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Introduction: This study aimed to evaluate the effects from the memory-triple (MT) heat treatment on the fatigue resistance of the Reciproc by comparison with the file systems of same geometry., Methods: Reciproc files subjected to MT heat treatment technology were designated as Group RMT and were compared with the original Reciproc (Group REC) and Reciproc Blue (Group REB). Each NiTi file from 3 groups (n = 15) was operated reciprocally with a repetitive up-and-down movement in the curved canal with 4 mm of pecking distance inside of the simulated canal at body temperature. When each file fractured, the time until fracture was recorded. The length of the fractured fragment was measured. Fractured fragments were observed under scanning electron microscope (SEM) to evaluate the topographic features of the surface. Differential scanning calorimetry (DSC) analysis was performed to estimate phase transformation temperatures. One-way analysis of variance and Duncan post hoc comparison were applied to compare among the groups at a significance level of 95%., Results: RMT showed significantly higher fracture resistance (P < .05), whereas there was no difference in fatigue resistance between REC and REB. SEM examination showed the files from the 3 groups had similar topographic features. RMT showed a peak of austenite peak (Ap) at a temperature (52°C) higher than body temperature, whereas REC and REB showed Ap at 37 and 32°C, respectively., Conclusions: Under the condition of this study, the new heat treatment technique of MT technology could enhance the fatigue fracture resistance of the reciprocating files made of M-wire and Blue-wire., (Copyright © 2024 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to compare the physicochemical properties and biocompatibility of various calcium silicate-based bioceramic sealers (CSBSs)., Methods: Four recently developed CSBSs, including AH Plus Bioceramic Sealer (AHB), EndoSequence BC Sealer (ESB), TotalFill BC Sealer (TTB), and Bio-C Sealer (BIC), were compared with the epoxy resin-based sealer AH Plus (AHP). Their physical properties, including flow, setting time, radiopacity, dimensional stability, and pH, were evaluated according to the International Organization for Standardization (ISO) 6876. Their cytotoxicity in human periodontal ligament fibroblast (hPDLF) was assessed through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and compared. Additionally, cell attachment to the sealer surface was analyzed using green fluorescent protein and confocal laser scanning microscopy to evaluate cell viability. Data were analyzed using a one-way analysis of variance to determine the difference between groups for categorical variables, followed by Tukey's post hoc test at the significance level of 95%., Results: The flow, setting time, and radiopacity of all tested CSBSs satisfied the ISO 6876/2012 standards. Further, these CSBSs showed shrinkage after immersion in distilled water for 30 days and complied with the ISO 6876/2001 requirements. The pH values of AHB, ESB, TTB, and BIC were greater than 11, whereas AHP had a pH of 6.69 after 4 weeks. CSBS showed excellent biocompatibility compared with that of AHP (P < .05). Confocal laser scanning microscopy showed that alive hPDLFs were attached well to all the tested CSBSs but not to AHP., Conclusions: CSBSs have similar physical characteristics within the ISO standards and higher biocompatibility than epoxy resin-based sealers., (Copyright © 2023 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to investigate the influence of mass and the polar moment of inertia on the torsional behavior of nickel-titanium rotary instruments to understand which parameter of cross-sectional design had a key role in terms of torsional resistance., Methods: Four different instrument models were designed and meshed using computer-aided engineering software (SolidWorks; Dassault Systems, Waltham, MA). Instrument models shared the same characteristics, except for cross-sectional design; triangle, rectangle, square, and hollow square geometry was selected. Finite element analysis was performed simulating a static torsional test using the FEEPlus internal solver (Solid Works). Von Mises stress and torsional load at fracture were calculated by the software. Linear regression analysis was performed to investigate the relationship of the polar moment of inertia, cross-sectional area, inner core radius, and mass per volume on the torsional resistance of nickel-titanium rotary instruments., Results: The polar moment of inertia positively affected the maximum torsional load with the highest level of correlation (R 2 = 0.917). It could be stated that the higher the polar moment of inertia is, the more maximum torsional load at fracture is present. Mass and cross-sectional area had a lower level of correlation compared with the polar moment of inertia (R 2 = 0.5533). According to this, 2 instruments with the same mass/mm and/or cross-sectional area could have different torsional resistance., Conclusions: The polar moment of inertia can be considered as the most important cross-sectional factor in determining the torsional resistance of rotary instruments over metal mass and cross-sectional area., (Copyright © 2021 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Previously published studies have deeply investigated the characteristics of flexural and torsional resistance of nickel-titanium rotary instruments, but none of them investigated the relationship between the 2 stresses. The objective of the present study was to evaluate the influence of flexural stresses over torsional resistance., Methods: Sixty S-One 20.04 files (Fanta Dental, Shanghai, China) were used in the present study (N = 60) and divided into 3 test groups of 20 files. A customized device made of a mobile structure with a connection that holds the handpiece and the artificial canal was used for the experiment to make the measurements repeatable. The artificial canals were created with a 90° curvature, a 60° curvature, and lastly a straight canal. Each file was rotated at 300 rpm with a maximum torque value of 5.5 Ncm with the apical 2 mm firmly secured in a vise. The torque at fracture and the time to fracture were recorded by the software integrated in the handpiece and evaluated through statistical analysis., Results: Statistical analysis found significant differences in the values of torque to fracture (TtF) between these 3 groups (P < .05). The 90° curved canal group showed the highest TtF value, and the 60° curved canal group showed a higher TtF value than the straight canal group., Conclusions: The results of the present study demonstrated a positive influence of flexural stresses over torque at fracture of rotary files. When nickel-titanium instruments were used in a 90° or 60° curvature, the values of torque at fracture increased compared with the same instruments that rotated in the straight canal., (Copyright © 2020 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to determine and compare the difference in the volume of dentin and enamel removed (DER) to prepare 3 different access cavities and to propose a standardization of the access cavities according to their volume of DER., Methods: One hundred twenty maxillary and mandibular molars and premolars were assigned to 3 subgroups for each tooth type (n = 10): the traditional endodontic cavity (TEC) group; the conservative endodontic cavity (CEC) group with partial unroofing and convergent walls; and the ultraconservative endodontic cavity (UEC) group, preserving most part of the pulp chamber roof and the occlusal surface. The sliced image data of cone-beam computed tomographic images before and after access cavity preparation were exported as Digital Imaging and Communications in Medicine files and imported into the MeVisLab framework system (MeVis Research, Bremen, Germany). After segmentation, the volumes of coronal dentin and enamel were measured, and the difference in the percentage of volume of DER for endodontic access cavity preparation was calculated. The data were subjected to statistical analyses (analysis of variance) with