Aim: to evaluate micro tensile bond strength of new generation composite resins with dentin. Methods: Extracted human premolars teeth (n=48)were used to preper one hundred and sixty eight sticks .Specimens divided into two equal main groups according to types of composite used (A1; Xtra fil bulk-fill and A2; Tetric-N-Ceram bulk-fill). Then each main group were subdivided according the adhesive approach used into two equal subgroups (B1; total each and B2; self-etch). According to dentin depths each subgroup were further categorized into two equal categories according to dentin depths (C1; superficial and C2; deep). The μ-tensile bond strength was evaluated using universal testing machine at a crosshead speed of 0.5 mm/min. until failure occurred. Data were recorded, tabulated and statistically analysed.. Results: showed significant (p<0.05) effect of composite and dentin level on μ-tensile bond strength, while the effect of adhesive showed non-significant (p>0.05) dentin.Conclusion: Xtra-Fill bulk-fill has higher bond strength than Tetric Bulk-fill. Additionally, Total-etch adhesive system has higher bond strength than self-etch with the superficial dentin while self-etch adhesive system has higher bond strength with the deep dentin

Aim:The purpose of this study was to evaluate the effect of Zirconium oxide (ZrO 2 ) nanofillers powder with different concentration (1.5%, 3%, 5% and 7%) on the transverse strength and impact strength of heat-polymerized acrylic resin. Materials and Methods: Zirconium oxide powders with different concentrations (1.5%, 3%, 5% and 7%) were incorporated into heat-cure acrylic resin (PMMA) and processed with optimal condition (2.5:1 Powder/monomer ratio, conventional packing method and water bath curing for 2 hours at 95˚C) to fabricate test specimens of PMMA of dimensions (65 x 10 x 2.5mm) for the transverse strength and (60 x 7 x 4mm) for impact strength. PMMA without additives was prepared as a test control. Two types of mechanical tests; transverse strength and impact strength were carried out on the samples. The recorded values transverse strength in (MPa) and impact strength in (J) were collected, tabulated and statistically analyzed. One way analysis of variance (ANOVA) and Tukey's tests were used for testing the significance between the means of tested groups which are statistically significant when the P value ≤ 0.05. Results:Addition of Zirconium oxide nanofillers to PMMA significantly increased the transverse strength and impact strength Conclusion: Zirconium oxide nanofillers added to PMMA has a potential as a reliable denture base material with increased transverse strength and impact strength. According to the results of the present study, the best mechanical properties were achieved by adding 7%wt ZrO 2 concentration.