Multi sectional dental zirconia milling block, process of production and use thereof

Abstract

The invention relates to a porous dental milling block comprising at least two geometrically defined Material Sections A and B, Material Section A comprising a tetragonal zirconia crystal phase in an amount A-T in % and a cubic zirconia crystal phase in an amount A-C in %, Material Section B comprising cubic zirconia crystal phase in an amount B-T in % and cubic zirconia crystal phase in an amount B-C in %, wherein (amount of tetragonal phase A-T in %)/(amount of cubic phase content A-C in %)>1 and (amount of tetragonal phase content B-T in %)/(amount of cubic phase content B-C in %)<1. The invention also relates to a process of production of the porous dental milling block and its use for producing a dental article.

What is claimed is: 
     
         1 . A process of producing a porous dental milling block comprising the steps of:
 a. casting a sol (I) containing zirconia crystallites into a mould (I), the zirconia crystallites having a crystal phase composition (1),   b. transferring the sol (I) to a gel body (I),   c. optionally transferring the gel body (I) to a mould (II),   d. casting a sol (II) containing zirconia crystallites so that it gets into contact with gel body (I), the zirconia crystallites having a crystal phase composition (2),   e. transferring sol (II) into a gel body (II),   f. optionally repeating steps (d) and (e) thereby casting additional sol(s) into either mould (II) or another mould to which the gel bodies of either step (d) or obtained after conducting step (e) have been transferred,   g. removing solvent contained in the gel bodies to obtain an aerogel,   h. heat-treating the aerogel to obtain a porous dental milling block according to  claim 1 .   
     
     
         2 . A process of producing a porous dental milling block comprising the steps of:
 providing a Mixture A of a Sol S1-T and a Sol S2-C,
 Sol S1-T comprising tetragonal zirconia crystallites, 
 Sol S2-C comprising cubic zirconia crystallites, 
   the amount of tetragonal zirconia crystallites in Sol S1-T (in wt.-% with respect to the whole Mixture A) being greater than the amount of cubic zirconia crystallites in Sol S2-C (in wt.-% with respect to the whole Mixture A),   the mixture further comprising a polymerizable system containing polymerizable component(s) and initiator component(s),   providing a Mixture B of a Sol S2-T and a Sol S2-C,
 Sol S2-T comprising tetragonal zirconia crystallites, 
 Sol S2-C comprising cubic zirconia crystallites, 
   the amount of tetragonal zirconia crystallites in Sol S2-T (in wt.-% with respect to the whole Mixture B) being smaller than the amount of cubic zirconia crystallites in Sol S2-C (in wt.-% with respect to the whole Mixture B),   the mixture further comprising a polymerizable system containing polymerizable component(s) and initiator component(s),   conducting one of the following steps:
 optionally curing Mixture A to obtain a dental milling block precursor A, 
 optionally curing Mixture B to obtain a dental milling block precursor B, bringing into contact 
 if present, Mixture A with Mixture B or 
 if present, dental milling block precursor A with Mixture B or 
 if present dental milling block precursor B with Mixture A 
   to obtain System AB,
 curing System AB to obtain a dental milling block precursor AB, 
 if present, removing remaining solvent, 
 heating the dental milling block precursor AB to a temperature where the components of the polymerizable system or polymerized system pyrolyse to obtain a porous dental milling block according to  claim 1 . 
   
     
     
