Effect of Denture Cleansers to Silicone Soft Liners Interface Adhesion

Objective: To investigate the effect of denture cleansers on silicone soft liners interface adhesion to Polymethylmetacrylate (PMMA) denture base. Method: 135 specimens (10mm x 10mm x 6mm) were prepared.  The denture bases were treated with respective primer/adhesive prior to lining procedure (GC Soft liner, Tokuyama Tough and Mollosil), and the surface roughness before and after surface treatment were measured (Ra). Fifteen specimens from each soft liner group were immersed in different denture cleansers (Distilled water, Polident and Steradent) daily and stored in distilled water at 37±1°C. Five specimens from each group were then examined after Days 1, 30 and 90 for: (i) mode of failure and (ii) gap formation at interface. Measurements were done at margin, at 2.5mm and 5.0mm from margin of each specimen. Result: Significant difference (p<0.001) in mean surface roughness changes in GC soft and Tokuyama Tough groups was observed.  The highest and lowest Ra values were observed in Tokuyama Tough (mean±SD=0.1613µm±0.0869) and Mollosil (mean ±SD= -0.0044µm±0.0142) group respectively. After Day 30, Mollosil specimens immersed in Steradent demonstrated largest interface gap formation at the margin (median and interquartile range= 4.362, 2.360) and at 2.5 mm from margin (median and interquartile range= 2.720, 1.746). Adhesive failure was the commonest at specimens’ margin between soft liner-denture base interfaces (77.8%). After 90 days, all specimens exhibited adhesive failure at margin (p>0.050) but at 5.0mm section, mixed mode type of failure was observed (33.3%).  Mollosil demonstrated largest gap formation at 2.5mm section (median and interquartile range = 3.885, 2.469) while Tokuyama tough specimens at 5.0mm (median and interquartile range = 2.610, 0.845). Conclusion: Steradent demonstrated increase in interface gap compared to Polident®. Among the soft liners used, GC soft liner had the smallest gap formed.  There was significant but moderate correlation between surface roughness and interface gap.