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

The Er: YAG laser was proven to successfully ablate enamel. This study was aimed to investigate the applicability of using this laser in preparing the enamel surface for porcelain laminate veneering in comparison with the high speed handpiece regarding the fracture strength loading of the veneers. Twenty human maxillary central incisors extracted were selected. They were divided into two equal groups [group I and group II], group I: High speed handpiece prepared specimens and group II: Er: YAG laser prepared specimens for measuring microleakage by a binocular stereomicroscope. The results of the microleakage assessment showed significant difference in the microleakage scores at the incisal margins of [Gr. I (group I)] the high speed handpiece compared to [Gr. II (group II)] the Er: YAG laser and significance comparing the microleakage scores at the cervical margins of both groups (Gr. I) and (Gr. II). Also, there were significant differences comparing incisal to those at the cervical margins of (Gr. I) the high speed handpiece, while in (Gr. II) the Er:YAG laser group, a marked significant difference were found between the microleakage scores at the incisal margins compared to the cervical margins. Conclusion:The difference in microleakage assessment between laser and the high speed hand piece specimens was significant and affect the longevity of the porcelain laminate veneers.(1614) Mohamed I. Ebrahim, et al.