Investigation of the bond strength of a polyvinylsiloxane based matrix material with different hardness values to the denture base

Recent studies presented silicone based resilient liners with clinically successful results regarding their use as matrix materials in implant supported complete dentures. However, long term in-vivo studies reported the debonding of these materials from denture bases as the most frequently seen clinical complication. The aim of this study was to investigate the bond strength of a polyvinylsiloxane based matrix material with different hardness values (Retention.sil) to denture base. A total of 480 acrylic blocks (240 Promolux, 240 Promolux High Impact), 10 for each group were manufactured. Samples were divided into 4 groups as control, acid (30 sec phosphoric acid), monomer (180 sec monomer), acid+monomer (30 sec phosphoric acid + 180 seconds monomer). These surface treatment groups were further divided into 3 subgroups as Retention.sil 200-400-600 and samples were finished with 2mm thick Retention.sil packed between acrylic blocks. All samples were subjected to thermo-cycling of 1000 cycles before tensile bond strength testing. Results were recorded in megapascals (MPa). Mechanical failure modes were also macroscopically observed. Threeway ANOVA Test, Oneway ANOVA Test (as supplementary) and Student's t- test were used for statistical evaluation. The results showed Retention.sil 400 to have the highest and Retention.sil 200 the lowest bond strength. No statistically significant differences were found between surface treatments in Promolux High Impact groups. Among Promolux groups acid application showed a significant increase in bond strength with Retention.sil 200 and decrease in other subgroups; whereas an increase in bond strength in all monomer groups and significant decrease in all acid + monomer groups were found. Retention.sil 200 samples resulted in only cohesive and Retention.sil 600 samples resulted in only adhesive failure, whereas retention.sil 400 samples showed all three types of failures. Keywords: Resilient liners, polyvinylsiloxane, implant supported complete denture, bond strength.