Purpose: This study was designed to assess the chelating capacity of chitosan acetate and chitosan citrate on intraradicular dentin using environmental scanning electron microscope (ESEM) and quantity calcium content of intraradicular dentin using energy dispersive X-ray microanalyzer (EDX). Materials and Methods: sixty freshly extracted human single rooted lower premolars were instrumented with Revo-S files till size AS 35.The samples were dispensed into 5 groups according to the final rinse used and control group (10 samples each); Group I: irrigated with 0.2% chitosan acetate, Group II: irrigated with 0.2% chitosan citrate, Group III: irrigated with 1% acetic acid, Group IV: irrigated with 1% citric acid, Group V: irrigated with 17% EDTA and control group which was divided into;(VIa) :5 samples irrigated with sterile saline and (VIb): 5 samples were neither prepared nor received any treatment. Samples were grooved longitudinally and the cleanliness of the root canals and smear layer were evaluated at three root levels using ESEM. The calcium content of intraradicular dentin of five samples from each experimental group (I,II,III,IV,V) and the samples of control group (VIa and VIb) was measured using EDX. Results: At three root levels; there was a statistical difference among the tested groups and control group in the median scores of smear layer However, there was no statistical difference in the median scores of smear layer among the tested groups. Comparing the smear layer scores within each tested group, apical level has the highest median smear layer score compared to other two levels. Regarding calcium content, the highest mean calcium content was recorded in samples treated with saline followed by samples that did not receive any irrigation. However, no statistical difference among tested groups. Conclusion: chelating potential of 0.2% chitosan acetate and 0.2% chitosan citrate is comparable to that of 17% EDTA when used as final rinse without much altering the calcium content of intraradicular dentin compared to 17% EDTA.

Purpose: This study assessed the adhesion of C-point filling system to retreated root canal walls. Materials and Methods: Eighty extracted upper incisors were prepared using Protaper Universal rotary files then the samples were distributed into 2 main groups. Group I: primary treated, Group II: retreated. Each group was further distributed into 4 subgroups; Subgroup A: Samples were filled with gutta-percha. Subgroup B: Samples were filled with gutta-percha and AH Plus sealer. Subgroup C: Samples were filled with C-point. Subgroup D: Samples were filled with C-point and BioCeramic sealer (BC). The push out test was carried out. The sealer penetration inside the dentinal tubules was evaluated using scanning electron microscope (SEM). Results: regarding the results of group I(primary treated) and II (retreated), at all levels, the highest mean bond strength value was recorded in primary treated samples, while the lowest value was recorded in retreated samples. Among the tested groups there was no statistically significant difference except for subgroup B(Gutta-percha/AH plus) at the middle and apical levels while in subgroup D(C-point/BC sealer) at the middle level, there was a statistical significant difference among the tested groups. SEM observation of sealer/ dentin interface revealed few traces of sealer penetration in samples retreated with C-point and BC sealer. Conclusion: C-Point/BC sealer showed better adhesion to the intraradicular dentin in primarily treated group compared to gutta-percha /AH Plus sealer. While the adhesion of C-point filling system to intraradicular dentin negatively affected by the retreatment procedure.