In vitro evaluation of cyclic loading on retention strength of Retention.sil and O/ring attachments for tooth supported overdenture

Statement of Problem: Numerous different attachments are used to retain overdentures. Hence, there is a need to assess new chairside attachment system based on polyvinylsiloxane (Retention.sil [R.S]) to know its in vitro behavior to be used clinically. Purpose: To assess and compare the retentive force of two female matrix retention system (R.S with a conventional O-ring [OR] attachment system) in tooth-supported overdenture. Materials and Methods: Completely edentulous mandibular model with two canine root-anchored ball attachments for overdentures were fabricated. A total of 30 mandibular dentures were made and divided to form two groups, each with a different attachment design. One group (test) received 5 pairs of R.S attachments while the other group (control) received 15 pairs of ORs. Retention force was measured by subjecting them to 540 cycles of insertion and de-insertion cycles (representing 6 months functional life) in axial direction before and after thermocycling. Results: Statistical analysis comprised Kolmogorov–Smirnov test, Friedman test, and Wilcoxon signed-rank test (α = 0.05). The initial retention of R.S attachments was 5.90 ± 0.77 N and of ball/OR 17.36 ± 3.81 N. The final retention of R.S attachments was 5.41 ± 0.72 N and of ball/OR 12.91 ± 3.18 N. The OR developed higher retentive force as compared to the R.S attachments (P < 0.05). However, no significant changes in retention force were observed for R.S groups after repeated dislodging and thermal undulation. Conclusion: Both systems presented acceptable retention capacities after 540 cycles. The newly developed R.S attachments can provide an alternative to OR attachments for short-term retention. Clinical studies are however required to elucidate the long-term performance of these materials.