Medication-related osteonecrosis of the jaw triggered by endodontic failure in oncologic patients.

OBJECTIVES: To describe the association between endodontic treatment failure and medication-related osteonecrosis of the jaw (MRONJ) in a cohort of oncologic patients in therapy with antiresorptive and antiangiogenic drugs. MATERIALS AND METHODS: Patients were selected as affected by MRONJ in absence of the common local risk factors (oral surgical procedures or ill-fitting dentures) but showing failure of previous endodontic treatment performed at least 6 months before the starting of antiresorptive/antiangiogenic therapies. Jaw lesions were all surgically treated and patients underwent a strict clinical and radiological follow-up. RESULTS: Among 18 patients, who developed 18 MRONJ, the only detectable local risk factor was the presence of teeth with failed endodontic treatment (more precisely, root canal underfilling in eight cases, root canal overfilling in two cases, root perforation in three cases, root fracture in five cases). All patients completely healed after surgical procedure and no recurrence was observed. CONCLUSIONS: Endodontic treatment failure should be considered a local risk factor for MRONJ development in oncologic patients. For such reason, it is mandatory to carefully evaluate them prior than the beginning of antiresorptive and antiangiogenic drugs administration.

ESE position statement on root resorption.

This Position Statement on root resorption represents the consensus of an expert committee convened by the European Society of Endodontology (ESE). The statement is based on current clinical and scientific evidence as well as the expertise of the committee. The aim is to provide clinicians with authoritative information on the aetiology, histopathology, clinical presentation and recommendations for the management of root resorption. It is the intention of the committee to update this position statement at appropriate intervals as further evidence emerges.

Present status and future directions: Surgical extrusion, intentional replantation and tooth autotransplantation.

Surgical extrusion, intentional replantation and tooth autotransplantation procedures are important treatment options that clinicians may consider performing in their day-to-day clinical practice. Despite compromised teeth are generally considered for extraction, clinicians must be aware that these cases could be suitable for management by these alternative predictable treatment options. Surgical extrusion, intentional replantation or tooth autotransplantation have similar treatment protocols which includes atraumatic tooth extraction, visualisation of the root portion and replantation. Surgical extrusion is defined as the 'procedure in which the remaining tooth structure is repositioned at a more coronal/supragingival position in the same socket in which the tooth was located originally'. Intentional replantation is defined as the 'deliberate extraction of a tooth and after evaluation of root surfaces, endodontic manipulation and repair, placement of the tooth back into its original position'. Tooth autotransplantation is defined as the 'transplantation of an unerupted or erupted tooth in the same individual, from one site to another extraction site or a new surgically prepared socket'. The same team previously published a narrative review (International Endodontic Journal. 2020, 53, 1636) and European Society of Endodontology position statement (International Endodontic Journal. 2020, 54, 655) on this topic in International Endodontic Journal. The aim of the current updated review was to provide the reader a complete overview and background on these procedures, to established clear clinical protocols and step-by-step for technically perform these therapies in their clinical practice and to establish future directions on the topics. The clinicians must periodically update their knowledge about these three procedures to achieve success.

Influence of shaft length on torsional behavior of endodontic nickel-titanium instruments.

