Influence of mucosal tissue height on implant crestal bone: A 10-year follow-up of a controlled clinical trial

Objective: To evaluate the 10-year influence of soft tissue height (STH) on crestal bone level changes (CBC) in bone-level implants with non-matching internal conical connections. Material & Methods: From the initial 97 patients, 59 (19 men, 40 women, age 55.86 +/- 9.5 years) returned for the recall visit. Based on baseline STH, they were categorized into T1 (thin STH <= 2 mm, n = 33), T2 (thin STH augmented with allogenic tissue matrix (ATM), n = 32), and C (thick STH >2 mm, n = 32). Implants were placed in the posterior mandible using a one-stage approach and received single screw-retained restorations. Clinical (PPD, BOP, PI) and radiographic examinations were conducted after 10 years, with CBC calculated mesial and distal to each implant. Results: After 10 years, implants in surgically thickened (T2) or naturally thick STH (C) showed bone gains of 0.57 +/- 0.55 mm and 0.56 +/- 0.40 mm, respectively (p < 0.0001) shifting from an initial CBC of -0.21 +/- 0.33 mm to 0.36 +/- 0.29 mm in the thick STH group and -0.2 +/- 0.35 mm to 0.37 +/- 0.29 mm in the surgically thickened STH group. Implants in naturally thin STH yielded a non-significant trend of bone loss (-0.12 +/- 0.41 mm; p > 0.05). Conclusions: Implants in thin STH (<= 2 mm) exhibited greater CBC over the study period. Significant bone gains were observed in thick STH cases, indicating that naturally thick STH or STH augmentation with ATM may contribute to maintain CBC in long-term around implants. Clinical significance: This is the first long-term follow-up study suggesting that adequate soft tissue height around implants helps maintain stable peri-implant bone levels. While tissue thickness plays a key role, other factors also interact with peri-implant tissue height to sustain crestal bone stability over time.