101 Maxillary implant overdentures: peri-implant infections Nevertheless, since different techniques and implant systems were used in both groups, meaningful risk factor analyses cannot be performed on the present data. Renvert et al.15 reported relatively high implant level incidences of 26.2% and 30.4% at seven years and 32.1% and 39.% at thirteen years, using a MBLC threshold of 1 mm. Recalculating our results with a threshold of 1 mm provides incidences of 4.0% and 10.3% at 5 years and 9.6% and 19.2% at 10 years for the anterior and posterior group, respectively. The differences between studies in reported outcomes may be explained by the degree of maintenance. While other studies16-18,20 and the present studies’ patients were included in a regular maintenance program, Renvert et al.15 were unable to verify any aftercare since the patients were referred back to their general practitioner. A continued lack of maintenance was studied by Costa et al.30 in a group of partially edentulous patients diagnosed with peri-implant mucositis. They reported a significantly higher peri-implant mucositis and peri-implantitis incidence in patients that were not preventively maintained. Romandini et al.31 studied a group of edentulous patients that did not receive any aftercare for at least 7 years and showed a high prevalence of peri-implantitis and implant loss, especially in the maxilla. Although the latter two studies did not include a well maintained control group, these results suggest a possible effect of lacking maintenance on peri-implant diseases. Susceptibility The results suggest an increase in peri-implantitis severity in affected implants between 5 and 10 years. The extent of peri-implant mucositis and peri-implantitis also seems to increase over time. Yet, Table 6.5 shows a fairly constant proportion of patients without a MBLC of > -1 mm (~80% in the anterior group and ~70% in the posterior group). This suggests that patients who are susceptible to peri-implantitis have a higher risk of developing more severe and extensive forms of peri-implantitis over time, while the risk for patients with healthy peri-implant tissues is low. It is, however, important to realize that since the original studies were not specifically designed to identify peri-implant diseases, these statements should be interpreted with caution. Moreover, though extent and severity appear to increase over time, the effect on overdenture survival and thus the clinical relevance are debatable, since the implant loss due to peri-implantitis was limited to 1.5%. Nevertheless, as stated by Derks and Tomasi9, these calculations can be valuable for a good understanding the epidemiology of peri-implant diseases and may therefore be a valuable addition for future prospective longitudinal studies. Conclusion Within the limitations of this study and using the case definitions proposed at the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions, it can be concluded that fully edentulous patients with implant-supported maxillary overdentures show high incidences of peri-implant mucositis, peri-implantitis occurs in one of ten patients after 5 years and in one of five patients after 10 years, but with a high implant survival after 10 years. 6
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