2Gabris K, Tarjan I, Rozsa N. Dental trauma in children presenting for treatment at the Department of Dentistry for Children and Orthodon- tics. Budapest, 1955-1999 [ J ]. Dent Traumato1,2001,17 ( 3 ) : 103 - 108.
3Hunter ML, Hunter B, Kingdon A, et al. Traumatic injuryto maxillary incisor teeth in a group of Scaah Wales School children [ J ]. Endod Dent TraumatO1,1990,6 (6) :260.