The Influence of Palatal Coverage on the Retention Force and FatigueResistance of Mini Dental Implant Maxillary Overdenture

Purpose: evaluation and comparison of the influence of palatal coverage on the retention force and fatigue resistance of attachment system of mini dental implant (MDIs) overdenture. Materials and methods: heat-cured polymethylmethacrylate resin maxillary acrylic resin models were used for this study. Five 2.5 × 13 mm dummy mini-dental implants with O-ring attachment were placed parallel to each other. Ten palateless implant retained overdenture, and ten full coverage implant retained overdenture were constructed on the models. Both of them, retention and cyclic fatigue tests of each overdenture were measured using BENDAO tools of the universal testing machine and average reading was calculated. Result: (Group I) mini-dental implant overdenture with palatal coverage recorded higher retention means value (25.55 ± 2.17 N) than (group II) mini-dental implant overdenture without palatal coverage (palate-less overdenture) (24.215 ± 3.64 N). the cyclic fatigue test for the (group I) mini-dental implant overdenture with palatal coverage Showed that the retention decreased significantly with time as indicated by ANOVA test (p < 0.05), While for (group II) mini-dental implant overdenture without palatal coverage (palate-less overdenture) was found that the retention was insignificant decrease in the first month; then it significantly decrease in the remaining periods of the study as indicated by ANOVA test (p < 0.05). Conclusion: Within the limitations of this in vitro study it can be concluded that the mini-dental implant overdenture with palatal coverage showed superior retentive properties when compared with mini-dental implant overdenture without palatal coverage (palate-less overdenture). Both study groups showed a reduction in retention after cyclic fatigue period.