OBJECTIVESTo investigate the occlusal characteristics and the condition of tooth abrasion in patients with cracked tooth and to discuss the etiology of the cracked tooth and the relationships between occlusal disorder, tooth abrasion and cracked tooth.

METHODSTwenty-seven patients with cracked tooth were selected. The occlusal courses were recorded by T-ScanIII system in intercuspal position, protrusive movement and lateral movement. Teeth with cracked tooth were regarded as the cracked tooth group, and the healthy adjacent teeth as the control group. The distribution of premature contact, occlusal interference, the center of occlusal force were examined. The abrasive conditions of the two groups were recorded according to the Smith tooth wear index and compared.

RESULTSThere were more teeth with occlusal interference in cracked tooth group (20 teeth) than in the control group (6 teeth), which was significantly different (OR = 5.67, chi(2) = 8.45, P = 0.003). In 24 patients with single affected tooth, the center of occlusal force (COF) located in the inside and outside ellipse were 6 teeth (25%) and 18 teeth (75%) respectively, Z test showed that there were statistical differences between the cracked tooth group and normal people. In cracked tooth group, the proportion of the teeth with abrasion was higher in teeth with occlusal interference than those without occlusal interference (chi(2) = 4.79, P = 0.029).

CONCLUSIONSThe formation of the cracked tooth was related to the occlusal disorder and associated with the tooth abrasion.