or general negative effects on the organism. The integrity of the prosthesis was not compromised. The shade of the prosthesis remained unchanged.

 Example 2.

 A dental prosthesis is made in the form of a monolithic bridge structure, consisting of a chromium-cobalt alloy plate base with vestibular coating decorated in titanium oxynitride.

 The prosthesis base plate is made, polished, washed and placed in a vacuum chamber as shown in Example 1.

 The treatment of the base plate of the dental prosthesis is carried out until the time of admission of nitrogen into the vacuum chamber, as described in example 1. Instead of nitrogen, it is sent into the vacuum chamber. a mixture of nitrogen and oxygen (80% by volume of nitrogen + 20% by volume of oxygen) and the pressure in the chamber is adjusted to 666.5 mPa or 5.10 3 mm of Hg. It is then deposited on the surface of the base plate a layer of titanium oxynitride (decorative vestibular coating). When the thickness of this coating reaches 10 micrometers, the plasma sources are turned off, the admission of said gas mixture is stopped, the negative voltage is removed on the prosthesis and the pivoting device is stopped. Ten minutes later, the prosthesis is removed from the chamber.

The vestibular coating has a micro-hardness of 22.5.103 2
MPa or 2300 kgf / mm, shade corresponding to that of a high-grade gold alloy and strong adhesion to the base.

The prosthesis obtained is sealed in the patient's oral cavity with bisphate cement. Observations carried out for 2 years did not reveal any local or general harmful effects on the organism. The shade of the prosthesis obtained did not change,
Example 3.

 A dental prosthesis is manufactured in the form of a monolithic structure in dental bridge, being in the form of a base-plate in chromium-cobalt alloy with esthetic vestibular coating in zirconium nitride.

 The base plate of the dental prosthesis is made, it is polished, it is washed and it is placed in a vacuum chamber as indicated in example 1.

 The vacuum chamber is provided with three plasma sources in which the evaporated material is zirconium. The ionic cleaning is carried out by bombardment with zirconium ions and the esthetic vestibular coating is applied as in Example 1. The deposition is carried out until a layer 20 micrometers thick is obtained.

 The coating obtained has a microhardness of 24.5 × 10 3 MPa or 2500 kgf / mm 2, a shade corresponding to that of a high-grade gold alloy and high adhesion to the base plate.

 The prosthesis obtained is sealed in the patient's oral cavity with bisphate cement. Observations made over four years did not reveal any local or general negative effects on the patient's body.

 Example 4.

 A dental prosthesis is manufactured in the form of a monolithic structure, in a dental bridge, consisting of a chromium-cobalt alloy plate base with an esthetic vestibular coating of titanium and zirconium nitrides (7026 by mass of titanium nitride and 30% by mass zirconium nitride).

 The denture base plate is made, polished, washed and placed in a vacuum chamber as shown in Example 1.

 The vacuum chamber is provided with three plasma sources, in one of which the evaporated material is zirconium, and in the other two, titanium. The ionic cleaning of the baseplate is carried out as indicated in example 1. Then a negative voltage of 200 V is applied to the baseplate, the sources of titanium and zirconium plasma are activated, the sources of titanium plasma of the arc currents of 90 A, and in the zirconium plasma source, of 80 A. Then we admit nitrogen into the vacuum chamber, we establish its pressure at 666.5 mPa or 5.10 3 mm of Hg. It then deposits on the surface of the base plate an esthetic vestibular coating which consists of a mixture of titanium nitrides and zirconium (7026 by mass of titanium nitride and 3026 by mass of zirconium nitride).

When the thickness of this coating reaches 12 micrometers, the plasma sources are deactivated, the admission of nitrogen is stopped, the pivoting device is immobilized, the tension on the dental prosthesis is removed and the dental prosthesis of the room.

 The esthetic vestibular coating has a hardness of 25.5.103 MPa or 2600 kgf / mm2, a shade corresponding to that of a high-grade gold alloy and strong adhesion to the base plate.

 The prosthesis obtained is sealed in the patient's oral cavity with bisphate cement. Observations made over four years did not reveal any local or general negative effects on the patient's body. Analyzes of the patient's saliva did not detect the presence of zirconium or titanium. The shade of the prosthesis remained unchanged.

 Example 5.

 A dental prosthesis is manufactured in the form of a monolithic bridge structure, consisting of a base plate of chromium-cobalt alloy with a vestibular coating -esthetic in a mixture of titanium nitrides and zirconium (0.1% in mass of zirconium nitride and 99.9% by mass of titanium nitride).

 The base plate of the dental prosthesis is made, washed, polished and placed in a vacuum chamber as indicated in Example 1.

 The vacuum chamber is provided with three plasma sources, the evaporated material of which is an alloy composed of 99.9% by mass of titanium and 0.1% by mass of zirconium.

 The esthetic vestibular coating is deposited as indicated in Example 1 until a layer 15 micrometers thick is obtained. The coating obtained has a microhardness of 24.5.103 MPa or 2500 kgf / mm2, a shade corresponding to that of a high-grade gold alloy, and a strong adhesion to the base plate.

 The prosthesis obtained was fixed in the patient's mouth with bisphate cement. Observations made over four years did not reveal any local or general negative effects on the patient's body. The shade of the prosthesis remained unchanged.

 Example 6.

 A dental prosthesis is manufactured in the form of a monolithic structure in dental bridge, consisting of a base plate in chromium-cobalt alloy with an esthetic vestibular coating composed of two layers, one of which that contiguous to the base plate, is composed of a mixture of titanium and zirconium carboxynitrides (67% by mass of titanium carboxynitride and 33% by mass of zirconium carboxynitride), and the second, of titanium nitride.

