Abstract: A photocuring resin composition for orthodontics is disclosed, comprising:(a) 5.about.50% by weight of a urethane bond-free (meth)acrylate having an average molecular weight of 100.about.300 and having at least one unsaturated double bond;(b) 10.about.60% by weight of a urethane bond-containing (meth)acrylate having an average molecular weight of 300.about.5,000 and having at least one unsaturated double bond;(c) 5.about.30% by weight of a crosslinked polyurethane powder;(d) 10.about.50% by weight of an inorganic filler; and(e) 0.03.about.3% by weight of a photocuring initiator.

Abstract: There is disclosed a primer composition comprising[A] a reaction product of:(1) a hydroxyl group-containing organic compound composed of;(a) an epoxy group-containing alcohol represented by the general formula [I]: ##STR1## wherein, R.sup.1 is a hydrocarbon group having 1 to 15 carbon atoms, or an organic group in which the same or different hydrocarbon groups are bonded to each other by an ether bond or an ester bond; and each of m and n is a value of 1 or more; and(b) a hydroxyl group-containing (meth)acrylate represented by the formula [II]:(CH.sub.2 .dbd.CR.sup.2 COO).sub.a R.sup.3 [II]wherein R.sup.2 is a hydrogen atom or a methyl group; R.sup.3 is a substituted or unsubstituted hydrocarbon group, or a group in which the same or different hydrocarbon groups are bonded to each other by ether bond or the ester bond, the R.sup.