RESUMO
OBJECTIVES: Water sorption and water solubility adversely affect the mechanical properties and biocompatibility of the denture material. This study aimed to evaluate the water sorption and solubility of three direct hard reline acrylic resins and a heat-curing one after immersion in food-simulating agents. MATERIALS AND METHODS: This study was performed on four groups of samples (n = 10 per group). The samples were made of three direct hard reline acrylic resins (TDV Cold Liner Rebase, Tokuyama Rebase II Fast, GC Reline Hard) and a heat-curing one (Meliodent). Each group was divided into four subgroups (n = 10) to undergo 7-day immersion in distilled water, 75% ethanol/water, 0.02 N citric acid, and heptane. Water sorption and solubility were calculated according to Oysaed and Ruyter formula. The statistical analyses were done by using SPSS software (version 22). Kruskal-Wallis H Test and Dunn's test were used to detect any significant difference among the groups (P < 0.05). RESULTS: The median range of water solubility and water sorption values were -0.87-4.92 and 3.75-27.25 µg/mm3, respectively. The median solubility and sorption values of different resins differed significantly in the same solution (P < 0.05). Besides, immersion in different solutions caused significant differences in the median solubility and sorption values of each reline material (P < 0.05), except for Meliodent whose solubility was not significantly affected by different solutions (P = 0.16). CONCLUSIONS: Water sorption and solubility values of the tested hard reline resins were within the range of International Standards Organization 1567:1999. Given the low sorption and solubility values, these hard reline materials can be safely used in clinical situations.
RESUMO
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.
