Etching process

Abstract

The invention relates to an etching process for the surface treatment of a tooth replacement component comprising an implant, a ceramic abutment, and a ceramic prosthetic restoration. An inner surface of the prosthetic restoration and / or the part of the abutment which is intended to receive the prosthetic restoration is brought into contact with an etchant, the etchant containing the following reactants: a polyprotic acid, at least one alkali salt, and water.

Description

[0001] Etching process

[0002] The present invention relates to an etching method for the surface treatment of a dental prosthesis component.

[0003] STATE OF THE ART

[0004] Acid etching processes known from the state of the art in the field of ceramic dental restorations primarily aim to improve the osseointegration of dental implants. WO 2020 / 244814 is representative of a large number of patent publications. This document discloses a dental implant that has various areas with different surface roughnesses, which enables improved deposition of different tissue cells. The abutment itself has lamellae. These lamellae are preferably one or more horizontal microgrooves in the surface of the abutment. This special surface design is intended to improve the final fixation of the prosthetic restoration.

[0005] The use of acid etching processes is also widespread in dental laboratories and dental practices. One example is the surface treatment of silicate ceramic-based crowns, which are usually adhesively bonded to enamel and dentin. Light- and dual-curing luting composites are used. The prerequisite for this is that the silicate ceramic is etched with hydrofluoric acid (HF 5%) (approx. 60 seconds); this results in a micro-retentive surface, which is then wetted with silane. Hydrofluoric acid etching of glass-based ceramics with subsequent silanization has been an established and proven process for decades. However, for occupational health and safety reasons, hydrofluoric acid etching is considered one of the most critical workflows in dental practices. In the past, there have therefore been repeated efforts to replace hydrofluoric acid. One example of this is ammonium polyfluoride.This reacts with the silicate ceramic surface and creates a rough etching pattern.

[0006] Zirconium oxide-based oxide ceramics must be distinguished from silicate ceramics. Currently, common practice in ceramic pretreatment is blasting with aluminum oxide. The aluminum oxide powder typically has a grain size of < 50 micrometers and the process is carried out with a blasting pressure between 0.5 and 1 bar. However, it is known that mechanical surface treatment processes, such as sandblasting, have a negative impact on the mechanical stability of oxide ceramics.

[0007] Overall, the surface treatment of the ceramic serves to improve the bond, for example, between the abutment or tooth stump and the crown. According to current knowledge, approximately 10 N is sufficient to remove the crown from the abutment, for example. SUMMARY OF THE INVENTION

[0008] An object of the invention is to avoid at least one disadvantage known from the prior art.

[0009] This problem is solved by the invention defined in the independent patent claims.

[0010] The etching method according to the invention relates to a surface treatment of a dental prosthesis component, which comprises a part that can be inserted into the bone as a replacement for the tooth root (implant), and an abutment (supporting pillar), which represents the connecting part (mesostructure) between the dental implant and a prosthetic restoration (e.g., dental crown, bridge). The abutment and prosthetic restoration are made of ceramic. The etching method according to the invention is used, for example, in the treatment of surfaces, for example, the area of ​​a dental crown that is bonded to the abutment or a tooth stump. This is the inner surface of the dental crown.

[0011] The term "prosthetic restoration" refers to the part of the dental prosthesis component that is located above the gum line. An example of a prosthetic restoration is a dental crown. The prosthetic restoration has a surface modeled on a natural tooth and an initially untreated inner surface. The inner surface is the side of the prosthetic restoration that is intended for connection to the abutment or tooth stump. "Untreated" means that the inner surface is only treated when the prosthetic restoration is placed in order to achieve an improved bond, for example, between the dental crown and the abutment or tooth stump.

[0012] According to the invention, that part of the abutment, the so-called adhesive surface, which is intended to receive the prosthetic restoration and / or an inner surface of the prosthetic restoration, for example that of a dental crown, is brought into contact with an etching agent.

[0013] With the method according to the invention, the surface of the abutment and / or an inner surface of a prosthetic restoration is treated, resulting in an improved bond between these two parts or between a prosthetic restoration and the tooth stump. The pretreated surface creates a sufficient bond between the abutment and the prosthetic restoration or between the tooth stump and the prosthetic restoration, which can withstand chewing pressure and alternating bending loads.