a level of significance set at P < .05., Results: The percentage of volume of DER was less than 6% for the UEC group, up to 15% for the CEC group, and more than 15% for the TEC group, with a statistically significant difference among all groups in all of the tooth types analyzed (P < .05)., Conclusions: The present study showed significantly different percentages of volume of DER among the groups analyzed (ie, UEC < CEC < TEC). A standardization of access cavity preparation was proposed according to the percentage of volume of DER., (Copyright © 2020 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: Ultraconservative access cavities (UCACs) have been proposed to reduce crown weakening, but there is no consensus about their design and size and about their advantages and disadvantages, which are also related to how differently they are performed. The purpose of the present study was to evaluate the possible use of a novel Dynamic Navigation System (DNS) in planning and executing UCACs and its precision in vitro, compared with a manual approach (MA) without any guide., Methods: Twenty radiopaque, artificial teeth replicas were randomly divided into 2 identical groups and scanned using cone-beam computed tomography. In the first group (MA) MB1 canal orifice was reached, starting from the central part of the molar occlusal surface, using a micro endodontic bur. In the second group, DNS allowed to plan and execute a more direct, straight-line truss access. After cavity preparation, teeth were scanned again, and cone-beam computed tomography images were compared. Data were statistically analyzed with analysis of variance test., Results: Significant differences (P < .05) were found in the tested parameters between the 2 groups. The DNS group was significantly more precise, showing smaller mean values in the angulation (4.8°) and in the maximum distance from the ideal position (0.34 mm), when compared with MA group (mean values, 21.2° and 0.88 mm, respectively)., Conclusions: Hence, we may conclude that the use of DNS increased the benefits of UCACs by minimizing the potential risk of iatrogenic weakening of critical portions of the crown and reducing negative influences to shaping procedures., (Copyright © 2020 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Dynamic navigation systems were introduced to facilitate dental implantology by improving the accuracy of dental implant positioning. Dynamic navigation integrates surgical instrumentation and radiologic images by using an optical positioning device controlled by a dedicated computerized interface. These features could help in reducing the risk of unintentional iatrogenic damage to nearby anatomic structures and perform minimally invasive or flapless surgery, leading to reduced patient postoperative discomfort and improved healing. The present case report showed the use of the Navident dynamic navigation system (ClaroNav, Toronto, Ontario, Canada) by an undergraduate student for bone cavity preparation and root-end resection in the surgical endodontic treatment of a lesion in an upper lateral incisor. The system allowed precise localization of the root and precise apicoectomy with a minimal invasive cavity. The dynamic navigation system allowed the student to precisely direct the bur in 3 dimensions. The osteotomy and root-end resection were easily and quickly performed by the undergraduate student with a minimally invasive approach without iatrogenic errors. The navigation system allowed the operator to precisely perform a minimally invasive osteoctomy and root-end resection during endodontic surgery. The development of dedicated surgical navigation systems for endodontic surgery could facilitate the operator's maneuvers and reduce the risk of iatrogenic errors., (Copyright © 2019 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aims of this in vivo cone-beam computed tomographic (CBCT) study were to evaluate the prevalence, characteristics, and correlations between the fused rooted maxillary first and second molars as well as their consequent merged and C-shaped canals in a Saudi Arabian population., Methods: CBCT imaging of 726 maxillary first and second molars from 208 subjects of Saudi origin were evaluated in the present study. The prevalence of fused rooted maxillary molars, merged canals, C-shaped configurations, and correlations between the presence of fused rooted teeth between first and second molars were examined as the primary outcome. Differences by sex, location in the jaw, and bilateral symmetry (similarity between right- and left-side teeth in the same patient) were evaluated as the secondary outcome. The Z test was used for differences in the independent proportions, the chi-square test was used for differences between sex and locations, and the Cohen kappa test was used for bilateral symmetry. The kappa test was also used for intrarater reliability. A value of P < .05 was considered significant., Results: The prevalence of fused rooted maxillary first and second molars was 7% and 21%, respectively. Within fused rooted teeth, the presence of merged canals was 8.3% and 32.1%, whereas the prevalence of C-shaped canals was 8.3% and 5.1% in first and second maxillary molars, respectively. Among 57 subjects who had fused rooted maxillary molars, 19.3% showed a correlation between first and second molars. In fused rooted maxillary molars, 3.8% first molars and 13% second molars were bilaterally symmetrical. There were no statistically significant differences between sexes and right- and left-sided fused rooted maxillary molars, merged canals, or C-shaped canals., Conclusions: Maxillary second molars presented more complex external and internal morphology compared with maxillary first molars, with an overall prevalence of 14% of fused rooted maxillary molars and 3.7% merged and 0.8% C-shaped canal configurations for all maxillary molars. The clinician should be aware of such challenges, and for a better treatment outcome, the use of CBCT imaging (small field of view) and an operative dental microscope can be considered when a preoperative periapical radiograph shows signs of fused rooted maxillary molars., (Copyright © 2019 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of the present study was to investigate the impact of ambient temperature on the life span of nickel-titanium (NiTi) files., Methods: Cyclic fatigue testing of NiTi instruments was performed in a stainless steel artificial canal. During the experiment, 4 different temperatures (0°C, 20°C, 35°C, and 39°C) were used in a thermostatic bath controlled using electronic and infrared controls. Eighty R25 Reciproc Blue (VDW, Munich, Germany) and 80 R25 Reciproc (VDW) instruments were reciprocated in the artificial canal until fracture occurred, and the time to fracture and the length of the fractured fragment were recorded. The phase transformation temperature for 3 instruments of each type was analyzed by differential scanning calorimetry. One-way analysis of variance and Bonferroni tests were used to statistically analyze the data at a 5% significance level (P < .05)., Results: Reciproc Blue instruments were significantly more resistant to cyclic fatigue than Reciproc at all the temperatures tested (P < .05). Fatigue resistance was proportionally higher as the environmental temperature decreased (0°C > 20°C > 35°C > 39°C). No significant difference was registered for the length of the fractured fragment of both instruments tested at all temperatures tested (P > .05)., Conclusions: Blue alloy significantly increases the cyclic fatigue resistance of Reciproc files compared with M-Wire alloy. Temperature significantly affects the life span of NiTi files. When the ambient temperature increases between 0°C and 35°C, the fatigue resistance of the files statistically decreases., (Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: This study investigates the accuracy of 3D Endo software (Dentsply Sirona, Salzburg, Austria) to determine the working length when using preoperative cone-beam computed tomographic (CBCT) scans of extracted teeth, compared with conventional CBCT software and an electronic apex locator (EAL)., Methods: CBCT scans of 30 