Analysis of retention and wear of ball attachments

Objective: To evaluate the retention and the wear of different prefabricated precision ball attachments consecutively during long-term use. Method and Materials: Six commercially available ball attachment systems were selected. The balls were attached to stylized implants fixed in metal casts. The matrices were fixed in a stylized unilaterally removable partial denture (RPD). Using a chewing simulator with 8 units, 50,000 joining and separating cycles of the matrices were performed. After each joining movement, an eccentric load of 100 N was applied to the RPD at a distance of 12 mm from the ball attachment. The retention forces were measured at intervals. Results: Initially, median retentive forces varied between 8.2 N and 14.0 N. During the test, patterns in retention changes were identified. At the end of the test, one group with a matrix using precious alloy lamellae and a titanium ball showed significantly higher median retention forces (10.4 N) than the other ball attachments (1.0 N to 3.7 N). Also, the wear of the ball attachments varied considerably. Conclusion: Within the limitations of this study, the material combination of a precious gold alloy matrix and a titanium ball seems to be favorable for long-term retention. Keywords: ball attachment, implant, retention, wear