[0014] When the abutment or tooth stump is connected to the prosthetic restoration, a retentive connection is primarily created, with a conventional cement (e.g., zinc oxide phosphate or glass ionomer) being used as the adhesive. The bond between the abutment or tooth stump and the prosthetic restoration is primarily based on friction. The surface of the abutment or tooth stump and the surface of the prosthetic restoration intended for connection to the abutment or tooth stump are available as adhesive surfaces. The aim is to achieve a definitive connection between the prosthetic restoration and the abutment or tooth stump. Cementation requires a retentive surface treatment, which is created using the method according to the invention. Appropriate roughness of the adhesive surface is crucial for the bond and adhesion, because the prosthetic restoration is essentially wedged into the abutment or tooth stump.

[0015] Unlike the abutment or the inner surface of the prosthetic restoration, the tooth stump, especially its surface, is not treated with the etching process, but rather with a diamond grinding wheel with an average grain size between 1.5 and 1.51 micrometers (pm). This achieves the desired roughness.

[0016] The method according to the invention can be used for the surface treatment of all parts of a dental prosthesis component made of ceramic, especially oxide ceramic. This includes the abutment and the prosthetic restoration, such as dental crowns or bridges. In the prosthetic restoration, the method according to the invention is used particularly in the area intended for connection to the abutment or tooth stump.

[0017] The abutment and implant can be a one-piece or a two-piece design. In the two-piece design, the implant and abutment are two separate parts that are connected by the dentist. In the one-piece design, the implant and abutment are made as a single piece.

[0018] The application of the inventive method is not limited to the one-part or two-part variant. The etchant used according to the invention comprises a polybasic acid, at least one alkali metal salt, and water.

[0019] The polybasic acid is a strong acid with a pKa value of ^4.

[0020] The etchant used comprises, in a preferred embodiment, a mixture of sulfuric acid, sodium fluoride, hydrofluoric acid, and water, with the weight percentage of the individual etchant components varying during the etching process. HSO4 is formed during the process. _Ions that also act as acids and contribute to etching.

[0021] The process according to the invention is based on the reaction of sodium fluoride with sulfuric acid, which is generally as follows:

[0022] And more precisely:

[0023] The use of a mixture of sulfuric acid and sodium fluoride results in hydrofluoric acid as a reaction product. Three acids are available for etching the ceramics: the sulfuric acid used, the hydrofluoric acid formed in situ during the reaction, and the hydrogen sulfate ions formed.

[0024] In the etching process, the proportion in weight percent of the individual etchant components depends on the etching time.

[0025] An advantage of the inventive process is that the hydrofluoric acid is not applied directly, but rather forms as a reaction product, which reacts immediately and is consumed in the process. This facilitates the handling of the ingredients in the dental laboratory or dental practice.

[0026] The concentration of the polybasic acid used is between 60

[0027] % and 90 wt. %, preferably 70 wt. % or more, particularly preferably 80 wt. %.

[0028] For example, 100 g of 80% sulfuric acid is prepared from 96% sulfuric acid by mixing 83.33 g of 96% sulfuric acid and 16.67 g of H2O at 20°C. To produce the desired sulfuric acid concentrations, sulfuric acid with a starting concentration of 95-97% is preferably used.

[0029] The etchant used comprises 2% to 5% of a fluorine-containing alkali salt, preferably 3%. In a preferred embodiment, the alkali salt is a fluorine-containing alkali salt, preferably sodium fluoride. Further examples of usable fluorine-containing alkali salts are: potassium fluoride, potassium hydrogen difluoride, ammonium fluoride, or lithium fluoride.

[0030] The treatment temperature during the process is between 50°C and 100°C, preferably 80°C.

[0031] The alkali salt used is NaF with a purity of > 99.5%

[0032] The etching time of the procedure, during which the abutment or prosthetic restoration is exposed to the etchant, is between 12 and 48 hours, preferably 24 hours.

[0033] In the present invention, the abutment and the prosthetic restoration are made of a ceramic material. This material is an oxide-based ceramic with zirconium oxide (ZrO2), preferably with a proportion of yttrium oxide (Y2O3) or with a proportion of aluminum oxide (Al2O3) and yttrium oxide (Y2O3). These ceramics are also referred to as high-strength ceramics (strengths over 350 MPa), which have a correspondingly high inherent stability. The ceramic material used in the method according to the invention is sintered. The abutment or an inner surface of the prosthetic restoration is not further treated, for example, neither polished nor sandblasted, before etching with the method according to the invention.

