Infiltrant for dental ceramics

Abstract

An infiltrant comprising from 90 to 99.9 wt.-% of at least one polymerizable monomer, oligomer or prepolymer and from 0.05 to 10 wt.-% of a polymerization initiator, the infiltrant having a dynamic viscosity of 0.3 to 100 mPa.Math.s (23 C.); for use in a method for strengthening a fixed ceramic dental prosthesis in the oral cavity.

Claims

1. A method for strengthening a fixed ceramic dental prosthesis in the oral cavity comprising the following steps: a) drying of a ceramic surface layer, b) applying onto the dried ceramic surface layer an infiltrant comprising from 90 to 99.9 wt.-% of at least one polymerizable monomer, oligomer or prepolymer and from 0.05 to 10 wt.-% of a polymerization initiator, the infiltrant having a dynamic viscosity of 0.3 to 100 mPa.Math.s (23 C.), and c) curing the infiltrant in the ceramic surface layer.

2. The method of claim 1, wherein drying of the ceramic surface layer is by purging said ceramic surface layer with an organic solvent having an Evaporation Index of 1 to 35.

3. The method of claim 2, wherein said organic solvent has an Evaporation Index of 1 to 15.

4. The method of claim 1, wherein prior to drying said ceramic surface layer, said ceramic surface layer of said fixed prosthesis is cleaned and/or rinsed.

5. The method of claim 1, wherein after applying said infiltrant, the method comprises cleaning the surface of the ceramic surface layer from adherent infiltrant.

6. The method of claim 1, wherein after curing said infiltrant in said ceramic surface layer, said method comprises cleaning and/or polishing the surface of the ceramic surface layer.

7. The method of claim 1, wherein said infiltrant has a dynamic viscosity of 0.3 to 60 mPa.Math.s (23 C.).

8. The method of claim 7, wherein said infiltrant has a dynamic viscosity of 0.3 to 30 mPa.Math.s (23 C.).

9. The method of claim 7, wherein said infiltrant has a dynamic viscosity of 2 to 15 mPa.Math.s (23 C.).

10. The method of claim 1, wherein said infiltrant comprises 3-30 wt. % of polymerizable monomers, oligomers or pre-polymers having one or more further functional group(s) selected from: a) hydroxy group (OH), b) groups containing a hydroxy group, c) silanol groups (SiOH), d) groups which can be hydrolyzed to yield silanol groups.

11. The method of claim 10, wherein said groups containing a hydroxy group are selected from the group consisting of carboxylic acid groups (COOH), phosphoric acid ester groups (OPO(OH).sub.2), and phosphonic acid groups (PO(OH).sub.3).

12. The method of claim 10, wherein said infiltrant comprises at least 65 wt.-% of polymerizable monomers, oligomers or pre-polymers having 2 or more polymerizable groups.

13. The method of claim 12, wherein said infiltrant comprises: a) 45 to 75 wt.-% of polymerizable monomers, oligomers or pre-polymers having 2 polymerizable groups, b) 20 to 50 wt.-% of polymerizable monomers, oligomers or pre-polymers having 3 or more polymerizable groups c) 3-30 wt.-% of polymerizable monomers, oligomers or pre-polymers having one or more further functional group(s) selected from: i) hydroxy group (OH), ii) groups containing a hydroxy group, iii) silanol groups (SiOH), and iv) groups which can be hydrolyzed to yield silanol groups.

14. The method of claim 13, wherein said groups containing a hydroxy group are selected from the group consisting off carboxylic acid groups (COOH), phosphoric acid ester groups (OPO(OH).sub.2), and phosphonic acid groups (PO(OH).sub.3).

15. The method of claim 13, wherein said infiltrant comprises: a) 2.5-9.5 wt.-% of polymerizable monomers, oligomers or pre-polymers having one or more silanol groups (SiOH), or groups which can be hydrolyzed to yield silanol groups, and b) 0.5-7.5 wt.-% of polymerizable monomers, oligomers or pre-polymers having one or more carboxylic acid groups (COOH), phosphoric acid ester groups (OPO(OH).sub.2) or phosphonic acid groups (PO(OH).sub.3).