Torsional stresses are one of the most frequent causes of intracanal separation of nickel-titanium endodontic instruments, which represents a great concern of endodontists. For this reason, torsional resistance of rotary instruments has been deeply investigated by determining all parameters that can influenced it, that can be summarized in: (1) Tooth-related factors, (2) Strategy-related factors and (3) Instrument-related factors. This study was conducted to examine the influence of shaft length on torsional resistance of a nickel-titanium rotary instrument and if it should be considered as an Instrument-related factor. With this aim, 120 Twisted Files Adaptive M-L (TFA M-L) NiTi instruments (SybronEndo, Orange, CA, USA) were divided into 6 experimental groups (n = 20), according to instruments length and size: Group 1, 20 TFA M-L1 25/08 23 mm; Group 2, 20 TFA M-L1 25/08 27 mm; Group 3, 20 TFA M-L2 35/06 23 mm; Group 4, 20 TFA M-L2 35/06 27 mm; Group 5, 20 TFA M-L3 50/04 23 mm; and Group 6, 20 TFA M-L3 50/04 27 mm. All instruments were submitted to a static torsional test, blocking each instrument at 3 mm from the tip and rotating it until its fracture. Torque to Fracture (TtF) and fragments length were registered and all data were statistically analyzed. Results showed that Groups 2, 4 and 6 had a higher TtF, respectively, than Groups 1, 3 and 5, which differ from the former just for shaft length. Group 6 showed the highest torsional resistance (1.31 ± 0.08 Ncm), whilst Group 1 the lowest (0.40 ± 0.08 Ncm). According to that, it can be stated that the longer the instrument, the higher the torsional resistance is, proving that shaft length should be considered as an important factor about torsional resistance.

Nickel-Titanium Rotary Instruments: An In Vitro Comparison (Torsional Resistance of Two Heat-treated Reciprocating Files).

AIM AND OBJECTIVE: The present study aims to evaluate the difference in torsional resistance of two reciprocating nickel-titanium (Ni-Ti) rotary files: WaveOne Gold and EdgeOne Fire. MATERIALS AND METHODS: A total of 40 nickel-titanium rotary instruments (n = 40): 20 WaveOne Gold Small (WOGS) and 20 EdgeOne Fire Small (EOFS) were divided into two groups. Each instrument was tested using a torsional resistance device already validated in previous studies to evaluate and compare torsional resistance. The static torsional test was implemented by blocking each instrument at 3 mm from the tip and rotating it until fracture with a reciprocating motion. Torque to fracture (TtF) and fragment length (FL) were measured and statistically analyzed. RESULTS: Statistical analysis of TtF found significant differences between the two groups (p<0.05). The EOFS showed higher TtF if compared to WOGS, with a mean value and a standard deviation of 3.05 ± 0.07 (N cm) against 2.97 ± 0.08 (N cm). Data for FL showed no significant differences (p>0.05) between the two groups. CONCLUSION: According to the results of this study, it is reasonable to assert that EOFS instruments showed a higher torsional resistance if compared to the WOGS. CLINICAL SIGNIFICANCE: As evidenced by this study, EOFS should be considered as a safer solution, in terms of torsional resistance, if compared to WOGS, reducing the risk of intracanal separation due to excessive torsional load.

Incidence of Different Types of Intracanal Fracture of Nickel-Titanium Rotary Instruments: A Systematic Review.

AIM: The aim of this systemic review is to investigate these parameters by analyzing the characteristics of fractured instruments to determine which is the most relevant mechanical stress that induces intracanal separation in vivo. BACKGROUND: The fracture of nickel-titanium (Ni-Ti) instruments is a result of flexural fatigue and torsional fatigue. An electronic search was conducted in MEDLINE database, Web of Science, and Cochrane following preferred reporting items for systematic reviews and meta-analyses guidelines. Data were collected and the key features from the included studies were extracted. Overview quality assessment questionnaire scoring assessed the quality of the articles. A total of 12 articles were selected, where the lowest score was 13. REVIEW RESULTS: Considering Ni-Ti rotary instruments, this overall evaluation comprehends 939 broken instruments with an incidence of fracture of 5%. Out of the 12 selected articles, 10 studies revealed that flexural failure was the predominant mode (range of 62-92%). It appears that motion plays an important role when it comes to mechanisms of fracture. The majority of defects found in hand-operated instruments were in the form of torsional failure. Although the major cause of separation of rotary instruments is flexural fatigue, smaller instruments show more torsional fracture than the larger instruments. The average fragment length was found to be 2.5 mm and 3.35 mm, respectively, for torsional failure and flexural failure. The risk of bias depends on fractographic analysis. CONCLUSION: Flexural fatigue is the predominant mode of fracture in rotary Ni-Ti instruments. The type of motion and size of the instrument seem to affect the mechanism of fracture. Fragment length may show a strong association with the type of fracture mechanism. CLINICAL SIGNIFICANCE: This systemic review found that flexural fatigue is the most relevant mechanical stress that induces intracanal separation in vivo. Moreover, in clinical practice, the fragment length might be an excellent indicator of the type of fracture.

Operative Torque Analysis to Evaluate Cutting Efficiency of Two Nickel-Titanium Rotary Instruments for Glide Path: An In Vitro Comparison.

AIM AND OBJECTIVE: The aim and objective of this study was to evaluate and compare the cutting efficacy of two different nickel titanium rotary instruments by a novel methodology: the operative torque (torque and time needed to progress toward the apex). MATERIALS AND METHODS: Ten fresh extracted upper first premolars with two canals were instrumented with a KaVo (Biberach, Germany) and a KaVo 1:1 handpiece at 300 rpm with maximum torque set at 2 N. One canal was instrumented with ProGlider NiTi rotary instruments (Dentsply Sirona Endodontics, Ballaigues, Switzerland), with tip size of 16.02, and the other one with EgdeGlidePath rotary instrument (EdgeEndo, Albuquerque, New Mexico). Mean instrumentation time, mean torque values, and maximum torque values were evaluated for each instrument. The significance level was set at p <0.05. RESULTS: EdgeGlidePath instruments reached the working length in significantly less time with a significantly smaller amount of torque when compared to ProGlider (p >0.05). No instruments exhibited flute deformation or underwent intracanal failure. CONCLUSIONS: Operative torque is related to the capability to cut dentin and progress toward the apex: the smaller the torque values, the higher the cutting ability (and safety). Operative torque is also dependent on debris removal and irrigation techniques. Nevertheless, both operative torque and instrumentation time are clinically relevant parameters for evaluating instruments' performance (i.e., cutting ability). CLINICAL SIGNIFICANCE: Operative torque during endodontic instrumentation helps understanding the overall performance in terms of both cutting efficiency and safety.

Future Trends in Endodontics: From the Virtual Assessment of the Anatomy to the Computer-driven Approach.

Root canal treatment is one of the most challenging practices in dentistry as the complexity and the variability of the endodontic space can often lead the operator to create false trajectories or missing canals. The technical advances in the development of even more efficient and resistant endodontic instrument reached important results in the last few years with the adoption of NiTi alloys and thermal treatments, which could increase the flexibility and the resistance of the instruments.1,2.

How to Improve Properties of Nickel-Titanium Rotary Instruments.

In the last decades, the use of nickel-titanium (Ni-Ti) rotary instruments has become the most effective and popular method among endodontists for shaping root canals, even if there are still concerns regarding the increased risks of intracanal breakage or weakening of the instruments.1,2 So manufacturers started to modify the cross-sectional geometrical aspects of the files in order to improve their resistance to torsional and cyclic fatigue. Design is a major feature in determining instruments' properties including cutting efficiency, removal of debris, stresses generated during instrumentation, and the relative resistance to these stresses; however, a perfect design is not existing and any change in design is likely to provide some advantages but also some disadvantages.3,4.

Academic Dental Activities and COVID-19 Pandemic.

COVID-19 pandemic has strongly and rapidly affected routine lifestyle and consequently, dental business, practice, and education. During the pandemic period, most Governments worldwide made specific regulations or recommendations to close practices, to avoid non-urgent dental therapies and treat only dental emergencies. Some recent surveys1,2 showed how dentists perceived the COVID-19 risk and how they reacted: by modifying their way of working, by reducing aerosol producing procedures, by improving staff and patient's safety with the increased use of personal protective equipment, environmental disinfection and limited access to dental offices, increasing use of remote consulting and triage.

Potential of Operative Torque in Evaluating NiTi Instruments.

The role of nickel-titanium (NiTi) in the production of endodontic instruments increased in the last few decades; therefore, the way of evaluation of its performance increased as well. Nowadays, there are several ways to evaluate NiTi instruments, divided into static and dynamic tests. The static ones are cyclic fatigue tests, torsional resistance tests, flexibility, and cutting efficiency tests. These methodologies have been deeply used to evaluate some of the metallurgical properties of the instruments on the market. Up-to-date, we know very well the behavior of NiTi under static conditions, but these knowledges are too fragmented to be relevant for understanding and evaluating the complexities of intracanal instrumentation. Starting from the purpose to introduce the variable of movement in the testing procedure, some dynamic tests have been proposed, such as dynamic cyclic fatigue test.1,2 Although these kinds of studies were capable of evaluating more precisely the behavior of rotary instruments inside the root canal, they could not take into account, at this moment, the complexities of stresses that instruments undergo during the shaping procedure.3-5 Therefore, some of these tests are not accepted anymore by the scientific community and on the contrary they do not help the general practitioner to orientate in the large amount of rotary instruments present on the market.6 This tends to withdraw the general dentistry from the scientific literature, wearing a groove between the practice and the science.7 Starting from these ideas, in the last couple of years some authors started to think the proper way to real-time evaluation of the performance of NiTi rotary instruments inside the root canal. To do so, a countable and repeatable measurement of instrument's developed stresses was needed. Setzer and Böhme8 first used the torque generated by Revo-S, Vortex, and ProFile to evaluate their performance during instrumentation. The so-called "operative torque" is the summation of torque generated in each point of the instrument during its simultaneous movement around its own axis and up and down inside the canal. The recorded values are influenced by both torsional and flexural stresses, becoming this way a reliable method to analyze, evaluate, and compare the performance of NiTi instruments inside the root canal.9 This methodology is applicable for not only in vitro but also in vivo measurement, as demonstrated by Gambarini et al.10 The main drawback of this kind of evaluation is the not well-determined correlation between the torsional and the flexural stresses; therefore, it is still unpredictable how each influence the other. In conclusion, the potential of real-time torque measurement is wide and still unexplored, but further studies are needed to better understand how torque is developed inside the root canal.

Centering Ability of a New Nickel-Titanium Rotary Instruments with a Peculiar Flat-side Design: An In Vitro Study.

AIM: The aim of the present study was to investigate the role of the flat design compared with a non-flat designed instrument on the centering ability in a simulated root canal system. MATERIALS AND METHODS: Two file systems were chosen: the F-One (Fanta Dental, Shanghai, China) and a prototype with the same design but without the flat-side design. A total of 50 simulated L-shaped root canals in resin blocks were shaped with a new instrument each. Pre- and postcanal preparation images were captured and superimposed to measure and compare the canal transportation and evaluate the centering ability of each file. The t test was performed and the level of significance was set at p < 0.05. RESULTS: Prototype files removed significantly less resin from the inner and the outer parts of the canal and showed significantly higher mean transportation values. CONCLUSION: It can be concluded that the F-One file system demonstrated better shaping ability compared with the prototype file system in L-shaped resin-simulated canals. CLINICAL RELEVANCE: The present study showed the safety of the flat-side design, minimizing the risk of iatrogenic errors such as ledging, perforation, or zipping of the root canal.

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.

Fatigue Resistance of Two Nickel-Titanium Rotary Instruments before and after Ex Vivo Root Canal Treatment.

AIM: The aim of the present study is twofold: to evaluate cyclic fatigue resistance differences of two different nickel-titanium rotary instruments, brand new and after an ex vivo instrumentation of single root extracted teeth. MATERIALS AND METHODS: Twenty new S One 20.06 were randomly divided into two groups. The first group (n = 10) was immediately subjected to a cyclic fatigue test (S One Group I). The second group (n = 10) (S one Group II) performed a cyclic fatigue test after three ex vivo root canal treatment with a single-file technique. The same process has been carried out for 20 M-Two 20.06 instruments. RESULTS: Mean time to fracture (TtF) for Group I was 51.14 ± 1.28 for S One and 32.62 ± 0.17 for M-Two 20.06 and for Group II was 46.00 ± 0.99 for S One and 27.75 ± 1.58 for M-Two 20.06. The reduction in TtF values from Group I to Group II was 11% for S One and 15% for M-Two. Statistical analysis found significant differences in all the groups examined (p value < 0.05). Mean fragment length (FL) for Group I was 3.07 ± 0.17 for S One and 3.05 ± 0.14 for M-Two 20.06 and for Group II was 3.05 ± 0.07 for S One and 3.05 ± 0.14 for M-Two 20.06. Statistical analysis was pursued, and no significant difference was found (p value > 0.05). CONCLUSION: The S-One showed significantly more resistance to cyclic fatigue stress than M-Two for both new and used instruments. This validates the hypothesis that the AF H wire enables the S One files to endure more the cyclic fatigue stresses. CLINICAL SIGNIFICANCE: This study demonstrates the cyclic fatigue resistance of a new endodontic instrument after repetitive usage.

Nonsurgical Retreatment Using Regenerative Endodontic Protocols: A Case Report.

AIM AND OBJECTIVE: The aim of this case report was to describe regenerative endodontic procedures (REPs) of the previously treated mature teeth with long-term results. BACKGROUND: Regenerative endodontic procedures are aimed to treat apical periodontitis and regenerate the pulp-dentin complex in necrotic teeth. However, there is no consensus in using REPs in the previously treated mature teeth. The aim of this case report was to describe REPs of the previously treated mature teeth with long-term results. CASE DESCRIPTION: A 25-year-old woman presented pain on chewing on 15 and swelling (WHO numbering system). The tooth had been endodontically treated and restored 4 years ago. After removing the old root canal filing, the roots were irrigated with 2.5% sodium hypochlorite and 17% EDTA using sonic activation. Calcium hydroxide (CH) was used as medicament for 3 weeks. At the second visit, CH was removed, and canals were irrigated as like as the first visit. Apical bleeding was induced, and concentrated growth factors (CGFs) were placed inside the root canal. The tooth has been followed up to 3 years. CONCLUSION: The tooth was functional and asymptomatic at the recall visits. Since the first-year follow-up, the tooth responded to the electric pulp test and the thermal test. Radiological examinations revealed healing of apical lesion and hard tissue deposition. CLINICAL SIGNIFICANCE: Regenerative endodontic procedures can offer an advantage over traditional endodontic procedures in terms of tertiary healing, with a predictable, user-friendly procedure also for retreatment cases.

Fine Aerosols and Perceived Risk of COVID-19 among Italian Dental Practitioners: An Experimental Survey.

AIM: The aim of the present study was to take a survey on Italian practitioners concerning the perceived risks of aerosol contamination in COVID-19 times and their attitude toward modifications of treatment protocols to reduce this risk. MATERIALS AND METHODS: Power analysis calculated a minimum sample size of 150 participants at 99% confidence level with a 5% margin of error. To homogenize responses elicited by different preventive measures by various national governments, only Italian dentists were included in the survey: overall 500 responses were collected. RESULTS: Of the 500 analyzed respondents, there were 266 females and 234 males; 379 practitioners were allocated in the more experienced groups, and the remaining 121 in the less experienced group based on less or more than 5 years of practice. The 70% of the dentists consider the dental practice more dangerous for the diffusion of COVID-19 than other social activities. The 5% consider dental practice more dangerous only for the patients. Aerosol contamination was perceived as a risk from the most dentist (70%), but there was agreement on the most dangerous way of cross infection in dental settings. Most of the dentists (55%) believed implementations in their protocols were needed to reduce the risk of COVID-19 infections. No significant differences were found within the groups: both women and men, as well as practitioners with different experience levels (younger or older than 35 years) perceived very similarly the problems related to COVID-19 in dentistry (p > 0.05). CONCLUSION: The survey demonstrated that COVID-19 had a great impact on dental practitioners; it increased not only fear of aerosol contamination during dental treatments but also influenced the fear of close contacts. SIGNIFICANCE: Airborne and waterborne infections are related with dental treatments and considered the preferred ways of diffusion for COVID-19. The risk of aerosol-related infections could interfere with the clinical practice of the dentist, during the COVID-19 pandemic; the limitations that provided changes to everyday behavior could affect the perception of the safety of the operators, staff, and patient and this could also affect economically the dental office.

Management of a Complex Case during COVID-19 Time Using One-day Digital Dentistry: A Case Report.

AIM AND OBJECTIVE: The aim of the present case report is to describe the digital management of an implant prosthetic rehabilitation performed by the use of different digital technologies, which allowed to successfully perform in 1 day both the surgical and the prosthetical stages with a minimally invasive approach and a high standard of care. BACKGROUND: Coronavirus disease-2019 (COVID-19) pandemic is affecting dental everyday practice. Clinicians have to reduce the number of patients per day and the time they spend in the dental office. Minimally invasive and digital approaches, with less possible exposure and interaction, are suggested to reduce the risk of infection. CASE DESCRIPTION: The failure of a short-span implant prosthetic rehabilitation combined with pain and mobility of the involved teeth was the main complaint reported by a 78-year-old male patient, who asked an urgent appointment to solve the problem. An intraoral scanner allowed the clinician to immediately take a preliminary digital impression of the arch to be treated. The resulting 3D files were sent by e-mail to the dental technician who provided a digital wax-up for the computerized workflow. Computer-aided implantology (CAI) performed using an in-office cone-beam computed tomography (CBCT) allowed clinician to guide the surgical approach in a prosthetic manner. Such an integration inside a well-defined workflow was the key for a successful and rapid treatment. CONCLUSION: By using new innovative digital technology, the treatment was completed in 1 day, reducing the risk of COVID-19 by limiting the number of appointments and reducing contacts in confined environments like the dental office and public transportations. It also helped to reduce materials production and people movement in the treatment of dental emergency. CLINICAL SIGNIFICANCE: The possibility of performing an effective treatment saving time by using efficient technology and a minimally invasive procedure highlights the importance of digital planning in order to optimize every single step of the treatment. Digital workflow reduces also the movement of potentially infected materials from the office to the dental laboratory.

Nonsurgical Management and 2-year Follow-up by means of Cone Beam Computed Tomography of an Invasive Cervical Resorption in a Molar.

BACKGROUND: Invasive cervical resorption (ICR) is a relatively uncommon form of external tooth resorption, characterized by an invasive nature. It is usually painless and detection of lesions is often made incidentally. Three-dimensional imaging techniques, such as cone beam computed tomography (CBCT), are useful in the diagnosis and management of ICR as the true extent of the defect cannot always be estimated using conventional radiographs. AIM: The aim of this article is to report on the successful treatment of ICR in mandibular first molar by nonsurgical approach and follow-up by means of CBCT. CASE REPORT: An 18-year-old patient was referred with a complaint of unusual radiolucency in the mesial cervical area of tooth #19 with unknown etiology. Cone beam computed tomography was performed to assess the extent of the lesion in three spatial levels and diagnosis of Heithersay class III ICR was made. This case presented with ICR (Heithersay class III) on tooth #19. Nonsurgical root canal treatment and removal of the lesion from the coronal access was performed; the resorptive defect was filled with dual-cure, self-adhesive, resin-modified glass ionomer cement (RMGIC); 6-month follow-up X-ray film showed no changes at the lesion site and tooth was asymptomatic; 1-year follow-up X-ray film showed slight mesial bone loss and a probing depth of 3 mm; finally, 2-year follow-up CBCT images showed no recurrence and no further bone destruction at the lesion site. CONCLUSION: The intraoral radiographs revealed the resorptive changes in two dimensions; therefore, the actual extent and location of the lesions are not fully understood. On the contrary, CBCT is a very useful tool to achieve a proper diagnosis; it detects the extent of the defect more accurately and hence, improves the treatment outcomes of ICR. CLINICAL SIGNIFICANCE: The ICR is usually seen as a late complication to traumatic injuries of the teeth; it is essential, therefore, that the patients who were exposed to situations that can damage the integrity of periodontal tissue need to have careful periodic recalls and X-ray examinations.

Cutting efficiency of nickel-titanium rotary and reciprocating instruments after prolonged use.

The aim of the present study was to compare the cutting efficiency of Twisted File instruments used in continuous rotation or TF Adaptive motion and evaluate if prolonged use significantly affected their cutting ability. 20 new NiTi instruments were used in the present study (TF tip size 35, 0.06 taper; Sybron-Endo, Orange, CA, USA), divided into 2 subgroups of 10 instruments each, depending on which movement was selected on the endodontic motor. Group 1: TF instruments were activated using the program TF continuous rotation at 500 rpm and torque set at 2 N; Group 2: TF instruments were activated using the reciprocating TF Adaptive motion. Cutting efficiency was tested in a device developed to test the cutting ability of endodontic instruments. Each instrument cut 10 plastic blocks (10 uses) and the length of the surface cut in a plastic block after 1 min was measured in a computerized program with a precision of 0.1 mm. Maximum penetration depth was calculated after 1 use and after 10 uses, and mean and standard deviation (SD) of each group was calculated. Data were statistically analyzed with a one-way ANOVA test (P < 0.05). TF instruments used in continuous rotation (Group 1) cut a mean depth of 10.4 mm (SD = 0.6 mm) after the first use and 10.1 mm (SD 1.1 mm) after 10 uses, while TF instruments used with the Adaptive motion cut a mean depth of 9.9 mm (SD = 0.7 mm) after the first use and 9.6 mm (SD = 0.9 mm) after 10 uses. There was no statistically significant difference between the two groups investigated (P > 0.05) nor between instruments after 1 or 10 uses. In conclusion, the TFA motion showed a lateral cutting ability similar to continuous rotation and all tested instruments exhibited the same cutting ability after prolonged use.

Cyclic fatigue of instruments for endodontic glide path.

Endodontic glide path is the creation of a smooth patency from canal orifice to apex, which can be performed manually or with small tapered NiTi rotary instruments. The use of stainless steel (SS) hand K-files inserted in a reciprocating handpiece can be a possible alternative to create a mechanical glide path. The aim of this study was to compare the cyclic fatigue resistance between SS K-files used in a reciprocating motion and NiTi rotary instruments in artificial curved canals. Ten SS size 15 K-files used with the M4 handpiece (SybronEndo, Glendora, CA, USA) and ten PathFiles (Maillefer-Dentsply, Ballaigues, CH, Switzerland) NiTi rotary instruments size 16, 0.02 taper were tested for resistance to cyclic fatigue. The time to fracture inside an artificial curved canal was recorded for each instrument. Data were analyzed by one-way ANOVA and Tukey HSD test. Mean time (and SD) to failure was 464 s (±40.4) for the Group PF (NiTi rotary PathFile), and 1049 s (±24.8) for the Group M4 (SS K-files reciprocating) with a statistically significant difference between the two groups (p = 0.033). The SS 15 K-files used with the M4 handpiece showed a significant greater resistance to cyclic fatigue when compared to the NiTi rotary PathFiles. Therefore, the use of small size SS files in a reciprocating motion might be a rational choice for the creation of a mechanical endodontic glide path in curved root canals.