Caroliene Meijndert

145 General discussion and conclusions literature (after 1 year: -0.10 mm, Vanlioglu, 2014; after 5 years: -0.12 mm, Hosseini et al., 2020; -0.19 mm, Berberi et al., 2014) but, in other studies, the marginal bone loss was slightly higher (after 1 year: -0.48 mm, De Bruyckere et al., 2018; -0.3 mm, Levine et al., 2019; after 5 years: -0.43 mm, Canullo et al., 2018; -0.47 mm, Eghbali et al., 2018). This discrepancy in marginal bone loss between studies might, amongst others, be related to the timing of the baseline measurement. The most marginal bone loss, probably as a result of bone remodeling, occurs in the first few months after implant placement (Pariente et al., 2020). When measuring the baseline after completing the prosthetic phase, for example in a delayed or conventional restoration protocol, the initial bone healing part is left out of the calculations. Another reason that could explain the discrepancy in bone loss between studies could be the implant abutment connection configuration applied in those studies. They all used platform switched internal conical connections. The fit and tightness of a connection between an implant and abutment can reduce micromovement and bacterial colonization at the interface, and hereby reducing bone loss at the crest. An internal, platform switched connection is accompanied by less marginal bone loss than an external or platform matched connection (Hsu et al., 2017; Caricasulo et al., 2018; Chapter 7 ). It has to be mentioned, however, that the 1-year differences in marginal bone loss observed between the various implant abutment connections are probably clinically irrelevant in the short term, but might become clinically relevant after a longer follow-up. Alveolar ridge preservation – delayed implant placement When implant treatment is not applicable yet at the time of tooth extraction, it is advised to perform alveolar ridge preservation immediately after tooth extraction (Cosyn et al., 2013; Benic et al., 2014). The studies described in this thesis used autologous bone combined with anorganic bovine bone particles. Chapter 2 demonstrates that there is no difference in marginal bone level changes with respect to the augmentation material applied to the alveolar reconstructions (autologous chin bone or anorganic bovine bone particles). We learnt from the study described in chapter 3 that there were no differences in peri-implant marginal bone level changes, either after 1 year, as described by Santing et al. (2013) or after 5 years in function, between the augmented and the non-augmented sites. Apparently, implants placed in healed sites comprised of native bone or of reconstructed bone behaved comparably in this respect, and both conditions were accompanied by satisfying aesthetics. According to Jung et al. (2018), the goal of alveolar ridge preservation is to avoid further augmentative procedures. Yet, it is important to note that in our and Zuiderveld’s 8