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DuqueJA, Fernandes SL, Bubola JP, Duarte MAH, Camilleri J, Marciano MA. The effect of mixing method on tricalcium silicate-based cement.International Endodontic Journal, 51, 69-78, 2018. Aim To evaluate the effect of three methods of mixing on the physical and chemical properties of tricalcium silicate-based cements. Methodology The materials evaluated were MTA Angelus and Portland cement with 20% zirconium oxide (PC-20-Zr). The cements were mixed using a 3 : 1 powder-to-liquid ratio. The mixing methods were manual (m), trituration (tr) and ultrasonic (us) activation. The materials were characterized by means of scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy. Flowability was analysed according to ANSI/ADA 57/2012. Initial and final setting times were assessed following ASTM C266/08. Volume change was evaluated using a micro-CT volumetric method. Solubility was analysed according to ADA 57/2012. pH and calcium ion release were measured after 3, 24, 72 and 168 h. Statistical analysis was performed using two-way analysis of variance. The level of significance was set at P = 0.05. Results The SEM analysis revealed that ultrasonic activation was associated with a homogeneous distribution of particles. Flowability, volume change and initial setting time were not influenced by the mixing method (P > 0.05). Solubility was influenced by the mixing method (P < 0.05). For pH, at 168 h, significant differences were found between MTA-m and PC-20-Zr-m (P < 0.05). For calcium ion release, PC-20-Zr-tr had higher values than MTA-m at 3 h, and MTA-tr had higher values than PC-20-Zr-m at 168 h (P < 0.05). Conclusions The ultrasonic and trituration methods led to higher calcium ion release and pH compared with manual mixing for all cements, whilst the ultrasonic method produced smaller particles for the PC-20-Zr cement. Flow, setting times and volume change were not influenced by the mixing method used; however, it did have an impact on solubility.

Objective This study aimed to evaluate the influence of the NiTi wire in Conventional NiTi (ProTaper Universal PTU) and Controlled Memory NiTi (ProTaper Gold PTG) instrument systems on the quality of root canal preparation.Material and Methods Twelve mandibular molars with separate mesial canals were scanned using a high-definition microcomputed tomography system. The PTU and PTG instruments were used to shape twelve mesial canals each. The canals were scanned after preparation with F2 and F3 instruments of the PTU and PTG systems. The analyzed parameters included the remaining dentin thickness at the apical and cervical levels, root canal volume and untouched canal walls. Data was analyzed for statistical significance by the Friedman and Dunn’s tests. For the comparison of data between groups, the Mann-Whitney test was used.Results In the pre-operative analysis, there were no statistically significant differences between the groups in terms of the area and volume of root canals (P>.05). There was also no statistically significant difference between the systems with respect to root canal volume after use of the F2 and F3 instruments. There was no statistical difference in the dentin thickness at the first apical level between, before and after instrumentation for both systems. At the 3 cervical levels, the PTG maintained centralization of the preparation on the transition between the F2 and F3 instruments, which did not occur with the PTU. Conclusion The Conventional NiTi (PTU) and Controlled Memory NiTi (PTG) instruments displayed comparable capabilities for shaping the straight mesial root canals of mandibular molars, although the PTG was better than the PTU at maintaining the centralization of the shape in the cervical portion.

Objective: The aim of this study was to evaluate the cyclic fatigue, torsional behavior and bending resistance of EdgeTaper Platinum [ETP (tip 25, taper 0.06)], Flex Gold [FG (tip 25, taper 0.08)], Pro-T [PT (tip 25, taper 0.08)] and ProTaper Gold [PTG (tip 25, taper 0.08)] systems. Methods: Rotary instruments of ETP, PT, FG, and PTG were used (n=30). Cyclic fatigue tests were performed using an artificial stainless-steel canal with a 60o angle and a 5-mm radius of curvature at body temperature (35°±1°C). The time and number of cycles to fracture (NCF) was recorded. The torsional test evaluated the torque and angle of rotation to failure at 3 mm from the tip according to ISO 3630-1. The fractured surface of each fragment was observed by using scanning electron microscopy (SEM). The bending test evaluated the torque required to bend the instruments at an angular deflection of 60°. Data were analyzed using one-way ANOVA and Tukey tests, and the level of significance was set at 5%. Results: The ETP had highest time until fracture and NCF than all the groups (P<0.05). The PTG had the highest torsional strength, followed by FG (P<0.05). The ETP had the highest angular rotation, followed by PT and PTG (P<0.05). The FG showed the highest bending resistance, followed by the PTG (P<0.05). Conclusion: In conclusion, the ETP and PT exhibited higher cyclic fatigue resistance, higher angular deflection values and lower bending force than FG and PTG. The PTG instruments showed the highest torsional strength and the lowest cyclic fatigue resistance.

