Thesis (M.Sc.)--Chulalongkorn University, 2013

The objective of this study was to evaluate and compare the effects of two desensitizing toothpastes and a regular fluoride toothpaste on microtensile bond strength of two adhesive agents to dentin. Materials and methods: The labial surfaces of forty bovine incisor crowns were ground flat, exposing dentin. The teeth were then randomly divided into four groups corresponding to the toothpaste used: 1) Sensodyne Rapid Relief (GlaxoSmithKline, UK), 2) Colgate Sensitive Pro-Relief (Colgate-Palmolive, Thailand), 3) Colgate Regular Flavor (Colgate-Palmolive, Thailand), and 4) immersed in artificial saliva (control). Each tooth in groups 1–3 was brushed with its respective dentifrice under constant loading (200 g) at 250 strokes/min for 2 minutes, twice daily for three days. Each group was then randomly divided for composite build-up using the following adhesive agents: 1) Optibond XTR (Kerr, USA), or 2) Optibond FL (Kerr, USA). After curing the adhesives, a light-cured resin composite (Premise, Kerr, USA) was used for a core build-up. The samples were sectioned into four 1± 0.1 mm thick specimens. The microtensile bond strength test was performed using a universal testing machine at a cross-head speed of 0.5 mm/min. The data were analyzed using two-way ANOVA and Tukey’s multiple comparison tests with significance set at p < 0.05. Fracture analysis of the debonded dentin surface was performed using a stereomicroscope. Results: Bond strength was significantly reduced by the application of desensitizing toothpastes (p < 0.0001). Moreover, the type of adhesive agents had a significant effect on bond strength (p < 0.0001). Conclusion: The use of desensitizing toothpaste may reduce bond strength of adhesives to dentin.