Resin composite bond integrity with desensitized dentin

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Objectives: To study the influence of using nano-hydroxyapatite or self-assembling peptides containing desensitizing agent on the dentin-resin composite microtensile bond strength and interfacial micromorphology.
Materials and methods: Standardized mid coronal flat dentin was obtained from a collected thirty molars. Exposed dentin surfaces were demineralized and randomly divided into three equal groups (10 each) according to the desensitizing agent used; without (control), nano-hydroxyapatite containing (Remin Pro, VOCO, Germany) or self-assembling peptide (CurodontTM Protect, Credentis, Switzerland). Desensitizing agents were uniformly distributed over the demineralized surfaces and left for 5 minutes/ once daily for 7 days. Specimens were stored in artificial saliva during the seven days. Resin composite (Aelite Aesthetic Enamel, Bisco, Inc, Schaumburg, USA) core was built over the demineralized substrate after being bonded with All-Bond Universal adhesive (Bisco, Inc, Schaumburg, USA). Slabs with a cross-sectional area of approximately 1mm2 were obtained from all bonded specimens and subjected to microtensile bond strength testing at a cross head speed of 1.0mm/min. Fractured specimens were examined under a digital microscope at 50x to examine the failure mode. Micromorphological analysis for the resin dentin interface and fractured specimens were done using SEM. Statistical analysis was done using One way-ANOVA followed by Tuckey’s post hoc test for comparison (P≤ 0.05).
Results: The mean bond strength values recorded in (MPa) were (38.0(6.7)) Remin Pro, (30.17(6.3)) Curodont and (30.65(6.4)) control with a statistical significant difference between them. Adhesive failure was prominent in Curodont, however, cohesive and mixed failures were common in the other two groups. Micromorphological analysis revealed crystal deposits along the hybrid layer and resin tags in Remin Pro group and defective hybridization with Curodont.
Conclusions: Dentin desensitization has not any adverse effect on the resin composite bond integrity. The use of Nano-hydroxyapatite containing agent plays a role in the reinforcement of hybrid layer.