This Position Statement represents a consensus of an expert committee convened by the European Society of Endodontology (ESE) on the use of Cone Beam Computed Tomography (CBCT). The statement is based on the current scientific evidence, and provides the clinician with evidence-based criteria on when to use CBCT in Endodontics. Given the dynamic and changing nature of research, development of new devices and clinical practice relating to CBCT, this Position Statement will be updated within 3 years, or before that time should new evidence become available.
Aim To compare shaping ability and cleaning effectiveness of two reciprocating single-file systems with Mtwo and ProTaper rotary instruments during the preparation of curved root canals in extracted teeth. Methodology A total of 80 root canals with curvatures ranging between 25 degrees and 39 degrees were divided into four groups of 20 canals. Based on radiographs taken prior to instrumentation, the groups were balanced with respect to the angle and the radius of canal curvature. Canals were prepared to the following apical sizes: Mtwo: size 35 using the single-length technique; ProTaper: F3, instruments were used in a modified crown-down manner; Reciproc and WaveOne: size 25. Using pre- and post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis program. Preparation time and instrument failures were also recorded. These data were analysed statistically using anova and StudentNewmanKeuls test. The amounts of debris and smear layer were quantified on the basis of a numerical evaluation scale and were analysed statistically using the KruskalWallis test. Results During preparation no file fractured. All instruments maintained the original canal curvature well with no significant differences between the different files (P = 0.382). Instrumentation with Reciproc was significantly faster than with all other instruments (P 0.05), while ProTaper showed significantly more residual debris (P 0.05). Conclusions Under the conditions of this study, all instruments maintained the original canal curvature well and were safe to use. The use of Mtwo and Reciproc instruments resulted in better canal cleanliness in the apical part compared with ProTaper and WaveOne.
P>Aim To investigate the probability of and factors influencing periapical status of teeth following primary (1 degrees RCTx) or secondary (2 degrees RCTx) root canal treatment. Methodology This prospective study involved annual clinical and radiographic follow-up of 1 degrees RCTx (1170 roots, 702 teeth and 534 patients) or 2 degrees RCTx (1314 roots, 750 teeth and 559 patients) carried out by Endodontic postgraduate students for 2-4 (50%) years. Pre-, intra- and postoperative data were collected prospectively on customized forms. The proportion of roots with complete periapical healing was estimated, and prognostic factors were investigated using multiple logistic regression models. Clustering effects within patients were adjusted in all models using robust standard error. Results The proportion of roots with complete periapical healing after 1 degrees RCTx (83%; 95% CI: 81%, 85%) or 2 degrees RCTx (80%; 95% CI: 78%, 82%) were similar. Eleven prognostic factors were identified. The conditions that were found to improve periapical healing significantly were: the preoperative absence of a periapical lesion (P = 0.003); in presence of a periapical lesion, the smaller its size (P < 0.001), the better the treatment prognosis; the absence of a preoperative sinus tract (P = 0.001); achievement of patency at the canal terminus (P = 0.001); extension of canal cleaning as close as possible to its apical terminus (P = 0.001); the use of ethylene-diamine-tetra-acetic acid (EDTA) solution as a penultimate wash followed by final rinse with NaOCl solution in 2 degrees RCTx cases (P = 0.002); abstaining from using 2% chlorexidine as an adjunct irrigant to NaOCl solution (P = 0.01); absence of tooth/root perforation (P = 0.06); absence of interappointment flare-up (pain or swelling) (P =0.002); absence of root-filling extrusion (P < 0.001); and presence of a satisfactory coronal restoration (P < 0.001). Conclusions Success based on periapical health associated with roots following 1 degrees RCTx (83%) or 2 degrees RCTx (80%) was similar, with 10 factors having a common effect on both, whilst the 11th factor 'EDTA as an additional irrigant' had different effects on the two treatments.
