Method for producing an implant blank

Abstract

A method for producing an implant blank (100), in particular a dental implant blank from a starting body, said implant blank (100) comprising at least one first area, which is a surface area (102), and a second area, which is a core area (101), wherein the surface area (102) has at least one bioactive surface material (502) and extends from at least one first surface (103) in the direction of the core area (101), and the core area (101) has at least one carrier material that can be subjected to mechanical load. The starting body has a porosity for controlling a targeted distribution of the bioactive surface material (502) within the starting body and is loaded with a solution (500) of the bioactive surface material (502) in a first step, which is a loading step. In a second step, which is a distribution control step, the distribution of the bioactive surface material (502) within the starting body is controlled such that the solution (500) has a higher concentration within the surface area (102) than within the core area (101), the control being effected by regulating one or more environmental parameters in a closed environment (200), in particular by regulating the humidity and/or the pressure and/or the temperature.

Claims

1. A method for producing an implant blank (100) from a starting body, said implant blank (100) comprising at least one first area, which is a surface area (102), and a second area, which is a core area (101), wherein the surface area (102) has at least one bioactive surface material (502) and extends from at least one first surface (103) in the direction of the core area (101), and the core area (101) has at least one carrier material that can be subjected to mechanical load, characterized in that the starting body has a porosity for controlling a targeted distribution of the bioactive surface material (502) within the starting body and is loaded with a solution (500) of the bioactive surface material (502) in a first step, which is a loading step, and in a second step, which is a distribution control step, the distribution of the bioactive surface material (502) within the starting body is controlled such that the solution (500) has a higher concentration within the surface area (102) than within the core area (101), the control being effected by regulating one or more environmental parameters in a sealed closed environment (200), wherein the distribution of the bioactive surface material (502) is effected within the starting body by a convection current, and wherein a direction of flow and velocity are controlled by targeted generation of environmental parameter gradients by adjusting humidity differences or pressure differences or temperature differences with respect to different surfaces of the starting body.

2. The method according to claim 1, characterized in that the loading of the starting body with the solution (500) of the at least one bioactive surface material (502) is effected via at least one second surface of the starting body, which is a loading surface (104, 106), wherein the loading surface (104, 106) is a surface other than the first surface (103).

3. The method according to claim 2, characterized in that the loading surface (104, 106) for loading the starting body with the bioactive surface material (502) is arranged outside the closed environment (200).

4. The method according to claim 2, characterized in that the concentration of the solution (500) is constant during the loading step or during the loading of the starting body.

5. The method according to claim 2, characterized in that the bioactive surface material (502) is crystallizable, and is crystallized in a third step, which is a crystallization step within the surface area (102) or in the area of the first surface (103).

6. The method according to claim 5, characterized in that the bioactive surface material (502) is form-fittingly or force-fittingly arranged within pores (107) of the surface area (102) of the starting body.

7. The method according to claim 6, characterized by a crystal-growing step, wherein crystals of the bioactive surface material (502) grow from the porosity of the surface area (102) to a crystalline layer (503), said crystalline layer (503) covering at least a portion of the first surface (103) of the starting body.

8. The method according to claim 7, characterized by a pore-forming step, wherein the crystals or the crystalline layer (503) of the bioactive material (502) are subjected to a heat treatment forming pores or increasing the surface roughness (506).

9. The method according to claim 7, characterized in that a morphology or structure (506) or surface (506) or porosity of the crystalline layer (503) or of the crystals of the bioactive surface material (502) are affected by the solvent (500).

10. The method according to claim 2, characterized by a coefficient of thermal expansion balancing step, wherein the starting body is rinsed with a balancing solution having zirconium or calcium or cerium.

11. The method according to claim 2, characterized by a sintering step, wherein by the sintering step, a material bond or a chemical bond between the bioactive surface material (502) and the carrier material is generated.

12. The method according to claim 1, characterized in that the concentration or a concentration profile of the solution (500) is controlled within the starting body by drying or vaporization.

