Could calcium hypochlorite and grape seed extract keep the mechanical properties of root dentin and fracture resistance of weakened roots?

Pre-Sealing of Endodontic Access Cavities for the Preservation of Anterior Teeth Fracture Resistance

OBJECTIVE

Sodium hypochlorite solution (NaOCl) is an effective canal irrigant but interferes with the mechanical features of dentin and the bonding capability of adhesives when restoring endodontically treated teeth. This study evaluated whether access cavity resin sealing before using canal irrigant would augment the resistance of endodontically treated anterior teeth against fracture.

METHODS

Sixty maxillary incisors underwent endodontic treatment in five groups (n = 12). Irrigation with 5.25% NaOCl and 17% ethylenediaminetetraacetic acid (EDTA) was performed in all groups except for Group 5. After root canal obturation, in Group 1, the access cavity was kept unrestored. In Group 2, immediate restoration after obturation was achieved. For Group 3, delayed restoration after 1 week was provided. In Group 4 (pre-sealed), before canal irrigation, the dentin surface of access cavities was sealed using self-adhesive composite resin (Vertise Flow) and then restored after obturation. In Group 5, which was saline irrigated, immediate restoration was performed. After storage and thermal cycling for 5000 cycles at 5°C-55°C with a dwell time of 15 s and a transfer time of 5 s, teeth were statically loaded by a universal testing machine until a fracture occurred. Data were collected as the fracture resistance (FR) and analyzed using the one-way analysis of variance and Tukey's tests.

RESULTS

FR significantly differed between all groups (p < 0.001). The lowest FR was recorded in the unrestored group (284 ± 86 N), which was not statistically different from the immediately restored group (p = 0.065). The pre-sealed group exhibited the highest FR value (810 ± 127 N, p ≤ 0.02 vs. other groups). The FR of the saline-irrigated and delayed restored groups was almost similar (p = 0.13).

CONCLUSIONS

NaOCl/EDTA irrigation resulted in an adverse effect on FR. Delayed restoration could reduce this adverse effect. Access cavity pre-sealing with flowable composites led to a higher FR than conventional methods and may be considered an effective step during treatment procedures.

Interactions between calcium hypochlorite and irrigants commonly used in endodontic practice: a chemical analysis

INTRODUCTION

This study aimed to identify possible products resulting from chemical interactions between calcium hypochlorite [Ca(OCl)₂] and other irrigants for endodontic use using electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QTOF-MS).

METHODS

The 5.25% Ca(OCl)₂ was associated with either 70% ethanol solution, distilled water, saline solution (0.9% sodium chloride), 5% sodium thiosulfate, 10% citric acid, 17% EDTA, or 2% chlorhexidine (CHX). The reaction ratio was 1:1 and the products obtained were analyzed by ESI-QTOF-MS.

RESULTS

The interactions between Ca(OCl)₂ and CHX generated an orange-brown precipitate, without identification of para-chloroaniline (PCA), and between Ca(OCl)₂ and sodium thiosulfate a milky-white precipitate. Furthermore, when the oxidizing agent was associated with EDTA and citric acid, chlorine gas was released. As for the other associations, 70% ethanol, distilled water, and saline solution, no precipitation or gas release occurred.

CONCLUSION

The orange-brown precipitate occurs due to the chlorination of guanidine nitrogens, and the milky-white precipitate is due to the partial neutralization of the oxidizing agent. The release of chlorine gas occurs due to the low pH of the mixture, which results in the rapid formation and decomposition of chlorine. In this context, an intermediate rinsed with distilled water, saline solution and ethanol between Ca(OCl)₂ and CHX, citric acid and EDTA seems to be appropriate to prevent the formation of by-products when these irrigants need to be used in the canal. Furthermore, if it is necessary to use sodium thiosulfate, a larger volume of the solution must be used than that used for the oxidizing solution.

Effect of sodium/calcium hypochlorite on adhesion and adaptation of fiber posts luted with a dual resin cement

This study aimed to evaluate the effect of different concentrations of sodium hypochlorite (NaOCl) and calcium hypochlorite [Ca(OCl)2] on the bond strength and adaptation of glass fiber posts luted with a dual-curing resin cement. Fifty decoronated premolars were sectioned 14 mm from the apex and endodontically treated. The root canal filling was partially removed. The specimens were divided into 5 groups (n=10) according to the irrigant for post space irrigation: 0.9% sodium chloride (NaCl), (control); 2.5% NaOCl; 5.25% NaOCl; 2.5% Ca(OCl)2; and 5.25% Ca(OCl)2. For each group, irrigation was performed with 5 ml of solution. Afterward, the posts were luted with a dual-curing resin cement. One slice from each third was obtained and submitted to the push-out test and failure modes analysis. An additional slice from the middle third was submitted to confocal images for analysis of adaptation failures (gaps). Two-way ANOVA, Tukey's post-hoc, Kruskal-Wallis with Bonferroni adjusted, and chi-square tests, analyzed data. The group treated with 5.25% NaOCl showed lower bond strength values and generated more cohesive failures compared to the control (p < 0.05). Bond strength decreased from coronal to apical in the post space (p < 0.001). The groups treated with NaOCl had the highest percentages of gaps compared to the control (p < 0.05). Regardless of concentration, Ca(OCl)2 did not influence the bond strength and the occurrence of gaps (P > 0.05). Ca(OCl)2 is a good option for irrigating the post space before luting a fiber post with a dual-curing resin cement.