Effects of mechanical and chemical hygiene methods on the O-ring system-retained overdenture: A simulated two-year evaluation.

Background: Cleaning overdentures is challenging due to their complex metallic structures, which often create small and irregular areas that are difficult to clean. Thus, it is necessary to find an effective and safe method for their maintenance.

Objectives: The aim of the study was to evaluate the effects of hygiene methods on the dimensional changes and retention force of the O-ring system over a simulated two-year period.

Material And Methods: A total of 54 specimens with 2 O-rings each were distributed into 9 groups: control - no cleaning; brushing - blue®m toothpaste (BM); brushing - Trihydral toothpaste (TR); immersion - NitrAdine® (Ni); immersion - 5 mg/mL chitosan solution (Ch); and combined methods: BM+Ni, BM+Ch, TR+Ni, TR+Ch. The deformation and retention force were evaluated every 6 months for 2 years. The statistical analysis was performed using two-way analysis of variance (ANOVA) and Pearson's correlation test (α = 0.05).

Results: The BM+Ch group exhibited smaller changes in diameter after 6 months (Δ(T1-T0)) than the control and BM+Ni groups, both internally and externally (p < 0.001). In addition, the BM+Ch group demonstrated greater retention forces at 6 months (p = 0.024) and 18 months (p = 0.028) in comparison to the TR+Ch group. The TR+Ch group exhibited a negative correlation with changes in the external diameter (r = -0.334, p = 0.021), while BM+Ch showed a negative correlation with changes in the internal diameter (r = -0.334, p = 0.021). The Ni group demonstrated a negative relationship with changes in both the internal (r = -0.296, p = 0.041) and external diameters (r = -0.405, p = 0.004).

Conclusions: A combination of brushing with blue®m toothpaste and immersion in the chitosan solution demonstrated satisfactory results in maintaining the retention force of the O-ring system.