premolars were obtained. Using OnDemand3D software (Cybermed, Seoul, Korea), the measurement obtained from the coronal reference to the apical foramen (AF) was recorded as the conventional CBCT length. Then, using 3D Endo software (Dentsply Sirona), the suggested length (3D-SL) and the operator-adjusted length (3D-OL) were obtained. Teeth were accessed, and the actual length was measured. Finally, the teeth were embedded in alginate to obtain the electronic length (EL) using the EAL Root ZX (J Morita, Tokyo, Japan). The means of the absolute values and the percentages of distribution of the tested measurement methods were compared to the actual length., Results: No difference was found regarding the mean measurements (analysis of variance, P > .05). All the CBCT measurements presented a high reliability (Dahlberg's formula). The measurements within a ±0.5-mm range from the AF were 86.6% for the 3D-SL, 80% for the 3D-OL and EL, and 73.3% for the CBCT length. The EL presented significantly fewer underestimated measurements (P < .05). The 3D-OL and 3D-SL presented significantly fewer measurements beyond the AF (P < .05)., Conclusions: The preoperative working length determination using 3D Endo was reliable and similar to conventional CBCT software. However, the combined use of CBCT with an EAL is required to increase the accuracy in the location of the AF., (Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: This review analyzes the increasing role of magnetic resonance imaging (MRI) in dentistry and its relevance in endodontics. Limits and new strategies to develop MRI protocols for endodontic purposes are reported and discussed., Methods: Eligible studies were identified by searching the PubMed databases. Only original articles on dental structures, anatomy, and endodontics investigated by in vitro and in vivo MRI were included in this review. Original articles on MRI in dentistry not concerning anatomy and endodontics were excluded., Results: All the consulted studies showed well-defined images of pathological conditions such as caries and microcracks. The enhanced contrast of pulp provided a high-quality reproduction of the tooth shape and root canal in vitro and in vivo. Assessment of periapical lesions is possible even without the use of contrast medium., Conclusions: MRI is a nonionizing technique characterized by high tissue contrast and high image resolution of soft tissues; it could be considered a valid and safe diagnostic investigation in endodontics because of its potential to identify pulp tissues, define root canal shape, and locate periapical lesions., (Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The purpose of this study was to evaluate in vitro the efficacy of both the electronic apex locator (EAL) and auto apical reverse (AAR) functions of the endodontic motor MM Control (Micro-Mega, Besançon Cedex, France) compared with Root ZX II (J Morita, Tokyo, Japan)., Methods: After cervical preflaring, the actual lengths (ALs) of 36 single-rooted teeth were obtained up to the apical foramen. The EAL measurements at the marks "APEX" and "0.5" of both devices were obtained using an alginate model. The teeth were divided randomly into 2 groups (n = 18), and root canal preparation was performed with rotary instruments using the AAR function (0.5 mark) of each motor. The length provided by the AAR was compared with the visual length after preparation (AL2). The differences between the electronic lengths and the respective visual measurements were assigned as negative for lower or positive when higher. The means of the absolute values and the percentages of distribution of the electronic measurements between devices were compared., Results: There was no difference between the devices in terms of the means of the EAL measurements or AAR length (analysis of variance, P > .05). However, the EAL function of MM Control presented a greater percentage of measurements >1.01 mm longer than AL (chi-square, P < .01). The AAR function provided an acceptable apical limit in 83.3% of the cases for Root ZX and 77.8% of the cases for MM Control., Conclusions: The AAR function of both MM Control and Root ZX II provided an adequate apical limit of preparation in vitro. However, the use of only the EAL function of MM Control resulted in significantly more cases of overextended readings., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The literature reveals controversies regarding the formation of para-chloroaniline (PCA) when chlorhexidine (CHX) is mixed with sodium hypochlorite (NaOCl). This study aimed to investigate the stability of PCA in the presence of NaOCl and to examine the in vitro cytotoxic effects of CHX/NaOCl reaction mixtures., Methods: Different volumes of NaOCl were added to CHX (mix 1) or PCA (mix 2). Upon centrifugation, the supernatant and precipitate fractions collected from samples were analyzed using high-performance liquid chromatography. The cytotoxic effects of both fractions were examined on human periodontal ligament and 3T3 fibroblast cell lines., Results: High-performance liquid chromatographic analysis showed no PCA signal when NaOCl was mixed with CHX (mix 1). In mix 2, the intensity of PCA was decreased when NaOCl was added to PCA, and chromatographic signals, similar to that of CHX/NaOCl, were also observed. The mortality of precipitates exerted on both cell lines was lower compared with that of supernatants., Conclusions: The discrepancy in the data from the literature could be caused by the instability of the PCA in the presence of NaOCl. The CHX/NaOCl reaction mixture exhibits a wide range of cytotoxic effects., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of the present study was to analyze how a low environmental temperature can affect the fatigue life of instruments made by different types of heat-treated nickel-titanium alloys., Methods: The flexural cyclic fatigue of 40 new specimens for each of the following systems was tested for cyclic fatigue resistance: ProTaper Universal F2 (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper Gold F2 (Dentsply Tulsa Dental Specialties, Tulsa, OK), Twisted Files SM2 (SybronEndo, Orange, CA), Mtwo #25.06 (VDW, Munich, Germany), and Vortex Blue #30.04 and #40.06 (Dentsply Tulsa Dental Specialties). Instruments were tested at 2 different environmental temperatures: 20°C (±2°C) for room temperature (RT) group and -20°C (±2°C) for the cooled environment (CE) group (n = 20). The number of cycles to failure (NCF) and the length of the fractured fragment (FL) were recorded. The means and standard deviations of NCF and FL were then calculated; NCF data were statistically analyzed using a paired t test between groups RT and CE for each instrument tested (P < .05), whereas FL data were analyzed using analysis of variance (P < .05)., Results: The mean NCF values measured were significantly higher for the CE groups than the RT groups in all the systems tested (P < .05). The increase in cyclic fatigue resistance varied from 274%-854%. No differences in FL were registered among the different groups (P < .05)., Conclusions: A low environmental temperature determines a drastic increase in the flexural fatigue resistance of NiTi endodontic instruments manufactured with traditional alloy and different heat treatments., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The purpose of this study was to compare in vitro the fracture strength of root-filled and restored teeth with traditional endodontic cavity (TEC), conservative endodontic cavity (CEC), or ultraconservative "ninja" endodontic cavity (NEC) access., Methods: Extracted human intact maxillary and mandibular premolars and molars were selected and assigned to control (intact teeth), TEC, CEC, or NEC groups (n = 10/group/type). Teeth in the TEC group were prepared following the principles of traditional endodontic cavities. Minimal CECs and NECs were plotted on cone-beam computed tomographic images. Then, teeth were endodontically treated and restored. The 160 specimens were then loaded to fracture in a mechanical material testing machine (LR30 K; Lloyd Instruments Ltd, Fareham, UK). The maximum load at fracture and fracture pattern (restorable or