Initiator system with polymerizable thiourea component, dental composition and use thereof

1. An initiator system for curing a dental composition, the initiator system comprising

a hydroperoxide component,

a transition metal component comprising ions of Cu, Ti, V, Cr, Mn, Fe, Co, Ni, Zn or mixtures thereof,

a polymerizable thiourea component, the polymerizable thiourea component comprising a thiourea moiety which is attached to a (meth)acrylate moiety through a C 3-11 alkyl chain and having the formula

MA-S-TU-R

with

MA: (meth)acrylate,

S: C 3-11 alkyl,

TU: NH—CS—NH

R: C 1 to C 6 alkyl or cyclo alkyl.

2. The initiator system according to claim 1 , the hydroperoxide component and polymerizable thiourea component being present in a molar ratio of 3/1 to 1/2 with respect to the ratio of hydroperoxide moiety and thiourea moiety.

3. The initiator system according to claim 1 , the hydroperoxide component being selected from tetramethylbutyl hydroperoxide, t-butyl hydroperoxide, t-amyl hydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide, p-isopropylcumyl hydro-peroxide, diisopropylbenzene hydroperoxide, and diisopropylbenzene dihydroperoxide, benzene hydroperoxide, pinane hydroperoxide, 5-phenyl-4-pentenylhydroperoxide, and mixtures thereof.

4. The initiator system according to claim 1 , the polymerizable thiourea component having an average water-contact angle of more than 10° determined over a time period of 0 to 12 s at 23° C.

5. The initiator system according to claim 1 , the polymerizable thiourea component being selected from N-(5-methacryloxypentyl)-N′-ethyl thiourea, N-(5-meth-acryloxypentyl)-N′-cyclohexyl thiourea, N-(5-methacryloxyundecyl)-N′-ethyl thiourea and mixtures thereof.

6. The initiator system according to claim 1 , the transition metal component comprising copper acetate, copper chloride, copper benzoate, copper acetylacetonate, copper naphthenate, copper carboxylates, copper bis(1-phenylpentan-1,3-dione) complex, copper salicylate, complexes of copper with thiourea, ethylenediaminetetraacetic acid and/or mixtures thereof.

7. The initiator system according to claim 1 comprising in addition a photo-initiator.

8. The initiator system according to claim 1 comprising a stabilizer component(s) comprising a free-radical moiety.

9. The initiator system according to claim 8 , the stabilizer(s) being selected from 2,2-diphenyl-1-picrylhydrazyl, 4-hydroxy-2,2,6,6-tetramethyl-piperidine 1-oxyl, 2,2,6,6-Tetramethyl-piperidinyloxyl, 2,6-di-tert-butyl-α-(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-1-ylidene)-p-tolyloxyl, triphenylmethyl radical, 2,6-bis(1,1-dimethylethyl)-4-methylphenol and mixtures thereof.

10. A dental composition comprising

the initiator system according to claim 1 ,

polymerizable components comprising acidic moieties,

optionally filler(s),

optionally additive(s).

11. The dental composition according to claim 10 comprising

the initiator system in an amount of 0.1 to 5 wt. %,

polymerizable components comprising acidic moieties in an amount of 0.5 to 15 wt. %,

polymerizable components not comprising acidic moieties in an amount of 1 to 50 wt. %

water in an amount of 0.25 to 20 wt. %,

acid-reactive filler in an amount of 5 to 70 wt. %,

non acid-reactive filler in an amount of 0 to 40 wt. %,

polyacid in an amount of 1 to 25 wt. %,

additive(s) in an amount of 0 to 15 wt. %,

wt. % with respect to the dental composition.

12. The dental composition according to claim 1 provided as a two-part composition comprising an acidic part and a non-acidic part,

acidic part and non-acidic part being provided in a ratio of 3:1 to 1:3 with respect to volume,

the acidic part comprising

polymerizable components with acidic moiety,

optionally polymerizable components without acidic moiety,

the hydroperoxide component,

the transition metal component,

polyacid,

non acid-reactive filler,

water,

additive(s),

the non-acidic part comprising

polymerizable components without acidic moiety,

optionally a photo-initiator,

the polymerizable thiourea component,

acid-reactive filler,

non-acid-reactive filler,

additive(s).

13. A kit of parts comprising the dental composition according to claim 10 and the following parts alone or in combination: dental milling block; dental crown; mixing tips; dental adhesive; dental conditioner.