 The base plate of the dental prosthesis is made, it is polished, it is washed and it is placed in a vacuum chamber as indicated in example 1. The vacuum chamber is provided with three plasma sources in one of which the evaporated material is zirconium, and in the other two, titanium. The ion baseplate cleaning is carried out as indicated in Example 1. Then a negative voltage of 200 V is applied to the baseplate. The titanium and zirconium sources are activated, all the sources are set up. arc currents of 90 A. Then admit into the vacuum chamber a mixture of nitrogen, oxygen and methane (80% by volume of nitrogen, 10% by volume of oxygen, 10% by volume of methane) by establishing a pressure in the chamber of 133.3 mPa or 1.10 3 mm of Hg. It then deposits on the surface of the support a first layer of the esthetic vestibular coating, which consists of a mixture of titanium carboxynitrides and of zirconium (67 by mass of titanium carboxynitride and 33% by mass of zirconium carboxnitride).

 When the thickness of said layer reaches 6 micrometers, the source of zirconium plasma is deactivated, the admission of said gaseous mixture is stopped and nitrogen is admitted by establishing its pressure in the room at 666.5 mPa or at mm de-Hg. A layer of titanium nitride is then deposited, constituting the second layer of the esthetic vestibular coating.

 When the thickness of the titanium nitride layer reaches 3 micrometers, the plasma sources are deactivated, the admission of nitrogen is stopped, the negative voltage on the prosthesis is removed and the pivoting device is stopped . Ten minutes later, the prosthesis is removed from the chamber.

 The esthetic vestibular coating obtained has a microhardness of 25.5.103 MPa or 2600 kgf / mm21, a shade corresponding to that of high-grade gold alloys, and strong adhesion to the base plate. The dental prosthesis obtained is sealed in the patient's oral cavity with bisphate cement. Observations made over two years did not reveal any local and general negative effects on the patient's body. The shade of the prosthesis remained unchanged.

 Example 7.

 We manufacture a dental prosthesis in the form of a monolithic structure in dental bridge, constituted by a base plate in chrome-cobalt alloy with an esthetic vestibular coating composed of two layers, one of which, adjacent to the base plate consists of cyanonitride. titanium, and the second, titanium oxynitride.

 The base plate of the dental prosthesis is made, it is polished, it is washed and it is placed in a vacuum chamber as indicated in Example 1.

 The treatment of the base plate of the dental prosthesis is carried out until the time of admission of the nitrogen into the vacuum chamber as described in Example 1. Instead of nitrogen we admit into the vacuum chamber a mixture of nitrogen and acetylene (95% by volume of nitrogen and 5026 by volume of acetylene) by establishing in the chamber a pressure of 106.6 mPa or 8.10 mm of Hg. It is then deposited on the surface da the base plate a layer of titanium cyanonitride. When said layer reaches a thickness of 5 micrometers, the admission of the abovementioned gas mixture is interrupted and a gas mixture of nitrogen and oxygen is admitted (90% by volume d (nitrogen and 109 s by volume of oxygen) by establishing in the chamber a pressure of 800 mPa or 6.10 3 mm of Hg and by depositing a layer of titanium oxynitride. When the thickness of the titanium oxynitride layer reaches 5 micrometers, the plasma sources are deactivated, the admission of the gas mixture is interrupted, the negative voltage on the prosthesis is removed and the pivoting device is stopped. . Ten minutes later, the prosthesis is removed from the chamber.

The esthetic vestibular covering obtained has a
3 microhardness of 23.5.103 MPa or 2400 kgf / mm2, a shade corresponding to that of high-grade gold alloys and strong adhesion to the base plate.

 The dental prosthesis obtained is sealed in the patient's oral cavity with bisphate cement. Observations made over two years did not reveal any local and general negative effects on the patient's body. The shade of the prosthesis remained unchanged.

 Example 8.

 A dental prosthesis is manufactured in the form of a monolithic structure in dental bridge, constituted by a base plate in chromium-cobalt alloy with esthetic vestibular coating composed of two layers, one of which, the one adjacent to the base plate, consists of titanium monoxide, and the second, titanium nitride. The base plate of the dental prosthesis is made, it is polished, it is washed and it is placed in a vacuum chamber as indicated in Example 1.

 The treatment of the dental prosthesis base plate is also carried out until the nitrogen is admitted into the vacuum chamber as indicated in example 1.

 Instead of nitrogen, oxygen is sent to the vacuum chamber, establishing a pressure of 66.65 mPa or mm of Hg there. A layer of titanium monoxide is then deposited on the surface of the base plate. . When the thickness of this layer reaches 5 micrometers, the admission of oxygen is interrupted and nitrogen is sent into the chamber by establishing a pressure of 666, 5mPa or 5.10 3 mm of H-g. A second layer consisting of titanium nitride is then deposited.

When the thickness of the titanium nitride layer reaches 5 micrometers, the plasma sources are deactivated, the nitrogen admission is interrupted, the negative voltage on the prosthesis is removed and the pivoting device is stopped.

Ten minutes later, the prosthesis is removed from the chamber. The aesthetic vestibular coating obtained has a micro hardness of 24.5.103 MPa or 2500 kgf / mm2, a shade corresponding to that of high-grade gold alloys and strong adhesion to the base plate. The dental prosthesis obtained was sealed in the patient's oral cavity with bisphate cement. Observations made over two years did not reveal any local and general negative effects on the patient's body.

 Example 9.

 A dental prosthesis is produced in the form of a monolithic bridge structure consisting of a chromium-cobalt alloy base plate with an esthetic vestibular coating consisting of a mixture of titanium nitrides and zirconium (33% by mass of nitride of zirconium and 67% by mass of titanium nitride), and bearing a protective layer of titanium.