[0034] An exemplary composition of such a ceramic, which is sold by Shenyang Upcera Co., Ltd under the product name «Upcera zirconia block», has the following composition: Zirconium oxide (ZrO2) and hafnium oxide: 94%

[0035] Aluminum oxide < 0.5%

[0036] Yttrium oxide < 5.5%

[0037] Due to treatment with the etching process according to the invention, that part of the abutment intended for connection to a prosthetic restoration (the so-called bonding surface) has a mesoporous surface structure, preferably with a pore diameter between 2 nm and 50 nm. A similar situation applies to the inner surface of the prosthetic restoration, for example, the dental crown, treated with the process according to the invention. Furthermore, it was found that that part of the abutment intended for connection to a prosthetic restoration also has a macroporous surface structure, preferably with a pore diameter greater than 50 nm. A similar situation applies to the inner surface of the prosthetic restoration, for example, the dental crown, treated with the process according to the invention.

[0038] It was found that when using a lower concentration of sulfuric acid, the ceramic surface was severely etched, whereas when using a very high concentration of sulfuric acid (e.g., 96% concentration) in the etchant, the roughening of the surface was significantly less pronounced. BRIEF DESCRIPTION OF THE FIGURES

[0039] Aspects of the invention are explained in more detail with reference to the exemplary embodiments shown in the following figures and the associated description. They show:

[0040] Fig. 1 shows photos of ceramic samples made of oxide ceramics with the main component ZrO2 in an untreated state (a) and treated

[0041] Condition (b) - (f).

[0042] Fig. 2 shows a scanning electron microscope image of an untreated sample at a magnification of 1,500x (a) and 10,000x (b); Fig. 3 shows a scanning electron microscope image of a sample treated with the etching process according to the invention at a magnification of 1,500x (a) and 10,000x (b);

[0043] Fig. 4 shows a scanning electron microscope image of a sample treated with the etching process according to the invention, at a magnification of 1,500 times (a) and 10,000 times (b).

[0044] WAYS TO IMPLEMENT THE INVENTION

[0045] Figure 1 shows photographs of ceramic samples made of oxide ceramics with ZrO2 as the main constituent, in an untreated state (a) and in a state treated with the inventive method (b) - (f). During treatment with the inventive method, the treatment duration was 24 hours. During the tests, the treatment temperature and the reactant concentration of sulfuric acid (H2SO4) were varied. Treatment temperature is understood to be the temperature that remains essentially constant throughout the treatment period (e.g., 24 hours). The etching process is carried out, for example, in a furnace. The reactant concentration of the alkali salt sodium fluoride (NaF) remained constant at 3% in all tests (b) - (f). Figure 1 (b) shows the ceramic sample treated with 40% sulfuric acid and an etchant temperature of 60°C. The sample was etched in the edge regions under the selected conditions.In the central region of the sample, the surface remained unchanged. In Figure 1 (c), in comparison to Figure 1 (b), the concentration of H2SO4 was maintained at 40%, and the etchant temperature was raised from 60°C to 80°C. According to Figure 1 (c), the edge region was also etched, while the central region of the sample remained essentially unchanged. In Figures 1 (d) - 1 (f), the etchant temperature was kept constant at 80°C, and a 60% sulfuric acid solution (Figure 1 (d), a 70% sulfuric acid solution (Figure 1 (e)), and an 80% sulfuric acid solution (Figure 1 (f)) were used. The etching time in all experiments was 24 hours. In all three cases (d) - (f), a homogeneous but varying degree of etching of the entire surface of the sample was achieved. The samples from Figure 1 (e) and Figure 1 (f) were examined in more detail under the scanning electron microscope with regard to their surface structure (see Figure 3 and Figure 4).It was found that when using seventy percent sulfuric acid, the ceramic surface was massively etched, whereas when using eighty percent sulfuric acid in the etchant, the roughening of the surface was much less pronounced.

[0046] Figure 2 shows a scanning electron microscope (SEM) image of an untreated sample at a magnification of 1,500x (a) and 10,000x (b). The sample is a sintered ceramic based on zirconium oxide (ZrO2). Untreated means that the sample has not undergone any prior abrasive treatment before being subjected to the etching process according to the invention, i.e. the sample shown is unpolished and has not been pre-treated using a sandblasting process. Figure 3 shows a scanning electron microscope image of a sample treated with the etching process according to the invention at a magnification of 1,500x (a) and 10,000x (b). This is an SEM image of the sample from Figure 1 (f). 80% sulfuric acid with 3% sodium fluoride (NaF) was used. The treatment temperature was 80°C and the etching time was 24 hours.As clearly visible in the magnification (1,500x), treatment with the inventive method leads to a homogeneous roughening of the sample surface, resulting in a mesoporous structure.

