In vivo evaluation of operative torque generated by two Nickel-Titanium rotary instruments during root canal preparation

Objectives This in vivo study evaluated the operative torque and preparation time of ProTaper NEXT (Dentsply Maillefer; Ballaigues, Switzerland) and EdgeFile X7 (EdgeEndo; Albuquerque, New Mexico, United States) rotary systems during root canal preparation of maxillary premolars. Materials and Methods Ten double-rooted maxillary premolars with independent canals were selected. Each canal in each tooth was prepared with one of the rotary systems (n = 10), ProTaper NEXT or EdgeFile X7. The instruments were rotated at 300 rpm with maximum torque set at 2 N.cm using an electric motor (KaVo; Biberach, Germany) that automatically recorded torque values at every 1/10th of a second (ds). Statistical Analysis Operative torque (N.cm) and preparation time (s) of the first shaping instrument (size 17/.04) of both rotary systems were recorded and statistically compared using the Mann-Whiney U test with a significance level set at 5%. Results No instrument exhibited flute deformation or underwent intracanal failure. No differences were found between the instruments regarding the maximum (peak) torque values (p > 0.05). EdgeFile X7 17/.04 required significantly less preparation time (3.75 seconds interquartile range [IQR]: 3.2-9.0) than ProTaper NEXT X1 (15.45 seconds IQR: 8.35-21.1) (p < 0.05). The median operative torque values of ProTaper NEXT X1 (0.26 N.cm; IQR: 0.18-0.49) were significantly higher compared with EdgeFile X7 17/.04 (0.09 N.cm; IQR: 0.05-0.17) (p < 0.05). Conclusions Although no difference was found between the median peak torque values of ProTaper NEXT X1 and EdgeFile X7 17/.04 instruments, the operative torque and instrumentation time results were impacted by their different designs and alloys during clinical preparation of root canals

Fatigue resistance of new and used nickel-titanium rotary instruments: a comparative study

Aim of the present study was twofold. First, to evaluate in vitro, the performance of two different NiTi rotary instruments in one molar case; then, to evaluate their resistance to cyclic fatigue, compared to new ones

Role of the flat-designed surface in improving the cyclic fatigue resistance of endodontic NiTi rotary instruments

The aim of this study was to investigate the role of the flat-designed surface in improving the resistance to cyclic fatigue by comparing heat-treated F-One (Fanta Dental, Shanghai, China) nickel-titanium (NiTi) rotary instruments and similar prototypes, differing only by the absence of the flat side. The null hypothesis was that there were no differences between the two tested instruments in terms of cyclic fatigue lifespan. A total of 40 new NiTi instruments (20 F-One and 20 prototypes) were tested in the present study. The instruments were rotated with the same speed (500 rpm) and torque (2 N) using an endodontic motor (Elements Motor, Kerr, Orange, CA, USA) in the same stainless steel, artificial canal (90° angle of curvature and 5 mm radius). A Wilcoxon-Mann-Whitney test was performed to assess the differences in terms of time to fracture and the length of the fractured segment between the flat- and non-flat-sided instruments. Significance was set at p = 0.05. The differences in terms of time to fracture between non-flat and flat were statistically significant (p < 0.001). In addition, the differences in terms of fractured segment length were statistically significant (p = 0.034). The results of this study highlight the importance of flat-sided design in increasing the cyclic fatigue lifespan of NiTi rotary instruments

A survey on perceived COVID-19 risk in dentistry and the possible use of rapid tests