unrestorable) were recorded. Fracture loads were compared statistically, and the data were examined with analysis of variance and the Student-Newman-Keuls test for multiple comparisons., Results: The mean load at fracture for TEC was significantly lower than the one for the CEC, NEC, and control groups for all types of teeth (P < .05), whereas no difference was observed among CEC, NEC, and intact teeth (P > .05). Unrestorable fractures were significantly more frequent in the TEC, CEC, and NEC groups than in the control group in each tooth type (P < .05)., Conclusions: Teeth with TEC access showed lower fracture strength than the ones prepared with CEC or NEC. Ultraconservative "ninja" endodontic cavity access did not increase the fracture strength of teeth compared with the ones prepared with CEC. Intact teeth showed more restorable fractures than all the prepared ones., (Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to evaluate the cyclic fatigue resistance of ProTaper Universal (PTU; Dentsply Maillefer, Baillagues, Switzerland) and ProTaper Gold (PTG, Dentsply Maillefer) nickel-titanium rotary files at room and intracanal temperatures., Methods: A total of 120 files were used to test the cyclic fatigue resistance of PTU (S1 and F2) and PTG (S1 and F2) in an artificial canal at room temperature (20°C) and at intracanal temperature (35°C). The number of cycles to failure and the fracture length of the fragment were recorded, and data were subjected to statistical analysis., Results: PTG registered no differences in fatigue life between the 2 temperatures tested (P > .05), whereas PTU showed a statistically significant reduction in fatigue life at intracanal temperature compared with room temperature (P < .05). PTG instruments exhibited a statistically higher resistance to cyclic fatigue than PTU instruments both at room and intracanal temperatures (P < .05). There were no statistically significant differences among the fracture length of separated instruments (P > .05)., Conclusions: Intracanal temperature influenced the cyclic fatigue resistance of instruments produced with traditional nickel-titanium, whereas it did not influence the fatigue life of instruments produced with gold heat treatment. Gold heating treatment enhances the resistance to cyclic fatigue of ProTaper instruments., (Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to compare the accuracy of 2 electronic apex locators (EALs), Apex ID (SybronEndo, Glendora, CA) and Root ZX (J. Morita, Tokyo, Japan), by means of micro-computed tomographic (micro-CT) imaging and to determine anatomic variations that may affect their accuracy., Methods: The root canal length (RCL) and working length (WL) of 33 single-rooted premolars were measured using a visual method, 3-dimensional micro-CT reconstructions, and 2 different EALs. Two different measurements were recorded for each EAL: at the "APEX/0.0" mark and at the "0.5" mark. The WL was determined using 2 different methods: method 1: at the "0.5 mark" of the apex locator and method 2: subtracting 0.5 mm from the "APEX/0.0" mark. The precision of measurements was compared with those recorded by micro-CT imaging. Apical foramen (AF) position and diameter, apical constriction (AC) diameter, distance between the AC and the AF, and the presence/absence of accessory canals were recorded from the micro-CT scans, and their correlation to the accuracy of EALs was determined., Results: There was no statistically significant difference in the RCL measurements by any of the different methods. There was a statistically significant difference in the WL recorded by micro-CT imaging compared with those by the visual method and at the "APEX/0.0 mark" - 0.5 mm (P = .031). There was no difference in the measurements acquired by any of the EALs. The "APEX/0.0 mark" - 0.5 mm was less accurate than the "0.5" mark. However, the results were not statistically significant (P > .05). The position of the AF and the AC-AF distance affected the accuracy of the RCL (P = .003) and the "0.5" mark (P = .013)., Conclusions: Root ZX and Apex ID are equally precise in determining the RCL and WL. The "0.5" mark can be used to determine the WL with high precision. Some anatomic variations may influence the accuracy of EALs., (Published by Elsevier Inc.)

The goal of this study was to develop an optimized drug delivery carrier for oral mucosa applications able to release in situ bioactive molecules by using biopolymeric materials. Among them chitosan and poly(lactic-co-glycolic acid) (PLGA) have gained considerable attention as biocompatible carriers able to improve the delivery of active agents. The formulation of such vehicles in the form of nanoparticles (NPs) could permit to exploit the peculiar properties of nanomaterials in order to enhance the efficacy of active agents. Chitosan (CS) and PLGA chlorexidine dihydrochloride (CHX)-loaded NPs were synthesized by ionotropic gelation and osmosis based methodology respectively. In order to facilitate NPs adhesion on human dental surfaces, two different strategies were employed: PLGA particles with an external shell of CS to produce a positive surface charge allowing CHX loaded PLGA NPs to interact with the negative charged dental surfaces, while CS particles were functionalized with peptidomimetic derivative glutathione (GSH). The morphology was investigated by scanning electron microscopy. A sustained release profile of CHX from CS NPs was achieved. CS-based NPs adhered on human tooth surfaces in a simulated brushing and rinsing process and their in vitro toxicity evaluation on Human Gingival Fibroblasts (HGFs) was between 20 and 60% in all experimental conditions. Thanks to their adhesion properties and low cytotoxicity, the synthesized CS-based formulations may be efficiently exploited for therapy purposes or to enhance in vivo dental care (i.e. preparation of toothpastes or other cosmetics for daily oral care)., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Introduction: The purpose of this study was to evaluate the cyclic fatigue resistance of 3 different nickel-titanium reciprocating instruments., Methods: A total of 45 nickel-titanium instruments were tested and divided into 3 experimental groups (n = 15): group 1, WaveOne Primary instruments; group 2, Reciproc R25 instruments; and group 3, Twisted File (TF) Adaptive M-L1 instruments. The instruments were then subjected to cyclic fatigue test on a static model consisting of a metal block with a simulated canal with 60° angle of curvature and a 5-mm radius of curvature. WaveOne Primary, Reciproc R25, and TF Adaptive instruments were activated by using their proprietary movements, WaveOne ALL, Reciproc ALL, and TF Adaptive, respectively. All instruments were activated until fracture occurred, and the time to fracture was recorded visually for each file with a 1/100-second chronometer. Mean number of cycles to failure and standard deviations were calculated for each group, and data were statistically analyzed (P < .05). Instruments were also observed through scanning electron microscopy to evaluate type of fracture., Results: Cyclic fatigue resistance of Reciproc R25 and TF Adaptive M-L1 was significantly higher than that of WaveOne Primary (P = .009 and P = .002, respectively). The results showed no statistically significant difference between TF Adaptive M-L1 and Reciproc R25 (P = .686). Analysis of the fractured portion under scanning electron microscopy indicated that all instruments showed morphologic characteristics of ductile fracture that were due to accumulation of metal fatigue., Conclusions: No statistically significant differences were found between the instruments tested except for WaveOne Primary, which showed the lowest resistance to cyclic fatigue., (Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The purpose of this study was to present a new periapical and endodontic status scale (PESS) that is based on the complex periapical index (COPI), which was designed for the identification and classification of periapical bone lesions in cases of apical periodontitis, and the endodontically treated tooth index, which was designed for endodontic treatment quality evaluation by