Aim To assess the ability of a recently developed tricalcium silicate-based cement (Biodentine (TM)) to induce reparative dentine synthesis and to investigate its capacity to modulate pulp cells TGF-beta 1 secretion. Methodology Biodentine (TM) was directly applied onto the dental pulp in an entire human tooth culture model. After various culture periods, the interaction of the material with dental pulp tissue was analysed on tissue sections. The effect of increasing surface area of this material on TGF-beta 1 secretion was investigated on pulp cell cultures and compared with that of MTA, calcium hydroxide and Xeno (R) III adhesive resin. After performing artificial injuries on pulp cell cultures, the materials eluates were added for 24 h and then TGF-beta 1 secretion was quantified by ELISA. Controls were performed by incubating intact cells with the culture medium, while injured cells TGF-beta 1 level was used as the baseline value. Results Biodentine (TM) induced mineralized foci formation early after its application. The mineralization appeared under the form of osteodentine and expressed markers of odontoblasts. Biodentine (TM) significantly increased TGF-beta 1 secretion from pulp cells (P < 0.03) independently of the contact surface increase. This increase was also observed with calcium hydroxide and MTA, but not with the resinous Xeno (R) III. The statistical analysis showed statistically significant differences between capping materials and the resinous Xeno (R) III (P < 0.001). Conclusions When Biodentine (TM) was applied directly onto the pulp, it induced an early form of reparative dentine synthesis, probably due to a modulation of pulp cell TGF-beta 1 secretion.
Aim To report several types of response of immature permanent teeth with infected necrotic pulp tissue and either apical periodontitis or abscess to revascularization procedures. Methodology Twenty immature permanent teeth with infected necrotic pulp tissue and either apical periodontitis or abscesses from 20 patients were included. The teeth were isolated with rubber dam, and pulp chambers was accessed through the crowns. The canals were gently irrigated with 5.25% sodium hypochlorite with minimal mechanical debridement. Calcium hydroxide was used as an inter-appointment intracanal medicament and placed into the coronal half of the canal space. After resolution of clinical signs and symptoms, bleeding was induced into the canal space from the periapical tissues using K-files. The coronal canal space was sealed with a mixture of mineral trioxide aggregate (MTA) and saline solution. The access cavity was filled with composite resin. These immature permanent teeth with infected necrotic pulp tissue and apical periodontitis/abscesses were followed up from 6 to 26 months. Results Five types of responses of these immature permanent teeth with infected necrotic pulp tissue and apical periodontitis/abscess to revascularization procedures were observed: type 1, increased thickening of the canal walls and continued root maturation; type 2, no significant continuation of root development with the root apex becoming blunt and closed; type 3, continued root development with the apical foramen remaining open; type 4, severe calcification (obliteration) of the canal space; type 5, a hard tissue barrier formed in the canal between the coronal MTA plug and the root apex. Conclusions Based on this case series, the outcome of continued root development was not as predictable as increased thickening of the canal walls in human immature permanent teeth with infected necrotic pulp tissue and apical periodontitis/abscess after revascularization procedures. Continued root development of revascularized immature permanent necrotic teeth depends on whether the Hertwigs epithelial root sheath survives in case of apical periodontitis/abscess. Severe pulp canal calcification (obliteration) by hard tissue formation might be a complication of internal replacement resorption or union between the intracanal hard tissue and the apical bone (ankylosis) in revascularized immature permanent necrotic teeth.
Plotino G, Grande NM, Testarelli L, Gambarini G. Cyclic fatigue of Reciproc and WaveOne reciprocating instruments. International Endodontic Journal, 45, 614618, 2012. Abstract Aim To evaluate the cyclic fatigue resistance of Reciproc (R) and WaveOne (R) instruments in simulated root canals. Methodology Two groups of 15 NiTi endodontic instruments of identical tip size of 0.25 mm were tested, group A; Reciproc (R) R25 and group B: WaveOne (R) primary. Cyclic fatigue testing was performed in a stainless steel artificial canal manufactured by reproducing the instruments size and taper. A simulated root canal with a 60 degrees angle of curvature and 5-mm radius of curvature was constructed for both the instruments tested. The centre of the curvature was 5 mm from the tip of the instrument and the curved segment of the canal was approximately 5 mm in length. The Reciproc (R) instruments were activated using the preset programme specific for the Reciproc (R) instruments, whilst the WaveOne (R) instruments were activated using the preset programme specific for the WaveOne (R) instruments. All instruments were rotated until fracture occurred and the time to fracture (TtF) and the length of the fractured tip were recorded and registered. Means and standard deviations of TtF and fragment length were calculated for each system and data were subjected to Students t-test (P 0.05) in the mean length of the fractured fragments between the instruments. Conclusions Reciproc (R) instruments were associated with a significantly higher cyclic fatigue resistance than WaveOne (R) instruments.
