Comparison of the Effect of Ball and Bar Attachment Designs on Retention and Stability of Mandibular Implant-Supported Overdentures

Objectives: The present study evaluated the effect of bar and ball attachment designs on retention and stability of a mandibular overdenture supported by four implants. Methods: An edentulous mandibular acrylic resin model with four implants in the anterior part of the ridge (A, B, D and E) was fabricated. A metal framework simulating the overdenture was also fabricated. Totally, 30 overdentures were divided into three groups based on the attachment design; BL: Four ball attachments in A, B, D and E positions; BB: One bar attachment between B and D positions and two ball attachments at positions A and E; BR: Bar attachments between the positions A, B, D and E with two posterior extensions. To evaluate the retention and stability of the overdenture, tensile dislodging forces were applied in three directions of vertical, oblique and anterior-posterior by a universal testing machine. One-way ANOVA and Tukey&rsquo;s HSD test were performed to analyze the data. All tests were carried out at 0.05 level of significance. Results: There were statistically significant differences between the groups in the peak load (P<0.001). The peak load values for vertical, oblique and anterior-posterior dislodging forces were the highest for BL with 49.38 &plusmn; 2.19 N, 52.19 &plusmn; 1.44 N, and 49.03 &plusmn; 5.89 N, respectively, while these values were the lowest for BR with 29.78 &plusmn; 2.52 N, 12.10 &plusmn; 0.45 N, and 6.26 &plusmn; 0.45 N, respectively. Conclusion: The attachment designs affected the retention and stability of mandibular implant-supported overdentures