95 Maxillary implant overdentures: peri-implant infections in the maxillary anterior region in a two-stage procedure. Small dehiscences were covered with a mixture of intra-oral bone and organic bovine bone and a resorbable membrane (Bio-Oss and Bio-Gide, Geistlich Pharma AG, Wolhusen, Switzerland). In the posterior group, implant treatment was preceded by a maxillary reconstruction procedure. Large autogenous bone grafts were harvested from the superior anterior medial part of the iliac crest. The cancellous bone was applied on both sinuses during maxillary sinus elevation procedure, while the cortical bone were used as buccal onlay grafts which were fixated with osteosynthesis screws to cover the exposed maxillary alveolar process. The wound was primarily closed. After three months of healing the osteosynthesis screws were removed after which four to six sandblasted, large grit, acid-etched implants were placed into the grafted sites (Straumann Standard SLA Ø 4.1 mm, Institut Straumann AG, Basel, Switzerland) in a one-stage procedure. Both groups’ participants who did not yet have an implant-retained mandibular overdenture received implants in the mandible simultaneously. After a three-month osseointegration period, a standard prosthodontic procedure was initiated. Since a 2-stage system was used on the anterior group, prosthetic treatment was preceded by second-stage surgery consisting of healing abutment placement. All the participants received bar-retained implant overdentures. The participants received oral hygiene instructions for their overdentures and bars, and annual routine maintenance appointments were scheduled. During maintenance the prostheses and peri-implant tissues were evaluated and if needed, prosthetic repairs or preventive therapy, such as the removal of calculus, was performed. In case of peri-implant mucositis or peri-implantitis, implants were treated following a clinical protocol consisting of non-surgical debridement, supportive oral hygiene instructions, and, in case of persistent inflammation and/or progressive marginal bone loss, additional surgical debridement. Adjunctive antiseptics were applied (chlorhexidine 0.12% mouth rinse for 14 days). For peri-implantitis treatment no antibiotics were prescribed. Data collection and analysis Data on biological complications (i.e., implants lost due to peri-implantitis or treated for peri- implantitis and peri-implant mucositis) from the 10-year follow-up were extracted from the participants’ medical files. The baseline, 5- and 10-year follow-up (T5 and T10) data on bleeding and/or suppuration on probing, pocket depth (PD) and marginal bone level change (MBLC) were collected from the original trials. For the clinical data, every implant was probed at four sites, viz. the mesial, labial, distal and lingual site. For bleeding on probing, the Modified Bleeding Index according to Mombelli et al. (1987) was used in the original studies (score 0: no bleeding when using a periodontal probe, score 1: isolated bleeding spots visible, score 2: a confluent red line of blood along the mucosal margin, score 3: heavy or profuse bleeding). These data were translated to BoP- (in case of a score 0) or BoP+ (in case of a score 1, 2 or 3). For the MBLC, standardized radiographs were obtained by using the long-cone paralleling technique with an individualized X-ray holder. Using measurement software (Biomedical Engineering, University Medical Center Groningen, the Netherlands) and the known implant dimension as a reference, 6
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