Radix Entomolaris in Mandibular First Molars: Report of 3 Cases

The radix entomolaris is an anatomical variation characterized by the presence of an additional root located in the distal-lingual region of mandibular molars. An accurate diagnosis is necessary to plan and institute effective endodontic therapy for teeth with this condition. The aim of this report was to present three cases of endodontic management in permanent mandibular first molars with radix entomolaris using contemporary technical resources. For diagnosis, periapical radiographs indicated the possibility of morphological alterations, which were confirmed in two cases by cone beam computed tomography (CBCT). Ultrasonic tips and magnification with operative microscopy were the auxiliary resources used for locating the root canals, which were prepared with NiTi rotary instrument systems and filled with gutta-percha by using the lateral condensation technique and AH Plus sealer. Resources such as periapical radiography, CBCT, magnification with operative microscopy, ultrasonic devices and NiTi instruments can be extremely valuable for use in the diagnosis and clinical approach to endodontic treatment of mandibular first molars with radix entomolaris.

Defects and Safety of NiTi Root Canal Instruments: A Systematic Review and Meta-Analysis

Aim: To review the reported defect and fracture rates of various NiTi instrumentation systems and identify factors that may influence the chance of NiTi file separation clinically.Data Sources: PubMed, EMBASE, and SCOPUS with controlled vocabulary and keywords in various combinations to identify articles that reported on the defects and/or fracture of NiTi instrument used clinically (Jan 1980 till Aug 2021), with additional search manually by going through the list of references of the initially screened articles. Those satisfying the inclusion and exclusion criteria were entered into the analysis.Study Eligibility Criteria, Participants, and Interventions: All studies from the said databases reporting on NiTi root canal instruments that were deformed or separated during normal clinical use.Study Appraisal and Synthesis Methods: Studies with data available and suitable for meta-analysis were grouped according to the general design of the NiTi instruments for comparison. Safety quotient value was calculated based on the rate of instrument distortion and fracture.Results: Various instrument designs exhibited different incidences of distortion and fracture, hence a different “safety quotient” (ratio of the amount of deformed instruments to that of fractures in use). Heat-treated files showed the highest safety quotient value. All brands of NiTi file demonstrated a statistically significantly lower incidence of fracture, if treated as disposable instruments after clinical use in a patient.Limitations: Inclusion of articles written in English only, and grouping of file systems into general design types in the analysis.Conclusions and Implications of Key Findings: NiTi endodontic files should be scrutinized for defects before being used in the root canal. Disposing the NiTi instruments after clinical use in a patient (so-called “single use”) is recommended for minimizing fracture clinically. Certain instrument designs tend to show discernible deformation before they should fracture in the next use.

Differential scanning calorimetric investigations of three rotary nickel-titanium instrument systems before and after simulated clinical uses

Background The transformation temperatures were important values, influencing the mechanical properties and clinical performance of nickel-titanium instruments. The aim of this study was to determine the transformation temperatures of three rotary nickel-titanium (NiTi) instruments: Reciproc, HyFlex CM Pro, and Neoniti before and after simulated clinical uses. Methods Ninety new NiTi instruments of three single-file instruments: Reciproc, HyFlex CM Pro, and Neoniti were divided into three groups. Thirty instruments of each group were divided into 3 subgroups (10 instruments for each subgroup): new, one-time simulated clinical used and sterilised, and three times simulated clinical used and sterilized subgroups. The instruments were in the as-received condition for the new subgroups, one time used in the plastic endo-training blocks and sterilised for the one-time subgroups, and three times used in the plastic endo-training blocks and sterilised for the three times subgroups. Each instrument in subgroups was cut into four small segments of 4–5 mm. All segments of instruments were analysed using Differential Scanning Calorimetry (DSC). Data was collected and analysed using SPSS version 20.0 with ANOVA test or Kruskal–Wallis test at the significant level of 0.05. Results There was not significant difference between before and after simulated clinical use with sterilised procedure in three NiTi instrument systems. The austenite-finish (Af) temperatures of three instrument systems were higher than that of the human body (37 °C), of these, the Af temperature of Neoniti was highest and that of HyFlex CM Pro was lowest. Conclusions The austenite-finish (Af) temperatures of three NiTi instruments were higher than that of human body temperature, therefore, material was in the phase transformation from martensite to austenite, gives the instruments more flexibility when used in the clinical situation.

