Association of crown emergence angle and profile with dental plaque and inflammation at dental implants

Background: The shape of implant restorations is critical for function and aesthetics. It may also be important in peri-implant tissue health preservation. This study aimed to associate the restorative contour of a single crown with marginal dental plaque accumulation, tissue inflammation and probing depths. Methods: Subjects with a single screw-retained implant restoration were clinically examined. The presence of dental biofilm, tissue inflammation and probing pocket depths were the dependent variables. The emergence angle, profile and depth of the mucosal tunnel were measured on superimposed digital scans of the crown soft-tissue complex, the removed crown mounted on an analogue and the soft tissue. Results: One hundred twenty two subjects (46.7% female, 68.9% never smokers, 77% with treated periodontitis and 52.5% participating in regular supportive peri-implant care) were examined. The emergence angles at the mucosal margin were 15.3 +/- 9.4 degrees, 12.7 +/- 8.5 degrees, 31.3 +/- 11.8 degrees and 19.2 +/- 9.8 degrees for the mesial, distal, vestibular and oral aspects of the crowns. The largest emergence profile angles were observed on the vestibular aspect (74.6% of cases), reaching a maximum of 61.7 degrees, and profiles were convex in 59% of cases. Generalized estimating equations indicated that the site-specific platform-level emergence angle and profile and depth of the mucosal tunnel were significantly associated with the presence of detectable plaque accumulation (p < .01) and bleeding on probing (p < .02). Conclusions: Subtle variations in the shape of the restorative crown are associated with biofilm accumulation and mucosal inflammation. These findings are important for 3D implant planning/positioning and preservation of peri-implant tissue health.