Purpose: This study sought to define the tissue responses at different implant-abutment interfaces by studying bone and peri-implant mucosal changes using a 5-year prospective randomized clinical trial design study. The conus interface was compared with the flat-to-flat interface and platform-switched implant-abutment systems. Materials and Methods: One hundred forty-one subjects were recruited and randomized to the three treatment groups according to defined inclusion and exclusion criteria. Following implant placement and immediate provisionalization in healed alveolar ridges, clinical, photographic, and radiographic parameters were measured at 6 months and annually for 5 years. The calculated changes in marginal bone levels, peri-implant mucosal zenith location, papillae lengths, and peri-implant Plaque Index and bleeding on probing were statistically compared. Results: Forty-eight conus interface implants, 49 flat-to-flat interface implants, and 44 platform-switched implants were placed in 141 subjects. Six platform-switched interface and eight flatto- flat interface implants failed, most of them within 3 months. After 5 years, 33 conical interface, 28 flat-to-flat interface, and 27 platform-switched interface implants remained for evaluation. Calculation of marginal bone level change showed a mean marginal bone loss of –0.16 ± 0.45 (–1.55 to 0.65), –0.92 ± 0.70 (–2.90 to 0.20), and –0.81 ± 1.06 (–3.35 to 1.35) mm for conical interface, flat-to-flat interface, and platform-switched interface implants, respectively (P < .0005). The peri-implant mucosal zenith changes were minimal for all three interface designs (0.10 mm and +0.08 mm, P > .60). Only 16% to 19% of the surfaces had presence of bleeding on probing, with no significant differences (P > .81) between groups. Interproximal tissue changes were positive and similar among the implant interface designs. Conclusion: Over 5 years, the immediate provisionalization protocol resulted in stable peri-implant mucosal responses for all three interfaces. Compared with the flat-to-flat and platform-switched interfaces, the conical interface implants demonstrated significantly less early marginal bone loss. The relationship of marginal bone responses and mucosal responses requires further experimental consideration. Keywords: esthetics, immediate loading, marginal bone levels, peri-implant mucosa, randomized controlled clinical trial

Purpose: The goal of this investigation was to define time-dependent peri-implant tissue changes at implants with different abutment interface designs. Materials and Methods: Participants requiring replacement of single maxillary anterior and first premolar teeth were recruited and treated under an institutional review board (IRB)-approved protocol. Implants, titanium abutments, and provisional crowns were placed in healed ridges 5 months following preservation after tooth extraction with recombinant human bone morphogenetic protein-2 (rhBMP-2). Twelve weeks later, permanent crowns were placed on patient-specific abutments and evaluated at 6, 12, and 36 months following implant placement. Clinical and radiographic assessments of abutments and crowns, peri-implant mucosa, and marginal bone levels were recorded. Results: The 3-year assessment included 45 conical interface (CI), 34 flat-to-flat interface (FI), and 32 platform-switched interface (PS) implants in 111 participants. At 3 years, the mean marginal bone level (MBL) change at CI, FI, and PS implants was -0.12, -1.02, and -1.04 mm, respectively (P = .014). "Zero" MBL loss or gain was measured over the 3-year period at 72.1% CI, 3.0% FI, and 16.6% PS implants. There was a minor change (0.0 to 0.3 mm) in peri-implant mucosal zenith positions over time and between groups. Eighty percent of CI implants, 61% of FI implants, and 84% of PS implants were observed to have a clinically stable periimplant mucosal zenith position with less than 0.5 mm of measured recession. Over the 36-month period, there were no significant changes in the location of mesial or distal papilla in any group. Conclusion: Significant differences in MBLs were observed at different implant interfaces. Conical implant interfaces, but not flat-to-flat or platform-switched implant interfaces, were associated with no MBL changes over 3 years. Peri-implant mucosal stability was generally observed. The relationship of marginal bone responses and peri-implant mucosal stability requires further evaluation. Keywords: esthetics, immediate provisionalization, marginal bone levels, peri-implant mucosa