Aim: The present study was conducted to assess the perceived risk of COVID-19 transmission in dental professionals (DPs), that include dentists and dental auxiliary staffs, and whether rapid tests should be a recommended tool to constrain the transmission of the COVID-19, and who should be bearing their cost (governments, dentists, or patients) through an online survey. Materials and methods: A sample size of n = 700 was recruited in the study. The study included DPs from all over the world. A randomized selection of samples was done through dental groups present on social networks. An online survey was conducted in April 2020, using the Google Form software to provide questions and collect and elaborate answers. Data were analyzed using the statistical software STATA and presented in terms of percentages. Results: About 78% of the study participants perceived a very high risk of COVID-19 contamination in dental settings. Nearly 80% of the study participants were willing to be subjected to rapid tests and the same could be performed on patients visiting their dental clinics, which could prevent the spread of the disease. About 55% of the participants had reported that additional costs for the rapid tests should be borne by the governments. Conclusion: The results of the present survey report that DPs do not feel safe and perceive a high risk of COVID-19 contagion and prevention of the disease could be done by performing rapid tests on dentists, dental staff, and patients visiting the dental clinics irrespective of age and gender of the participants. Significance: Since all the dentists and allied staff have perceived increased risk for COVID-19 transmission, it is important that preventive measures are implemented through rapid test kits at the earliest

Cyclic Fatigue of Different Nickel-Titanium Rotary Instruments: A Comparative Study

Since the introduction of nickel-titanium alloy to endodontics, there have been many changes in instrument design, but no significant improvements in the raw material properties, or enhancements in the manufacturing process. Recently, a new method to produce nickel-titanium rotary (NTR) instruments has been developed, in an attempt to obtain instruments that are more flexible and resistant to fatigue. NTR instruments produced using the process of twisting (TF, SybronEndo, Orange, CA) were compared to NTR instruments from different manufacturers produced by a traditional grinding process. The aim of the study was to investigate whether cyclic fatigue resistance is increased for TF NTR files. Tests were performed with a cyclic fatigue device that evaluated cycles to failure of rotary instruments inside curved artificial canals. Results indicated that size 06-25 TF instruments showed a significant increase (P< .05). In the mean number of cycles to failurewhen compared to the other tested 06-25 NTR. Hence, it can be concluded that size 06-25 TF NTR instruments were found to be significantly more resistant to fatigue than those produced with the traditional grinding process

Digital design of minimally invasive endodontic access cavity

New minimally invasive endodontic cavities have been described and proposed to preserve dentin (and enamel) through strategic access, including point endodontic access cavity (PEAC). There is no consensus to what extent PEAC contributes to tooth's resistance to fracture, because there is no agreement on how PEAC should be performed. The purpose of the present study is to describe and classify four different types of PEACs and to examine if a dynamic navigation system /DNS) could allow planning and precisely executing these cavities in vitro. Forty TrueTooth TM Replica # 3-001 models, were randomly divided into four identical groups of ten and scanned using a cone bean computed tomography (OP-Maxio 300, Instrumentarium-Kavo, Finland). Then, four different access cavities were planned and performed by using DNS (Navident dynamic navigation system, ClaroNav, Toronto, ON, Canada). For each tooth, a different PEAC was designed to obtain endodontic access to the main mesio-buccal canal (MB1), resulting in a different location of the entry point on the occlusal surface of the tooth. Precision was evaluated by comparing deviation in the inclinations between the planned and real cavity. Data were recorded and statistically analyzed. DNS allowed preparation of minimally invasive "straight line" cavities, with some differences in the accuracy

Torque range, a new parameter to evaluate new and used instrument safety

The aim of the present study is to evaluate operative torque, torque at failure and the difference between these two values-the "torque range"-of two different NiTi files. We also sought to evaluate and compare these parameters for new and used files. Forty S-One 20.06 and forty M-Two 20.06 were tested, divided in four equal groups (n = 10) for each brand. Ten instruments from each brand performed three root canal treatments each on standardized extracted single-rooted teeth. Afterwards, each group was subjected to the following two tests: operative torque and torsional resistance. Mean values for all the tested groups were calculated. The results for new instruments showed that S-One developed significantly higher operative torque, but higher torsional resistance. The results for used instruments showed that the S-One 20.06 developed less operative torque and higher mean torsional resistance value compared to the M-Two. Moreover, the percentage reduction of both values was significantly higher for M-Two. The results of the present study showed a safer torsional behavior of the S-One. These results could be related to the heat treatment and the manufacturing process