Radical Polymerization Inhibitors for Light-Curable Dental Materials

Abstract

The invention relates to light-curable dental materials comprising at least one polymerizable compound having at least one ethylenically unsaturated bond and a hexaarylbisimidazole, e.g. as a photopolymerization initiator. The invention also relates to the use of a hexaarylbisimidazole polymerization initiator in light curable dental materials and also to cured dental materials obtainable by light-curing the light-curable dental materials of the invention.

1 . A light-curable, dental material comprising
 (i) a polymerizable compound having at least one ethylenically unsaturated bond and   (ii) a hexaaryl bisimidazole.   
     
     
         2 . The light-curable dental material according to  claim 1 , further comprising an α,β-diketone as a polymerization initiator and optionally a polymerisation inhibitor. 
     
     
         3 . The light-curable dental material according to  claim 1 , further comprising a solid particulate filler. 
     
     
         4 . The light-curable dental material according to  claim 1 , wherein said hexaaryl bisimidazole has the following structure (I):
   Ar 3 T−TAr 3   (I)
   wherein each T is an imidazole moiety and each Ar stands for an optionally substituted aryl group that may be the same or different and wherein the substitution on different groups Ar may be the same or different.   
     
     
         5 . The light-curable dental material according to  claim 1 , wherein the hexaaryl bisimidazole is a homodimer or a heterodimer obtainable by oxidation of any of the triarylimidazoles represented by the following formula: 
       
         
           
           
               
               
           
         
         wherein Ar 1 , Ar 2 , and Ar 3  may be the same or different and each represents an optionally substituted aryl group and multiple Ar 1 , A 2 , or Ar 3  on the same hexaarylbisimidazole may be the same or different. 
       
     
     
         6 . The light-curable dental material according to  claim 1 , wherein the hexaaryl bisimidazole has the structure of the following formula: 
       
         
           
           
               
               
           
         
         wherein Ar 1 , Ar 2  and Ar 3  may be the same or different and each represents an optionally substituted aryl group and multiple Ar 1 , Ar 2  or Ar 3  on the same hexaarylbisimidazole compound may be the same or different. 
       
     
     
         7 . The light-curable dental material according to  claim 4 , wherein the aryl group is selected from phenyl and naphthyl. 
     
     
         8 . The light-curable dental material according to  claim 4 , wherein each aryl group may have 1 to 5 substituents selected from the group consisting of C 1-6 -alkyl, C 1-6 -alkoxy, hydroxy, halo, cyano, nitro, nitroso, mercapto, carboxyl, sulfonate, thiol, amino, phenyl, pyridyl, and trifluoromethyl. 
     
     
         9 . The light-curable dental material according to  claim 1 , wherein the concentration of said hexaaryl bisimidazole based on the total weight of all polymerizable compounds having at least one ethylenically unsaturated bond is from 0.01 to 2.0, preferably from 0.05 to 1.5, and most preferably from 0.1 to 1.0 weight-%. 
     
     
         10 . The light-curable dental material according to  claim 1 , further comprising a co-initiator selected from the following compound classes: thiols, heteroaromatic thiols, benzothiazoles, benzooxazoles, tertiary amines, alcohols, thiocarboxylic acids. 
     
     
         11 . The light-curable dental material according to  claim 1 , further comprising a sensitizer for extending the wavelength range usable for activating the hexaaryl bisimidazole. 
     
     
         12 . The light-curable dental material according to  claim 1 , wherein the light-curable dental material is selected from the group consisting of a dental composite, dental ionomer cement, dental sealant, dental adhesive, dental adhesion promoter, dental adhesion preventer, dental cement, dental crown-forming material, and dental impression material. 
     
     
         13 . Light-cured dental material obtained or obtainable by light curing the light-curable dental material of  claim 1 . 
     
     
         14 . The light-curable dental material according to  claim 1 , comprising a hexaaryl bisimidazole as a photoinitiator. 
     
     
         14 . Light-curable dental material comprising a solid particulate filler and a polymerizable matrix, wherein the polymerizable matrix comprises:
 (i) one or more polymerizable compounds each having at least one ethylenically unsaturated bond and   (ii) a hexaaryl   wherein the light-curable dental material is a dental composite.