Objective: The objective of this study was intended for evaluation the effect of different surface treatments on microtensile bond strength of two different luting resin cements to two CAD/CAM resin ceramic materials with dentin. Materials and Methods: A total number of 112 samples were used for microtensile bond strength test (µ-TBS). Samples were divided into two equal main groups according to type of resin ceramic used (Vita Enamic [ENA] and Lava Ultimate [LVU]). Then each main group was subdivided according to the surface treatment performed into four equal subgroups; Gr 1 (sandblasting (SB) with Al 2 O 3 50µm), Gr 2(sandblasting (SB) with Al 2 O 3 110µm), Gr 3 (plasma etching), and Gr 4 (Hydrofluoric acid (HF) plus Silane), then two types of resin cements (Rely X Ultimate, Panavia f 2.0) were applied to the treated ceramics in each group. µ-TBS test was performed and the data statistically analyzed. Results: The results of this study revealed that; LVU recorded statistically significant higher µ-TBS than ENA. Rely X Ultimate recorded statistically significant higher µ-TBS than Panavia F 2.0. Conclusion: LVU has higher µ-TBS than ENA with all surface treatments except with HF plus Silane ENA has higher µ-TBS than LVU.

Purpose: this study aimed to evaluate the biocompatibility of Mineral Trioxide Aggregate (MTA) versus Biodentine and Retro MTA extracts at three observation periods (24h, 48h, and 72h) using MTT-Assay. Materials and Methods: 72 wells in three culture insert plates were used in this study. MTA, Biodentine and Retro MTA cements were evaluated in a fresh state. Passage four of human PDL cells were included in this study. After cells preparation and culturing, an extract of the three tested materials was prepared and cultured with the complete media in addition to 5×10 4 cells were implanted into each well 24h earlier and incubated in a stem cell incubator. MTT Assay was used to evaluate in vitro cytotoxicity, calculated the viable cells by hundred percent using ELISA system and the inverted light microscope used to reassure their confluence. After three different observation periods (24h, 48h, and 72h), evaluation of cell viability was done after exposure to the material extracts. Results: MTA and Biodentine cements showed no statistically significant differences at all the observation periods. However, Retro MTA cement resulted in a statistically significant difference at all the observation periods but none of them below the cut level. Meanwhile, all the materials extracts resulted in a statistically significant increase in cytotoxicity at 24h and then decrease at 48h and finally a little increase in cytotoxicity at 72h. Conclusions: All the tested materials showed low cytotoxicity and are comparable to the old standard MTA.