Description

EXAMPLES

(1) The following substances were used in the examples

(2) TABLE-US-00001 Abbre- Substance viation Triethylene glycol dimethacrylate (Evonik, Germany; TEDMA ~10 mPa * s at RT) 1,6-Hexanediol dimethacrylate (Esstech, US) HDDMA Diurethane dimethacrylate, mixture of isomers, CAS UDMA 72869-86-4 (Genomer 4297, Rahn, Switzerland) Bisphenol A glycerolate dimethacrylate, CAS 1565-94-2 BisGMA (CCP Composites, US) Ethoxylated (EO).sub.3 trimethylolpropane triacrylate ETMPTA (Miramer 3130, Rahn, Switzerland, ~60 mPa * s at RT) Trimethylolpropane trimethacrylate (Visiomer TMPTMA TMPTMA, Evonik, Germany) 3-(Trimethoxysilyl) propyl methacrylate (Dynasylan MEMO MEMO, Evonik, Germany, ~3 mPa * s at RT) 10-Methacryloyl-oxydecyl-dihydrogenphosphate MDP Camphorquinone (Rahn, Switzerland) CQ 2-Ethylhexyl-p-dimethylaminobenzoate (Genocure EHA EHA, Rahn, Switzerland) Butylated hydroxytoluene BHT Ethyl-p-dimethylamino benzoate, 99% purity, Alfa Aesar EDAB Poly(methyl methacrylate), Degacryl MW 332, Evonik PMMA Industries,

Preparatory Example 1

(3) In a light protected glass container 59.2 parts per weight TEDMA, 14.8 parts per weight ETMPTA, 0.5 parts per weight CQ, 0.8 parts per weight EHA and 0.0015 parts per weight BHT were mixed and the mixture was stirred at ambient temperature by means of a magnetic stirrer until a homogeneous clear solution was obtained. This solution was kept at room temperature under exclusion of light (which may cause curing). In a light protected glass container 75 parts per weight of the solution were mixed with 25 parts per weight of MEMO by means of a magnetic stirrer until a clear and homogeneous solution was obtained. Thereafter this infiltrant was used for the treatment of damaged ceramic surfaces.

(4) The viscosity of the infiltrant was measured using a Malvern Kinexus Rheometer (Malvern Instruments GmbH, Germany) equipped with a coaxial cylinder device for the measurement of liquids according to DIN 53019 with a cone of 25 mm in diameter in a cylinder of 27 mm diameter at a temperature of 23 C. A volume of approximately 18 ml of the infiltrant was used in the cylinder. The measurement was made under exclusion of ambient light to prevent polymerization. The following parameters were applied: Table of shear stresses from 0.1 Pa to 1 Pa. The viscosity value at 0.126 Pa shear stress was taken. The viscosity of the infiltrant was 6.2 mPa.Math.s.

Preparatory Examples 2 to 7

(5) In a light protected glass container under yellow light conditions for each preparatory example substances were mixed as specified in Table 2 and the mixtures were stirred at ambient temperature by means of a magnetic stirrer until homogeneous clear solutions were obtained. The solutions were kept at room temperature under exclusion of light until the infiltrants were used for the treatment of damaged ceramic surfaces.

(6) The viscosity of the infiltrants was measured using a dynamic plate/plate viscometer (DSR, Dynamic Stress Rheometer, Rheometric Scientific, Inc., US). Measurements took place in steady stress sweep mode with slot sizes of 0.1 to 0.5 mm in the range from 0 to 50 Pa shear stress without preliminary shearing of the infiltrants. The viscosity of the infiltrants is given in Table 1.

(7) TABLE-US-00002 TABLE 1 Compositions prepared in the preparatory examples; values given in parts per weight; viscosity of the samples according to the method described. Preparatory Example Substance 1 2 3 4 5 6 7 TEDMA 59.2 32.0 28.8 30.4 28.83 22.4 22.4 HDDMA 57.5 51.34 54.5 51.69 40.1 40.1 UDMA BisGMA ETMPTA 14.8 8.0 7.2 7.6 7.21 30.0 TMPTMA 30.0 MDP 5.1 5.0 5.0 5.0 5.0 MEMO 25 5.0 CQ 0.5 0.5 0.5 0.5 0.5 0.5 0.5 EHA 0.8 EDAB 2.0 2.0 2.0 2.0 2.0 2.0 BHT 0.0015 0.002 0.003 0.003 0.002 0.002 0.002 PMMA 4.76 Viscosity/ 6.2 7.1 8.9 9.1 56.4 13.7 11.8 mPa .Math. s

Example 1Healing of Damaged Dental Ceramic Surface Using an Infiltrant

(8) Ceramic specimen (disks, =12.5 mm and 1.2 mm in thickness) were produced using a glass-ceramic powder material (VM9, Vita Zahnfabrik) by condensation and sintering. Sintering was conducted in an oven (Vacumat 4000, Vita Zahnfabrik) according to the following program: 55 C./min heating rate, holding time of 1 min at 940 C. under vacuum and cooling rate of 30 C./min. The sintered discs were reduced to the final thickness by grinding with a diamond wheel and subsequently mirror polished with SiC papers (Buehler) from 320, 600, 100, 1200, 2500 down to 4000 grit on the side subjected to tension.

