Micropush-out dentine bond strength of a new gutta-percha and niobium phosphate glass composite

Abstract

Aim: To characterize an experimental gutta-percha and niobium phosphate glass composite (GNB) applied with a thermoplastic technique to the root canals without sealer in a moist environment and to evaluate its micropush-out bond strength to root canal wall dentine.

Methodology: The root canals of sixty human mandibular pre-molars were prepared using rotary NiTi instruments and irrigation with sodium hypochlorite and EDTA. The teeth were then randomly divided into three groups according to the root filling material used: AH plus sealer and gutta-percha (AH), EndoSequence BC gutta-percha without sealer (GBC), and GNB without sealer. The root canals were filled with a single cone using warm vertical condensation. Push-out bond strengths associated with the filling materials in slices from middle root thirds was determined 30 days after root filling. The failure mode was analyzed with SEM. Analysis using EDX and SEM-EDS was carried out to verify the composition and distribution of the particles of the tested materials. Data were statistically analyzed by one-way anova and Tukey's test (P < 0.05).

Results: AH and GNB groups had bond strengths of 2.83 ± 0.64 MPa and 2.68 ± 0.84 MPa, respectively, with no significant difference between them (P > 0.05). The GBC group had the lowest mean bond strength (1.34 ± 0.42 MPa), which was significantly different compared with the other groups (P < 0.05). Cohesive failures prevailed in the AH group, whereas failures were mixed in the GBC and GNB groups. The SEM-EDS analysis on the surface and in the bulk of GBC revealed only a superficial coating of bioceramic particles. Glass particles were detected both on the surface and in the bulk of GNB.

Conclusions: The experimental root filling composite (GNB) had an ability to adhere to root canal wall dentine equal to the current gold standard root filling with gutta-percha and sealer (AH Plus).

Keywords: gutta-percha; niobium; obturation; phosphate glass; push-out bond strength; root canal filling.