Caroliene Meijndert

147 General discussion and conclusions level observed in the 1, 5 and 10 year follow-up studies ( Chapter 2-6 ). However, we did not measure the actual buccal bone thickness during the follow-up appointments. Thus it is important that future studies measure the dimensional changes of the buccal bone and show whether these changes are a reason for mucosa stability or not. Cone beam computer tomographic methods are commonly available now to measure the buccal bone thickness. These methods, however, have their limitations because metallic artefacts limit the visualization quality of the bone around the implants, leading to an underestimation of the bone thickness (Ritter et al., 2014; Vanderstuyft et al., 2019). Papillae Changes in the appearance of the papilla can be recorded in mm and/or with an index as described, for example, by Jemt et al. (1997). In general, it can be said that the papilla changes observed in the various studies reported in this thesis were minor throughout the evaluation periods. There are various theories about the formation of interdental papillae approximal to an implant. Cosyn et al. (2012) performed a multivariate analysis of risk factors for soft tissue recessions in the anterior maxilla and gave, for example, surgery with a ridge reconstruction as a risk factor for interproximal recession. In the study in which we applied extensive reconstructive surgery prior to implant placement ( Chapter 2 ), only 20% of the patients scored a full papillae fill in the Implant Crown Aesthetic Index. These less favourable outcomes can be a result of the poor pre-operative state of the site and/or with the reconstructive surgery subsequently needed. According to Jung et al. (2018), the mucosa attachment level at the neighbouring teeth is a predominant factor in the establishment of the papillae. It can be argued that the bone resorption after a tooth extraction causes recession of the mucosa around the neighbouring teeth, resulting in a retraction of the gingiva attachment level at the rootsurface. Reconstructing the alveolar bone with a bone augmentation does not regenerate the cementum at the root surface of neighbouring teeth, and thus does not re-establish the original gingival attachment levels, resulting in an incomplete papilla fill proximal to the implant. Furthermore, when flap elevation is needed to gain access to the site for augmentation, this can also result in disrupted papillary tissue attachments (Jung et al., 2018). According to Cosyn et al. (2012), other factors that might influence the presence or absence of papillae are: the actual presence of a contact point, the distance from the contact point to the interproximal bone peak (when ≤5 mm, increased likelihood of a present papilla) and the tooth-to-implant distance (when ≥2.5 mm, increased likelihood 8