Objectives: To investigate the shear bond strength of dentin surfaces using different self-etching bonding systems after treating with a desensitizing agent at different time intervals.   Materials and methods: 63 sound upper premolars were used, the ‎occlusal aspect was sectioned at the middle in a ‎vertical direction into buccal and ‎palatal halves. Each ‎specimen was mounted and a flat dentin surface was ‎prepared at the middle third of each specimen. The sectioned samples were divided into 3 groups according to the bonding agent n=42. One-half of each tooth was treated with desensitizing agent Quadrant FiniSense then both halves were bonded with one of the three self-etching bonding systems (G-Premio bonding‎,  i Bond,  Clearfil S3 bound plus). ‎After adhesive procedures, a composite resin was applied against the tooth to form ‎a cylinder ‎(2mm×4mm) and cured. From each group 14 specimens were stored in distilled water at 37° C for 24 ‎hours, 7 days, and 72 days.  At the end of each interval, the samples were tested for the shear bond strength using a universal testing machine (Instron). Data were analyzed using the Independent t-test and One Way ANOVA Test and Duncan’s Multiple Range Test.   Results: All bonding systems showed lower bonding strength when samples were treated with desensitizer with a significant difference at all time intervals except for the i bond group which showed no significant difference in bond strength at a period of 7 and 72 days in treated and without desensitizer treated samples.    Conclusion: Obliteration of dentinal by dentin desensitizer may have a negative effect on the bonding strength of the self-etching bonding systems.

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AIM: The aim of the present study was to evaluate and compare the amount of apically extruded debris using three engine driven systems. METHODS: Sixty mandibular premolars with single root were used. The samples were divided into three groups with 20 teeth for each group: group 1 Neolix Neoniti A1 (25, 0.08), group 2 WaveOne GOLD Primary (25.07, red), and group 3 Protaper Next (PTN), using X1 (017/0.04), X2 (025/0.06) files. All files were used to prepare the root canals according to manufacturer instruction. Root canal preparation for each group was done according to manufacturer instructions using 16:1 gear reduction hand piece powered by a torque controlled electric motor. Debris collection was made using apparatus described by Myers and Montgomery. The extruded debris weight was measured by subtracting the weight of the empty Eppendorf tubes from the weight of the debris containing tubes results were statistically analyzed. RESULTS: One-way analysis of variance test revealed that there was statistically significant differences between all the three groups being tested (p < 0.001) showed that apical extrusion of the debris of WaveOne Gold was the least followed by Neolix Neoniti and finally PTN which showed the most apical extrusion of debris with a significant difference between all groups. CONCLUSIONS: WaveOne Gold was found to be the least apical extruded debris system among all groups.