13. The method according to claim 1, characterized by the following steps, (A) providing the porous starting body (B) placing the first surface (103) of a starting body within a closed environment (200), wherein at least a portion of a second surface (104, 106) of the starting body, which is a loading surface (104, 106), is located outside the closed environment (200), (C) loading the loading surface (104, 106) of the starting body with the bioactive surface material (502), wherein the bioactive surface material (502) is dissolved in a solvent (500), (D) controlling the distribution of the bioactive surface material (502), wherein the solution (500) has a higher concentration within the surface area (102) than within the core area (101) and the humidity or the pressure or the temperature is regulated to generate an environmental parameter gradient, (E) crystallizing the bioactive surface material (502), wherein the concentration of the solution (500) within the surface area (102) is increased by vaporization or evaporation or drying, and (F) forming a crystalline layer (503) of the bioactive surface material (502) by crystal growth.

14. The method according to claim 1, characterized in that the implant blank (100) is a dental implant blank.

15. The method according to claim 1, characterized in that the control of the targeted distribution being effected by regulating the humidity or the pressure or the temperature.

Description

BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS

(1) FIG. 1 shows a schematic representation of a dental implant which is screwed into the jawbone of a patient for receiving a dental prosthesis,

(2) FIG. 2 shows a flow chart for a schematic representation of the sequence of an exemplary production method according to the invention,

(3) FIG. 3 shows a schematic representation of a dental implant blank which is arranged in a closed environment for the production method according to the invention,

(4) FIG. 4 schematically shows the growth of a crystalline bioactive surface coating,

(5) FIG. 5 shows micrographs of a crystalline, bioactive surface coating according to the growth steps from FIG. 4,

(6) FIG. 6 shows a micrograph of a crystalline surface coating with isolated areas,

(7) FIG. 7 is a schematic representation of an alternative embodiment of the method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(8) FIG. 1 schematically shows a dental prosthesis 1, in particular a crown, with a dental implant 2 arranged thereunder, compared to a tooth 3 with underlying tooth root 4. The dental implant 2 comprises an implant body 5, which is provided with an external thread 6 and is provided for screwing into the jawbone 7 of a patient. Above the implant body 5 there is a transition section 8 which, depending on the design of the dental implant 2, can be made in one piece therewith or, as shown here, is screwed into the implant body 5. The transition section 8 is arranged within the gums 9 of the patient. The transition section 8 adjoins the so-called abutment 10, which protrudes from the gums 9 of the patient and is configured to receive the dental prosthesis 1. The surface of the implant body 5 is preferably configured as a bioactive surface, so that the surrounding jaw bone 7 can heal into the implant body 5. The transition section 8, which is arranged within the gums 9, should have as smooth as possible, non-porous surface of a biocompatible material to prevent ingrowth of the gums and the colonization and multiplication of bacteria.

