Purpose: The purposes of this study were to develop a technique to measure the angulation between two implants and between each implant and reference planes, to analyze the relationship between the maintenance (adjustments and repairs) of ball-attachment mandibular implant overdentures and implant angulation, and to see if there is any correlation between surgeon experience and implant orientation. Materials and Methods: Final casts of 41 patients who had received two-implant ball-attachment
mandibular overdentures were used to measure implant angulations using digital photographs and plane geometry. The measured angles were compared with the number of adjustments and repairs of the prostheses and analyzed by surgeon experience for any trends. Results: No significant relationships were found between number of adjustments and repairs and the interimplant angles. However, there was a significantly higher number of repairs when the lingual inclination of an implant was ¡Ý 6.0 degrees (P =.033) or if the facial inclination was < 6.5 degrees (P = .036). Less experienced surgeons had a significantly greater tendency to place implants that diverged from each other in the frontal plane (P =.045) and with a facial or lingual inclination in the sagittal plane (P =.035). Conclusion: While interimplant angulation did not appear to affect prosthesismaintenance, individual implants with a lingual inclination ¡Ý 6 degrees and a facial inclination < 6.5 degrees were associated with significantly more prosthesis repairs. There was a tendency for implants placed by less experienced surgeons to demonstrate greater inclination. Int J Prosthodont 2001;14:523¨C530.