Diederik Hentenaar

138 Chapter 6 additional use to geographically map the crown contour in a 360 degree aspect, thus including the lingual or buccal contour, monitoring implants using CBCT cannot be used as standard follow-up examination, considering the ALARA (as low as reasonably achievable)-principle. Further, changes of the interproximal bone levels could be superimposed across radiographs. In a study by Malloy et al. 2017 inaccurate results were reported when measuring bone-levels on radiographs of cadaver specimens as a result of x-ray angulation (33). Moreover perceived bone level changes on radiographs less than 1mm are more likely due to human error than to actual change because of inaccuracy of examiners (34). Considering this, the amount of implants then showing actual change in this study (>1mm) seems very low, accentuating the healthy status of the majority of implants assessed. At last, given the two different implant brands, with two different diameters placed on premolar and molar position included in this study, a relatively heterogeneous data set was evaluated. However, it seems unlikely that the aforementioned differences would have influenced the marginal bone level, taken into account the small amount of implants showing a small amount of marginal bone loss. To confirm our data and more profoundly understand the mechanisms by which the crown contour could influence peri-implant health, future research on the influence of the crown contour using the measurement method described in this study, should consider to evaluate various confounding factors (e.g. implant depth, width of occlusal table, implant diameter of implant design, implant abutment connections of abutment design) in a larger, homogeneous group of implants. Conclusively, within the limitation of this study, no correlation appears to exist between the cervical crown contour i.e. first 3mm above the implant platform and peri-implant marginal bone loss around two-piece platform-switched implants after 5 years of function. Platform switched implants seem to perform well in terms of peri-implant hard and soft-tissue health up to 5 years, taken into account a priori periodontal healthy, non-smoking patients, and treatment by experienced implant and restorative specialists.