Comparison of Tensile Bond Strength of Permasoft® and GC Reline Soft® Resilient Liners after Denture Base Surface Pretreatment

Abstract

Objectives: The surface treatment of intaglio denture base surface by sandblasting followed by Methyl Methacrylate (MMA) monomer might enhance the bond strength of resilient liners. The purpose of this study was to evaluate and compare Tensile Bond Strength (TBS) of two resilient liners after surface treatment of Polymethyl Methacrylate (PMMA) resins by sandblasting and MMA monomer. Materials and Methods: One hundred and sixty PMMA resin blocks were randomly divided into eight groups of 20 blocks each based on type of resilient long term liner used (P=PermaSoft and G=GC Reline Soft) and the surface treatment performed (C=untreated Controls, S=Sandblasted, M=MMA monomer treated and SM=Sandblasted and MMA monomer treated: Group PC (PermaSoft untreated Controls), PS (PermaSoft Sandblasted), PM (PermaSoft MMA monomer treated) and PSM (PermaSoft Sandblasted and MMA monomer treated, GC (GC Reline Soft untreated Controls), GS (GC Reline Soft Sandblasted), GM (GC Reline Soft MMA monomer treated) and GSM (GC Reline Soft Sandblasted and MMA monomer treated). Each specimen was prepared by joining two PMMA resin blocks having standard dimensions of 10 × 10 × 40mm with either of the resilient liner of thickness of 10 × 10 × 3mm. The prepared 80 specimens were subjected to testing of TBS by universal testing machine. Also, the types of failure, whether adhesive, cohesive or mixed, were determined by stereomicroscope. One-way ANOVA followed by Tukey post hoc test was used to compare TBS of different surface treatment group with similar resilient liner. Student T-test was used to compare TBS of different resilient liner with similar surface treatment. The level of significance was set at 0.05. Results: There was highly significant difference in mean TBS of four surface treatment subgroups within both the groups (P<0.001). The Tukey post hoc test showed significant difference (P<0.05) between group PC=0.837 ± 0.120MPa and PSM=1.104 ± 0.234MPa; and GS=1.304 ± 0.261MPa and GM=2.053 ± 0.784MPa and highly significant difference (P<0.001) between group PS=0.741 ± 0.103 MPa) and PSM=1.104 ± 0.234MPa); and GS=1.304 ± 0.261MPa) and GSM=2.176 ± 0.262MPa. The mean TBS of GC Reline Soft was significantly higher (<0.001) than PermaSoft in various surface treatment groups. The overall modes of failures were predominantly cohesive type (63.75%) followed by mixed type (18.75%) and adhesive type (17.50%). Conclusions: All groups tested had mean bond strength values greater than the minimum acceptable standard (0.44MPa) for clinical application. MMA monomer treatment alone or in combination with sandblasting resulted in increase of the mean TBS whereas sandblasting resulted in decrease of the mean TBS of both PermaSoft and GC Reline Soft specimens.