(9) FIG. 2 shows a method sequence according to the invention by way of example with reference to a flow chart. In a first step (A), a porous starting body, for example, a cylindrical zirconia ceramic blank having a diameter of 16.5 mm, a height of 16 mm and a total mass of 10.32 g is provided. The starting body is placed in a closed environment in a second step (B). This can be a cylindrical chamber. A first surface of the starting body, at which the formation of a bioactive surface coating is to take place, is arranged completely within the closed environment, wherein a second surface or at least a part of the second surface, which is a loading surface, is arranged outside the closed environment. In a third step (C), the loading surface of the starting body is loaded with a solution of a bioactive surface material. The solution is a hydroxyapatite sol prepared by dissolving 2.5 g of calcium nitrate and 1.5 g of triethyl phosphate in 40 g of ethanol. The precursors of the sol are present in the ratio Ca/PO.sub.4= 10/6. The maximum absorption capacity of the pores of the zirconia ceramic blank is 1.55 g of the solvate. Simultaneously with or subsequent to the loading (C), the distribution (D) of the bioactive surface material is effected, the solution having a higher concentration within the surface area than within the core area. For controlling, at least one environmental parameter, in particular the humidity and/or the pressure and/or the temperature is regulated for generating environmental parameter gradients. Preferably, a temperature of 25° C. and a humidity of 30% are set in the chamber, resulting in a temperature or humidity gradient between the first surface and the loading surface. In an optional CAD/CAM processing step (E), the cylindrical ceramic blank can be milled into the desired spatial form. The distribution of the bioactive surface material may be controlled prior so as to give volume areas with increased concentration of the bioactive surface material within the starting body. These areas preferably become outer surfaces or surfaces of an implant blank by the subsequent milling. In a crystallization step, the bioactive surface material is crystallized, whereby the concentration of the solution within the surface area is increased by vaporization and/or evaporation and/or drying up to a saturation concentration. During a crystal growth step (F), a crystalline layer of the bioactive surface material is formed starting from the first surface of the starting body. Depending on the desired layer thickness and structure of the crystalline surface coating, the growth phase takes for example, three days within the closed chamber. To terminate the crystal growth, the starting material is rinsed for a further two days with pure solvent, preferably ethanol, in order to remove residues of the hydroxyl apatite sol, in particular from the core area of the starting body. If the starting body was previously loaded by means of parallel loading, i.e., with a loading body having multiple loading zones arranged side by side, the need for rinsing can be avoided. By means of the parallel loading, it is possible to load the core area with a solution which in turn does not contain any bioactive surface material, while simultaneously supplying bioactive surface material to the surface area. In this way, the core area remains completely free of HAp residues during the method and also after completion of the dental implant, since the pores of the core area are “blocked” by taking up the HAp-free solution. Subsequently, drying for three days at 25° C. and 20% humidity can take place. By increasing the hydroxyapatite sol concentration, the crystal growth is accelerated, by increasing the duration of the crystal growth step, a higher layer thickness can be set. Another option in this context is to increase the drying time to 30 days at 22° C. and 40% humidity. A final end- or densely sintering turns the bioactively coated implant blank finally into the implant. The sintering takes place in a sintering furnace in a range of 1300-1600, usually at about 1450° C. (depending on manufacturer or material) for 4 hours. The sintering process causes calcification, resulting in a synthetic hydroxyapatite. A final heat treatment at 150-200° C. for an additional 4 hours is advantageous. For another 10-50 hours, a hydrothermal heat treatment should be included 150-200° C. to convert tricalcium phosphate (TCP) to hydroxyapatite (HAp).

(10) FIG. 3 shows a schematic representation of a rotationally symmetrical dental implant blank or starting body 100, which is arranged in a closed environment 200. In the present example, the sealed environment 200 is configured as a chamber 201, but it could also be, for example, a cabinet or space for receiving multiple or a plurality of dental implant blanks 100. The dental implant blank 100 is configured in one piece and has an implant body 105, a transition section 108 and an abutment 110. Furthermore, the dental implant blank 100 comprises a core area 101 and a surface area 102 which, starting from a first surface 103, extends in the direction of the core area 101 and preferably merges seamlessly with the core area 101. The first surface 103 comprises the lateral surface as well as the outer surface of the hemispherical end section of the dental implant blank 100 and is arranged entirely within the closed environment 200. The transition section 108 adjoins the implant body 105 and ends in the abutment 110, which protrudes from the closed environment. In the area of the transition section 108, the closed environment is sealed to the outer environment 300 by means of an insulation 202 (not shown), for example a silicone gasket or the like.

(11) The outer surface 104 of the abutment 110 and the bearing surface 106 facing in the direction of the abutment of the transition section 108 are each arranged as a second surface or loading surface. For this purpose, the abutment 110 is received by a loading body 400, which is located in a loading reservoir 401. The loading body 400 is provided with a recess 402 whose shape is adapted to the dimensions of the abutment 110 in order to receive the abutment 110. The use of the loading body 400 is an optional implementation of the method. Alternatively, the loading surfaces, i.e. the outer surface 104 and/or the bearing surface 106 may also be arranged directly within the loading reservoir 401. The loading body 400 has a first loading zone 404 and a second loading zone 405, which, as described above, are suitable for receiving different solutions or identical solutions having different concentrations. According to an alternative embodiment which is not shown, the dental implant blank 100 is made in two parts. In this variant, the abutment 110 is unscrewed from the implant body 105, so that only the bearing surface 106 rests on the loading body 400. A recess 402 for receiving the abutment 110 is therefore not required. Instead of the recess 402, for example, the second loading zone 405 could be arranged to allow a parallel loading of the bearing surface 106. In this way, the core area 101 could, for example, be loaded with pure solvent 501 or with a solution 500, which in particular has cerium and/or calcium and/or zirconium, but no bioactive surface material 502, while at the same time the surface area 102 is loaded with a solution 500 comprising a bioactive surface material 502 via the same bearing surface 106. This ensures that the core area 101 remains free of bioactive surface material 502.