Torsional Resistance of Heat-Treated Nickel-Titanium Instruments under Different Temperature Conditions

This study compared the torsional resistance of heat-treated nickel-titanium (NiTi) instruments under different temperature conditions. Four thermomechanically treated single-use NiTi rotary instruments were selected for this study: OneShape (OS), OneCurve (OC), WaveOne Gold (WOG) and HyFlex EDM (HFE). Each instrument was further subdivided by temperature into 2 subgroups. Maximum torque and the distortion angle until fracture occurred were evaluated. Differential scanning calorimetry analysis was performed to measure the phase transformation temperature. Statistical analysis was performed using a two-way ANOVA and t-test (p < 0.05). Fractured fragments were observed using scanning electron microscopy (SEM). The two-way ANOVA showed no significant differences for different temperature conditions. At both room (RT) and body temperature (BT), OS was predominantly austenite while HFE was martensite. OC and WOG were predominantly martensite at RT and mixed phase at BT. At BT, more than half of WOG was martensite, while half of OC was austenite. SEM examination showed no topographical differences between instruments in different temperature groups. In relation to a limitation of this study, there was no difference in torsional resistance of NiTi rotary instruments between the BT and RT conditions. This implies that clinicians do not need to consider a decrease of torsional resistance of heat-treated NiTi instruments at BT.

Evaluation of Dentinal Crack Formation by ProTaper Next, HyFlex CM and Wave One Reciprocating File Systems at the Apical and Middle Third of Root in Mandibular Molars - An In-Vitro Scanning Electron Microscope Analysis

BACKGROUND Advances in root canal instruments have led to lesser frequency of dentinal crack formation. Not many studies have been reported in literature that compare crack formation using instruments based on control memory (CM) and M wire technology. The study intended to evaluate and compare the prevalence of dentinal cracks formed by ProTaper Next (Dentsply Maillefer, Ballaigues, Switzerland), HyFlex CM (Coltene, Whaldent) and Wave One (Dentsply, Maillefer) reciprocating file systems at the apical and middle third of the mesiobuccal root canal of mandibular molars under scanning electron microscope (SEM). METHODS Forty-five extracted sound human mandibular molars were decoronated and mesial roots were retained followed by root canal instrumentation using ProTaper Next, HyFlex CM and WaveOne reciprocating files. Roots were then sectioned perpendicular to the long axis of teeth and viewed under scanning electron microscope to detect the presence of cracks. RESULTS ProTaper Next system produced more cracks compared with HyFlex and Wave One (P < 0.05) but there was no statistically significant difference between all the three groups. All the file systems showed more incidences of cracks in the apical third compared to middle third. CONCLUSIONS All the NiTi instruments produced cracks and the highest incidence of cracks was seen in the apical third compared to middle third region. KEY WORDS Dentinal Cracks, HyFlex CM, ProTaper Next, Root Canal, Wave One

Methods for Removing Fractured Endodontic Instruments in Root Canal : A Brief Systematic Review

