Bonding of a Gingival Shade Composite to a Denture Base

Objective: To determine an effective surface preparation for the bonding of a gingival shade composite resin to a denture base resin. Methods: The flat surfaces of a heat-processed denture base resin (Acron clear, GC, Tokyo, Japan) abraded with up to 400-grit silicon carbide paper were prepared in one of the following ways: 1) no preparation; 2) 4-META resin (Super-Bond C&B ivory, Sun Medical, Moriyama, Japan) monomer (dry); 3) dichloromethane and silane coupling agent (Clearfil Ceramic Primer, Kuraray Medical, Tokyo, Japan); 4) 4-META resin monomer (wet); or 5) 4-META resin slurry. A highly filled gingival shade composite resin (Meta color Prime art accessory color paste Gum, RS1, Sun Medical) was applied (5.0 mm in diameter) and polymerized with a light-polymerizing unit. The specimens were shear tested for a 24-hour maximum fracture load in a universal testing machine. The specimens from Groups 3-5 were thermocycled in water between 5„aC and 55„aC for 10,000 cycles and then tested. The data were analyzed statistically using a one-way ANOVA, Newman-Keuls post hoc comparison and the Student t-test (95% confidence level). Results: Before thermocycling, Group 1 yielded the lowest fracture load (2.3 ± 5.6 N), and Groups 4 and 5 yielded a higher fracture load (405.7 ± 31.0 N and 473.2 ± 45.5 N, respectively) than the other Groups (p<0.05). After thermocycling, Group 5 exhibited a greater fracture load (432.2 ± 65.0 N) compared to Group 4 (326.0 ± 42.0 N) (p<0.05). The fracture load was not significantly reduced by thermocycling in Group 5 (p>0.05). Conclusion: Within the limitations of the present study, the application of chemically activated 4-META resin slurry as glue and the prompt subsequent procedures were effective at bonding the gingival shade composite resin to a denture base resin.