(12) The loading reservoir 401 is filled with a fixed volume of a solution 500 which comprises a solvent or a dissolver 501, in particular distilled water, ethanol and/or acetic acid and a bioactive surface material or solvate 502 such as hydroxyapatite. The loading reservoir 401 is sealed against the outer environment 300 to prevent evaporation of the solvent, which would lead to a change in the concentration of the solution. Alternatively and not shown, closable inflows and outflows can be provided to allow a continuous refilling of the solution 500 or to change the concentration of the solution 500, if necessary. During the loading step, the solution 500 is supplied to the loading surfaces 104, 106 by means of the loading body 400, which has one or more loading zones 404, 405. The solution is absorbed from the loading surfaces 104, 106 due to the capillary force and/or concentration differences or environmental parameter gradients that are adjustable within the closed environment 200 relative to the loading reservoir 401. To complete the loading step, the loading reservoir 401 and the loading body 400 are removed.

(13) During the distribution control step, which may be concurrent or subsequent to the loading step, a convection flow 503 is generated within the pores of the dental implant blank 100. For this purpose, environment parameter gradients, in particular by changing the temperature, the pressure and/or the humidity are generated within the closed environment 200. Chamber 201 has suitable means for this purpose. The solution is preferably directed to the first surface 103 or to the surface area 102 of the dental implant blank 100.

(14) In order to start the crystallization of the bioactive material 502, drying and/or vaporization of the solvent 501 on the first surface 103 of the dental implant 100 is achieved by (hot) air nozzles 203. The temperature and the volume flow of the air supply can be controlled independently of one another. In order to discharge the supplied air and the vaporized solvent 501, chamber 201 has a ventilation flap 204. Alternatively or additionally, other venting means, such as valves, outlets or the like may be provided. By drying and/or vaporization, the concentration of the dissolved bioactive surface material 502 at the first surface 103 and within the pores of the surface area 102 is increased up to a saturation concentration. Within the pores of the surface area 102, initial crystals are formed which, starting from the first surface 103, form a crystalline layer or a crystalline surface coating 503. In order to ensure an air supply as uniformly as possible by means of the (hot) air nozzles, the loading reservoir 401 is rotatably mounted on a turntable 403, whereby the dental implant blank 100 is rotatable within the chamber 200.

(15) In a subsequent crystal growth step, the crystalline surface coating 503 grows to the desired layer thickness. Further, during the crystal growth step, solution 500 may be loaded, the distribution of the solution 500 may be controlled by regulating environmental parameter gradients, and drying and or vaporization of the solvent 501 may be effected at the first surface 103 of the dental implant blank 100. The duration of the crystal growth step depends on the desired layer thickness as well as the amount of bioactive surface material 502 with which the dental implant blank 100 was or is loaded. A UV lamp 204 integrated in the chamber contributes to the faster curing of the crystalline surface coating 503.

(16) In an optional coefficient of thermal expansion balancing step, the dental implant blank 100 is loaded with a balancing solution 500 containing cerium and/or zirconium and/or calcium. For this purpose, the outer surface 104 of the abutment 110 is preferably used as the loading surface, in order to introduce the balancing solution 500 in a targeted manner into the core area 101 of the dental implant blank. Alternatively, the solution can also be introduced into the core area by means of the distribution control step. The purpose of the balancing solution 500 is to remove any residues of the bioactive surface material 502 from the core area. A cleaning of the core area can also be carried out by rinsing with pure solvent 501. On the other hand, a thermal expansion coefficient balancing takes place in that the residual volume of the pores is filled with cerium and/or zirconium and/or calcium, whereby a profile of the thermal expansion coefficient starting from the first surface 103 towards the core area 101 arises.

(17) In a final end- or densely sintering step, the dental implant blank 100 is densely sintered to the finished dental implant at temperatures around 1450° C. Here, the crystalline surface coating 503 obtains its final structure, wherein the layer thickness decreases by the sintering process.

