RESUMEN
Objective To observe the results of crown lengthening surgery on the teeth with subgingival defect.Methods Crown lengthening surgery was performed on 54 terior teeth,which were divided into two groups based on probing depth of pre-operation:group A (<3 mm) and group B (3-4 mm).All teeth were restored 8 weeks after operation and followed-up to 1 year.The parameters of plaque index (PLI),suleus bleeding index (SBI),maximal defect probing depth (PD) and mobility degree (MD) at different times were measured,respectively.Results PLI,BI and PD were significantly improved during the follow-up period (P<0.01).The success rates of both groups were 96.8% and 69.6%, respectively (P<0.01).No significant difference about MD in the group A one year after restoration (P>0.05),but a significant improvement in the group B (P<0.01).Conclusion Crown lengthening surgery is a good method on the teeth with subgingival defect,but one must select the right indication.