The base plate of the dental prosthesis is manufactured, it is polished, it is washed and it is placed in a vacuum chamber as indicated in example 1. The ionic cleaning of the plate is carried out by bombardment with titanium ions as indicated in example 1. Then a negative voltage of 200 V is applied to the base plate, a second titanium plasma source is activated, an arc current of 80 A is established there and a coating is deposited 3 micrometer thick titanium protector. Then a third zirconium plasma source is put into action, an arc current of 90A is established in the three plasma sources and one admits into the nitrogen chamber by establishing a pressure of 666.5 mPa or 5.10 3 mm from
Hg. The esthetic vestibular coating consisting of a mixture of titanium nitrides and zirconium is deposited. When the thickness of this coating reaches 10 micrometers, the plasma sources are deactivated, the admission of gas is interrupted. , the negative voltage on the prosthesis is removed and the pivoting device is stopped.

 The technical and medical characteristics of the dental prosthesis correspond to those indicated in Example 4.

 Example 10.

 A dental prosthesis is produced in the form of a unitary crown of stainless steel with a decorative vestibular coating of titanium nitride and a tantalum protective layer. A cylindrical stainless steel fork is heated to 800-9000C and subjected to stamping in order to obtain a blank of crown of required shape. Then we proceed to the annealing of the blank at high temperature, we check the precision of its adjustment on the stump of the tooth and we finalize it according to the bite. -Then remove the oxides from the crown blank by immersing it in a liquor of the following composition (g / l): sulfuric acid 100, nitric acid 150, hydrofluoric acid 30. The blank is kept in said liquor until to the complete removal of the oxide (20-60 s). Then wash the blank of the crown with running water and dry it, polish it with fine grain abrasive compositions (0, 5 - 1 micrometer). The base plate obtained from the prosthesis is washed in an ultrasonic bath of hot water (70-800C) containing 396 by mass of synthetic detergents and then with petrol and ethyl alcohol. Then the base plate is placed in the chamber of a vacuum unit on the drum of a swivel device. The vacuum chamber is provided with three plasma sources; in one, the evaporated material is tantalum, in. the other two the evaporated material is titanium.

 Vacuum is applied in the vacuum chamber to a residual pressure of 1.333 mPa or 1.10 5 mm of Hg, the pivoting device is started, a negative voltage of 800 V is applied to the base, a tantalum plasma source by establishing in said source an arc current of 200 A.

 Ionic cleaning of the base plate is carried out by bombardment with tantalum ions for 2 min. Then a negative voltage of 50 V is applied to the base plate and a protective layer of tantalum is deposited. When the thickness of the protective layer reaches 3 micrometers, two titanium plasma sources are activated by establishing an arc current of 90 A there; the tantalum plasma source is deactivated, the base plate a negative voltage of 180 V and sent to the nitrogen chamber by establishing its pressure in the chamber at 666.5 mPa or 5.10 3 mm Hg; a vestibular coating of titanium nitride is then deposited. When the thickness of this layer reaches 9 micrometers, the plasma sources are turned off, the nitrogen admission is stopped, the negative voltage is removed, the pivoting device is stopped. Two minutes later the prosthesis is removed from the chamber.

The dental prosthesis obtained has a microhardness of 24.5.103 2
MPa or 2500 kgf / mm2, its color corresponds to that of high-grade gold alloys, high wear resistance (190 times higher than that of .gold alloys). The prosthesis obtained was sealed in the patient's oral cavity with bisphate cement. Observations over four years did not reveal any negative local or general effects on the patient's organism. The shade of the prosthesis remained unchanged.

 Example 11.

 A dental prosthesis is produced in the form of a brazed dental bridge structure consisting of a chromium-nickel stainless steel plate and a gent-cadmium arc solder, with a protective chromium layer and with a decorative vestibular coating in a mixture of titanium and zirconium nitride (0.5% by mass of zirconium nitride and 99.526 by mass of titanium nitride).

 We make the blanks for the crowns of the dental bridge prosthesis as shown in Example 10. Then, using a wax model, we pour the intermediate part of the prosthesis (veneers and artificial teeth) and, by brazing with silver and cadmium brazing, a unitary structure of the prosthesis base plate is obtained.

Then, the oxides are removed, polished and washed as indicated in Example 10.

 Then immerse the base plate in a galvanic bath to apply a protective layer of chromium.

 As the aqueous chromating electrolyte, the following composition is used (g / l): chromic anhydride 250, sulfuric acid 2.5. The deposition is carried out at an electrolyte temperature of 600C and a current density of 50 A / dm2.

A protective layer of chromium with a thickness of 8 micrometers is deposited under the conditions indicated.

 Then the baseplate is polished with its protective chromium coating by means of fine-grained diamond pastes, it is washed in an ultrasonic bath of hot water containing 3% by mass of synthetic detergents, with petrol and with ethyl alcohol.

Then the base plate is placed in a vacuum chamber on the drum of the swivel device. The vacuum chamber is equipped with three plasma sources containing as material to evaporate an alloy of titanium and zirconium (0.5% by mass of zirconium and 99.5% by mass of titanium)
The ionic cleaning of the base plate is carried out by bombardment with titanium and zirconium ions, and the decorative vestibular coating is deposited with a mixture of titanium nitrides and zirconium 8 micrometers thick as indicated in the example. 1.

 The prosthesis obtained has the same technical and medical characteristics as the characteristics cited for the prosthesis of Example 5.

Example 12
A dental prosthesis is made in the form of a monolithic dental bridge structure constituted by a chromium-cobalt alloy base plate with a decorative vestibular coating of titanium oxynitride and with an intermediate layer of a mixture of titanium and titanium nitride.

The base plate of the dental prosthesis is made, it is polished, it is washed and it is placed in a vacuum chamber, as indicated in Example 1.

