Bond strength of hard direct reline materials to heat-cured acrylic denture base after immersion in denture cleansers

Background: Immersion-type denture cleansers are commonly used for denture hygiene maintenance. Hence, it is crucial to investigate the effect of denture cleansing solutions on bond strength between direct reline materials and denture base resin. Aims: This in vitro study aimed to determine the effect of denture cleansers on bond strength between direct hard reline materials and denture base resin. Materials and Methods: Cylindrical columns of hard-liners (Hard GC Reline, TDV Cold Liner Rebase, Tokuyama Rebase II Fast) were bonded to heat-polymerized denture base resin. A total of fifty specimens were fabricated for each reline material and divided into five groups (n = 10): Group I (control): No solution was used; Group II: Specimens were stored in distilled water for 60 days; Groups III, IV, and V: Specimens were stored in distilled water for 60 days with daily immersion in either sodium hypochlorite, calgon + sodium hypochlorite, or dentipur tablet for 5 min. The shear bond strength was examined at a cross-head speed of 1 mm/min. Failure mode was evaluated by stereomicroscope. Statistical Analysis: Data were analyzed by two-way ANOVA and Chi-square test (α=0.05). Results: The results showed no significant interaction between the direct hard-liners and denture cleansers (P = 0.119). Hard GC Reline had the highest bond strength, followed by Tokuyama Rebase II Fast, and then, TDV Cold Liner Rebase. No significant difference existed in bond strength between samples immersed in water and cleansers or between the cleansers themselves. Hard GC Reline had more mixed failure mode compared to TDV Cold Liner Rebase and Tokuyama Rebase II Fast. There was a significant correlation between mixed mode of failure and higher values of bond strength (P = 0.008). Conclusions: Within the limitations of the present study, denture cleansing solutions could not significantly influence the bond strength between hard direct liners and denture base resin.