Objective: Evaluating the marginal microleakage of two different composite resins with three different restorative techniques in class V cavities with the cervical margins within the cementoenamel junction.         Methods: Sixty standardized box-shaped class V cavities of 2×2×3 mm (depth, length, width) prepared on the buccal and lingual surfaces of 30 freshly extracted healthy human premolars. The teeth randomly divided into two equal groups: group A (FiltekTM Z250 XT) and group B (BeautifilTM II LS giomer). Then each group is subdivided into 3 equal subgroups: group I (bulk technique-10 cavities), group II ( split horizontal technique-10 cavities) and group III (vertical technique-10 cavities) and filled according to the manufacturer’s instructions. The samples were subjected to thermocycling (5°C ±2°C & 55°C ±2°C with a 30 seconds dwell time) and immersed in 2% buffered Methylene blue solution at 37°C for 24 hours. The restorations were sectioned longitudinally in buccolingual direction through the centers of the restoration. Then evaluated for microleakage using a stereomicroscope at 10x magnification and scored as 0, 1, 2, and 3. Non-parametric Mann-Whitney and Kruskal-Wallis tests were used and p value ≤ 0.05 considred statistically significant. Results: Split increment horizontal layering technique showed statistically significant lower microleakage than vertical layering and bulk technique. While giomer showed less microleakage than Z250 but statistically not significant. Conclusions: The use of split horizontal technique and giomer composite offers better and less marginal microleakage in class V restorations.

Objective: To assess and compare the results on the bond strength of two adhesive agents that bond fresh amalgam to two types of composite restorations, and to check the mode of bond failure. Methods: Sixty standardized circular cavities were prepared in a block of polymethyl methacrylate with standardized dimensions. Fresh amalgam was condensed to fill the cavity, then a gelatin mold with standardized dimensions was placed over the fresh amalgam,and the composite resin was bonded to the amalgam. Samples were assigned into three main groups, each containing (20) samples. G1: Amalgam bonded to composite without adhesive agent, G2: Amalgam bonded to composite by single bond universal adhesive, G3: Amalgam bonded to composite by scotch bond MPP, and each group was divided into two subgroups of (n=10) (Nanofill and Nanohybrid composite) to measure shear bond strength, which was followed by evaluation of debonding in all samples under a stereomicroscope to assess the mode of failure. Results: All The results showed that G3 has higher shear bond strength than G1 and G2, and this is statistically significant at (p=0.001, p=0.005) respectively, while G1 has the lowest shear bond strength and a statistically non-significant difference from G2 at (p=0.539). It was also found that the type of composite resin has no effect on bond strength and statistically non-significant difference was found for any of the sub-groups. Following debonding of all the samples, they were examined under a stereomicroscope, and the adhesive failure present was about (%65), and mixed failure present about (%35), while cohesive failure was (%0). Conclusions: Highest bond strength was found with Scotch bond multi-purpose plus (SBMPP) agent compared to other groups. The strength of the fresh amalgam bonding to the composite resin without an adhesive agent was low. The bond strength with single bond universal adhesive was lower than with the SBMPP system.