Implant-Supported Mandibular Overdentures Retained with Ball or Bar Attachments: A Randomized Prospective 5-Year Study

Purpose: The aim of the present study was to evaluate the periimplant conditions and the maintenance requirements for implant-supported overdentures in the mandible retained with ball or bar attachments during a 5-year period. Materials and Methods: Twenty-six completely edentulous patients had two Astra Tech dental implants placed in the anterior part of the mandible. The denture attachment system for the patients was chosen randomly by drawing lots. Eleven patients drew the bar attachment system and fifteen patients drew the ball attachment system. Plaque Index, Gingival Index, and probing pocket depth were assessed around each implant. Periotest values were recorded, and periodically identical intraoral radiographs were obtained with a specially designed filmholding device. Results: No implants were lost from baseline to the 5-year registration. The periimplant conditions were very healthy after 5 years. No significant differences of the periimplant variables were recorded between the bar and the ball groups. During the first year of function, significantly more complications/repairs were registered in the bar group than in the ball group. In the following years, no significant differences were registered. The mean frequency of complications/repairs per patient per year was 1.0 in the bar group and 0.6 in the ball group during the 5-year observation period. Conclusion: Two implants with ball or bar attachment supported an overdenture in the mandible for 5 years with a 100% survival rate. No differences in marginal bone loss or health of the periimplant mucosa were observed between bar and ball attachment, but the frequency of technical complications/repairs per patient was higher around bar than ball attachments.