         3 . A process of producing a porous dental milling block comprising the steps of:
 providing a Sol S1-T comprising tetragonal zirconia crystallites,   providing a Sol S1-C comprising cubic zirconia crystallites,   the amount of tetragonal zirconia crystallites in Sol S1-T (in wt.-% with respect to the sum of crystallites in Sol S1-T and Sol S1-C) being greater than the amount of cubic zirconia crystallites in Sol S1-C (in wt.-% with respect to the sum of crystallites in Sol S1-T and Sol S1-C),   mixing Sol S1-T and Sol S1-C to obtain a Mixture A,   adding a polymerizable system containing polymerizable component(s) and initiator component(s) to Mixture A,   casting the mixture into a mould,   optionally curing the mixture to obtain a dental milling block precursor A,   providing a Sol S2-T comprising tetragonal zirconia crystallites having a tetragonal phase content,   providing a Sol S2-C comprising cubic zirconia crystallites having a cubic phase content, the amount of tetragonal zirconia in Sol S2-T (in wt.-% with respect to the sum of crystallites in Sol S2-T and Sol S2-C) being smaller than the amount of cubic zirconia in Sol S2-C (in wt.-% with respect to the sum of crystallites in Sol S2-T and Sol S2-C),   mixing Sol S2-T and Sol S2-C to obtain a Mixture B,   adding a polymerizable system to Mixture B,   bringing the dental milling block precusor A in contact with Mixture B to obtain System AB,   drying System AB to obtain a dental milling block precursor AB,   if present, removing remaining solvent,   heating the dental milling block precursor AB to a temperature where the components of the polymerisable system or polymerized system pyrolyse to obtain a porous dental milling block according to  claim 1 .   
     
     
         4 . A process of producing a porous dental milling block comprising the steps of:
 providing a Sol A,
 Sol A comprising tetragonal zirconia crystallites in an amount A-T in wt.-% and cubic zirconia crystallites in an amount A-C in wt.-%, 
 the amount of tetragonal zirconia crystallites in Sol A being greater than the amount of cubic zirconia crystallites in Sol A, 
 Sol A further comprising a polymerizable system containing polymerizable component(s) and initiator component(s), 
 providing a Sol B, 
 Sol B comprising tetragonal zirconia crystallites in an amount B-T in wt.-% and cubic zirconia crystallites in an amount B-C in wt.-%, 
 the amount of tetragonal zirconia crystallites in Sol B being smaller than the amount of cubic zirconia crystallites in Sol B, 
 Sol B further comprising a polymerizable system containing polymerizable component(s) and initiator component(s), 
   conducting one of the following steps:
 optionally curing Sol A to obtain a dental milling block precursor A, 
 optionally curing Sol B to obtain a dental milling block precursor B, bringing into contact 
 if present, Sol A with Sol B or 
 if present, dental milling block precursor A with Sol B or 
 if present, dental milling block precursor B with Sol A 
   to obtain System AB,
 curing System AB to obtain a dental milling block precursor AB, 
 if present, removing remaining solvent,
 heating the dental milling block precursor AB to a temperature where the components of the polymerizable system or polymerized system pyrolyse to obtain a porous dental milling block according to  claim 1 . 
 
   
     
     
         5 . A process of producing a dental ceramic article comprising the step of machining and optionally sintering the porous dental milling block as described in  claim 1 —to produce a dental ceramic article. 
     
     
         6 . The process of  claim 5 , wherein the dental ceramic article has the following features after sintering:
 Comprising two Material Sections A and B,   Material Section A being less translucent than Material Section B,   Density: at least about 98.5% of theoretical density;   Biaxial flexural strength: from about 450 MPa to about 2200 MPa;   Contrast ratio reflectance value of Material Section A: from about 40 to about 90%;   Contrast ratio reflectance value of Material Section B: from about 5 to about 40%.   
     
     
         7 . A kit of parts comprising at least one porous dental milling block as described in  claim 1  and a treatment solution. 
     
     
         8 . The kit of parts of  claim 7  further comprising application equipment. 
     
     
         9 . A kit of parts comprising at least one porous dental milling block obtained according to the process of  claim 1 , and a treatment solution. 
     
     
         10 . The kit of parts of  claim 9  further comprising application equipment. 
     
     
         11 . The process of  claim 1  further comprising the step of machining and optionally sintering the porous dental milling block to produce a dental ceramic article. 
     
     
         12 . The process of  claim 11 , wherein the dental ceramic article has the following features after sintering:
 Comprising two Material Sections A and B,   Material Section A being less translucent than Material Section B,   Density: at least about 98.5% of theoretical density;   Biaxial flexural strength: from about 450 MPa to about 2200 MPa;   Contrast ratio reflectance value of Material Section A: from about 40 to about 90%;   Contrast ratio reflectance value of Material Section B: from about 5 to about 40%.