means of cone-beam computed tomographic (CBCT) analysis., Methods: Periapical and endodontic status parameters were selected from the already known indexes and scientific literature for radiologic evaluation. Radiographic images (CBCT imaging, digital orthopantomography [DOR], and digital periapical radiography) from 55 patients were analyzed. All parameters were evaluated on CBCT, DOR, and digital periapical radiographic images by 2 external observers. The statistical analysis was performed with software SPSS version 19.0 (SPSS Inc, Chicago, IL). Chi-square tests were used to compare frequencies of qualitative variables. The level of significance was set at P ≤ .05., Results: Overall intraobserver and interobserver agreements were very good and good, respectively. CBCT analysis found more lesions and lesions of bigger dimension (P < .001). CBCT imaging was also superior in locating lesions in the apical part on the side compared with DOR and in the diagnosis of cortical bone destruction compared with both methods (P < .001). Through CBCT analysis, more root canals and more canals associated with lesions were found. The most informative and reproducible periapical and endodontic status parameters were selected, and a new PESS was proposed., Conclusions: The classification proposed in the present study seems to be reproducible and objective and adds helpful information with respect to the existing indexes. Future studies need to be conducted to validate PESS., (Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of the present study was to evaluate the difference in cyclic fatigue resistance between Vortex Blue (Dentsply Tulsa Dental, Tulsa, OK) and Profile Vortex nickel-titanium (Dentsply Tulsa Dental) rotary instruments., Methods: Two groups of nickel-titanium endodontic instruments, ProFile Vortex and Vortex Blue, consisting of identical instruments in tip size and taper (15/.04, 20/.06, 25/.04, 25/.06, 30/.06, 35/.06, and 40/.04) were tested. Ten instruments from each system and size were tested for cyclic fatigue resistance, resulting in a total of 140 new instruments. All instruments were rotated in a simulated root canal with a 60° angle of curvature and a 5-mm radius of curvature of a specific cyclic fatigue testing device until fracture occurred. The number of cycles to failure and the length of the fractured tip were recorded for each instrument in each group. The mean values and standard deviation were calculated, and data were subjected to 1-way analysis of variance and a Bonferroni t test. Significance was set at the 95% confidence level., Results: When comparing the same size of the 2 different instruments, a statistically significant difference (P < .05) was noted between all sizes of Vortex Blue and Profile Vortex instruments except for tip size 15 and .04 taper (P = 1.000). No statistically significant difference (P > .05) was noted among all groups tested in terms of fragment length., Conclusions: Vortex Blue showed a significant increase in cyclic fatigue resistance when compared with the same sizes of ProFile Vortex., (Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of the present study was to evaluate the cutting efficiency of 2 new reciprocating instruments, Reciproc and WaveOne., Methods: Twenty-four new Reciproc R25 and 24 new WaveOne Primary files were activated by using a torque-controlled motor (Silver Reciproc) and divided into 4 groups (n = 12): group 1, Reciproc activated by Reciproc ALL program; group 2, Reciproc activated by WaveOne ALL program; group 3, WaveOne activated by Reciproc ALL program; and group 4, WaveOne activated by WaveOne ALL program. The device used for the cutting test consisted of a main frame to which a mobile plastic support for the handpiece is connected and a stainless steel block containing a Plexiglas block (inPlexiglass, Rome, Italy) against which the cutting efficiency of the instruments was tested. The length of the block cut in 1 minute was measured in a computerized program with a precision of 0.1 mm. Means and standard deviations of each group were calculated, and data were statistically analyzed with 1-way analysis of variance and Bonferroni test (P < .05)., Results: Reciproc R25 displayed greater cutting efficiency than WaveOne Primary for both the movements used (P < .05); in particular, Reciproc instruments used with their proper reciprocating motion presented a statistically significant higher cutting efficiency than WaveOne instruments used with their proper reciprocating motion (P < .05). There was no statistically significant difference between the 2 movements for both instruments (P > .05)., Conclusions: Reciproc instruments demonstrated statistically higher cutting efficiency than WaveOne instruments., (Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of the present study was to use cone-beam computed tomography (CBCT) to analyze root canal anatomy and symmetry of maxillary and mandibular first and second molar teeth of a white population., Methods: A total of 201 patients who required CBCT examinations as part of their dental diagnosis and treatment were enrolled in the present study. Overall, 596 healthy, untreated, well-developed maxillary and mandibular molar teeth (161 maxillary first molars, 157 maxillary second molars, 117 mandibular first molars, and 161 mandibular second molars) were examined by CBCT to establish the symmetry in root and canal anatomy between right and left sides in the same patient by evaluating the number of roots and root canals and the root canal configuration., Results: Three separate roots with 3 separate canals was the normal anatomy of maxillary first and second molars. Most mandibular first and second molars had 2 separate roots, and the majority had 3 canals. In the present study, first molars, both maxillary and mandibular, exhibited greater asymmetry than the second molars. Maxillary first molars were found to be symmetrical in 71.1% of patients, whereas maxillary second molars were symmetrical in 79.6%. The remaining 28.9% and 20.4% of patients, respectively, showed asymmetry. Around 30% of the mandibular first molars and 20% of the mandibular second molars showed asymmetry., Conclusions: The results of the present study reported a percentage of symmetry that varied from 70%-81%. These variations in symmetry should be taken in high consideration when treating 2 opposite molars in the same patient, because their anatomy may be different in up to 30% of the cases., (Copyright © 2013 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of this study was to evaluate the resistance to flexural fatigue of Reciproc R25 (VDW, Munich, Germany), WaveOne Primary (VDW, Munich, Germany), Mtwo (Sweden & Martina, Padova, Italy), and Twisted File (TF; SybronEndo, Orange, CA) instruments used in continuous rotation or in 2 different reciprocating motions., Methods: A total of 180 nickel-titanium files from 4 brands marketed, 2 for use in reciprocating motion (ie, Reciproc R25 and WaveOne Primary) and 2 for use in continuous rotation (ie, Mtwo and TF both taper .06/0.25 tip diameter), were tested. Forty-five instruments for each brand were divided into 3 groups (n = 15) on the basis of the motion tested: continuous rotation (group 1: 300 rpm) and reciprocal motion (group 2: "RECIPROC ALL" mode and group 3: "WAVEONE ALL" mode). The resistance to cyclic fatigue was determined by counting the number of cycles to failure in a 60° curve with a 5-mm radius. Data were analyzed through 2-way analyses of variance., Results: The cyclic fatigue resistance of the 2 reciprocating motion instruments (ie, "RECIPROC ALL" and "WAVEONE ALL") was significantly higher than the continuous rotation in each brand (P < .001). No significant difference was observed in cyclic fatigue between the 2 different reciprocal motions tested in each brand (P > .05). When considering the appropriate clinical motion for each brand, no significant difference in cyclic fatigue was found between TF, Mtwo, and Reciproc R25 instruments, whereas the cyclic fatigue resistance of WaveOne files was less than the other 3 brands (P < .05)., Conclusions: Reciprocal motion showed a significantly higher cyclic fatigue resistance