Bovine teeth can reliably substitute human dentine in an intra-tooth push-out bond strength model?

AIM: To investigate the reliability of using bovine teeth as an alternative to human teeth in an intra-tooth push-out model by comparing the bond strength of three root canal sealers in both tooth substrates. METHODOLOGY: From human and bovine incisors (12 per group), one 1-mm disc was obtained from each root. On each disc, three standard 0.8-mm-diameter holes were drilled through the dentine. After irrigation, the holes were filled with one of three root canal sealers: AH Plus, MTA Fillapex or Total Fill BC Sealer. Tooth slices were kept in contact with sterile gauze moistened in PBS solution (pH = 7.2) for 7 days at 37 °C, and finally, a push-out load was applied until sealer dislocation. The bonded interface area was calculated to obtain data in MPa. The push-out data for each sealer and the overall push-out data for human and bovine teeth were compared (Mann-Whitney U). Kruskal-Wallis was used to study the sealers behaviour at each of the dental substrates. Multiple comparisons were performed using Mann-Whitney U after Bonferroni correction (P < 0.05). RESULTS: Dentine substrate did not influence the push-out of either individual sealers or overall sealers tested (Mann-Whitney U, P > 0.05). In both human and bovine samples, AH Plus performed better than BC Sealer and MTA Fillapex, whilst BC Sealer also provided a superior push-out compared to MTA Fillapex (Mann-Whitney U, P < 0.05). CONCLUSION: When using an intra-tooth model, bovine teeth did not significantly influence the bond strength of sealers.

Do smear-layer removal agents affect the push-out bond strength of calcium silicate-based endodontic sealers?

AIM: To evaluate the effect of 17% ethylenediaminetetraacetic acid (EDTA), 2.25% peracetic acid (PA) or 10% citric acid (CA) on the push-out bond strength of calcium silicate-based endodontic sealers [MTA Fillapex (Angelus, Londrina, Brazil) and Total Fill BC Sealer (FKG, La Chaux-de-Fonds, Switzerland)] to root dentine after different periods of immersion in phosphate-buffered saline (PBS). AH Plus (Dentsply DeTrey, Konstaz, Germany) was used as a reference material for comparison. METHODOLOGY: Thirty human maxillary incisors were selected and three 1-mm discs were obtained from the middle third of each root. On the axial surface of each disc, three 0.8-mm-diameter holes were drilled through the dentine. After standardized irrigation, each dentine disc from the same root was treated for smear-layer removal with one of the three tested chelating solutions: EDTA, PA or CA. After that, the holes were dried with paper points and filled with one of the three test root canal sealers. The filled dental slices were further immersed in PBS solution (pH 7.2) for 7 days (T1) or 30 days (T2) at 37 °C, before the push-out assay. Friedman, Kruskal-Wallis and Mann-Whitney tests were used respectively to estimate the impact of the independent variables (solutions, sealers and period of PBS immersion) on the push-out bond strength. The level for significance was set at α = 5% and data were further subjected to a Bonferroni correction. RESULTS: Solutions and periods of immersion did not significantly influence the displacement resistance (P = 0.285, and P = 0.104, respectively) of sealers to root dentine. On the other hand, the type of sealer significantly affected the push-out bond strength (P = 0.000). AH Plus was associated with greater resistance to dislodgment compared with Total Fill BC Sealer and MTA Fillapex (P = 0.000). MTA Fillapex resulted in the lowest push-out bond strength (P = 0.000). CONCLUSION: The use of different chelating agents did not influence the push-out bond strength of endodontic sealers. Calcium silicate-based sealers had lower push-out bond strength values compared with a conventional epoxy resin-based sealer (AH Plus).