Purpose: To investigate the prevalence of interproximal contact loss between implant-supported fixed prostheses and adjacent teeth and its impact on marginal bone loss and to identify potential risk factors. Materials and Methods: Patients who received implant-supported fixed prostheses at Saint-Joseph University between the years 2011 and 2017 and met the inclusion/exclusion criteria were eligible to participate in this retrospective study. Interproximal contacts were evaluated with a 70-μm dental floss and confirmed visually and by periapical radiographs. Contact was considered open if the floss passed without resistance. Plaque Index and bleeding on probing were assessed, and radiographic bone loss around implants was measured at recall. Results: Eighty-three patients (183 interproximal contact points) were evaluated. Interproximal contact loss between implant-supported fixed prostheses and adjacent teeth occurred in 32.8%; among mesial contact points, 42.1% had interproximal contact loss, whereas 14.5% had interproximal contact loss on the distal side. In interproximal contact loss sites, a mean marginal bone loss of 0.73 mm was noted; the difference was statistically significant compared with marginal bone loss at sites with interproximal contact (P = .017). Age, sex, smoking status, periodontal status, implant sites, and the type of restoration were not significantly associated with interproximal contact loss or marginal bone loss. Sites with interproximal contact loss were 2.24 times more likely to present bleeding on probing than others. Conclusion: Interproximal contact loss occurred in 32.8% of implant-supported fixed prostheses, and a positive relationship between interproximal contact loss and marginal bone loss was found, which suggests that interproximal contact loss should be included as a prosthetic implant complication. Future research aiming at identifying the causative factor for interproximal contact loss is necessary. Keywords: implant complications, implant prosthesis, interproximal open contacts, marginal bone loss