Purpose: To analyze the influence of pristine matrix and O-ring dimensions on retention force and its reproducibility in single one-piece mini dental implants (MDIs) with ball patrices under in vitro conditions.
Materials and Methods: Three different matrix/O-ring combinations (MH1, MH2, and MH3) were evaluated (n = 50 measurements each) on 1.8-mm–diameter implants. The matrices were manually mounted on the implants and subsequently removed in a vertical linear manner using a metal pin with two strain gauges, which recorded the maximum force during disconnection. The O-rings were exchanged after five disconnections, and the mean retention force was calculated, resulting in a total of 50 values for each matrix/O-ring combination. Mean and SD retention forces with 95% CI were calculated. ANOVA was used to test the global difference, and post hoc pairwise comparisons were subsequently applied. The level of significance was set at P < .05.
Results: ANOVA (global P < .0001) and pairwise comparisons (all P < .001) demonstrated statistically significant differences between the three different matrix/O-ring combinations with mean values of 5.18 N (MH 1), 6.73 (MH 2), and 9.08 (MH 3). Within each combination, retention force variations of > 1 N could not be demonstrated; ie, by exchanging O-rings, a similar retention force can be reestablished.
Conclusion: Matrix and O-ring dimensions have a significant influence on retention forces in one-piece MDIs. Pristine O-rings demonstrated highly reproducible initial retention forces in all matrices.