The vacuum chamber is provided with three plasma sources containing titanium as material to evaporate. The ionic cleaning of the base plate is carried out as indicated in example 1. Then a negative voltage of 200 V is applied to the base plate, the two other plasma sources are activated, a current d is established there. arc of 80 A and nitrogen is admitted into the chamber by gradually bringing its pressure from 1.333 mPa or 1.10 5 mm of Hg to 13.33 mPa or 1.10 4 mm of
Hg throughout the duration of the deposition of an intermediate layer 6 micrometers thick. The content of the intermediate layer of titanium nitride increases with the thickness of 0.018 by mass up to 90% by mass.

 When the thickness of the intermediate layer reaches 6 micrometers, the admission of nitrogen is interrupted and a mixture of nitrogen and oxygen is admitted (85% by volume of nitrogen and 15% by volume of oxygen) in establishing a pressure of 666.5 mPa or 5.10 3 mm Hg. A decorative vestibular coating 25 micrometers thick is then deposited.

 The technical and medical characteristics of the prosthesis obtained correspond to the characteristics indicated in Example 2.

 Example 13.

 A dental prosthesis is produced in the form of a monolithic bridge structure consisting of a chromium-cobalt alloy base plate with a decorative vestibular coating of a mixture of titanium nitride and zirconium nitride (50% by mass of titanium nitride + 50% by mass of zirconium nitride), and with an intermediate layer of a mixture of tantalum and tantalum nitride.

 The prosthesis base plate is made, polished, washed and placed in a vacuum chamber, as shown in Example 1.

 The vacuum chamber is equipped with three plasma sources, one of which contains tantalum, the second, titanium, and the third, zirconium. The ionic cleaning is carried out as indicated in example 10. Then a negative voltage of 100 V is applied to the base plate and nitrogen is admitted into the chamber, gradually increasing its pressure from 1.333 mPa or 1.10 5 mm of Hg at 106.64 mPa or 8.10 4 mm Hg for the duration of the deposition of an intermediate layer with a thickness of 4 micrometers. The tantalum nitride content of the intermediate layer in thickness increases from 0.01 26 in mass up to 95% by mass, When the thickness of the intermediate layer reaches 4 micrometers, the plasma sources of titanium and zirconium are put into action, the arc currents are established at 90 A, and the d action the plasma source with tantalum, a negative voltage of 250 V is applied to the plate base. Then nitrogen is admitted into the chamber by establishing a pressure of 533.2 mPa or 4.10 3 mm Hg therein, and a decorative vestibular coating of a mixture of titanium nitrides and zirconium is deposited.

When the thickness of said layer reaches 9 micrometers, the plasma sources are deactivated; the nitrogen admission is interrupted, the negative tension on the prostheses is removed and the pivoting device is stopped. Ten minutes later, the prosthesis is removed from the chamber. The technical and medical characteristics of the prosthesis obtained correspond to those indicated in Example 6.

 Example 14.

 A dental prosthesis is produced in the form of a brazed dental bridge structure consisting of a chromium-nickel stainless steel plate and a silver-zinc brazing with a decorative vestibular coating of titanium nitride and an intermediate layer of a mixture of chromium and chromium nitride. The prosthesis base plate is made and washed as indicated in Example 11.

Then the base plate is placed in a vacuum chamber, on the drum of a pivoting device. The vacuum chamber is provided with three plasma sources, one of which contains chromium as the material to evaporate, and the two wall spells, titanium.

 Vacuum is applied in the vacuum chamber to a residual pressure of 1.333 mPa or 1.10 5 mm Hg, the pivoting device is activated, a negative voltage of 700 V is applied to the base plate, activates the chromium plasma source by establishing an arc current of 70 A, and ionic cleaning is carried out for four minutes.

Then a negative voltage of 30 V is applied to the base plate, the arc current in the plasma source is established at 90 A and nitrogen is sent into it. bedroom. The nitrogen pressure is gradually increased from 1.333 mPa or 1.10 5 mm Hg to 40 mPa or 3.10-4 mm Hg, throughout the duration of the deposition of an intermediate layer with a thickness of 4 micrometers. The chromium nitride content increases with the thickness of the intermediate layer from 0.01% by mass to 90% by mass. Consequently, the microhardness of said layer increases by 3.9.103
MPa or 400 kgf / mm2 at 25.5.103MPa or 2600 kgf / mm2. When the thickness of the intermediate layer reaches 4 micrometers, two titanium plasma sources are activated, the arc current is established at 90 A, a negative voltage of 180 V is applied to the base plate, the chromium plasma source is deactivated. Then nitrogen is sent into the chamber, establishing its pressure at 666.5 mPa or 5.10 3 mm Hg, and a decorative vestibular coating of titanium nitride with a thickness of 10 micrometers is deposited. When this coating reaches a thickness of 10 micrometers, the plasma sources are deactivated, the nitrogen admission is interrupted, the tension on the prostheses is removed and the pivoting device is stopped. The prosthesis obtained has technical and medical characteristics corresponding to those indicated in Example 1.

 Example 15.

 We manufacture a dental prosthesis in the form of a brazed dental bridge structure consisting of a chromium-nickel stainless steel plate and silver-zinc brazing bearing a decorative vestibular coating of zirconium nitride, an intermediate layer of a mixture of chromium and chromium nitride, and a protective layer of chromium. The prosthesis base plate is made and washed as indicated in Example 11.

 Then the base plate is placed in a vacuum chamber on the drum of the swivel device. The vacuum chamber is provided with three plasma sources, one of which contains chromium as the material to be evaporated, and the other two, zirconium. The ionic cleaning of the base plate is carried out as indicated in Example 14.