[0047] Figure 4 shows a scanning electron microscope image of a sample treated with the etching process according to the invention, at a magnification of 1,500x (a) and 10,000x (b). This is the sample from Figure 1 (e). A 70% sulfuric acid solution with 3% sodium fluoride (NaF) was used. The treatment temperature was 80°C, and the etching time was 24 hours. As clearly visible at the magnification (1,500x), the surface structure after etching differs from that in Figure 3. It is evident that the sample surface was severely attacked, forming plate-like structures. The extreme roughness is already visible to the naked eye. The degree of etching is severe.

Claims

PATENT CLAIMS 1. Etching method for surface treatment of a dental prosthesis component comprising an implant, a ceramic abutment and a ceramic prosthetic restoration, characterized in that an inner surface of the prosthetic restoration and / or that part of the abutment which is intended to receive the prosthetic restoration is brought into contact with an etching agent, wherein the etching agent contains the following reactants: a polyprotic acid, at least one alkali salt and water.

2. Etching process according to claim 1, characterized in that the reactant concentration of the polyprotic acid is between 60 wt. % and 90 wt. %, preferably more than 70 wt. %, particularly preferably 80 wt. %.

3. Etching process according to one of the preceding claims, characterized in that the reactant concentration of the alkali salt is 2% to 5%, preferably 3%.

4. Etching process according to one of the preceding claims, characterized in that at least one alkali salt is a fluorine-containing alkali salt, for example sodium fluoride, potassium fluoride, potassium hydrogen difluoride, ammonium fluoride or lithium fluoride, preferably sodium fluoride is used. Etching process according to any one of the preceding claims, characterized in that the polyprotic acid is a strong acid, preferably with a pKa value of less than 4. Etching process according to any one of the preceding claims, characterized in that the polyprotic acid is sulfuric acid. Etching process according to any one of the preceding claims, characterized in that the treatment temperature is between 50°C and 100°C, preferably 80°C. Etching process according to any one of the preceding claims, characterized in that the etching time is between 1.2 hours and 48 hours, preferably 24 hours. Etching process according to any one of the preceding claims, characterized in that the etching process is not preceded by any additional mechanical treatment steps of the ceramic abutment or the inner surface of the prosthetic restoration, for example, sandblasting and / or polishing.Etching process according to one of the preceding claims, characterized in that the ceramic abutment used in the process. and / or the prosthetic restoration comprises a sintered ceramic material based on zirconium oxide (ZrO2), preferably with a proportion of yttrium oxide (Y2O3) or based on zirconium oxide (ZrO2), preferably with a proportion of aluminum oxide (Al2O3) and yttrium oxide (Y2O3). 1 1 . An abutment or a prosthetic restoration, characterized in that the area of ​​the abutment which is provided for a connection, preferably a retentive connection with the prosthetic restoration and / or the inner surface of the prosthetic restoration, is treated with an etching process according to one of the preceding claims 1 to 10. 1 2. The abutment or prosthetic restoration according to claim 1 1 , characterized in that the abutment or prosthetic restoration comprises a sintered ceramic material based on zirconium oxide (ZrO2), preferably with a proportion of yttrium oxide (Y2O3) or based on zirconium oxide (ZrO2), preferably with a proportion of aluminum oxide (Al2O3) and yttrium oxide (Y2O3).

13. Prosthetic restoration according to claim 1 2, characterized in that the prosthetic restoration comprises on its inner surface a sintered ceramic material based on zirconium oxide (ZrO2), preferably with a proportion of yttrium oxide (Y2O3) or based on zirconium oxide (ZrO2), preferably with a proportion of aluminum oxide (Al2O3) and yttrium oxide (Y2O3).

4. Abutment or prosthetic restoration according to any one of claims 11 to 13, characterized in that the part of the abutment intended for connection with a prosthetic restoration and / or the inner surface of the prosthetic restoration has a mesoporous surface structure after treatment with an etching process according to claims 1 to 10, preferably with a pore diameter between 2 nm and 50 nm.

5. Abutment or prosthetic restoration according to any one of claims 11 to 14, characterized in that the part of the abutment intended for connection with a prosthetic restoration and / or the inner surface of the prosthetic restoration has a macroporous surface structure after treatment with an etching process according to claims 1 to 10, preferably with a pore diameter greater than 50 nm.

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