Effect of Temperatures on Cyclic Fatigue Resistance of 3 Different Ni-Ti Alloy Files.

OBJECTIVE: The aim of this study was to investigate and compare the effect of temperature on the cyclic fatigue resistance of conventional (ProTaper Universal [PTU]), Gold-Wire (ProTaper Gold [PTG]), and Fire-Wire (EdgeTaper Platinum [ETP]) nickel-titanium alloy files. METHOD: Twenty files from each system were tested for cyclic fatigue resistance in an artificial canal model. The experiments were performed at room temperature and body temperature in controlled temperature water. Magnified videos were recorded using a dental operating microscope integrated camera during testing to detect file fracture. The number of cycles to failure (NCF) was calculated. The type of failure was investigated macroscopically and microscopically with a dental operating microscope and scanning electron microscope, respectively. RESULT: The NCF at room temperature was significantly higher compared with body temperature in each system (P < .001). Compared at the same temperature, the ETP group demonstrated the highest NCF, followed by the PTG and PTU groups (P < .001). All files demonstrated cyclic fatigue failure macroscopically and microscopically. CONCLUSIONS: The 3 alloy files were affected by temperature. The cyclic fatigue resistance was reduced at the higher temperature and increased at the lower temperature. If the files are geometrically identical, files made of Fire-Wire are preferred compared with Gold-Wire and conventional nickel-titanium alloys based on cyclic fatigue resistance.

Effects of ethylenediaminetetraacetic acid on stem cells from the apical papilla: In vitro study.

Background/purpose: Ethylenediaminetetraacetic acid (EDTA) is used as an irrigant in regenerative endodontic treatment. The present study aimed to investigate the effects of EDTA on stem cells from apical papilla (SCAPs) in vitro. Materials and methods: Human SCAPs were isolated and characterised. The cells were treated with media supplemented with EDTA at concentrations ranging from 1.25% to 17%. Cell proliferation and apoptosis were examined using MTT assay and annexin V/propidium iodide staining. Cell migration was determined by a scratch assay. Gene expression was evaluated using a real-time polymerase chain reaction. Mineral deposition, a hallmark of osteogenesis in vitro, was determined using alizarin red s staining. Results: Overall, SCAPs exhibited mesenchymal stem cell characteristics. EDTA treatment at 2.50% and 1.25% did not significantly exhibit cytotoxicity and alter cell morphology. However, EDTA attenuated cell proliferation and reduced MKI67 mRNA expression in SCAPs. Further, EDTA significantly induced early cell apoptosis at 48 h. Cell migration was delayed with EDTA treatment. After maintaining SCAPs in an osteogenic induction medium, EDTA diminished mineral deposition by SCAPs on day 14. Conclusion: EDTA treatment exhibits adverse effects on SCAPs in vitro. Hence, EDTA exposure to periapical tissues should be avoided to minimise the negative impacts on SCAPs cells in regenerative processes.

Comparison of the efficacy of three different supplementary cleaning protocols in root-filled teeth with a bioceramic sealer after retreatment-a micro-computed tomographic study.

OBJECTIVE: The present study evaluated the efficacy of three different supplementary cleaning protocols on the removal of bioceramic-based root canal filling materials from oval-shaped canals. MATERIALS AND METHODS: A total of 36 human mandibular premolars were instrumented and obturated with gutta-percha and iRoot SP using the single-cone technique. Retreatment was performed with ProTaper Universal retreatment files. The samples were randomly divided into the following supplementary cleaning protocols: conventional syringe irrigation (CSI), passive ultrasonic irrigation (PUI), and XP-endo Finisher R (XPR). The samples underwent micro-CT scanning to quantify the amount of residual filling materials after retreatment and after performing the cleaning protocols. The volume of filling material removal was analyzed by one-way analysis of variance and post hoc Bonferroni and Games-Howell tests (P < 0.05). RESULTS: There were significant differences in the amount of root canal filling material removal in every comparison group (P < 0.05). The XPR removed significantly more residual filling materials (P < 0.01) followed by PUI and CSI (P < 0.05). Similar efficacy was found in the total root canal and all root thirds. CONCLUSIONS: The additional use of XP-endo Finisher R and passive ultrasonic irrigation effectively removed the bioceramic-obturated root filling materials from the oval-shaped canals. However, none of the techniques completely removed the filling materials. CLINICAL RELEVANCE: The XP-endo Finisher R and passive ultrasonic irrigation exhibited greater efficacy compared with syringe irrigation in the reduction of residual filling materials after retreatment in root-filled teeth with a bioceramic sealer.

Prevalence of C-shaped Canals and Three-rooted Mandibular Molars Using CBCT in a Selected Thai Population.

Introduction: C-shaped canals and three rooted mandibular molars are challenging to treat. These anatomies are commonly found in mandibular molars, especially in the Mongoloid population. However, there is no report on these anatomies using cone-beam computed tomography on all three mandibular molars in Thais. The objectives of this study were to determine the prevalence of C-shaped canals and three-rooted mandibular molars in Thais and investigate whether there is a relationship between these morphology and gender. Methods and Materials: Three pre-calibrated observers independently determined the presence of each anatomy using a specific protocol in 753 molars from cone-beam computed tomographic images. The three observers randomly re-evaluated 20% of the samples to determine inter- and intra-observer agreement using Cohen's Kappa statistic. The relationship of these root canal anatomy with sex was analysed by the Chi-square test. Results: The prevalence of C-shaped canals and three-rooted molars was 0.39% and 12.1%, 42.4% and 3.9%, and 16.6% and 9.1% in first, second, and third mandibular molars respectively. The inter-/intra-observer reliability of the results was extremely high. Conclusion: This cross-sectional study showed the prevalence of C-shaped canals in mandibular second molars was relatively high and should be considered normal root canal anatomy in Thais. The prevalence of three-rooted molars was highest in first molars and frequently found in third molars. Cone-beam computed tomography was a reliable technique to determine root canal anatomy.

Shaping ability of ProTaper NEXT, ProTaper Universal and iRace files in simulated S-shaped canals.

The aim of this study was to determine the shaping ability of three nickel-titanium endodontic file systems by comparing three parameters: canal deviation, apical foramen position and instrumentation time. A glide path was established in 30 simulated S-shaped canal blocks that were randomly assigned into three groups (n = 10): ProTaper Universal, ProTaper NEXT and iRace. Each group was instrumented per its manufacturer's directions. Pre- and postoperative images were superimposed to determine any canal deviation or change in apical foramen position. The instrumentation times were recorded. The iRace system resulted in the least mean canal deviation. The apical foramen position was least shifted by the iRace system. The iRace system also required the least instrumentation time. The iRace system demonstrated the most favourable shaping ability in all three parameters.