Aim To evaluate the influence of larger apical canal enlargement in curved canals using reciprocating systems subjected to various heat treatments. Methodology Ninety mandibular premolars with root curvatures ranging from 20° to 30° were selected and scanned by microcomputed tomography (micro‐CT) before and after root canal preparation with reciprocating systems (n = 30): Reciproc Blue (RB size 25, .08 taper and size 40, .06 taper; VDW, Munich, Germany), WaveOne Gold (WOG size 25, .07 taper and size 35, .06 taper; Dentsply Sirona, Ballaigues, Switzerland) and ProDesign R (PDR size 25, .06 taper and size 35, .05 taper; Easy Dental Equipment, Belo Horizonte, Brazil). Canal transportation, untouched areas, and apical and total root canal volumes were measured. Statistical analysis was performed with the nonparametric Kruskal–Wallis and Dunn's tests and a significance level set at 5%. Results The between‐group comparison revealed no significant difference in untouched areas, canal transportation, and apical root canal volume among the groups (P > 0.05). However, WOG size 35, .06 taper was associated with a significant increase in the percentage of total canal volume in comparison to the PDR size 35, .05 taper (P < 0.05). The within‐group comparison revealed a significant decrease in untouched areas, increase in apical and total root canal volume for all groups when using a larger instrument (P < 0.05). There was no significant difference in transportation among the groups and when a larger apical preparation was created (P > 0.05). Conclusions Larger apical enlargement of curved canals was associated with a decrease in untouched areas, an increase in root canal volume and maintenance of canal trajectory. In addition, all systems were safe and provided similar root canal shapes.

AimTo evaluate the influence of three engine‐driven NiTi file systems manufactured from different NiTi alloys for the preparation of second mesiobuccal (MB2) canals in extracted maxillary first molars using a micro‐computed tomographic (micro‐CT) scanner.MethodologyThirty maxillary molars with two canals in the mesiobuccal root were selected and randomly divided into three groups (n = 10): Reciproc [REC; size 25, .08 taper; VDW, Munich, Germany], ProDesign R [PDR; size 25, .06 taper; Easy, Belo Horizonte, Brazil] and Mtwo [MO; size 25, .06 taper; VDW, Munich, Germany]. Before and after root canal preparation of the MB2 canal, the teeth were scanned using a micro‐CT to evaluate canal transportation, centring ability, dentine thickness and volume change. The working time to achieve working length was also evaluated. All parameters were compared statistically using the Kruskal–Wallis and Dunn test for multiple comparisons, with a significance level of 5%.ResultsThere was no significant difference amongst the groups regarding canal transportation and centring ability (P > 0.05). However, the PDR size 25, .06 taper group had significantly lower canal volume and volume of dentine removal compared with a MO size 25, .06 taper and REC size 25, .08 taper (P < 0.05). A root perforation was detected in MO size 25, .06 taper and REC size 25, .08 taper groups, respectively. Regarding the working time, the PDR size 25, .06 taper required a significantly longer time to achieve working length than MO size 25, .06 taper and REC size 25, .08 taper (P < 0.05).ConclusionsAll NiTi systems had similar canal transportation, centring ability and increase in apical volume after preparation of MB2 canals. However, the PDR size 25, .06 taper had less volume of dentine removal, absence of root canal perforation and required a longer time to accomplish the root canal preparation.

The aim of this study was to evaluate three reciprocating systems and complementary cleaning methods on filling material removal during retreatment of flattened canals. Thirty-six mandibular incisors were prepared using rotary instruments up to size 25.08 and filled using the single-cone technique. Subsequently, the teeth were divided into three groups (n = 12) according to retreatment procedures: Reciproc Blue (RB): 25/0.08 and 40/0.06; ProDesign R (PDR): 25/0.06 and 35/0.05; and WaveOne Gold (WOG): 25/0.07 and 35/0.06. The remaining filling volume materials were assessed by means of micro-CT imaging before and after retreatment. After this, the specimens were subdivided into three groups according to complementary cleaning methods: XP-Endo Shaper (30/0.01); passive ultrasonic irrigation (PUI); 60 oscillatory instrumentation with #30 H-file, and micro-CT scan was taken. Then, the roots were cut in half and the samples were analyzed by scanning electron microscope (SEM). The data were analyzed statistically using Kruskal-Wallis and Dunn's Multiple Comparison test with significance level of 5%. None of the reciprocating files promoted complete removal of filling material and there was no statistical difference between the groups, regardless instrument size (p > 0.05). Complementary cleaning methods increased remnant filling removal (p < 0.05). XP-endo Shaper significantly reduced the amount of filling material in the apical and middle thirds, compared with H-files (p < 0.05), with no difference with PUI. In the SEM, there was no statistical difference among the instruments (p > 0.05). The reciprocating systems showed similar effectiveness in removing root filling material. Complementary cleaning method with the XP-Shaper enhanced filling material removal.