Influence of Axial and Angled Implants on Marginal Bone Loss in All-on-Four Implant-Supported Rehabilitation: A Retrospective Cohort Study

Abstract

ObjectivesThe aim of this study was to compare marginal bone loss levels between axially and angled installed implants in maxillary rehabilitation utilizing the All-on-Four concept, while also examining the impact of terminal cantilever size on implant/prosthesis set survival.Materials and MethodsThis retrospective cohort study involved 11 patients (44 implants) who received implant-supported prostheses with immediate loading. Radiographic evaluations were conducted on the day of prosthesis delivery, including panoramic and periapical radiographs, establishing the baseline (T0). Follow-up periapical radiographs were taken at 6 months (T1), 1 year (T2), and 2 years (T3) post-prosthesis delivery. Panoramic radiographs were used to determine implant angulation and the size of terminal cantilevers. Marginal bone loss on the mesial and distal aspects of each implant was assessed across study periods.ResultsStatistical analysis revealed no significant difference in marginal bone loss between axially and inclined implants. Terminal cantilever lengths ranged from 6.11 to 17.15 mm, with a decrease observed in cases with implants tilted up to 30°. However, no significant difference in cantilever lengths was found between the two groups (group 1: tilts 0°–30°, group 2: tilts above 30°). The survival rate of the implant/prosthesis sets was 100%.ConclusionIn conclusion, there were no statistically significant differences in marginal bone loss between axial and inclined implants. Implant inclination allowed for prostheses with smaller terminal cantilevers, contributing to a balanced distribution of stresses on the implant/prosthesis set. Further randomized clinical trial should be conducted to confirm the presented findings.