Han L, Okiji T. Uptake of calcium and silicon released from calcium silicate-based endodontic materials into root canal dentine. International Endodontic Journal, 44, 1081-1087, 2011. Aim To compare Biodentine and White ProRoot mineral trioxide aggregate (MTA) with regard to Ca and Si uptake by adjacent root canal dentine in the presence of phosphate-buffered saline (PBS). Methodology Root canals of bovine incisor root segments were instrumented, filled with either Biodentine or MTA (n = 20 each) and then immersed in Ca-and Mg-free PBS for 1, 7, 30 or 90 days (n = 5 each). Unfilled, unimmersed dentine specimens (n = 5) served as controls. The specimens were sectioned longitudinally, and the ultrastructure of the dentinematerial interface and the elemental composition/distribution in the materialadjacent dentine were analysed using a wavelength-dispersive X-ray spectroscopy electron probe microanalyser with image observation function. Data were statistically analyzed using one-way anova and Tukeys honestly significant difference test or the MannWhitney U-test. Results Along the materialdentine interface, both materials formed a tag-like structure that was composed of either Ca- and P-rich crystalline deposits or the material itself. The width of a Ca- and Si-rich layer detected along the dentine layer of the materialdentine interface showed increases over time. The Ca- and Si-rich layer width was significantly larger (P < 0.05) in Biodentine than MTA at 30 and 90 days. Conclusions Both Biodentine and MTA caused the uptake of Ca and Si in the adjacent root canal dentine in the presence of PBS. The dentine element uptake was more prominent for Biodentine than MTA.
Aim To describe a novel canal preparation technique using only one Ni‐Ti rotary instrument. Summary In this novel technique, the canal is negotiated to the working length with a size 08 hand file. Then, the canal preparation is completed with an F2 ProTaper instrument used in a reciprocating movement. In larger canals, the use of additional hand files may be required to complete the apical enlargement. Key learning points • A novel canal preparation technique is introduced using only one Ni‐Ti rotary instrument in a reciprocating movement. • The advantages of the technique include a reduced number of instruments, lower cost, a reduced instrument fatigue and the elimination of possible prion cross‐contamination associated with the single use of endodontic instruments.
The assurance of the quality of a service rendered by a member of the dental profession is an essential feature of any system of peer review in dentistry. This document addresses two essential elements: (i) appropriateness of treatment modality and (ii) quality or level of treatment rendered. In revising these guidelines the European Society of Endodontology is responding to a public and professional need. In receiving care of a specialized nature such as endodontic treatment, patients need and deserve treatment that meets the standard of care generally given by competent practitioners. The European Society of Endodontology has the expertise and professional responsibility necessary to assist the dental profession by instituting guidelines on the standard of care in the special area of Endodontics. In accepting this responsibility the European Society of Endodontology formulated treatment guidelines that are intended to represent current good practice. This document is the revised version of an earlier consensus report [ International Endodontic Journal (1994) 27 , 115–24]. As there is not one single way of performing treatment, these guidelines have been formulated in broad terms.
