The composition for hard tissue repair of the present invention is characterized by comprising 5 to 98.95 parts by weight of a monomer (A), 1 to 75 parts by weight of a (meth) acrylate polymer (B) and 0.05 to 20 parts by weight of a polymerization initiator composition (C) containing an organoboron compound (c1), with the proviso that the total amount of the components (A), (B) and (C) is 100 parts by weight. The composition undergoes small-scale heat generation during curing and can ensure a sufficient working time.본 발명의 경조직 보수용 조성물은, 모노머(A) 5~98.95중량부, (메타)아크릴레이트 중합체(B) 1~75중량부, 및 유기 붕소 화합물(c1)을 포함하는 중합 개시제 조성물(C) 0.05~20중량부((A), (B), 및 (C)의 합계 100중량부)를 함유하는 것을 특징으로 한다. 상기 조성물은, 경화시의 발열이 작고, 게다가, 작업시간을 충분히 확보할 수 있다.