Introduction: In the scenario of endodontic treatment, fracture of the instrument complicates the endodontic procedure by obstructing debridement, delaying the completion of treatment, and affecting the patient's dental experience. When a file fractures during root canal treatment, several treatment options are available. Fractured endodontic instruments inhibit optimal cleaning and filling of root canals. Objective: To carry out a brief systematic review study to present the main clinical outcomes of different types of techniques for removing fragments of endodontic instruments in root canals. Methods: The rules of the Systematic Review-PRISMA Platform were followed. The research was carried out from November 2020 to January 2021 and developed based on Scopus, PubMed, and SCIENCE DIRECT. The quality of the studies was based on the GRADE instrument and the risk of bias was analyzed according to the Cochrane instrument. Results: A total of 132 articles were found involving the removal of fragments of endodontic instruments. A total of 80 articles were evaluated in full and 30 were included and evaluated in the present study. It has been found that the probability of successful removal of a fractured instrument is reported to range from 53 to 95%, with more than 80% of fractured instruments being removed by the use of ultrasound. Also, long fragments (0.4 mm) can adsorb ultrasonic energy and hinder its loosening. Nickel-titanium (NiTi) instruments with their pseudo-elasticity, especially the newly developed heat-treated NiTi instruments are more ductile and flexible compared to conventional NiTi2. Conclusion: Fractured instruments can be removed by a variety of methods, such as good ultrasonic tips, microtubule devices, and hemostatic pliers/forceps. Removing a fractured file is associated with considerable risk, and therefore the fragment must be circumvented. A cost-benefit analysis of the treatment should be considered before selecting a definitive treatment for the patient.

Cyclic Fatigue of Dental NiTi Instruments after Plasma Nitriding

This study investigated the possibility of nitride NiTi instruments using low-temperature plasma nitriding technology in a standard industrial device. Changes in the properties and fatigue life of used NiTi instruments before and after low-temperature nitriding application were investigated and compared. Nontreated and two series of plasma-nitrided NiTi instruments, designed by Mtwo company with tip sizes of 10/.04 taper, 15/.05 taper, and 20/.06 taper, were experimentally tested in this study. All these instruments were used and discarded from clinical use. The instruments were tested in an artificial canal made of stainless steel with an inner diameter of 1.5 mm, a 60° angle of curvature, and a radius of curvature of 3 mm. A low-temperature plasma nitriding process was used for the surface treatment of dental files using two different processes: 550 °C for 20 h, and 470 °C for 4 h. The results proved that it is possible to nitride dental instruments made of NiTi with a low-temperature plasma nitriding process. Promising results were achieved in trial testing by NiTi instruments nitrided at a higher temperature. Plasma-nitrided files were found to have, in some cases, significantly higher values than nontreated files in terms of fatigue life. The results showed that the nitriding process offers promising possibilities for suitably modified surface properties and quality of surface layer of NiTi instruments. Within the limitations of the present study, the cyclic fatigue life of plasma-nitrided NiTi dental files can be increased using this surface technology.

Evolutionary Leap in Endodontics. Case report

The Leap protocol combines the newest and most active association of reciprocal-rotary instrumentation, aluminum insert ultrasonic, and diode laser. The reciprocal-rotary technique consists of Niti instruments used in different motions depending on the stage of the treatment and promotes the balanced cutting effectiveness and reduced risk of fracture files. Moreover, it creates a centered and tapered shape. The aluminum tip for the ultrasonic unit delivers agitation, emulsification, and cavitation of antiseptic solutions that improve the cleaning. The dye and laser use cause the ablation and final disinfection. This paper describes the case of a patient with asymptomatic apical periodontitis in an upper first right molar submitted to endodontic treatment performed with Leap protocol. After conventional procedures, the root canals were prepared by using reciprocal-rotary instrumentation techniques. Between each file a new solution was placed and activated with the ultrasonic handpiece. At the end of instrumentation, the root canals were aspirated, dried with paper points, the indocyanine dye was placed into the root canals and, DaVinci laser was used for 30 seconds. The gutta-percha cones matching the final Niti file were used coated with AH Plus sealer. A periapical radiograph was taken to verify obturation and its anatomical complexity. Six months after the procedure, the patient was asymptomatic, and the radiographic examination showed healthy periradicular tissues. It is concluded that the use of Leap protocol in conventional endodontic treatment was effective, suggesting that this therapy may provide additional benefits to patients when compared to the conventional technique.