 Then a negative voltage of 30 V is applied to the base plate, an arc current of 90 A is established in the plasma source and a protective layer of chromium with a thickness of 4 micrometers is deposited. When the desired thickness of the protective layer is reached, an intermediate layer is deposited as indicated in Example 14. The deposit of the decorative vestibular coating is carried out as indicated in Example 15, with the only difference being that of metal to evaporate cn uses zirconium.

 The decorative vestibular coating of the prosthesis has a microhardness of 24.5,103 or 500 kgf / mm2, its color corresponds to that of a high-grade gold alloy and said coating is characterized by strong adhesion of the layers to each other and to the baseplate. The prosthesis obtained was sealed in the patient's oral cavity with bisphate cement. Observations made over four years did not reveal any local or general negative effects on the patient's body.

 Example 16.

 A dental prosthesis is produced in the form of a monolithic bridge structure consisting of a chromium-cobalt alloy base plate with a decorative vestibular coating composed of a layer of titanium carboxynitride and a layer of titanium oxynitride, with an intermediate layer of a mixture of titanium and titanium nitride and a protective layer of titanium.

The base plate of the prosthesis is made, polished, washed and placed in a vacuum chamber as indicated in Example 1.

 The vacuum chamber is provided with three plasma sources in which titanium is used as the material to be evaporated. The ionic cleaning of the base plate is carried out as indicated in Example 1. Then a negative voltage of 180 V is applied to the base plate, the two other plasma sources are activated, currents are established there. 80 A arc and a protective layer 6 micrometers thick is deposited. Then an intermediate layer of a mixture of titanium and titanium nitride is deposited as indicated in example 12, with the only difference that the nitrogen pressure is brought to a value of 93.3 mPa or 7.10 4 mm Hg. This in turn increases the titanium nitride content at the limit of contact with the decorative vestibular coating up to 99% by mass. When the thickness of the intermediate layer reaches 6 micrometers, the nitrogen intake, the arc currents in the plasma sources are brought to 90 A and a gas mixture of nitrogen, methane and oxygen is admitted into the chamber (85% by volume of nitrogen, 5 in volume of oxygen and 10% by volume of methane), the pressure in the chamber is brought to 266.6 mPa or 2.10 3 mm of Hg and a decorative vestibular coating of titanium carboxynitride is deposited on the first layer.

When the thickness of this layer reaches 3 micrometers, the admission of the abovementioned gas mixture is interrupted and a gas mixture of nitrogen and oxygen (90% nitrogen + 10% oxygen) is admitted, by establishing a pressure of this mixture of 666.5 mPa or 5.1Q 3 mm of Hg, and the second layer of the decorative vestibular coating of titanium oxynitride is deposited.

When the thickness of said layer reaches 3 micrometers, the plasma sources are deactivated, the admission of the gas mixture is interrupted, the negative voltage on the prosthesis is removed and the pivoting device is stopped. Ten minutes later, the prosthesis is removed from the chamber.

 The prosthesis obtained has a microhardness of 24.5.103 MPa or 2,500 kgf / mm2, strong adhesion between the layers and with the base plate and its shade corresponds to that of a gold alloy of high titer. The prosthesis obtained is sealed in the patient's oral cavity with bisphate cement. Observations over two years did not detect any local or general negative effects on the patient's body. The shade of the prosthesis remained unchanged.

Example 17
A dental prosthesis is produced in the form of a brazed dental bridge structure, consisting of a chromium-nickel stainless steel plate base and a silver and cadmium solder with a decorative vestibular coating of a mixture of titanium nitrides. and zirconium (67% by mass of titanium nitride and 33% by mass of zirconium nitride), and an additional layer of cobalt.

 The base plate of the prosthesis is made and washed as indicated in Example 11.

 Then immerse the base plate in a galvanic bath to deposit the additional layer of cobalt.

The following composition (g / l) is used as the aqueous solution for depositing the coating: cobalt sulfate 500, sodium chloride 17, boric acid 45. The additional layer of cobalt is deposited under a current density of 3 A / cm2, an electrolyte temperature of 450C, pH = 4. An additional layer of cobalt with a thickness of 8 micrometers is deposited.

 Then the base plate obtained is polished with pastes of fine granulations. Then the base plate is washed and it is placed in a vacuum chamber as indicated in example 1. The decorative vestibular coating is deposited as indicated in example 9, the deposition is carried out until obtaining a layer with a thickness of 25 micrometers. When the thickness of the decorative vestibular coating reaches 25 micrometers, the deposition process is interrupted as indicated in Example 9.

 The technical and medical characteristics of the prosthesis obtained correspond to those which were indicated in Example 4.

 Example 18.

 A dental prosthesis is produced in the form of a structure brazed in a dental bridge, consisting of a base plate in chromium-nickel stainless steel and in silver and cadmium brazing with a decorative vestibular coating of titanium oxynitride and a layer complementary to molybdenum.

 The base plate of the prosthesis is made and washed as indicated in example 11. Then the base plate is placed in a vacuum chamber, on the drum of a pivoting device.

 The vacuum chamber is provided with three plasma sources, one of which contains molybdenum as the material to be evaporated, and the other two of titanium.

 Vacuum is applied in the vacuum chamber to a residual pressure, 2.6 mPa or 2.10 5 mm Hg, the pivoting device is activated, a negative voltage of 600 V is applied to the base plate , the plasma source of molybdenum is activated, an arc current of 130 A is established and the cleaning of the base plate by ions for three minutes. Then a negative voltage of 25 V is applied to the base plate and an additional layer of molybdenum 5 micrometers thick is deposited.

