Effect of synthetic and natural-derived novel endodontic irrigant solutions on mechanical properties of human dentin.

This study aimed to evaluate the effects of different synthetic and natural-derived root canal irrigants (6% sodium hypochlorite [NaOCl], 6% calcium hypochlorite [Ca(OCl)2] and 6.5% grape seed extract [GSE]) on dentin mechanical properties (flexural strength, ultimate tensile strength [UTS] and fracture resistance). Rectangular-shaped beams and hourglass-shaped sections obtained from mid-coronal and root dentin were treated with 6% NaOCl, 6% Ca(OCl)2 or 6.5% GSE for 30 min. The irrigant solutions were replaced every 5 min. Then, the dentin specimens were rinsed with distilled water (DW) followed by incubation with 17% EDTA for 1 min, and thoroughly rinsed with DW again. Specimens from the control group were tested without prior irrigation. After treatment with the irrigants, dentin beams were used to assess the flexural strength (n = 10) while UTS was evaluated using the root dentin hourglass-shaped sections (n = 10). Similarly, roots with 1 mm of dentinal wall thickness were obtained from human teeth and treated with the same irrigant solutions (n = 10). A compressive loading was applied to the coronal surfaces of roots until fracture. The values of each mechanical test were statistically analyzed individually by one-way ANOVA followed by Tukey HSD test (P < 0.05). NaOCl significantly reduced the mechanical properties of dentin in all mechanical tests (P < 0.05) and no statistical difference was found among Ca(OCl)2, GSE and control group (P > 0.05). It can be concluded that Ca(OCl)2 and GSE may be alternative irrigant solutions, since they do not negatively affect the dentin mechanical properties.

Effectiveness of final decontamination protocols against Enterococcus faecalis and its influence on bond strength of filling material to root canal dentin.

AIM: The aim of this study was to evaluate the effectiveness of final decontamination protocols against Enterococcus faecalis and their influence on bond strength of filling material to root canal dentin. MATERIAL AND METHODS: Ninety root canals were enlarged with ProTaper system and inoculated with E. faecalis for 15days. Sixty samples were randomly divided into six groups (n=10) and subjected to following protocols: G1-distilled water(control), G2-2% chlorhexidine, G3-QMix, G4-6.5% grape seed extract, G5-photodynamic therapy with optical fiber and G6-photodynamic therapy without optical fiber. The percentage of bacterial reduction was checked by counting of CFUs. The remaining 30 samples were subjected to the same decontamination protocols (n=5) and filled with gutta-percha and AH Plus sealer in order to perform the push-out test. Data from both tests were subjected to one-way ANOVA followed by Tukey's post hoc procedure (α=0.05). RESULTS: The greatest bacterial reduction was observed for 2% chlorhexidine, QMix and 6.5% grape seed extract, with no statistically significant difference between them. Photodynamic therapy, with and without optical fiber, demonstrated a significantly higher reduction than distilled water, with no statistically significant difference between them (p<0.05). For the push-out test, final decontamination protocols showed similar bond strength values (p<0.05), with the highest incidence of cohesive failure in all groups. CONCLUSIONS: The tested final decontamination protocols showed effectiveness against E. faecalis and did not interfere with the bond strength of filling material to root canal dentin.