Lenherr P, Allgayer N, Weiger R, Filippi A, Attin T, Krastl G. Tooth discoloration induced by endodontic materials: a laboratory study. International Endodontic Journal,similar to 45, 942949, 2012. Abstract Aim To investigate the discoloration potential of endodontic materials using a bovine tooth model. Methodology Two hundred and 10 dentine-enamel cuboid blocks (10 x 10 x 3.5 mm) were prepared out of the middle thirds of bovine tooth crowns. Standardized cavities were prepared in the walls of the pulp chamber leaving 2 mm of enamel and dentine on the labial wall of the crown. The specimens were randomly assigned to 14 groups (n = 15). Endodontic materials were placed into the cavities as follows: group A: empty, group B: blood, group C: calcium hydroxide, group D: ApexCal, group E: Ultracal XS, group F: Ledermix, group G: triple antibiotic paste (3Mix), group H: grey MTA(GMTA), group I: GMTA + blood, group J: white MTA (WMTA), group K: WMTA + blood, group L: Portland cement (PC), group M: PC + blood and group N: AH Plus. The cavities were sealed with composite and stored in water. Standardized colour measurement (VITA Easyshade compact) was performed at the following intervals: prior to (T0) and after placement of the filling (T1), 1 week (T2), 1 month (T3), 3 months (T4), 6 months (T5) and after 1 year (T6). Colour change (?E) values were calculated. A two-way analysis of variance was used to assess significant differences between the endodontic materials. The mean values of all groups were compared using the Tukey multiple comparison test (a = 0.05). Results Significant differences were detected amongst the experimental groups after 12 months (P < 0.0001). The lowest colour change values were observed in the groups N (AH Plus, 3.2 +/- 1.5), A (empty, 3.8 +/- 1.4), L (PC, 4.1 +/- 1.7), C (calcium hydroxide, 4.7 +/- 1.5), E (Ultracal XS, 5.1 +/- 1.9) and J (WMTA, 7.9 +/- 6.7). The most discoloration was measured in groups G (3Mix, 66.2 +/- 9.9) and F (Ledermix, 46.2 +/- 11.6). PC showed the best colour stability amongst the Portland cement-based materials; however, when contaminated with blood (group M), a significantly higher ?E value (13.6 +/- 4.2) was detected (P = 0.032). Conclusion Materials used in endodontics may stain teeth. Therefore, the choice of material should not rely solely on biological and functional criteria, but also take aesthetic considerations into account.
This position statement represents a consensus of an expert committee convened by the European Society of Endodontology ( ESE ) on revitalization procedures. The statement is based on current clinical and scientific evidence as well as the expertise of the committee. The goal is to provide suitably trained dentists with a protocol including procedural details for the treatment of immature teeth with pulp necrosis as well as a patient consent form. Revitalization is a biologically based treatment as an alternative to apexification in properly selected cases. Previously published review articles provide more detailed background information and the basis for this position statement ( Journal of Endodontics, 39 , 2013, S30; Journal of Endodontics, 39 , 2013, 319; Journal of Endodontics , 40 , 2014, 1045; Dental Traumatology , 31 , 2015, 267; International Endodontic Journal, 2015, doi: 10.1111/iej.12606 ). As controlled clinical trials are lacking and new evidence is still emerging, this position statement will be updated at appropriate intervals. This might lead to changes to the protocol provided here.
Aim To compare the resistance to cyclic fatigue of WaveOne Gold (WOG), Reciproc and WaveOne (WO) nickel-titanium files in an artificial root canal with a double (S-shaped) curvature. Methodology A total of 120 new WOG primary, Reciproc R25 and WO primary files were tested in an artificial, stainless steel canal with an S-shape (diameter, 1.4 mm and length, 18 mm). Forty files from each system were rotated until fracture to calculate the number of cycles to failure (NCF). The length of each fractured fragment was recorded. Data were analysed using one-way analysis of variance and Tukey's post hoc tests. Results The WOG primary (apical curvature: 928.87 +/- 293.69; coronal curvature 1102.32 +/- 397.39 NCF) had higher cyclic fatigue resistance than Reciproc R25 and WO primary in the apical and coronal curvatures (P 0.05). There was no difference in fractured fragment lengths of the WOG primary, Reciproc R25, and WO primary files in either the apical or coronal curvature (P > 0.05). Conclusions WaveOne Gold primary files exhibited greater cyclic fatigue resistance than Reciproc R25 and WO primary in an artificial canal with an S-shape.
Aim To compare the efficacy of reciprocating and rotary techniques with that of hand files for removing gutta-percha and sealer from root canals. Methodology The root canals of fifty-four human extracted maxillary central incisors were cleaned and shaped using a crown-down technique to a size 40 and filled with gutta-percha and a zinc oxide-eugenol-based sealer using a lateral compaction technique. Teeth were divided into three groups according to the technique used for removing the root filling material: group I - Gates-Glidden burs and stainless steel hand files up to size 50; group II - rotary technique with NiTi Mtwo R files and additional Mtwo files to size 50, 0.04 taper; group III - reciprocating technique with the Reciproc instrument R50, size 50, 0.05 taper. Chloroform was used as a solvent in all groups. Teeth were then split longitudinally and photographed under 89 magnification. The images were transferred to a computer, and the total canal space and remaining filling material were quantified. The ratio of remaining filling material to root canal periphery was computed with the aid of Image Tool 3.0 software. The mean percentages of remaining filling material and time required to remove it were compared using the Kruskal-Wallis and Mann-Whitney tests (P 0.05). The time required to remove filling material was significantly shorter (P < 0.05) in group III (194 s), followed by group II (365 s) and group I (725 s) (P < 0.05). Conclusion Remaining endodontic filling material was observed on the canal walls of all teeth regardless of the technique used. Hand files combined with Gates-Glidden burs (group I) and the reciprocating technique (group III) removed more filling material from the canal walls than the Mtwo R files. The reciprocating technique was the most rapid method for removing gutta-percha and sealer, followed by the rotary technique and the hand file technique.