in all brands compared with continuous rotation. No differences were found between the 2 reciprocating motions., (Copyright © 2013 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The purpose of this study was to evaluate cyclic fatigue fracture resistance of engine-driven nickel-titanium (K3XF) instruments under reciprocating movement in various angles., Methods: Fifty K3XF size 40 taper 0.06 nickel-titanium instruments were divided randomly into 5 groups of 10 each. All instruments were subjected to cyclic fatigue tests. Instruments in groups 1-4 were tested by using different reciprocating motions, whereas instruments of group 5 (control group) were used in continuous rotation. All instruments were rotated or reciprocated until fracture occurred. Time to fracture was recorded, and data were statistically analyzed by using one-way analysis of variance, followed by Tukey honestly significant difference test for comparison between different groups., Results: All reciprocating groups (groups 1-4) showed a significant increase in time to failure when compared with group 5 (continuous rotation) (P < .05). Mean time was significantly higher in group 1, followed by group 2. No significant difference was found between groups 3 and 4 (P = .251). Increasing the clockwise angle of reciprocation and consequently increasing the angle of progression for each reciprocation cycle reduced the resistance to cyclic fatigue., Conclusions: Movement kinematics (reciprocating movements in various angles) had a significant influence on the cyclic fatigue life of the tested nickel-titanium instruments., (Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The goal of the present study was to test the fatigue resistance of nickel-titanium rotary files in a double curvature (S-shaped) artificial root canal and to compare those results with single curvature artificial root canals., Methods: Two nickel-titanium endodontic instruments consisting of identical instrument sizes (constant .06 taper and 0.25 tip diameter) were tested, ProFile instruments and Vortex instruments. Both instruments were tested for fatigue inside an artificial canal with a double curvature and inside a curved artificial canal with a single curvature. Ten instruments for each group were tested to fracture in continuous rotary motion at 300 rpm. Number of cycles to failure (NCF) was calculated to the nearest whole number, and the length of the fractured fragment was measured in millimeters. Data were statistically analyzed with a level of significance set at 95% confidence level., Results: The NCF value was always statistically lower in the double curved artificial canal when compared with the single curve (P < .05) in both the apical and coronal curvatures. Statistically significant differences (P < .05) were noted between instruments of the same size of different brand only in the single curve; ProFile registered a mean of 633.5 ± 75.1 NCF, whereas Vortex registered a mean of 548 ± 48.9 NCF., Conclusions: Regardless of the differences between the instruments used in the present study, the results suggest that the more complex is the root canal, the more adverse are the effects on the cyclic fatigue resistance of the instruments., (Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The purpose of this study was to evaluate the effect of autoclave sterilization on cyclic fatigue resistance of rotary endodontic instruments made of traditional and new nickel-titanium (NiTi) alloys., Methods: Four NiTi rotary endodontic instruments of the same size (tip diameter 0.40 mm and constant .04 taper) were selected: K3, Mtwo, Vortex, and K3 XF prototypes. Each group was then divided into 2 subgroups, unsterilized instruments and sterilized instruments. The sterilized instruments were subjected to 10 cycles of autoclave sterilization. Twelve files from each different subgroup were tested for cyclic fatigue resistance. Means and standard deviations of number of cycles to failure (NCF) and fragment length of the fractured tip were calculated for each group, and data were statistically analyzed (P < .05)., Results: Comparing the results between unsterilized and sterilized instruments for each type of file, differences were statistically significant (P < .05) only between sterilized and unsterilized K3XF files (762 versus 651 NCF). The other instruments did not show significant differences (P > .05) in the mean NCF as a result of sterilization cycles (K3, 424 versus 439 NCF; Mtwo, 409 versus 419 NCF; Vortex, 454 versus 480 NCF). Comparing the results among the different groups, K3 XF (either sterilized or not) showed a mean NCF significantly higher than all other files (P < .05)., Conclusions: Repeated cycles of autoclave sterilization do not seem to influence the mechanical properties of NiTi endodontic instruments except for the K3 XF prototypes of rotary instruments that demonstrated a significant increase of cyclic fatigue resistance., (Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Introduction: The aim of the present study was to evaluate the bending properties of Hyflex instruments, which exhibit a lower percent in weight of nickel (52 Ni %wt) and compare them with other commercially available nickel-titanium (NiTi) rotary instruments., Methods: Ten instruments with tip size 25, 0.06 taper of each of the following NiTi rotary instrumentation techniques were selected for the study: Hyflex, EndoSequence, ProFile, Hero, and Flexmasters. All instruments from each group were tested for stiffness by comparing their bending moment when they attained a 45-degree bend. Experimental procedures strictly followed testing methodology described in ISO 3630-1. All data were recorded and subjected to statistical evaluation by using analysis of variance test. Statistical significance was set at P < .05)., Results: Statistical analysis of the data revealed that Hyflex files were found to be the most flexible instruments, with a significant difference (P < .05) in comparison with the other instruments. Among the other files, a significant difference has been reported for EndoSequence instruments compared with ProFile, Hero, and FlexMaster (P < .05), whereas no significant differences have been reported among those 3 files (P > .05)., Conclusions: Results of the present study have illustrated an increased flexibility of the new NiTi alloy over conventional NiTi alloy, and they highlight the potential of the new manufacturing process., (Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Objective: The aim of this study was to investigate the influence of the shape of 3 different artificial canals on the trajectory followed by different nickel-titanium rotary instruments., Study Design: Ten ProFile and Mtwo instruments, tip sizes 20 and 25, taper .06, were tested in 3 simulated root canals with an angle of curvature of 60 degrees and radius of curvature of 5 mm but with different shapes. Geometric analysis of the trajectory that each instrument followed inside the 3 different artificial canals was performed on digital images, determining 3 parameters: angle and radius of the curvature and the position of the center of the curvature. Mean values were then calculated for each instrument size in all of the artificial canals. Data were analysed using 1-way analysis of variance, Holm t test, and Student t test to determine any statistical difference (P < .05)., Results: In all instrument sizes, a statistically significant difference was noted among the artificial canals for the radius and angle of curvature. No statistically significant difference was noted between instruments of the same size for the radius and angle of curvature and the position of the center of the curve when measured in the canal constructed on the dimension of the instruments., Conclusions: Different instruments follow different trajectories in artificial canals constructed with the same parameters of curvature but different shapes, depending on their different bending properties. All of the instruments respected the established parameters of curvature only when the artificial canal is designed on the dimension of the instruments., (Copyright 2010 Mosby, Inc. All rights reserved.)