 Then the plasma sources of titanium are activated, arc currents of 90 A are established there, the plasma source of molybdenum is deactivated and a base layer of molybdenum is applied to the base plate negative voltage of 200 V. Then admits into the chamber a gaseous mixture of nitrogen and oxygen (80 gus by volume of nitrogen and 20% by volume of oxygen), establishing a pressure of 666.5 mPa or 5.10 3 mm Hg, and a decorative vestibular coating of titanium oxynitride 15 micrometers thick is deposited.

 The technical and medical characteristics of the prosthesis correspond to those indicated in Example 2.

 Example 19.

 We manufacture a dental prosthesis in the form of a brazed dental bridge structure consisting of a chromium-nickel stainless steel plate and in silver and cadmium solder with a decorative vestibular coating of a mixture of titanium nitride and of zirconium nitride (30% by mass of titanium nitride + 70% by mass of zirconium nitride) and an additional layer of zirconium.

 The base plate is made, it is polished and washed as indicated in example 11. Then the base plate is placed in a vacuum chamber, on the drum of a swiveling device. The vacuum chamber is provided with three plasma sources, one of which contains titanium to be evaporated, and the other two, zirconium.

We vacuum in the vacuum chamber to a residual pressure of 1.3 mPa or 1.10 5 mm Hg, we turn on the swivel device, we apply a negative voltage of 900V to the plate base, we put in action the zirconium plasma source, establishing an arc current of 80
A. For three minutes, the ionic cleaning of the base plate is carried out by bombardment with zirconium ions. Then a negative voltage of 50 V is applied to the base plate, a second zirconium plasma source is activated by establishing an arc current of 80 A therein, and an additional layer of zirconium of a thickness is deposited of 3 micrometers. Then a decorative vestibular coating of a mixture of titanium nitrides and zirconium is deposited. The technical and medical characteristics of the prosthesis correspond to those which were indicated in example 6.

 Example 20.

 A dental prosthesis is produced in the form of a brazed dental bridge structure consisting of a chromium-nickel stainless steel plate and a silver and cadmium solder with a decorative vestibular coating of zirconium nitride and a complementary coating of nitride. molybdenum. The base plate of the prosthesis is made, it is polished and washed as indicated in Example 11.

 Then the base plate is placed in a vacuum chamber, on the drum of a pivoting device. The vacuum chamber is provided with three plasma sources; one of which contains molybdenum as the material to evaporate, and the other two of which are zirconium.

Then a vacuum is made in the vacuum chamber until a residual pressure of 2.6 mPa or 2.10 5 mm of
Hg, the pivoting device is activated, a negative voltage of 600 V is applied to the base plate, the plasma source of molybdenum is activated by establishing an arc current of 130 A. It is carried out for 3 minutes the ionic cleaning of the base plate by bombardment with molybdenum ions.

 Then a negative voltage of 25 V is applied to the base plate, nitrogen is admitted into the chamber by establishing a pressure of 106.6 mPa or 8.10 4 mm of Hg, and an additional layer of molybdenum nitride is deposited 5 micrometers thick. When the complementary layer reaches a thickness of 5 micrometers, the zirconium plasma sources are activated by establishing arc currents of 90A, the plasma source of molybdenum is put out of action, it is applied to the plate- bases a negative voltage of 200 V and sends nitrogen into the chamber, establishing a nitrogen pressure of 533.2 mPa or 4.10 3 mm of Hg there. This deposits a decorative vestibular coating of zirconium nitride 15 micrometers thick. The decorative vestibular coating obtained has a microhardness of 24.5.103 MPa or 2,500 kgf / mm2. Its color corresponds to that of high-grade gold alloys and the coating has strong adhesion.

 The prosthesis thus obtained was sealed in the patient's oral cavity with bisphate cement. Observations made over three years did not reveal any negative local or general influence on the patient's body. The shade of the prosthesis has not changed.

During the period indicated, no layer separations were observed at the places of the soldering, nor blackening of the layers at the place of the soldering.

 Example 21.

 A dental prosthesis is manufactured in the form of a brazed structure in dental bridge constituted by a base plate in chromium-nickel steel and in silver and zinc brazing with a vestibular-decorative coating of titanium nitride, with a intermediate layer of a mixture of chromium and chromium nitride and with a complementary layer of nickel.

 We make the base plate of the prosthesis; polish and wash as shown in Example 11.

 Then the base plate is immersed in a galvanic bath for the application of an additional layer of nickel. The following composition (g / l) is used as aqueous liquor for the application of said layer: nickel sulfate 300, magnesium sulfate 50, sodium chloride 10, boric acid 30. The coating is applied at an electrolyte temperature of 40 "C, a current density of 3 A / dm2 and a pH of 4.0.

 After the application of the additional layer of 4 micrometers thick, the prosthesis is washed with running water and subjected to polishing.

 Then the base plate is placed in a vacuum chamber on the drum of a swivel device. The vacuum chamber is provided with three plasma sources, one of which contains as material to evaporate chromium, and the other two, titanium. Then an intermediate layer of a mixture of chromium and chromium nitride 5 micrometers thick is deposited, as indicated in example 14.

 Then deposit the decorative vestibular coating of titanium nitride 8 micrometers thick. The deposition process is stopped as indicated in example 1. Ten minutes after the prosthesis is removed from the chamber. The prosthesis obtained has the same technical and medical characteristics as the prosthesis described in Example 1.

 Example 22.

 We manufacture a dental prosthesis in the form of a brazed structure in dental bridge constituted by a plate-base in chrome-nickel stainless steel and in silver and cadmium brazing with a decorative vestibular coating in two layers, one of which, adjacent to the base plate, consists of a mixture of titanium and zirconium cyanonitrides (6796 by mass of titanium cyanonitride and 33% by mass of zirconium cyanonitride), while the second layer consists of a mixture of titanium and zirconium nitrides (67% by mass of titanium nitride and 332% by mass of zirconium nitride), and an additional layer of chromium.

