Sodium hypochlorite (NaOCl), an effective endodontic irrigant against Enterococcus faecalis (EF), is harmful to periapical tissues. Natural pineapple-orange eco-enzymes (M-EE) and papaya eco-enzyme (P-EE) could be potential alternatives. This study aimed to assess the antimicrobial efficacy of M-EE and P-EE at different concentrations and fermentation periods against EF, compared to 2.5% NaOCl. Fermented M-EE and P-EE (3 and 6 months) at various concentrations were mixed with EF in a 96-well plate incubated for 24 h anaerobically. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of M-EE and P-EE were determined via EF growth observation. EF inhibition was quantitatively measured and compared between different irrigants using the one-way analysis of variance (ANOVA), and different fermentation periods using the independent-samples T-test. M-EE and P-EE showed MIC at 50% and MBC at 100% concentrations. There was no significant difference in antimicrobial effect when comparing M-EE and P-EE at 50% and 100% to 2.5% NaOCl. P-EE at 6 months fermentation exhibited higher EF inhibition compared to 3 months at concentrations of 25% (p = 0.017) and 0.78% (p = 0.009). The antimicrobial properties of M-EE and P-EE, at both 100% and 50% concentrations, are comparable to 2.5% NaOCl. They could therefore be potential alternative endodontic irrigants, but further studies are required.

This study aimed to evaluate and compare the frequency of microcracks and its severity at different root canal dentin locations, after preparation with thermomechanically heat‐treated engine‐driven nickel‐titanium instruments. Forty mandibular premolars were assigned to four experimental groups (n = 10): ProTaper Next, ProTaper Gold, WaveOne Gold and Reciproc Blue. After pre‐instrumentation micro‐computed tomography scans, the root canals were prepared to size 25. Following post‐instrumentation scans, pre‐ and post‐instrumentation scanned images were analysed for the presence and extent of dentinal defects. A total of 56 500 cross‐sectional images were obtained, showing that less than 2.3% with pre‐existing dentinal microcracks. No new microcracks were identified during the post‐instrumentation analyses. No significant association was found between the types of dentinal defects, file motions and sequences. Thermomechanically heat‐treated rotary files did not induce the formation of new microcracks. There was also no association between the kinematic motions and sequences of the rotary instruments to the types of dentinal defects.

This study was aimed to determine the coefficient thermal expansion (CTE) of colloidal-processed slip-casted novel nanozirconia (Zir) and to elucidate the effect of the differences in CTE values between zirconia cores and veneering porcelains on core–veneer shear bond strength (SBS). CTE measurement was performed on core materials (CMs; Zir and Cercon® [Cer]) and veneering ceramics (VCs; Ceram Kiss® [CK], VITA VM9® [VM9], and IPS e.max Ceram® [e.max]). The SBS test was conducted on six groups of core–veneer samples (Zir–CK, Zir–e.max, Zir–VM9, Cer–CK, Cer–e.max, and Cer–VM9). The mean CTE values (× 10^− 6/°C ± standard deviation) of Zir and Cer were 7.86 ± 0.47 and 7.82 ± 0.49, respectively. CK, VM9, and e.max recorded mean CTE values of 7.20 ± 0.62, 7.20 ± 0.29, and 7.10 ± 0.46, respectively. No statistically significant differences were found among the CTE values of CMs and between those of VCs. Zir–VM9 recorded the highest mean SBS value (MPa) of 149.48 ± 67.64, whereas Cer–e.max produced the lowest SBS value of 44.07 ± 16.49. Combinations with high CTE disparities produced low SBS values. CTE discrepancies affected the SBS of veneered zirconia restorations. The novel zirconia showed similar performance and can be used as an alternative to commercial zirconia.