Introduction: Fractured rotary nickel-titanium (NiTi) instruments have been classified into those that fail as a result of cyclic flexural fatigue or torsional failure or a combination of both. Clinically, NiTi rotary instruments are subjected to both torsional load and cyclic fatigue, and ongoing research aims to clarify the relative contributions of both factors to instrument separation., Methods: To date, there is no specification or international standard to test cyclic fatigue resistance of endodontic rotary instruments. As a consequence, several devices and methods have been used to investigate in vitro cyclic fatigue fracture resistance of NiTi rotary endodontic instruments. In nearly all studies reported in the endodontic literature, the rotating instrument was either confined in a glass or metal tube, in a grooved block-and-rod assembly, or in a sloped metal block., Results: There has been no mention of the "fit" of the instrument in the tube or groove. As the instrument is likely to be fitting loosely, the description of the radius of curvature in those studies is likely to be overstated (ie, the file was actually bent less severely than reported, adding a variability in the amount of flexural stress)., Conclusions: This review analyzed several devices that have been used in endodontic literature for cyclic fatigue testing and found that differences in the methodology affected the fatigue behavior of rotary instruments and, consequently, the outcome of these studies. An international standard for cyclic fatigue testing of NiTi rotary instruments is required to ensure uniformity of methodology and comparable results.

Objective: The objective of this study was to investigate the trajectory of NiTi rotary instruments of the same size but different design in an artificial root canal manufactured for cyclic fatigue test., Study Design: Eight groups of instruments with tip size 25, 0.06 taper with different design were tested in a simulated root canal with an angle of curvature of 60 degrees and radius of curvature of 5 mm milled in a stainless steel block with a tapered shape corresponding to the dimensions of the instruments tested. Geometric analysis of the trajectory that each instrument followed inside the artificial canal was performed on digital images, determining 3 parameters: angle and radius of the curvature and the position of the center of the curvature. Mean values were then calculated for each group. Data were analyzed using 1-way ANOVA and Holm t test to determine any statistical difference (P < .05)., Results: All the instruments tested followed the curvature established with little variations and ANOVA test did not show significant difference among the different groups for all the parameters analyzed (P > .05)., Conclusions: The results of the present study emphasized the importance of using an artificial canal specifically constructed on the dimensions of the instrument tested to reduce this approximation in cyclic fatigue tests. The artificial canal manufactured for the present study seems to guarantee that different NiTi rotary instruments may follow a precise and repeteable trajectory in terms of radius and angle of curvature.

The aim of the present study was to investigate whether cyclic fatigue resistance is increased for nickel-titanium instruments manufactured by using new processes. This was evaluated by comparing instruments produced by using the twisted method (TF; SybronEndo, Orange, CA) and those using the M-wire alloy (GTX; Dentsply Tulsa-Dental Specialties, Tulsa, OK) with instruments produced by a traditional NiTi grinding process (K3, SybronEndo). Tests were performed with a specific 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 < 0.05) in the mean number of cycles to failure when compared with size 06-25 K3 files. Size 06-20 K3 instruments showed no significant increase (p > 0.05) in the mean number of cycles to failure when compared with size 06-20 GT series X instruments. The new manufacturing process produced nickel-titanium rotary files (TF) significantly more resistant to fatigue than instruments produced with the traditional NiTi grinding process. Instruments produced with M-wire (GTX) were not found to be more resistant to fatigue than instruments produced with the traditional NiTi grinding process.

Objective: A new manufacturing method to produce more flexible and resistant NiTi endodontic instruments has been recently developed. The purpose of the study was to determine whether this new manufacturing method produces NiTi instruments (TF) of superior flexibility., Study Design: Ten .06 size 25 prototype (TF) instruments (Sybron Endo) and ten 06.25 ProFile instruments (Dentsply-Maillefer) were evaluated for stiffness on bending. Test procedures strictly followed ANSI/ADA Specification No.28. Bending moment was measured when the instrument attained a 45 degrees bend. All data obtained were recorded and statistically analyzed using an ANOVA test., Results: Statistical analysis of data showed that bending moments were significantly greater (P < .05) for ProFile instruments (mean value 59.06 g/cm), compared to the prototype instruments (mean value 35.60 g/cm), thereby confirming the increased flexibility of TF instruments., Conclusion: Results of the present study demonstrate the ability of the new manufacturing process to produce more flexible NiTi rotary instruments.

