A dental composition comprising (a) one or more compounds having at least one polymerizable double bond; (b) a polymerization initiator system comprising a sensitizer; and an aromatic tertiary phosphine compound of the following formula: Z-R wherein Z is a group of the following formula R 1 (Ar)P- 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. (a) one or more compounds having at least one polymerizable double bond; (b) a polymerization initiator system comprising a sensitizer; and an aromatic tertiary phosphine compound of the following formula: Z-R wherein Z is a group of the following formula R 1 (Ar)P- 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. a sensitizer; and an aromatic tertiary phosphine compound of the following formula: Z-R wherein Z is a group of the following formula R 1 (Ar)P- 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; Z is a group of the following formula R 1 (Ar)P- wherein R 1 represents a substituted or unsubstituted hydrocarbyl group; Ar represents a substituted or unsubstituted aryl or heteroaryl group; 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;