(9) Specimens of the experimental groups were further prepared according to two surface treatments: (i) bur treatment with a coarse diamond bur (Komet bur #220) at 2500 rpm for 10 s with air cooling; (ii) sandblasted with 35 m-sized aluminum oxide particles at 2 bar pressure for 10 s in an angle of 45. An optical confocal profilometer was used to measure the mean roughness (Ra) of treated samples, which resulted in Ra=30 m for the grinded specimens, and Ra=5 m for the sandblasted specimens. The damaged surfaces were subsequently infiltrated.

(10) The infiltrant was applied twice with a micro brush onto the ceramic surface and left untouched for 30 s. After this time the infiltrant was removed from the surface using a cotton pellet, leaving the surface shiny. Subsequently, the infiltrated ceramic surface was light-cured, using a halogen blue-light lamp (Elipar Trilight, 3M ESPE) for 240 s at a light intensity of 800 mW/cm.sup.2. Light intensity was periodically controlled with a radiometer. After light-curing the ceramic discs were stored in vials containing distilled water, sealed and stored in a heating module at 37 C.

(11) After 24 h of water storage, the specimens from the control group (polished, n=15) and the experimental groups (grinded and sandblasted, n=15) were tested in flexure using the piston-on-three-balls set-up, according to the ASTM F 394-78 standard. The test was conducted in a universal testing machine (Zwick 2.5, Zwick, Germany) at a cross-head speed of 0.75 mm/min until fracture in air.

(12) Mean roughness (Ra) values for bur-treated and sandblasted samples were 30 m and 5 m, respectively. Shape and scale parameters for the Polished samples were as follows: m=10.3 and .sub.0=101.2 MPa. For Bur-treated samples: m=7.6 and .sub.0=66.4 MPa for Bur Control; m=9.0 and .sub.0=84.2 MPa for Bur Infiltrated. For Sandblasted samples: m=12.6 and .sub.0=78.2 MPa for Sandblasted Control; m=8.8 and .sub.0=99.98 MPa for Sandblasted Infiltrated. The increase in .sub.0 after infiltration was significant at a 95% level for both Bur-treated and Sandblasted samples. The infiltration of smaller defects (Sandblasted samples) restored the strength to the level of the polished control, being more efficient than infiltration of larger defects (Bur-treated samples).

(13) The infiltration of defects created by coarse bur or sandblasting has shown to increase the strength of dental ceramics in comparison to non-infiltrated damaged ceramic samples. The infiltration of small defects may restore the strength of dental ceramics to its initial values. The infiltration of damaged areas, whether created by the dentist during intra-oral adjustments or during function, has the potential to increase the lifetime of dental ceramic prostheses by delaying crack growth and fracture.

Example 2Surface Crack Healing With Infiltrants: Glass Versus Feldspathic Ceramics

(14) As comparison specimen Soda-lime glass discs (0=15 mm and 1.9 mm in thickness; Schott, Germany) were used. A Vickers indent (Zwick, Germany) was produced on the tensile side of the ceramic discs from example 1 and the Soda-lime glass discs (1 kg during 15 s for VM9 and 500 g during 15 s for glass). Infiltration was carried out as described in Example 1.

(15) After 24 h of water storage, the discs were tested in flexure using the piston-on-three-balls set-up. Weibull parameters m and .sub.0 were calculated (n=15 for VM9 and n=10 for glass) and mathematically corrected according to the n number. The infiltration depth into the Vickers indent was measured in samples infiltrated with a fluorescent dyed-infiltrant using a confocal laser scanning microscope (TCS SL, Leica, Germany).

(16) Shape and scale parameters for the Glass samples were as follows: m=7.0 and .sub.0=335.9 MPa for Polished; m=5.9 and .sub.0=106.8 MPa for Indented; m=8.2 and .sub.0=223.2 MPa for Infiltrated. Shape and scale parameters for the Ceramic VM9 samples were as follows m=10.3 and .sub.0=101.2 MPa for Polished; m=11.4 and .sub.0=63.52 MPa for Indented; m=5.1 and .sub.0=83.9 MPa for infiltrated. The increase in .sub.0 after infiltration was significant at a 95% level for both Glass and Ceramic. Infiltration depth in glass samples was recorded up to 18 m in depth, while in ceramics the infiltration depth was 2-4 m in depth (subsurface layer).

(17) As in glass, the infiltration of surface cracks with low-viscosity infiltrants and subsequent hardening is able to strengthen veneering ceramics and potentially prevent chipping events. The infiltration depth in ceramics is limited but does not seem to hinder its reinforcing effect.

