Factors influencing proximal contact loss between fixed implant prostheses and adjacent natural teeth: a retrospective study

Objectives: To investigate the causal factors of proximal contact loss (PCL) between an implant prosthesis and the adjacent natural teeth using cast model analysis.Materials and Methods: Patients who underwent restoration using dental implants in the posterior region were analyzed. To identify factors associ-ated with PCL incidence, cast model analyses were conducted based on sex, implant site, jaw position, Angle's classification, anterior overbite, pre-existing interproximal gap between consecutive (mesial side) natural teeth adjacent to the implant, generalized gap of the full arch, and mandibular anterior crowding. Chi-square, multivariate logistic regression, and multivariate generalized estimating equation (GEE) analyses were used to evaluate the impact of each factor. The incidence of PCL over time was analyzed using Kaplan-Meier analysis.Results: Of 653 implants, 293 implants were selected from 240 patients. Ninety implant sites (30.7%) showed PCL between the implant prostheses and the adjacent teeth. The analysis of PCL incidence revealed a gradual increase over time, with half of PCL cases occurring by 19.2 months. The chi-square test revealed significant associations between a pre-existing interproximal gap between adjacent natural teeth and a generalized overall gap in the corresponding arch and PCL (P=0.002 and P=0.027). The logistic regression (P=0.007, odds ratio [OR]: 2.684) and GEE (P=0.003, OR: 3.255) showed significant correlations between PCL and a pre-existing interproximal gap between adjacent natural teeth.Conclusion: The occurrence of PCL between implant prostheses and adjacent teeth is influenced by the pre-existing interproximal gap between con-secutive natural teeth adjacent to the implant. This factor should be carefully monitored