Abstract: PURPOSE: To investigate the effect of different implant systems on peri-implant soft tissue. METHODS: Forty patients requiring single implant therapy in posterior teeth at Dental and Ophthalmic Clinic of Putuo District from December 2020 to February 2021 were selected. Ten patients were implanted with bone level implants and 30 patients with soft tissue level implants. Periodontal exploration was performed at the buccal side, lingual side, mesial and distal axial angle of the implants, and the gingival crevicular fluid of these locations were taken to detect the enzyme level. The probing depth, aspartate aminotransferase (AST) and alkaline phosphatase (ALP) level of the two groups were compared at the day, 3 months, 6 months and 12 months after crown restoration. Statistical analysis was completed by SPSS 17.0 software package. RESULTS: The probing depth and ALP level of soft tissue level implants were significantly lower than those of bone level implants at the day, 3 months, 6 months and 12 months after crown restoration(P<0.05). At the day when crown restoration was accomplished, AST of soft tissue implant was significantly lower than that of bone level implant(P<0.05). AST in gingival crevicular fluid of bone level implants decreased rapidly in the following three time periods, and close to that of the soft tissue level implants(P>0.05) at last. CONCLUSIONS: Both bone level implants and soft tissue level implants have good clinical effects, but peri-implant soft tissues of the soft tissue level implants show better stability.

Key words: Implant, Bone level, Soft tissue level, Peri-implant soft tissue