 The base plate of the prosthesis is made and washed as indicated in example 11. Then the base plate is immersed in a galvanic bath and an additional layer of chromium 5 micrometers thick is deposited there, as indicated in example 11. Then polish, wash and set up the base plate provided with the additional layer deposited thereon as indicated in example 11. The vacuum chamber is provided with three plasma sources, the one contains as the metal to be evaporated zirconium, and the other two, titanium. Ionic cleaning of the base plate is carried out with its additional chromium layer by bombardment with zirconium ions, as indicated in Example 6.

Then the additional layer of a mixture of titanium and titanium nitride is deposited as indicated in example 12. Then a negative voltage of 220 V is applied to the base plate, the plasma sources of titanium are activated , arc currents of 90A are established at the three plasma sources.

Then a gaseous mixture of nitrogen and acetylene is admitted into the vacuum chamber (90% by volume of nitrogen and 10 by volume of acetylene), a pressure of 133.3 mPa or 1.10 3 is established in the chamber. mm of Hg, and the first layer of the decorative vestibular covering 9 micrometers thick is deposited.

After having reached the required thickness, the admission of the gaseous mixture is interrupted and nitrogen is sent into the chamber, by establishing in said chamber a nitrogen pressure of 666.5 mPa or 5.10 3 mm of Hg, and the second layer of the decorative vestibular coating is deposited with a mixture of titanium nitrides and zirconium 4 micrometers thick.

 The technical and medical characteristics of the prosthesis obtained correspond to the characteristics of the prosthesis indicated in Example 7.

 Example 23.

 We manufacture a dental prosthesis in the form of a brazed dental bridge structure consisting of a chromium-nickel stainless steel base plate and silver and cadmium solder with a decorative vestibular coating consisting of two layers, of which one, adjacent to the base plate, consists of a mixture of titanium and zirconium monoxides (33% by mass of titanium monoxide and 67% by mass of zirconium monoxide), while the second consists of a mixture of titanium and zirconium oxynitrides (33% by mass of titanium oxynitride and 67% by mass of zirconium oxynitride), and a complementary layer of chromium nitride.

 The base plate of the prosthesis is made and washed as indicated in example 12. Then the base plate is placed in a vacuum chamber, on the drum of a pivoting device.

 The vacuum chamber is provided with four plasma sources, one of which contains as material to evaporate chromium, the second, titanium, the third and fourth, zirconium. A vacuum is created in the vacuum chamber up to a pressure of 2.6 mPa or 2.10 5 mm of Hg., The pivoting device is switched on, a negative voltage of 700 V is applied to the plate, activates the chromium plasma source by establishing an arc current of 80 A.

 For four minutes the baseplate is cleaned by bombardment with chromium ions. Then a negative voltage of 30V is applied to the plate, the nitrogen is sent into the chamber by establishing its pressure at 53.3 mPa or mm of Hg, and an additional layer of chromium nitride of 4 micrometers is deposited. thickness. When the additional layer reaches the required thickness, two plasma sources of zirconium and one of titanium are put into action, by establishing arc currents of 90 A there, the plasma source of chromium is deactivated and a negative voltage of 200 V is applied to the base plate provided with a complementary coating of chromium nitride, then the admission of nitrogen to the chamber is interrupted, oxygen is admitted at a pressure of a0 mPa or 3.10 4 mm of Hg and a first layer of decorative vestibuary coating of a mixture of titanium and zirconium monoxides (33% by mass of titanium monoxide and 67 by mass of zirconium monoxide) with a thickness of 4 micrometers is deposited .

 Then the admission of oxygen is interrupted and a gaseous mixture of nitrogen and oxygen is admitted into the chamber (82 by volume of nitrogen and 1826 by volume of oxygen), a pressure of 666 is established in the chamber , 5 mPa or 5.10 3 mm Hg and a second layer of decorative vestibular coating is deposited with a mixture of titanium oxynitrides and zirconium 6 micrometers thick.

The decorative vestibular coating has a hardness of 21.6.103MPa or 22COkgf / mm2, strong adhesion to the intermediate layer and a shade corresponding to that of a high-grade gold alloy. The prosthesis obtained was sealed in the patient's oral cavity with bisphate cement. Observations made over two years did not detect any local or general negative influences on the patient's body. The integrity of the prosthesis coating was not compromised, the color of the prosthesis remained unchanged
Example 24.

 A dental prosthesis is produced in the form of a monolithic dental bridge structure constituted by a base plate of chromium-cobalt alloy with a decorative vestibular coating composed of three layers, one of which, adjacent to the base plate, is formed titanium cyanonitride, the second, titanium oxynitride, and the third, titanium nitride.

 The base plate of the dental prosthesis is made, it is polished, it is washed and it is placed in a vacuum chamber as indicated in example 1. The vacuum chamber is provided with three plasma sources containing titanium as material to evaporate. Ionic cleaning of the base plate is carried out by bombardment with titanium ions as indicated in Example 1. Then a negative voltage of 220 V is applied to the base plate, the plasma sources are activated by establishing a current of 90 A.

Then admits into the chamber a mixture of nitrogen and acetylene gas (90% by volume of nitrogen and 10% by volume of slow acety). A mixture pressure of 66.6 mPa or 5.10 = mm of Hg is established and the first layer of the decorative vestibular coating of titanium cyanonitride 4 micrometers thick is deposited.

 Then the admission of said gas mixture is interrupted and a gas mixture composed of nitrogen and oxygen (82% by volume of nitrogen and 18% by volume of oxygen) is admitted into the chamber by establishing a pressure in the chamber. of 133.3 mPa or 1.1Q 3 mm of Hg, and a second layer of decorative vestibular coating of titanium oxynitride with a thickness of 4 micrometers is deposited.

