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.

The Effect of Food-Simulating Agents on the Bond Strength of Hard Chairside Reline Materials to Denture Base Resin.

PURPOSE: To investigate the influence of food-simulating agents on the shear bond strength between direct hard liners and denture base acrylic resin. In addition, mode of failure was evaluated. MATERIALS AND METHODS: One hundred fifty cylindrical columns of denture base resin were fabricated and bonded to three types of hard reline materials (Hard GC Reline, Tokuyama Rebase II Fast, TDV Cold Liner Rebase). Specimens of each reline material were divided into five groups (n = 10) to undergo 12-day immersion in distilled water, 0.02 N citric acid aqueous solution, heptane, and 40% ethanol/water solution at 37°C. The control group was not immersed in any solution. The shear bond strength test was performed, and the failure mode was determined. Statistics were analyzed with two-way ANOVA and chi-square test (α = 0.05). RESULTS: Significant interaction was found between the hard liners and food simulating agents (p < 0.001). The shear bond strength of Tokuyama in 40% ethanol and TDV in heptane decreased significantly (p = 0.001, p < 0.001 respectively); however, none of the solutions could significantly affect the shear bond strength of Hard GC Reline (p = 0.208). The mixed failure mode occurred more frequently in Hard GC Reline compared with the other liners (p < 0.001) and was predominant in specimens with higher bond strength values (p = 0.012). CONCLUSIONS: Food simulating agents did not adversely affect the shear bond strength of Hard GC Reline; however, ethanol and heptane decreased the bond strength of Tokuyama and TDV, respectively. These findings may provide support to dentists to recommend restricted consumption of some foods and beverages for patients who have to use dentures relined with certain hard liners.

Evaluation of proliferation activity in dysplastic and nondysplastic oral lichen planus through the analysis of argyrophilic nucleolar organizer regions.

Lichen planus is a mucocutaneous disease, and its potential for malignant transformation is a subject of controversy. We found dysplastic changes in slide review of about 11% of oral lichen planus (OLP) in our previous research. Dysplastic changes can be an initial phase for carcinogenesis. The question is whether it is possible to detect early malignant changes in OLP through the evaluation of proliferation activity. The aim of this study was to compare the cell proliferation activity in dysplastic and nondysplastic oral lichen planus using the quantitative and qualitative analysis of argyrophilic nucleolar organizer region (AgNOR) and to compare candidal infection in these 2 groups. In this cross-sectional, observational, and analytical study, all 14 cases of confirmed dysplastic OLPs and 17 nondysplastic OLPs were stained with an AgNOR technique. Analysis of argyrophilic nucleolar organizer region dots were counted in 100 cells of basal and parabasal layers, and proliferation index (cells with ≥ 5 dots in nucleus) and variations in size of AgNOR dots were also evaluated. Periodic acid-Schiff staining was performed for detection of candidal infection. Mean AgNOR count in dysplastic OLP (2.39 ± 0.2) was more than nondysplastic OLP (2.27 ± 0.59). Candidiasis was found in 14.3% of dysplastic OLP and in 12.5% of nondysplastic OLP. There was no statistically significant difference between the 2 groups in mean AgNOR count (P = 0.62), variation in size of AgNOR dots (P = 1), proliferation index (P = 0.53), and candidiasis (P = 1). The current study showed slight difference in proliferation rate and candidal infection between dysplastic and nondysplastic OLP.