RESUMO
PURPOSE: After implants are placed into mandibular molar sites, it is assumed that crestal bone width will not change considerably over time. The purpose of this retrospective study was to determine crestal bone changes for implants placed into mandibular molar locations. The hypotheses for all groups (immediate, delayed, and grafted) were that no major changes in bone width of the posterior mandible would occur in the long term. MATERIALS AND METHODS: This is a retrospective cohort study involving 3 groups of patients within the senior author's practice who had at least 4 years of follow-up cone-beam computed tomograms available for measurement. The primary outcome variable, crestal width, was measured at 3 intervals, namely at tooth removal, before implant placement, and 4 to 5 years after placement. Group A underwent tooth extraction with immediate implant placement; group B underwent tooth extraction with delayed implant placement; and group C underwent tooth extraction with socket grafting and implant placement 4 months after grafting. Standardized cross-sectional cone-beam computed tomograms were used to measure ridge width. Two-sample t tests and regression analysis were used to compare crestal width measurements at different periods among groups. Analysis of variance was adapted to check whether ridge widths among groups were confounded by variables, such as age, gender, and medical comorbidities. RESULTS: Age, gender, medical comorbidities, and smoking were not statistically related to the outcome. Long-term comparisons indicated small yet significant (P = .0124) differences at the crestal level. The greatest change was for the grafted group, with width change from 12.4 ± 2.1 mm before extraction to 9.9 ± 1.8 mm 4 to 5 years after implant placement. Bone width changes 5 and 10 mm inferior to the crest did not change over time. CONCLUSION: Within the time course and sample size evaluated, the thickness of the buccal bone seems to be maintained over time, regardless of method used, with small yet important changes from before tooth removal through the long-term.