 Then the admission of said gas mixture is interrupted and nitrogen is admitted by establishing a nitrogen pressure of 666.5 mPa or 5.10 3 mm of Hg, and a third layer of decorative vestibular coating of titanium nitride of 5 micrometers thick.

 The decorative vestibular coating has a microhardness of 24.5.103 MPa or 2500 kgf / mm2, strong adhesion to the base plate and a shade corresponding to that of a high-grade gold alloy. The prosthesis obtained was sealed in the patient's oral cavity. Observations made over two years did not reveal any negative local or general influences on the patient's organism. The shade of the prosthesis remained unchanged. Coating integrity defects were not observed.

For the great majority of the claimed variants of dental prosthesis structures, sufficiently broad and in-depth mido-biological research has been undertaken which goes beyond the scope of clinical trials. The research was carried out in the following main directions:
1. Chemical and sanitary research by studies of the migration of metals from dental prosthesis to model environments.

 2. Tests of the effects of the material of the layers and their associations in the prosthesis on microorganisms, the microflora of the oral cavity or the development of cultures of living tissue.

 3. Histological and histochemical studies of the reactions of the body tissue around the implant with the coating (material) studied.

4. Studies of the functional state2 of the organism of the animals with the implant:
- general reactivity index;
- dynamics of body mass;
- proportion of histamine in the blood;
- vitamin C content in the blood;
- stability to functional loads;
- state of the central nervous system;
- liver and kidney functions.

 5. Histological and histochemical studies of the viscera (of the liver, kidneys, spleen, heart and adrenal capsules).

 6. Clinical trials of the claimed structures of dental prostheses.

 For certain types of structures of the claimed dental prostheses, the research program cited was carried out globally and led to positive results. For other types of structures, the program is nearing completion and makes it possible to formulate favorable forecasts.

Claims (9)

 1. Dental prosthesis composed of a base plate made up of a metal alloy endowed with anticorrosive properties and mechanical resistance, and at least one esthetic or decorative vestibular coating, characterized in that said decorative vestibular coating is produced in a material harder than the base plate and composed of nitrides of oxynitrides, carboxynitrides, cyanonitrides and / or monoxides of metals of the secondary family of group IV of the Periodic Table of the Elements, the thickness ratio said decorative vestibular covering with the thickness of the base plate being in a range from 1:10 to 1: 200.  2. A dental prosthesis according to claim 1, characterized in that it contains as a decorative vestibular coating material nitrides, oxynitrides, carboxynitrides and / or titanium and / or zirconium monoxides.  3. Dental prosthesis according to one of claims 1 and 2, characterized in that between the base plate of the prosthesis and its decorative vestibular coating is disposed a protective layer of metal more electronegative than the material of the decorative vestibular coating and capable to passivate in liquid media of the oral cavity, the ratio of the thickness of said protective layer to the thickness of the decorative vestibular coating being from 0.3: 1 to 1: 1.  4. A dental prosthesis according to claim 3, characterized in that as a protective layer metal it contains titanium, tantalum or chromium  5. Dental prosthesis according to one of claims 1 and 2> characterized in that between the decorative vestibular coating and the base plate of the dental prosthesis is an intermediate layer composed of titanium, tantalum or chromium mixed with a corresponding nitride, the nitride content in the thickness of the intermediate layer varying from 0.01 to 90-99.9% by mass, and the ratio of the thickness of the intermediate layer to the thickness of the decorative vestibular coating being in the range of 0.3:: 1 to 1: 1.  6. Dental prosthesis according to one of claims 3 and 4, characterized in that, between the decorative vestibular coating and the protective layer there is an intermediate layer composed of titanium, tantalum or chromium mixed with a corresponding nitride, the content nitride in the thickness of the intermediate layer varying from 0.01 to 9099.9% by mass, and the ratio of the thickness of the intermediate layer to the thickness of the decorative vestibular coating being 0.3: 1 1 : 1.  7. A dental prosthesis according to one of claims 1 and 2, characterized in that in the case where the base plate of the prosthesis is a structure of brazed elements of metal alloy endowed with anti-corrosion properties and with mechanical resistance, said prosthesis comprises, between the decorative vestibular covering and the base plate, an additional layer of cobalt, nickel, chromium, molybdenum or zirconium, or else chromium or molybdenum nitrides, the thickness ratio of the layer complementary to the thickness of the decorative vestibular covering being in the range of 0.5: 1 to 1: 1.  8. A dental prosthesis according to claim 5, characterized in that in the case where the base plate of the prosthesis is a structure of brazed elements of metal alloy endowed with anticorrosive properties and with mechanical resistance, said prosthesis comprises 1 between the layer intermediate and the base plate, an additional layer of cobalt, nickel, chromium, molybdenum or zirconium, the ratio of the thickness of the additional layer to the thickness of the decorative vestibular coating being included in the range of yes5: 1 to 1: 1.  9. A method of manufacturing a dental prosthesis, of the type comprising the manufacture of a base plate by brazing the elements of the dental prosthesis from a metal alloy endowed with anticorrosive properties and with mechanical resistance so as to form a single structure, and the deposition under vacuum of a decorative or aesthetic vestibular coating, characterized in that the brazed assembly zone of said structure, or the entire structure, is galvanized or by a vacuum process before the application of said vestibular coating, a complementary layer of cobalt, nickel, chromium, molybdenum or zirconium, or else a complementary layer of chromium nitride or molybdenum, the thickness ratio of said complementary layer to that of said vestibular coating being within the range of 0.5: 1 to 1: 1 respectively.