(18) The results of Example 1 and Example 2 are summarized in Table 2.

(19) TABLE-US-00003 TABLE 2 Biaxial flexural strengths of sintered ceramic discs and soda lime glass discs of Examples 1 and 2 with different pretreatments of the glass/ceramic surface. Infiltration of the surface was performed using the infiltrant from preparatory example 1. Example 1 Example 2 Feldspar glass ceramic disks Soda lime glass disks P S SI B BI I II W I II Mean roughness 5 30 [m] Weibull - m 10.3 12.6 8.8 7.6 9.0 11.4 5.1 7.0 5.90 8.20 Weibull - .sub.0 101.2 78.2 100.0 66.4 84.2 63.5 83.9 335.9 106.8 223.2 [MPa] Ppolished 4000 grit, Ssandblasted, SIsand-blasted and infiltrated, Bbur treated, BIbur treated and infiltrated, Iindented, IIindented and infiltrated, Wwithout treatment

Example 3Healing of Dental Ceramic Surfaces Damaged by Sandblasting Using the Infiltrants of Preparatory Examples 2-7

(20) Ceramic plates (1212 mm) were cut from fine structured feldspar ceramic blocks (Vitablocs Mark II, Vita, Germany) and reduced to the final thickness (1.30.05 mm) by grinding with a diamond wheel as described in Example 1.

(21) The ceramic plates were subjected to two different surface treatments:

(22) (i) mirror polished with SiC papers (Buehler) down to 4000 grit on the side subjected to tension and;

(23) (ii) sandblasted with 35 m-sized aluminum oxide particles at 2 bar pressure for 5 s in an angle of 45.

(24) Each infiltrant was applied once with a microbrush onto the ceramic surface and left untouched for 30 s. After this time the infiltrant was removed from the surface using a cotton pellet, leaving the surface shiny. Subsequently, the infiltrated ceramic surface was light-cured, using a halogen blue-light lamp (Unilux AC Kulzer) for 160 s at a light intensity of 800 mW/cm.sup.2. After light-curing, the infiltrated samples were stored dry at room temperature. The specimens from the control group (polished, n=15) and the experimental group (sandblasted, n=15) were tested in flexure using the piston-on-three-balls set-up according to the method 2 described above. The results of Example 3 are summarized in Table 3.

(25) TABLE-US-00004 TABLE 3 Biaxial flexural strengths of sandblasted ceramic discs of example 3 treated with infiltrants of the respective preparatory examples; comparison with polished discs and sandblasted discs not treated with an infiltrant. Example 3 Feldspar glass ceramic disks Sandblasted and infiltrated Preparatory Example No. pol- sand 4 3 5 6 ished blasted 2 MDP MEMO PMMA TA TM Biaxial 113.6 104.7 128.3 123.4 127.4 125.7 137.4 14 flexural strength [MPa]

Example 4Adhesion Test of Infiltrant on Ceramic

(26) To test the adhesion of infiltrants to feldspatic porcelain the adhesion test described above was applied. The results are summarized in Table 4.

(27) TABLE-US-00005 TABLE 4 Adhesion of infiltrants to Feldspatic ceramic rods in tensile testing Preparatory example No. 3 4 7 Adhesion/MPa 6.8 4.7 4.4

(28) Examples show that the degradation of the surface either by sandblasting or by indenting the ceramic surface yield marked deteriorations of the mechanical properties of the ceramic bodies (derived from biaxial flexural strength). The applied surface degradation methods serve as models for the intraoral degradation of ceramic restorations.

(29) The infiltration of the surface degraded specimens in Examples 1 and 2 results in improved mechanical properties up to the mechanical properties of the mirror polished original specimens.

(30) Using the infiltrants of example 3 (preparatory examples no. 2-7) yields mechanical properties even superior to the polished control.

(31) Particularly compositions containing extremely high amounts of monomers bearing two or three polymerizable groups in the molecule (preparatory examples no. 6 and 7) used as infiltrants for the ceramic surface show the highest reinforcing effect.

(32) From the data of example 4 it can be derived that the addition of a silane and an acid is preferred. Thereby the addition of only small amounts of silanes like MEMO and acids like MDP is preferred, in order to not decrease the amount of monomers bearing two or in particular three polymerizable groups in the molecule to an undesirably low extend.

(33) A higher durability and a greater potential for the stabilization of roughened dental ceramic surfaces can be expected in particular from ceramic infiltrants containing high amounts of crosslinkable Monomers comprising at least three polymerizable groups and lower amounts of monomers comprising a silanol group.