Effect of autoclave sterilisation and heat activated sodium hypochlorite irrigation on the performance of nickel-titanium rotary files against cyclic fatigue

The present study aims to assess the impact of heat-activated sodium hypochlorite (NaOCl) and/or autoclave sterilisation on the cyclic fatigue resistance (CFR) of heat-treated nickel-titanium rotary files used in root canal treatment. The CFR of One Curve (OC) files was evaluated under the following conditions: as received (Group 1; control), immersion in NaOCl at 23 ± 1ºC (Group 2), immersion in NaOCl at 60 ± 1ºC (Group 3), autoclave sterilisation at 135 1ºC (Group 4), combined treatment of autoclave sterilisation and immersion in NaOCl at 23 ± 1ºC (Group 5), and combined treatment of autoclave sterilisation and immersion in NaOCl at 60 ± 1ºC (Group 6). A simulated root canal in a zirconia block was utilised to test the performance of the files. All the types of treatments resulted in significant reductions in fracture resistance of the OC files. Immersion of the files in NaOCl at 23ºC revealed the smallest reduction, while combined treatment of autoclaving and immersion in NaOCl at 60ºC caused the greatest reduction. Autoclave sterilisation or exposure of OC files to 2.5% NaOCl adversely affect the cyclic fatigue life and increasing solution temperature or combined treatment caused additionally significant reduction in CFR

Root canal preparation using Hyflex EDM/CM VS Revo S in curved root canals, a comparative in-vitro study

Shaping ability, fracture resistance and speed are 3 critical prerequisites for NiTi rotary instruments. The purpose of this study was to compare root canal preparation in curved canals of molar teeth with the NiTi rotary Hyflex EDM/CM and Revo S systems in terms of canal shape, instrument separation and time of preparation. Mesiobuccal canals of 40 molar teeth with apical angles of curvature between 25 and 35 degrees were enlarged, shaped and cleaned with a torque controlled Endo IT motor(NSK-Japan): 20 canals with Hyflex EDM/CM and 20 other canals with the Revo S. Each instrument in both systems was used to prepare just 4 root canals. Standardized periapical radiographs were taken before and after preparation in order to determine canal transportation in each group. the time of preparation for each root canal was also recorded. Hyflex EDM/CM system gave a statistically less canal transportation and as a result, was preferable for preserving the original shape of the root canal (P=0.024). There was no significant statistical difference between the 2 systems in term of the preparation time. (P=0.09). Based on the results of this study, the Hyflex EDM/ CM NiTi rotary system maintains the original shape of curved root canals better than the Revo S with less possibility of instrument separation. © 2020

Prevalence and distribution of the middle mesial canal in mandibular first molar teeth of the Kerman population: A CBCT study

Purpose. Missed additional canals are one of the most important reasons for RCT failures in molar teeth. This study aimed to determine the prevalence and distribution of middle mesial canals in mandibular first molars of the Kerman population. Materials and Methods. A retrospective study was performed on de-identified cone beam image sets from 3 private radiology centers in Kerman. A total of 100 mandibular first molars from 62 patients (mean age 32 years) were included. Information regarding the patient's age and gender, the location of teeth, and the presence or absence of a MMC and also a second distal canal in MMC cases was recorded in an Excel table. Data were analyzed using SPSS software (IBM-USA). Results. The overall prevalence of MMCs in the mandibular first molars was 8.1 (10.0 in females and 6.3 in males). More cases of MMCs were seen on the right side (12.2) than the left side (3.4). One case of bilateral MMCs combined with bilateral second distal canals in the mandibular first molars was seen in a 26-year-old female. A further case of bilateral MMCs was found in a 32-year-old male but with single-canal distal roots on both sides. Conclusion. The overall prevalence of MMCs in the Kerman population (8.1) is at the lower end of the reported range of the international literature (0.26 to 53.8). In the cohort examined in this study, mid mesial canals were more prevalent in females and on the right side. There was no definite relationship between MMCs and second distal canals in the mandibular first molar teeth in the same subject. MMCs may be unilateral or bilateral. Careful exploration of the pulpal floor between canal orifices is essential to prevent missing the MMC, as this would cause undesirable clinical outcomes. © 2020 Maryam Kuzekanani et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited