• Humans
• Root Canal Therapy/instrumentation
• Root Canal Therapy/adverse effects
• Consensus
• Root Canal Preparation/instrumentation
• Root Canal Preparation/adverse effects

• austenite
• endodontics
• fatigue
• martensite
• nickel titanium
• root canal preparation
• root canal therapy
• torsional force

• Endodontic file
• File fracture
• File fracture management
• Separate file

Since there are no reviews of the literature on this theme, the aim of this narrative review is to summarize the metallurgical tests used in endodontics, pointing out their functional use and their pros and cons and giving readers a user-friendly guide to serve as an orientation aid in the plethora of metallurgical tests. With this purpose, a literature search for articles published between January 2001 and December 2021 was conducted, using the electronic database PubMed to collect all published articles regarding the metallurgical tests used in endodontics for the evaluation of NiTi rotary instruments. The search was conducted using the following keywords: “metallurgy”, “differential scanning calorimetry” (DSC), “X-ray diffraction” (XRD), “atomic force microscopy” (AFM), “energy-dispersive X-ray spectroscopy” (EDS), “focused ion beam analysis” (FIB) and “Auger electron spectroscopy” (AES) combined with the term “endodontics” or “NiTi rotary instruments”. Considering the inclusion and exclusion criteria, of the 248 articles found, only 81 were included in the narrative review. According to the results, more than 50% of the selected articles were published in one of the two most relevant journals in endodontics: International Endodontic Journal (22.2%) and Journal of Endodontics (29.6%). The most popular metallurgical test was DSC, with 43 related articles, followed by EDS (33 articles), AFM (22 articles) and XRD (21 articles). Few studies were conducted using other tests such as FIB (2 articles), micro-Raman spectroscopy (4 articles), metallographic analysis (7 articles) and Auger electron spectroscopy (2 articles).

• endodontic rotary instruments
• endodontics
• metallurgy
• nickel–titanium alloy
• root canal treatment

• Clinical use
• XP-endo Finisher R
• XP-endo Shaper
• defects
• nickel-titanium instrument
• retreatment

• Alloys
• Dental Instruments
• Equipment Design
• Nickel/chemistry
• Retreatment
• Root Canal Preparation
• Titanium/chemistry

The aim of this investigation was to detect defects that may occur to Reciproc endodontic files after a single use.

A sample of convenience of Reciproc files (VDW GmbH, Munich, Germany) that were used to prepare root canals of anterior or posterior teeth were collected. The files were divided equally into two groups: Group 1 (R25) files were used to prepare mesial root canals of 50 human permanent mandibular molars, and Group 2 (R40) included 50 files that were used to prepare permanent maxillary incisor teeth. Files were analyzed after single use by using a scanning electron microscope at X120 to detect changes in surface morphology. The data were statistically analyzed by using the χ² test, and statistical significance was set at P < 0.05.

A total of 96 Reciproc NiTi files were collected; of those, 67 (70%) were unaffected and 29 (30%) showed overall surface deformations. The types of deformation were blade disruption (22%), surface pitting (12%), and unwinding and tip deformation (1%). No microcracks were detected, and none of the studied files showed fracture. R40 was three times more likely to be deformed and showed blade disruption compared with R25 (P < 0.05).

Reciproc rotary NiTi files show high resistance to deformation after a single use. Blade disruption was the most frequent defect occurring in both the small and large files.

• Flexibility
• SEM
• niti alloy
• reciproc files
• resistance
• scanning electron microscopy

• endodontics
• iatrogenic disease
• root canal preparation
• root canal therapy

• Dental education
• Micro-CT
• Nickel-titanium
• Root canal preparation
• endodontic instrument

• Dental Instruments
• Dental Pulp Cavity/diagnostic imaging
• Dental Pulp Cavity/surgery
• Equipment Design
• Humans
• Molar/diagnostic imaging
• Molar/surgery
• Root Canal Preparation
• Titanium
• Tooth Root
• X-Ray Microtomography

To investigate the complications associated with the use of nickel titanium rotary instruments (NiTi-RIs) for root canal treatments (RCTs), in Saudi Arabia dental practice, and to explore the influencing factors.

After obtaining an ethical approval, two pilot studies were conducted to formulate the final questionnaire. The sample size was measured taking into consideration 60% expected response rates and confidence level of 99.9%. The questionnaire was emailed to 600 general dentists (GDs) randomly selected from the dental register and all of the endodontists (175). The email’s introduction clarified objectives of the study and guaranteed that all of the collected information would remain confidential. A reminder was sent after 10 weeks. The data were collected and analyzed using the chi-squared test at a 0.05 significance level.

With a 51% overall response rate, 71.9% off the respondents used NiTi-RIs. The majority (83.1%) experienced complications while using NiTi-RIs; with the instruments’ fracture being significantly the most common complication (52.7%) (p < 0.001). The majority (87.7%) experienced NiTi-RIs’ fractureat least once; with more endodontists (94.3%) than GDs (83.3%) (p < 0.001). The greater the number of weekly performed RCTs and participants’ experiences, the more NiTi-RIs fractures and the greater the number of fracture incidents (p < 0.001). While 60% of those who performed 1–3 RCTs per week experienced NiTi-RIs fractures, 100% of those who performed more than 12 RCTs per week did so. The highest percentage of those who experienced more than 10 fractured NiTi-RIs (60%) was within the group who performed more than 12 RCTs per week. Although fracture incidents decreased with a smaller number of reuses, there was no significant correlation between the number of fractured instruments and NiTi-RIs discard strategy (p ≥ 0.05).

Fracture incidence was the most common complication while using NiTi-RIs, regardless of the clinicians’ experiences and skills. While the single use may reduce NiTi-RIs fractures, to some extent, the greater number of RCTs performed per week was the most influential factor.

• Complications
• Endodontics
• Fracture
• NiTi
• Questionnaire
• Root canal
• Rotary
• Separated

• Dentin thickness
• Fractured instrument removal
• Microcomputed tomographic imaging
• Trepan bur/microtube technique

• Cyclic fatigue
• endodontics
• network analysis
• rotary endodontic instruments
• systematic review

• NiTi rotary system
• ProTaper Universal
• deformation
• dental instruments
• fracture

New designs and processing of Niquel-Titanium (NiTi) have been introduced to increase resistance to cyclic fatigue. The purpose of this study was to compare the cyclic fatigue resistance of 3 NiTi rotary instruments, ProTaper Next (PTN; Dentsply Maillefer, Ballaigues, Switzerland), Profile Vortex Blue (PVB; Dentsply Tulsa Dental, Tulsa, OK, USA) and ProTaper Universal (PTU; Dentsply Maillefer, Ballaigues, Switzerland).

A cyclic fatigue test was conducted operating instruments from ProTaper Next X2, Profile Vortex Blue 25.06 and ProTaper F2. A total of 234 instruments were rotated in 2 simulated stainless steel curved canals with different angles of curvature (45º and 60°) and 5-mm radius of curvature. The number of cycles to fracture (NCF) was calculated. Data were compared using 2-way analysis of variance and post-hoc Bonferroni test in software (SPSS 15.0, Chicago, IL). Statistical significance was set at P<0.05.

Profile Vortex Blue showed higher resistance to cyclic fatigue in both curved canals than ProTaper Next and ProTaper Universal (P<0.001). ProTaper Universal obtained the lowest resistance to cyclic fatigue in both canals (P<0.001).

Profile Vortex Blue was the most resistant to cyclic fatigue failure, followed by ProTaper Next and ProTaper Universal. Anatomical complexity (angle of curvature) and manufacturing process of NiTi are important factors for resistance to cyclic fatigue.

Key words:Cyclic fatigue, M-Wire, Protaper Next, ProTaper Universal, Profile Vortex Blue.

• Alloys/chemistry
• Biocompatible Materials
• Dental Instruments
• Humans
• Materials Testing
• Temperature
• Thermodynamics

• Cone-Beam Computed Tomography/methods
• Humans
• In Vitro Techniques
• Molar/diagnostic imaging
• Periapical Diseases/diagnostic imaging
• Postoperative Complications/diagnostic imaging
• Radiography, Dental, Digital/methods
• Root Canal Therapy

Intracanal instrument fracture is an unpredictable and problematic occurrence that can prevent adequate cleaning and shaping procedures and influence the prognosis of endodontic treatment. The prevalence of instrument fracture is reported to range between 0.28% and 16.2%. This article presents an overview of the prevention and management of instruments fractured during endodontic therapy on the basis of literature retrieved from PubMed and selected journal searches. Instrument fracture occurs because of reduced metal fatigue and/or torsional resistance. The reasons include canal morphology and curvature, manufacturing processes and instrument design, instrument use times and technique, rotational speeds and operator experience. With the development of various equipment and techniques, most of the retained instrument separations can be removed safely. However, in canals without associated periapical disease not every fractured separation should be removed from difficult locations because of the increased risk for root perforation and fracture. In difficult cases, either retain or bypass the fragment in the root canal and ensure regular follow-up reviews. Fractured instruments retained in the presence of periapical disease reduce significantly the prognosis of endodontically treated teeth, indicating a greater need to attempt the removal or bypass of the file separations. Apical surgery might be required in some instances, emphasizing the importance of preventing instrument fracture.

• Endodontics
• Instrument fracture
• Root canal preparation
• Prevention
• Management

• deformation
• fracture
• nickel-titanium
• reciprocation

The aim of this study was to assess the influence of operator experience level on the lifespan of the WaveOne Primary file (Dentsply Maillefer, Ballaigues, Switzerland) in extracted teeth.

Moderately curved canals of extracted maxillary and mandibular molars were randomly distributed into 2 groups: experienced and inexperienced operators. Ten files were allocated to each group (n = 10). Each canal was prepared until the working length was reached, and the same file was used to prepare additional canals until it separated. The number of canals prepared before file separation was recorded. The fragment length of each file was measured, and the location of the fragment in the canal was determined. Data were statistically analysed using the independent 2-sample t-test.

The 2 operators prepared a total of 324 moderately curved canals of maxillary and mandibular molars. There was no significant intergroup difference in the mean number of canals prepared (p = 0.27). The average lifespan of the WaveOne Primary file was 17.1 and 15.3 canals, and the longest lifespan was 25 and 20 canals, when used by experienced and inexperienced operators, respectively. There were no statistically significant intergroup differences in separated fragment length and location.

Within the limitations of this study, operator experience level appears to have no effect on the lifespan of the WaveOne Primary file in preparation of moderately curved canals. Single teeth with multiple canals can be prepared safely even by a novice operator by using a single file.

• Lifespan
• Operator experience
• Reciprocating
• Separation
• WaveOne

• Ni-Ti
• endodontics
• fracture
• hand instruments
• prognosis
• stainless steel

• HyFlex CM
• clinical
• defect
• instrument
• metallurgical property
• nickel-titanium

• Calorimetry, Differential Scanning
• Dental Alloys/chemistry
• Equipment Design
• Equipment Failure
• Hardness
• Humans
• Materials Testing
• Metallurgy
• Microscopy, Electron, Scanning
• Nickel/chemistry
• Root Canal Preparation/instrumentation
• Stress, Mechanical
• Surface Properties
• Temperature
• Titanium/chemistry
• Torsion, Mechanical
• X-Ray Diffraction

The aim of the present study was to evaluate the cyclic fatigue resistance of Mtwo NiTi rotary instruments after clinical use by 1 experienced and 1 novice operator.

Cyclic fatigue testing of instruments was performed on tapered artificial canals with a 5 mm radius of curvature and 60° angle of curvature. Twenty Mtwo instruments for each size were selected and divided into 2 groups: group A consisted of 10 instruments of each size used for shaping 10 root canals in molar teeth of patients by an experienced operator; group B consisted of 10 instruments of each size used for shaping 10 root canals in molar teeth of patients by a novice operator. Instruments were rotated until fracture occurred and the numbers of cycles to failure (NCF) were recorded. Data obtained were subjected to an independent sample t-test to determine statistical differences. The significance was determined at a 95% confidence level.

No statistically significant difference (P<0.05) was noted between the instruments of groups A and B for all sizes. More instruments with visible signs of plastic deformation were identified for the novice operator.

The clinical use of Mtwo NiTi rotary instruments by a novice operator did not significantly affect the cyclic fatigue resistance when compared with the control group of the same instrument sizes used by an experienced operator. It can be concluded that novice operators can use these instruments safely under the recommended technical guidelines.