Objectives : Proximal contact loss between posterior implant-supported fixed prostheses and adjacent teeth is frequently observed in clinical practice. The aim of this study was to evaluate potential factors of proximal contact loss using multivariate analysis.
Materials and Methods : One hundred thirty-five patients with 185 implant-supported fixed prostheses in the posterior region were included. At the follow-up visits, we examined proximal contact loss between 185 implant-supported prostheses and adjacent teeth with a 110-μm-thick contact gauge. We also evaluated age, monitoring period, region of implant (molar or premolar), crown-implant ratio, state of adjacent teeth (mobility, splinting and guidance) and Misch's bone density classification as potential factors. Statistical analyses were performed with the Mann-Whitney U test, Chi-squared test and logistic regression.
Results : One hundred seven of 185 proximal contacts (57.0%) were judged lost. The Mann-Whitney U test revealed that prostheses with proximal contact loss had greater crown-implant ratio than those without contact loss (p＜0.01). Bone density was associated with incidence of proximal contact loss. Cases with D1 and D2 classification more often showed contact loss than D3 and D4 (p = 0.01). With regard to adjacent teeth, with mobility (p = 0.02), non-splinting (p = 0.01) and participating in lateral guidance (p＜0.01) were related to proximal contact loss (Chi-squared test). In the logistic regression analyses, crown-implant ratio (OR = 7.17, p＜0.01), mobility of adjacent teeth (OR = 3.15, p = 0.03), splinting of adjacent teeth (OR = 0.35, p = 0.02) and bone density (OR = 0.44, p = 0.03) were significantly associated with proximal contact loss.
Conclusion : Proximal contact loss between implantsupported fixed prostheses was observed in 57% of prostheses in the present study. It was associated with greater crown-implant ratio, mobility of adjacent teeth, non-splinting of adjacent teeth and bone density.