Objectives: Methacrylic compounds such as 2-hydroxyethyl methacrylate (HEMA), triethylene glycol dimethacrylate (TEGDMA) and bisphenol A glycerolate (1 glycerol/phenol) dimethacrylate (Bis-GMA) are largely present in auto- or photopolymerizable composite resins. Since the polymerization reaction is never complete, these molecules are released into the oral cavity tissues and biological fluids where they could cause local adverse effects. The aim of this work was to verify the hypothesis that the biological effects of HEMA, TEGDMA and Bis-GMA - at a non-cytotoxic concentration - depend on the interaction with mitochondria and exert consequent alterations of energy metabolism, GSH levels and the related pathways in human promyelocytic cell line (HL-60)., Methods: The biological effects of methacrylic monomers were determined by analyzing the following parameters: GSH concentration, glucose-6-phosphate dehydrogenase (G6PDH) and glutathione reductase (GR) activity, oxygen and glucose consumption and lactate production along with cell differentiation and proliferation., Results: All monomers induced both cellular differentiation and decrease in oxygen consumption. Cells treated with TEGDMA and Bis-GMA showed a significant enhancement of glucose consumption and lactate production. TEGDMA and HEMA induced GSH depletion stimulating G6PDH and GR activity., Conclusions: All the monomers under study affect the metabolism of HL-60 cells and show differentiating activity. Since alterations in cellular metabolism occurred at compound concentrations well below cytotoxic levels, the changes in energy metabolism and glutathione redox balance could be considered as potential mechanisms for inducing clinical and sub-clinical adverse effects and thus providing useful parameters when testing biocompatibility of dental materials.

Purpose: The purpose of this study was to evaluate the cyclic fatigue of ProTaper nickel-titanium (NiTi) rotary instruments (Tulsa Dental, Tulsa, Okla) after multiple clinical uses., Study Design: Two hundred twenty-five ProTaper instruments were divided into 3 groups: A = 75 used as controls, B = 75 used in 2 molars (6-8 canals), and C = 75 used in 4 molars (12-16 canals). The number of rotations to breakage and the fractured tip length were recorded for each file and the mean was calculated by ANOVA., Results: No S1-2 or F1-2-3 instrument separated during intracanal use, even if they were reused for a number of cases (x 4 molar cases)., Conclusion: It is clear that prolonged reuse of NiTi rotary instruments strongly affects instruments' fatigue, but our data suggest the hypothesis that other factors (primarily errors and misuse) may be more accountable for intracanal instrument separation. Further studies could assess the cyclic fatigue of each instrument at different levels of the shaft by altering the radius of curvature.

This study investigated the cyclic fatigue resistance of used nickel-titanium rotary instruments, clinically operated by a traditional high-torque motor and a new low-torque electric motor. Fifty instruments (ProFile, Maillefer, Baillagues, Switzerland) for each of the following sizes were used: .06-25, .06-20, and .04-25. They were divided into three groups: A = 10 new instruments (control), B = 20 used instruments operated by a high-torque motor, and C = 20 used instruments operated by a low-torque motor. Each instrument was used in 10 clinical cases (at least six molars). Cyclic fatigue testing of new and used instruments was performed with a device that allowed the instruments to rotate freely inside a stainless-steel artificial canal at 350 rpm. Data were recorded and statistically analyzed. Mean (and SD) numbers of rotation-to-breakage cycles for .06-25, .06-20, and .04-25 instruments were, respectively: group A 463 (85), 535 (101), and 613 (105); group B 229 (64), 343 (92), and 233 (84); and group C 352 (77), 454 (89), and 466 (86). Results showed that group A instruments exhibited significantly higher values of rotation-to-breakage cycles (two-sample t test, p < 0.01), when compared with groups B and C, respectively. Statistically higher resistance to cyclic fatigue was noted for group C in all sizes compared with group B (two-sample t test, p < 0.01), showing that the use of endodontic motor with lower torque values reduced cyclic fatigue of nickel-titanium rotary instruments.

The purpose of the present scanning electron microscopic study was to investigate the efficacy of a combination of EDTA, NaOCl, and surface-active irrigating solutions during and after root canal preparation with ProFile nickel-titanium rotary instruments. Thirty canals were divided into three groups, instrumented and irrigated as follows: 5% NaOCl and a final flush with 17% EDTA were used for group A; group B specimens were irrigated using 17% EDTA, followed 15 s later by 1% TRITON X-100 (tensioactive agent) and then by 5% NaOCl; and group C specimens were irrigated with the same combination, but once shaping procedures were completed the irrigating sequence was repeated three times. After scanning electron microscopic evaluation, group C specimens exhibited the most effective debridement of the root canals. Results showed that tensioactive agent contributed to enhanced debridement. Cleaning was significantly improved once shaping procedures were completed.

Several previous studies have investigated the advantage of temperature on tissue-dissolving and antimicrobial properties of sodium hypochlorite. However, it is known that the chemical stability of sodium hypochlorite is adversely affected by exposure to high temperature. The purpose of this study was to investigate the effect of heating sodium hypochlorite to 50 degrees C on the stability of the solution. An iodometric titration test was used to evaluate the decomposition rates of heated and nonheated solutions over 30 days. Results showed that all specimens exhibited a minimal, gradual degradation versus time. However, no statistically significant difference (p < 0.05) was noted between the two groups. After 30 days, both heated and non-heated solutions maintained high available chlorine content and pH values consistent with excellent tissue-dissolving and antibacterial properties.

A new sealer that contains hydroxyapatite has been developed; the additive is assumed to influence apical healing, but it may also affect the sealing ability of the cement because of its composite structure. The purpose of this study was to evaluate the sealing ability of Bioseal and to compare it with that of another zinc oxide-eugenol sealer (Pulp Canal Sealer), using a lateral condensation technique and thermatic compaction of gutta-percha. The study was conducted on 42 straight roots, prepared to apical size 35 to 40 and randomly separated into four groups. After obturation, the roots were suspended for 1 wk in methylene blue and sectioned transversely for measuring penetration of the dye. In the roots filled with Bioseal, the mean penetration was 1.1 mm for lateral condensation and 1.5 mm for thermatic compaction. In the Pulp Canal Sealer groups, the values were 1.4 mm for both. The difference was not significant at the 5% level (Mann-Whitney U test), indicating that the additive did not adversely affect the sealing properties.

Different kinds of spreaders can be used in the lateral condensation technique. Selection of condensation instruments must not be empirical because the quality of the filling partly depends on the compatibility between the spreader and the prepared root canal. The shape of the instrument should allow for easy insertion to the proper length without any interference. On these bases the Authors evaluated and compared the morphology of some spreaders, and gave data and directions how to rationally use these instruments in clinical practice.