Aim: This study was designed to evaluate the effect of incorporation of hydroxyapatite nanorods into a resin composite restorative material and dental adhesive on shear bond strength to dentin and interfacial micromorphology after storage in different media. Materials and Methods: Ninety natural premolars (N=90) were selected for this study and randomly divided into three main groups (n =30) according to the material used (A), where A1: the resin composite restorative material reinforced with hydroxyapatite nanorods. A2: Adhesive resin material with incorporated hydroxyapatite nanorods, while A3: Resin composite (without nano-hydroxyapatite) as control group. Each group was subdivided into three subgroups (n=10) according the storage media (B) either Acid (B1), artificial saliva (B2) or distilled Water (B3).
All specimens were thermocycled then stored at room temperature and kept under each of the above mentioned media for 3 hours every day over 30 days (one month). All samples were individually and horizontally mounted on a Universal testing machine loaded to failure at cross head speed of 0.5 mm/ min then Shear bond strength was calculated. The fractured specimens were tested under scanning electron microscope to examine the dentin adhesive interface and mode of failure. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's post hoc significance difference tests. Differences were considered significant at P<0.05. Results: There was a statistically significant difference between groups (p ≤0.05). Adhesive resin with incorporated hydroxyapatite nanorods recorded statistically significant mean higher
shear bond strength (6.33±1.53, 11.35±0.78 and7.97±0.57) after storage in (acid, artificial saliva, distilled water), followed by resin composite incorporates nanorods