Abstract: Objective To explore the effect of the initial biological width of implant on marginal bone level (MBL). Methods 80 patients who received Straumann bone level implant and fixed prosthesis in the posterior dental area were selected. The oral panoramic radiographs of each implant at four time points (preoperative, postoperative, second-stage, follow-up) were measured. The soft and hard tissue space implanted immediately after operation above the shoulder level was defined as initial biological width (IBW), The IBW value was the initial mucosal thickness during equicrestal implantation, or the sum of mucosal thickness and implant depth during subcrestal implantation. IBW was grouped by 3.5 mm to compare MBL of follow-up implant. Results After 1–5 years of follow-up, 127 implants with 254 sites were included. IBW≥3.5 mm group demonstrated better MBL (0.40 mm vs. 0.00 mm, P＜0.05). With IBW≥3.5 mm, the marginal bone level of the implant was more likely to stabilize at or above the shoulder level (95.6% vs. 87.2%, P＜0.05). Conclusion Both mucosal thickness and implant depth affect implant MBL. For Straumann bone level system, with IBW≥3.5 mm, MBL is more likely to stabilize at or above the shoulder level.

Key words: Marginal bone level, Biologic width, Mucosal thickness , Implant depth