Dental composition containing high refractive index monomers

1. A curable dental composition comprising:

a) at least one dental resin comprising at least two ethylenically unsaturated groups;

b) a high refractive index monomer;

c) an addition fragmentation agent; and

d) optionally an inorganic oxide filler,

said high refractive index monomer is of the formula:

wherein

R 1 is H or C 1 -C 4 alkyl,

X 1 is —O— or —NR 1 —,

R 2 is a alkylene, optionally substituted by a hydroxyl group;

a is 1 or 2;

b is 0 or 1;

Y 10 is —O—CO—, —NR 3 —CO—, where R 3 is H, C 1 -C 4 alkyl, NH—CO—O—, or —O—CO—NH—, or

and

R RI is a high refractive index group selected from 2, 3-, and 4-biphenyl, 1-, 2, 3-, 4-, and 9-fluorenyl, 4-(1-methyl-1-phenethyl)phenoxyethyl; phenylthio; 1-, 2-, 3- and 4-napthyl, 1- and 2-naphthylthio; 2,4,6-tribromophenoxy; 2,4-dibromophenoxy; 2-bromophenoxy; 1-, and 2-naphthyloxy; 3-phenoxy-; 2-, 3- and 4-phenylphenoxy; 2,4-dibromo-6-sec-butylphenyl; 2,4-dibromo-6-isopropylphenyl; 2,4-dibromophenyl; pentabromobenzyl and pentabromophenyl.

2. The curable dental composition of claim 1 wherein the addition-fragmentation agent is of the formula:

wherein

R 21 , R 22 and R 23 are each independently Z m -Q-, a (hetero)alkyl group or a (hetero)aryl group with the proviso that at least one of R 21 , R 22 and R 23 , is Z m -Q-,

Q is a linking group have a valence of m+1;

Z is an ethylenically unsaturated polymerizable group,

m is 1 to 6;

each X 1 is independently —O— or —NR 1 —, where R 1 is H or C 1 -C 4 alkyl, and

n is 0 or 1.

3. The curable dental composition of claim 1 comprising at least 0.1 wt. %, of addition-fragmentation agent.

4. The curable dental composition of claim 1 wherein R 2 is —(C t H 2t )— or —[C t H 2t-1 (OH)], where t is 2 to 10.

5. The curable dental composition of claim 1 comprising:

a) 100 parts of at least one dental resin comprising at least two ethylenically unsaturated groups;

b) 1 to 50 parts by weight of the high refractive index monomer, relative to 100 parts by weight dental resin; and

c) at least 0.1 parts of addition-fragmentation agent(s), and

d) optionally an inorganic oxide filler.

6. The curable dental composition of claim 1 further comprising at least 1 part inorganic filler relative to 100 parts of dental resin.

7. The curable dental composition of claim 1 wherein the dental resin comprises an aromatic monomer having a refractive index of at least 1.50.

8. The curable dental composition of claim 1 wherein the dental resin is a low volume shrinkage resin.

9. The curable dental composition of claim 1 wherein the dental resin is an isocyanurate resin, a tricyclodecane resin, cyclic allylic sulfide resins; methylene dithiepane silane resins; and poly(meth)acryloyl-containing resins, or mixtures thereof.

10. The curable dental composition of claim 1 wherein the dental resin further comprises at least one other (meth)acrylate monomer is selected from ethoxylated bisphenol A dimethacrylate, 2-hydroxyethyl methacrylate, bisphenol A diglycidyl dimethacrylate, urethane dimethacrylate, triethlyene glycol dimethacrylate, glycerol dimethacrylate, ethylenegylcol dimethacrylate, neopentylglycol dimethacrylate (NPGDMA), polyethyleneglycol dimethacrylate, and mixtures thereof.

11. The curable dental composition of claim 1 wherein the inorganic oxide filler comprises nanoparticles.

12. The curable dental composition of claim 11 wherein the inorganic oxide nanoparticles comprise silica, zirconia, or mixtures thereof.

13. The curable dental composition of claim 11 wherein the inorganic oxide nanoparticles are in the form of nanoclusters.

14. The curable dental composition of claim 11 comprising a surface modified inorganic oxide filler.

15. A method of treating a tooth surface, the method comprising

a) providing a curable dental resin of claim 1 ;

b) placing the dental composition on a tooth surface in the mouth of a subject; and

c) hardening the hardenable dental composition.

16. The method of claim 15 wherein the dental composition is a dental restoration composition.

17. A dental article comprising the curable dental composition of claim 1 at least partially cured.

18. A universal dental restorative comprising:

a) 15-30 wt. % of a curable dental composition of claim 1 ;

b) 70-85 wt. % of an inorganic filler;

c) an initiator and

<2%, stabilizers or pigments.

19. A flowable restorative composite comprising:

a) 25-50 wt. % of a curable dental composition of claim 1 ;

b) 30-75 wt. % of an inorganic filler;

c) an initiator;

d) <2% stabilizers and pigments; and

e) optionally 5-60 wt. % monomers having an acid-functional group.