ABSTRACT
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'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 +/- 2.19 N, 52.19 +/- 1.44 N, and 49.03 +/- 5.89 N, respectively, while these values were the lowest for BR with 29.78 +/- 2.52 N, 12.10 +/- 0.45 N, and 6.26 +/- 0.45 N, respectively
Conclusion: the attachment designs affected the retention and stability of mandibular implant-supported overdentures