Low stress flowable dental compositions

Abstract

A photopolymerizable and photocleavable (P&P) resin monomer is derived from a reactive photoresponsible moiety via various linkages to form photopolymerizable monomers and/or oligomers.

1 . A method of reducing stress during curing of a polymerizable material of the type having a cross-linked network with a pre-gel phase and a post-gel phase, the improvement comprising selectively breaking at least a portion of the cross-link network thereby inducing a stress-relief period. 
     
     
         2 . A method as in  claim 1 , wherein the polymerizable is a photopolymerizable and photocleavable resin. 
     
     
         3 . A method as in  claim 2  wherein said resin is photocleavable upon exposure to UV light. 
     
     
         4 . A method as in  claim 2  wherein said resin has a segment selected from the group consisting of ortho-nitrobenzyl and α-hydroxyalkylphenone. 
     
     
         5 . A dental material comprising a photopolymerizable and photocleavable resin, wherein said resin forms a cross-linked network upon curing and which as a pre-gel and post-gel phase; at least a portion of said cross-linked network being breakable upon exposure to light. 
     
     
         6 . A dental material as in  claim 5 , wherein said resin has a segment selected from the group consisting of ortho-nitrobenzyl and α-hydroxyalkylphenone. 
     
     
         7 . A dental material as in  claim 5 , wherein said light is in the UV range.