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INTRODUCTION: Different irrigations solutions may cause alteration in the physicochemical properties of dentin structure thereby affecting the microhardness of root canal dentin. OBJECTIVES: to evaluate the effect of different irrigation protocols on microhardness of human root canal dentin. MATERIALS AND METHODS: Forty extracted single rooted lower premolars were used. All teeth were instrumented using manual stainless steel files and irrigated by 2ml distilled water between each file, then were sectioned by longitudinal splitting of each tooth. The root halves were randomly assigned into 4 parallel groups (n=10) and immersed for 5 minutes with one of the following irrigants: Group I: 10 ml of 2.5% Sodium Hypochlorite (NaOCL), Group II: 10 ml of 17% ethylene diamine tetra-acetic acid (EDTA) followed by 10 ml of 2.5% NaOCL, Group III: 10 ml of 2.5% NaOCL followed by 10 ml of 2% chlorhexidine digluconate (CHX), Group IV: 10 ml of 2.5% NaOCL followed by 10 ml distilled water then were followed by 10ml of 2% CHX. Ten root halves from each group were prepared to measure dentin microhardness at baseline measurement and after treatment to determine the change in microhardness, using Vickers tester. RESULTS: Data were analysed using t-test, ANOVA test and Post Hoc test.Group II showed the highest percentage decrease in microhardness values, followed by group III, then group IV and the lowest was group I. All groups showed a significant difference between each other (P < 0.05), except group III and IV. The coronal third showed the highest percentage decrease with significant difference between apical and middle thirds (P < 0.05), in which there was no significant difference between them. CONCLUSIONS: CHX is the best final irrigant if there is excellent intermediate flush for prevention of its precipitation with NaOCL.The coronal third needs conservative approach as it is the most affected third.

INTRODUCTION: Different irrigations may cause alteration in the composition of dentin, thereby affecting the adhesion of materials to dentin surfaces. OBJECTIVES: evaluate the effect of different irrigating protocols used as final rinse on the bond strength of the ActiV gutta percha. MATERIALS AND METHODS: Forty extracted single rooted lower premolars were used. Teeth were decoronated to standardize the root length to 15mm. The canals were instrumented using OneShape rotary system. Teeth were irrigated with 2.5% sodium hypochlorite then divided into four parallel groups according to the final rinse (n=10). GroupI: 10ml 17% Ethylene diaminetetraacetic acid, followed by 10ml of 2.5% NaOCL; GroupII: 10ml of 1.3%mixture of a tetracycline isomer, an acid and detergent (MTAD); GroupIII: 10ml of 2% chlorhexidine gluconate; GroupIV: 10ml 2.5% NaOCL(control). All the root canals were filled using ActiV GP. Slicing was done at the coronal and middle thirds for push-out test to measure bond strength. Then failure mode was evaluated under stereomicroscope. Data were analysed using t-test and one-way ANOVA test. RESULTS: Group III yielded significantly the highest mean push-out bond strength (2.91± 0.79 MPa), followed by group II (2.39± 0.89 MPa), then group IV (1.80± 0.61MPa) and finally group I (1.61± 0.52 MPa). The bond strength values of the middle sections were significantly higher than that of the coronal sections. The failure mode was predominantly cohesive in groups II and III and adhesive in groups I and IV. CONCLUSIONS: CHX and MTAD increased the bond strength of ActiV GP, while EDTA decreased the bond strength. The push out bond strength values were affected by the location of root segment. There was correlation between the push out bond strength values and the failure mode.

INTRODUCTION: polymerization shrinkage of composite resins causes stresses that may exceed the strength of the bond with the surrounding tooth structure, leading to interfacial failure. The use of an adhesive system is always required. OBJECTIVE: The purpose of this in vitro study was to compare the effect of total-etch adhesive system with self-etch adhesive system on microleakage of universal nano-hybrid composite resin when used to restore class V cavities in primary teeth. MATERIALS AND METHODS: The sample consisted of 50 freshly extracted sound primary teeth. Standardized class V cavity preparations on the buccal surfaces were prepared and the sample was randomly divided into 2 equal groups: Group I: 25 teeth received total etch adhesive system. Group II: 25 teeth received self-etch adhesive system. The cavities were restored with a universal nano-hybrid restorative material. All specimens were thermocycled and immersed in 0.5% basic fuchsine dye at 37C˚ for 24 hours. Basic fuchsine penetration was assessed on a 4 point grading scale (0 to 4) using a stereomicroscope to evaluate the microleakage of the restorations. RESULTS: Comparing the percentage of microleakage scores of group I and group II at occlusal margin it was found that, the group I was significantly lower than group II (p=0.041). As for percentage of microleakage scores for the gingival margin between groups I and II it was found that there was no significant difference (p=0.741). Comparing the percentage of microleakage scores at both the gingival and occlusal margis of group I and II, no significant difference was revealed (p=0.105) (p=0.278) respectively. The sum of occlusal and gingival percentage of microleakage scores of group I compared to group II revealed no significant difference (p=0.325).. CONCLUSION: There is no significant difference in microleakage sum scores between total etch and self-etch adhesive system groups. At the occlusal margin, total-etch adhesive system was significantly better than the self-etch adhesive systems. KEYWORDS: microleakage, total etch adhesive, self- etch adhesive, primary teeth.