(18) FIG. 4 schematically shows the course of the formation of a bioactive, crystalline surface coating 503 starting from a first surface 103 of a porous starting body or a dental implant blank 100. FIG. 5 in each case shows an associated microscopic image of the crystalline surface coating 503. FIGS. 4a and 5a show the formation of first crystal nuclei which form out of the pores 107 below condensed solvent droplets 504. The crystal seeds are grown after drying for 3 days on a first surface 103 of a porous zirconia ceramic. The zirconia ceramic was loaded prior with a hydroxyapatite sol (2.5 g of calcium nitrate, 1.5 g of triethyl phosphate dissolved in 40 g of ethanol). The drying was carried out in a device according to FIG. 2 at 25° C. and 30% humidity. By continuous removal of solvent, in particular by drying and/or evaporation and/or vaporization (see FIGS. 4b and 5b) for a further 48 hours, the crystal growth proceeds, whereby an increasingly dense bioactive, crystalline surface coating 503 is formed. By further increasing the duration of the growth step, a layer thickness of up to 2000 μm can be formed. Crystal interstices 505 are formed between the individual crystals, which compact by a final end-sintering at about 1450° C. to form the surface structure 506 of the bioactive, crystalline surface coating 503 (FIGS. 4c and 5c). For sintering, the implant blank 100 is placed in a sintering furnace. The temperature is increased in steps of 3° C. per minute to 1450° C. The implant blank 100 remains for about 2.5 hours at this temperature in the sintering furnace. Subsequently, the temperature in the oven is lowered in steps of 3° C. per minute to 200° C.

(19) FIG. 6 shows a micrograph of a crystalline surface coating 503, wherein individual areas 109 of the first surface 103 of the starting body 100 have been isolated from crystal growth or the formation of the crystalline surface coating 503. The diameter of an isolated area 109 is about 0.30 mm. The starting body used was a porous zirconia ceramic which was infiltrated or loaded with a hydroxyapatite sol. The hydroxyapatite sol used was prepared from 20 g of calcium nitrate, 20 g of distilled water and 12.8 g of triethyl phosphate. At the time of the absorption, the starting body had been subjected to crystal growth at 25° C. and 30% humidity already for 3 days in a device according to FIG. 2. Prior to loading, the areas 109 were isolated by paint application by means of a printer to prevent crystal growth. However, the isolation of the areas 109 can also be effected in other ways, for example by coating or by applying a film.

(20) In FIG. 7, an alternative variant of the method is shown schematically. As a starting body, for example, a cylindrical, plate-shaped, porous blank made of metal or ceramic is used. The blank is loaded simultaneously or sequentially with different solutions. Preferably, at least one first solution contains a bioactive, crystallizable surface material 502, at least one second solution of a chemical substance for affecting physical properties 600, for example for affecting the hardness, and at least one third solution of coloring components 700. The distribution of the respective solutions can be controlled in such a way that areas with an increased concentration of bioactive material, areas with increased concentration of hardness-reducing stabilizers 610 and areas with increased concentration of coloring components 710, for example for coloring with the gingival color pink, form. From the plate-shaped blank then a dental implant blank 100 and/or a dental prosthesis blank or also a jaw bone replacement blank 111 may be milled by CAD/CAM and subjected to the remaining process steps. 1 dental prosthesis 2 dental implant 3 tooth 4 tooth root 5 implant body 6 external thread 7 jaw bone 8 transition section 9 gums 10 abutment 100 porous starting body/dental implant blank 101 core area 102 surface area 103 first surface 104 outer surface, loading surface 105 implant body 106 bearing surface, loading surface 107 pores 108 transition section 109 area of the first surface 110 abutment 111 dental prosthesis blank/jaw bone replacement blank 200 closed environment 201 chamber 202 insulation 203 (hot) air nozzle 204 UV lamp 300 outer environment 400 loading body 401 loading reservoir 402 recess 403 turntable 404 first loading zone 405 second loading zone 500 solution 501 solvent/dissolver 502 bioactive surface material/solvate 503 crystalline layer/crystalline surface coating 504 solvent drop 505 crystal interstices 506 surface structure 510 area with increased concentration of bioactive material 600 chemical substance for affecting physical properties 610 area with increased concentration of hardness-lowering stabilizers 700 coloring components 710 area with increased concentration of coloring components