Abstract: Objective: To compare the effect of placing the definitive restorative abutment at the time of implant placement versus at a later stage on the soft and hard tissue changes around dental implant. Methods: Forty patients were randomized to control group and test group. Sixty implants were involved. In test group patients were received the definitive abutment at the moment of implant placement, while the patients in control group received healing abutment. Platform-switched implants were used. Final prostheses were delivered 12 weeks after the implant surgery. After 6 and 12 months, the restorations were completed, radiographic assessment of marginal bone level changes and clinical status of periimplant soft tissues were detected. Plaque index, sulcus bleeding index, pocket depth, and Jemt score as well as the changes in papilla filling were assessed. Results: A significant greater bone reduction from surgery to 6 months post-loading and 12 months (P=0.009 and P=0.004) were observed when comparing the control group [(-1.101±0.316)mm and (-1.223±0.302)mm] with test group [(-0.826±0.260)mm and (-0.933±0.243)mm]. A significant increase in papilla height was observed from loading to 12 months in all implants. There were no significant differences in plaque index, pocket depth, and sulcus bleeding index between the two groups. Conclusion: The connection and disconnection of healing abutments are associated with significantly increased bone loss during the healing period between implant placement and 6 months post-loading, when compared to one time abutment placement.

Key words: Dental implant, Dental implant-abutment design, Bone resorption