Today, dental implants are widely used for the replacement of missing teeth, but there are complications to their use such as peri-implantitis and infra-occlusion. It appeared from surveys on the attitudes and treatment strategies towards peri-implantitis that dental professionals both in the U.S.A. and Europe treat peri-implantitis based on evidence. However, they also differ relating to treatment preferences, mainly more antibiotics are prescribed in the U.S.A. Interestingly, in a microbiological study it was found that differences in the microbiome composition in the various peri-implantitis lesions are especially related to probing depth, implant disease status and presence of natural teeth. Especially, some well-recognized periodontopathogens were present in higher proportions in deep peri-implantitis pockets, and in peri-implant pockets of individuals also having natural teeth. For the treatment of peri-implantitis, there is no “gold standard”, so two clinical studies aimed to investigate the effectiveness of non-surgical and surgical therapeutic approaches. Non-surgical treatment, irrespective of antibiotics usage, results in reduction of probing depths but complete peri-implantitis resolution was not achieved. In contrast, the surgical reconstruction of peri-implantitis lesions with bovine-derived xenografts resulted in substantial radiographic defect fill and probing depth reduction. While natural teeth show some continuous eruption throughout life, this is not the case for dental implants. From a retrospective study in adults, it was found that single-implant–supported crowns in the anterior maxilla appeared to have an infraocclusion position over time and this is more pronounced for delayed placed implants and younger adults.