Dental composition

1. A dental composition comprising

(a) one or more compounds having at least one polymerizable double bond;

(b) a polymerization initiator system comprising

(b1) a sensitizer; and

(b2) an aromatic tertiary phosphine compound of the following formula (I):

Z—R   (I)

wherein

Z is a group of the following formula (II)

R 1 (Ar)P—   (II)

wherein

R 1 represents a substituted or unsubstituted hydrocarbyl group;

Ar represents a substituted or unsubstituted aryl or heteroaryl group;

R is an aryl group, substituted by one or more groups selected from a hydroxyl group, an amino group, a —NR 2 R 3 group (wherein R 2 and R 3 , which may be the same or different, are selected from C 1-6 alkyl groups), a carboxyl group, and a group having a polymerizable double bond;

wherein the group R 1 and Ar may be substituted by one or more groups selected from a hydroxyl group, an oxo group, a —NR 2 R 3 group (wherein R 2 and R 3 , which may be the same or different, are selected from a hydrogen atom and C 1-6 alkyl groups), a carboxyl group, and a group having a polymerizable double bond;

wherein the sensitizer is an 1,2-diketone or a phosphine oxide.

2. The dental composition according to claim 1 , wherein the polymerization initiator system further comprises

(b3) an electron-donor.

3. The dental composition according to claim 1 , wherein R 1 and Ar independently are aromatic hydrocarbyl groups selected from a phenyl group, a napthyl group, a tolyl group, a xylyl group, and a styryl group.

4. The dental composition according to claim 2 , wherein the electron-donor is a tertiary amine compound.

5. The dental composition according to claim 2 , wherein the polymerization initiator system comprises component (b1), (b2), and (b3) in a molar ratio ((b1):(b2):(b3)) of 1:(0.1 to 3.0):(0.0 to 3.0).

6. The dental composition according to claim 1 , which further comprises a solvent and/or a particulate filler.

7. The dental composition according to claim 1 , wherein the dental composition is a dental restorative or dental prosthetic composition.

8. The dental composition according to claim 7 , where the dental composition is selected from a dental adhesive composition, a dental composite composition, a resin modified dental cement, a pit and fissure sealer, a desensitizer and a varnish.

9. The dental composition according to claim 1 , wherein the aromatic phosphine compound is a compound of formula (I) wherein Z is a group of the following formula (III):

10. A polymerization initiator system comprising: (i) an aromatic phosphine compound of the following formula (I)

Z—R   (I)

wherein

Z is a group of the following formula (II)

R 1 (Ar)P—   (II)

wherein

R 1 represents a substituted or unsubstituted hydrocarbyl group;

Ar represents a substituted or unsubstituted aryl group;

R is an aryl group, substituted by one or more groups selected from a hydroxyl group, an amino group, a —NR 2 R 3 group (wherein R 2 and R 3 , which may be the same or different, are selected from C 1-6 alkyl groups), a carboxyl group, and a group having a polymerizable double bond;

wherein the group R 1 and Ar may be substituted by one or more groups selected from a hydroxyl group, a —NR 2 R 3 group (wherein R 2 and R 3 , which may be the same or different, are selected from a hydrogen atom and C 1-6 alkyl groups), a carboxyl group, and a group having a polymerizable double bond, and

(ii) a sensitizer selected from an 1,2-diketone

for use in the preparation of a dental composition.

11. The polymerization initiator system according to claim 10 , wherein the aromatic phosphine is 4-(diphenylphosphino)styrene.

12. The dental composition according to claim 2 , wherein the electron-donor (b3) is a compound of the following formula (IV):

L-H   (IV)

wherein L is a moiety of the following formula (V)

R a R b R c X—   (V)

wherein

X represents Si, Ge, or Sn and

R a represents a hydrogen atom, an organic moiety or a different moiety L;

R b and R c

which are independent from each other, represent an organic moiety.

13. The dental composition according to claim 12 , which comprises as sensitizer a combination of

(b1-a) a first sensitizer selected from an 1,2-diketone; and

(b1-b) a second sensitizer selected from iodonium salts.