Diederik Hentenaar

136 Chapter 6 Table 6. Pearson correlation of mesial and distal crown contour (angle) and clinical parameters Deepest pocket Gingiva index Sulcus bleeding Height mesial distal mesial distal mesial distal 1 mm Pearson Correlation 0.36 -0.065 -0.03 -0.059 0.094 0.041 Sig. (2-tailed) 0.003 0.601 0.811 0.635 0.448 0.741 N 67 67 67 67 67 67 2 mm Pearson Correlation -0.171 -0.126 0.029 -0.178 0 -0.024 Sig. (2-tailed) 0.166 0.309 0.814 0.149 0.998 0.845 N 67 67 67 67 67 67 3 mm Pearson Correlation -0.189 -0.166 0.059 -0.214 0.033 -0.05 Sig. (2-tailed) 0.126 0.178 0.637 0.082 0.791 0.686 N 67 67 67 67 67 67 DISCUSSION To the best of our knowledge, this is the first cross-sectional study with a 5-year evaluation that focussed on the influence of cervical crown contour on peri-implant marginal bone loss and soft tissue health in patients with platform-switched, posteriorly placed, two-piece implants. No correlation was found between marginal bone loss and the implant crown emergence angles for any of the evaluated heights. Neither correlations between the different emergence angles and clinical parameters were found at the 5-year evaluation, apart from a weak correlated incidental finding between the crown contour at the mesial 1mm height and deepest probing depth. Clinical parameters showed highly desirable levels of peri-implant health both at baseline and 5 years thereafter. Considering previous studies on marginal bone loss around platform- switched implants, showing bone loss ranging from 0.20 to 0.65 mm, outcomes of this study corroborate on those outcomes (3,4,8). A new measurement method was developed attempting to geometrically map the cervical crown contour. The measurement method described by Katafuchi et al. 2018 (20), based on a stone cast model measurement method of Yotnuengnit et al. 2008 (28) and designed for (natural) front teeth, used a tangent line to the most mesial/distal point of the implant crown for emergence angle calculation. Inherently, a variety in restoration heights were used for correlational analysis. Since the influence of the first 3 mm above implant level was of specific interest in this study, the former measurement method could therefore not be adopted. Using the new measurement method, on different crown heights (1,2,3 mm) angles were assessed with respect to the implant interface,