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

OBJECTIVES: To evaluate the effect of different endodontic irrigation protocols on dentin mechanical properties and fracture resistance of roots with 0.5 mm (weakened roots) and 1.5 mm of thickness. METHOD: Irrigation protocols were the following: Distilled water (DW) + Ethylenediamine tetraacetic acid (EDTA); grape seed extract (GSE) + EDTA; sodium hypochlorite (NaOCl) + EDTA; NaOCl + EDTA + GSE; calcium hypochlorite (Ca(ClO)2) + EDTA; Ca(ClO)2 + EDTA + GSE; chlorhexidine (CHX) + EDTA; CHX + EDTA + GSE. The samples were prepared and the values of microhardness, ultimate tensile strength (UTS), and flexural strength were obtained. Further, fracture resistance of roots with dentin thickness of 0.5 mm and 1.5 mm, and restored with fiberglass post relined with composite resin and metal crowns, were evaluated with same irrigation protocols previously described; the failure mode was evaluated as well. All tests presented normality in data distribution (Kolmogorov-Smirnov), and Analysis of Variance and Bonferroni test (α = 0.05) were performed. RESULTS: Higher reduction of dentin microhardness was observed in the NaOCl and NaOCl + EDTA + GSE groups (p < 0.0001). An increased in the UTS values was obtained in the CHX groups (p < 0.0001), while similar values were observed between the control and other groups (p > 0.05). The reduction of dentin flexural strength was observed in the NaOCl groups (p < 0.0001), while no significant changes were observed in the other groups (p > 0.05). With regard to fracture resistance, no statistical difference was obtained among the irrigation's protocols (p > 0.05), except for CHX (p = 0.0031) and CHX + GSE (p = 0.0001) that showed increased in fracture resistance values in roots with 1.5-mm thickness. An increased rate of irreparable failure was obtained in the NaOCl groups, whereas there was a predominance of repairable failure in the other groups. CONCLUSIONS: The endodontic irrigation protocol has a significant impact on the dentin mechanical properties; on the other hand, do not reduce the fracture resistance of root with 0.5 mm and 1.5 mm of thickness.

Effect of length post and remaining root tissue on fracture resistance of fibre posts relined with resin composite.

To investigate the influence of post length and amount of remaining root tissue on the fracture resistance of roots restored with fibre posts relined with resin composite. Ninety upper canine teeth were divided into nine groups (n = 10). The post spaces were prepared resulting in different lengths, as follows: group 2/3, preparations with lengths of 10 mm; group 1/2, preparations with lengths of 7·5 mm; and group 1/3, preparations with lengths of 5 mm. Each group was divided into 3 subgroups according to amount of remaining root tooth tissue (2, 1 mm or 0·5 mm of thick root). Fibre posts relined with resin composite were cemented, and all teeth were restored with metal crowns. The samples were submitted to the fracture resistance test in a universal testing machine, at an angle of 135° and speed of 0·5 mm min(-1) . Failure modes were observed and the data of fracture resistance were submitted to the anova and Tukey's (α = 0·05). No statistically significant difference in fracture resistance was found among different post lengths (P > 0·05). Remaining dentin thickness of 2 and 1 mm did not differ statistically in fracture resistance (P > 0·05), which was higher than of 0·5 mm dentin thickness (P < 0·05). A prevalence of repairable failure was observed in all groups. It can be concluded that the length of fibre post relined with resin composite did not influence fracture resistance, but thickness was an important factor for the restoration of endodontically treated teeth.

Effect of root canal sealers on bond strength of fibreglass posts cemented with self-adhesive resin cements.

AIM: This study evaluated the effects of different root canal sealers on the bond strength of a fibreglass post cemented with self-adhesive resin cements. METHODOLOGY: The root canals of 50 extracted maxillary single-rooted canine teeth were prepared with the crown-down technique and randomly divided into five groups according to the sealer used: group 1: control group, gutta-percha points only (no sealer); group 2: AH Plus (resin-based sealer); group 3: self-etch Epiphany (resin-based sealer); group 4: Sealer 26 (calcium hydroxide-based sealer); and group 5: Endomethasone (zinc oxide eugenol-based sealer). The root canals were filled with gutta-percha, the cold lateral compaction technique, except for group 3 where Resilon was used. Post spaces were prepared, and fibreglass posts were cemented with the self-adhesive cement RelyX Unicem. Bonded specimens were sectioned into 1-mm-thick slabs, and a push-out test was performed in a universal machine. Failure modes were observed and classified into five types: (i) adhesive between the post and resin cement; (ii) mixed, with resin cement covering 0-50% of the post diameter; (iii) mixed, with resin cement covering 50-100% of the post surface; (iv) adhesive between resin cement and root canal; and (v) cohesive in dentine. Data of bond strength were submitted to anova and Tukey test (α = 0.05). RESULTS: No significant difference was detected between control group, AH Plus, Epiphany and Sealer 26 (P > 0.05). The Endomethasone group had significantly lower bond strength values than the other sealers (P < 0.05). The prevalence of mixed fractures and adhesive cement-dentine failure was verified in the eugenol-containing sealer group; in the control group, the resin-based and calcium hydroxide-based sealer groups, the predominant mode of failure was the mixed type. CONCLUSION: Endomethasone interfered negatively with the bond to root dentine; however, AH Plus, Epiphany and Sealer 26 did not interfere in the bond strength of a fibreglass post cemented with self-adhesive resin cements.

Fracture resistance of roots prosthetically restored with intra-radicular posts of different lengths.

The purpose of this study was to assess the fracture resistance of roots that were prosthetically restored with intra-radicular posts of different lengths. Forty-five bovine incisors were sectioned 17 mm from their apices, endodontically treated and randomly divided into three experimental groups: GI, fibreglass posts luted at a depth of 12 mm; GII, 8 mm and GIII, 4 mm. All posts were luted with dual resin cement. Resin composite cores were prepared with standardized measurements, and all teeth were restored with metal crowns. The samples were submitted to the fracture resistance test in a universal testing machine, at an angle of 135 degrees and speed of 0.5 mm min(-1), until fracture occurred. The data, in MPa, were submitted to the analysis of variance (anova) followed by Tukey's test (alpha = 0.01). No statistically significant difference (P > 0.01) was found between GI (129.72 +/- 12.14) and GII (154.3 +/- 12.08), which presented the highest fracture resistance values. Group GIII (100.5 +/- 8.07) showed lower fracture resistance (P < 0.01) when compared with GI and GII. Within the limitations of this study, it was concluded that the post lengths influenced the fracture resistance of prosthetically restored roots. These results suggest that it is not necessary to perform excessive intra-radicular post-space preparation to improve the fracture resistance of roots.