Effect of Delaying Curing of Composite on Bonding to Dentin

In restoring teeth with composite resin, clinicians may delay curing composite until proper anatomy is achieved. Objective: This study was designed to evaluate the effect of time elapsed between application of a dental adhesive and curing subsequently placed composite. Four single bottle adhesives used in this study were: One-Step (OS) (BISCO), PQ1 (Ultradent Prod. Inc.), Prime & Bond N/T (P&B) (Dentsply/Caulk) and Clearfil Liner Bond 2V GLB (Kurary). Adhesives were selected based on the types of solvents. Time elapsed between application of adhesives and curing of subsequently placed composite (Z100, 3M) was 45 seconds (Control Group), 2 minutes and 5 minutes. Methods: Human molars flattened in dentin, imbedded in polymethylmethacrylate were used. The bonds were tested using an Instron Testing Machine at a crosshead speed of 1 mm/min. Results: The mean SBS (MPa) for four adhesives and three time tables (45 sec, 2 m and 5 m) respectively were: 45 sec. OS=30.5 ± 2.1, CLB=38.6 ± 4.1, PQ1 53.4 ± 3.3, P & B 40.8 ± 2.6. At 2 min. OS=27.7 ± 3.1, CLB=22.6 ± 10.6, PQ1=51.2 ± 3.5, P&B + 29.2 ± 15.9. At 5 min. OS=28.6 ± 2.3, CLB=20.2 ± 13.3, PQ1=43.6 ± 8.3, P&B=32.2 ± 13.8. Two-way analysis of variance showed significant differences between adhesives (P<.0001). With the exception of OS, the time elapsed between application of adhesives and curing the subsequently placed composite had adverse effect on dentin-composite bond. CLB and P&B showed significantly lower bond strength after 2 and 5 min. of delayed curing. The bond strength of PQ1 was reduced at 5 min of delayed curing. Conclusion: The adverse effect of time elapsed between the application of single bottle adhesives and curing of composite resin varied in this study. Supported by Ultradent Products Inc.