Effect of denture cleansers on surface hardness of resilient denture liners at various time intervals- an in vitro study

PURPOSE: This study was aimed to determine the effect of two chemically distinct denture cleansers and water on the surface hardness of acrylic and silicone based soft denture liners at various time intervals. MATERIALS AND METHODS: Two commonly used commercial resilient liner material were selected based on their chemical composition (silicone- and acrylic-based soft liners) for this investigation. 120 cylindrical specimens were made of 15 mm x 10 mm dimensions (according to ASTM: D-2240-64T) in a custom made metal mold. All specimens were stored in artificial saliva throughout the study. Forty specimens were cleansed daily in 0.5% sodium hypochlorite solution; forty were cleansed in sodium perborate and remaining forty specimens were daily rinsed in water. Testing was done at 1 week, 1 month, 3 months and 6 months for surface hardness using a Shore A Durometer. A mean of 3 reading for each sample was subjected to one-way ANOVA, Post Hoc test and pair-t test for statistical analysis. P values of less than 0.05 were taken as statistically significant. RESULTS: Surface hardness of all the samples was significantly higher after a period of 6 months irrespective of the cleansing treatment. Minor changes were observed between control, sodium hypochlorite and sodium perborate groups with time. Greater change was observed in surface hardness of acrylic-based soft denture liners as compared to silicone-based soft liners for all groups, as time progressed. CONCLUSION: Silicone-based soft denture liners performed significantly better in all cleansing treatments than acrylic-based soft denture liners.

Evaluation of tensile bond strength of heat cure and autopolymerizing silicone-based resilient denture liners before and after thermocycling.

Aim: To assess the effect of simulated mouth conditions reproduced with thermocycling on the tensile bond strength of two silicone based resilient denture liners with acrylic resin bases. Materials and Methods: Two silicone-based soft denture liners (Mollosil - Chairside autopolymerization and Molloplast B - Heat polymerization) were tested. For each liner, 30 specimens with a cross-sectional area of 10 Χ 10 mm and thickness 3 mm were processed between two acrylic blocks (Trevalon). Specimens were divided into a control group that was stored for 24 hours in water at 37°C and a test group that was thermocycled (2500 cycles) between baths of 5° and 55°C. Tensile bond strength (kg/cm 2 ) was determined in a universal testing machine using crosshead speed of 5 mm/min. Statistical Analysis Used: The student t-test was used to determine the significance of the difference in bond strength between the two liners. Results: The mean tensile bond strength for control and thermocycled specimens of the two liners were: Mollosil (6.82 kg/cm 2 and 8.41 kg/cm 2 ) and Molloplast-B (16.30 kg/cm 2 and 13.67 kg/cm 2 ), respectively. Comparison of bond strength of control specimens with thermocycled specimens of the liners indicated a significant difference for both Mollosil (P=0.045) and Molloplast-B (P=0.027). Comparison between control specimens of both liners and thermocycled specimens of both liners indicated a highly significant difference (P<0.001). Conclusions: Heat polymerized resilient denture liner Molloplast-B had higher tensile bond strength than autopolymerizing liner Mollosil regardless of thermocycling. The bond strength of Mollosil increased after thermocycling while that of Molloplast-B decreased after thermocycling. Clinical Implications: Although heat-polymerized denture liners require more processing time than autopolymerizing liners, but they display much better adhesion properties to denture base resin and should thus be preferred when soft liner has to be used for a longer duration of time.

The effect of fermented foods on the color change of soft denture liners / 대한치과보철학회지

STATEMENT OF PROBLEM: The clinical criteria of soft lining materials are resilience over an extended period, capability of forming a strong bond with denture base materials, dimensional stability, adequate tear strength, and color stability. Many researches and reports dealt with food colorants or denture cleanser, but not with fermented foods. PURPOSE: This study was designed to assess what fermented foods, such as soy sauce and red pepper paste that many Koreans have eaten, influence on the color stability of soft denture liners. MATERIAL AND METHODS: The color differences(delta E*) were measured by spectrophotometer with different immersion time. For the procedure, thirty disk-shape specimens per 4 soft denture liners(Molloplast-B(R), Ufi Gel SC(R), Dura Base(R), Sofreliner MS(R)) were fabricated with a thickness of 2mm and 16mm in diameter. Each 10 specimen were immersed into the beakers of fermented foods and distilled water, and L*, a*, and b* values were measured for the color difference(delta E*), on the 1st, 7th, and 28th day with spectrophotometer. RESULT AND CONCLUSION: 1. There were significant differences between samples(soy sauces, red pepper pastes, and distilled water) in Sofreliner MS(R) of 1st day after immersion(p<0.05). There were significant differences between samples in Sofreliner MS(R) and Ufi Gel SC(R) of 7th days after immersion(p<0.05). There were significant differences between samples in Molloplast-B(R) of 28th day after immersion(p<0.05). 2. In red pepper pastes, delta E* values of Molloplast-B(R), Ufi Gel SC(R), Sofreliner MS(R) were higher than 3.3. Those values were not clinically acceptable. In soy sauces, delta E* values of all denture liners were lower than 3.3. delta E* values of Ufi Gel SC(R) were higher than those of other denture liners. 3. Based on the above results, red pepper paste causes more discoloration than soy sauce.