Abstract: Objective To evaluate the effect of supportive periodontal therapy on maintaining the longterm effect of periodontal nonsurgical treatment. Methods A retrospective study was carried out on patients who have received periodontal treatment before in stomatology hospital. 16 of the patients received supportive treatment while 14 others didn′t. Clinical periodontal examination included periodontal probing depth (PD) and bleeding on probing positive position (BOP (+)). The above clinical examination indexes at the first visit,the return visit after 6 weeks,and the latest visit were analyzed and compared. Results 6 weeks later,PD and BOP(+) percentage in two groups decreased significantly and there was no statistically significant difference between the two groups. At the latest visit,the PD of supportive therapy group was 2.83 mm and the BOP(+) percentage was 15.49%. There was significant difference compared with the 1st visit.The PD of control group was 3.51 mm and the BOP(+) percentage was 60.42%.There was no statistically significant difference compared with the 1st visit,but there was significant difference when compared with the supportive therapy group. Conclusions Periodontal nonsurgical treatment can effectively control periodontitis but its longterm effect needs to be maintained through supportive periodontal therapy.

Key words: non –surgical treatment, supportive periodontal therapy, periodontitis