Aim To evaluate the cyclic fatigue fracture resistance of engine-driven F2 ProTaper instruments under reciprocating movement. Methodology A sample of 30 NiTi ProTaper F2 instruments was used. An artificial canal was made from a stainless steel tube, allowing the instruments to rotate freely. During mechanical testing, different movement kinematics and speeds were used, which resulted in three experimental groups (n = 10). The instruments from the first group (G1) were rotated at a nominal speed of 250 rpm until fracture, whilst the instruments from the second group (G2) were rotated at 400 rpm. In the third instrument group (G3), the files were driven under reciprocating movement. The time of fracture for each instrument was measured, and statistical analysis was performed using parametric methods. Results Reciprocating movement resulted in a significantly longer cyclic fatigue life (P < 0.05). Moreover, operating rpm was a significant factor affecting cyclic fatigue life (P < 0.05); instruments used at a rotational speed of 400 rpm (approximately 95 s) failed more rapidly than those used at 250 rpm (approximately 25 s). Conclusions Movement kinematics is amongst the factors determining the resistance of rotary NiTi instruments to cyclic fracture. Moreover, the reciprocating movement promoted an extended cyclic fatigue life of the F2 ProTaper instrument in comparison with conventional rotation.
Aim To evaluate the effect of dentine conditioning on migration, adhesion and differentiation of dental pulp stem cells. Methodology Dentine discs prepared from extracted human molars were pre-treated with EDTA (10%), NaOCl (5.25%) or H-2 O. Migration of dental pulp stem cells towards pre-treated dentine after 24 and 48 h was assessed in a modified Boyden chamber assay. Cell adhesion was evaluated indirectly by measuring cell viability. Expression of mineralization-associated genes (COL1A1, ALP, BSP, DSPP, RUNX2) in cells cultured on pre-treated dentine for 7 days was determined by RT-qPCR. Nonparametric statistical analysis was performed for cell migration and cell viability data to compare different groups and time-points (Mann-Whitney U-test, alpha = 0.05). Results Treatment of dentine with H2O or EDTA allowed for cell attachment, which was prohibited by NaOCl with statistical significance (P = 0.000). Furthermore, EDTA conditioning induced cell migration towards dentine. The expression of mineralization-associated genes was increased in dental pulp cells cultured on dentine after EDTA conditioning compared to H2O-pre-treated dentine discs. Conclusions EDTA conditioning of dentine promoted the adhesion, migration and differentiation of dental pulp stem cells towards or onto dentine. A pretreatment with EDTA as the final step of an irrigation protocol for regenerative endodontic procedures has the potential to act favourably on new tissue formation within the root canal.
P>Aim To investigate the probability of and factors influencing tooth survival following primary (1 degrees RCTx) or secondary (2 degrees RCTx) root canal treatment. Methodology This prospective study involved annual follow-up of 2 (100%) to 4 years (50%) of 1 degrees RCTx (759 teeth, 572 patients) and 2 degrees RCTx (858 teeth, 642 patients) carried out by Endodontic postgraduate students. Pre-, intra- and post-operative data were collected prospectively from consented patients. Information about extraction of the root filled tooth was sought from the patient, the referring dentist or derived from the patient's records and included the timing and reasons for extraction. Tooth survival was estimated and prognostic factors were investigated using Cox regression. Clustering effects within patients were adjusted in all models using robust standard error. Results The 4-year cumulative tooth survival following 1 degrees RCTx [95.4% (93.6%, 96.8%)] or 2 degrees RCTx [95.3% (93.6%, 96.5%)] was similar. Thirteen prognostic factors were identified. Significant patient factors included history of diabetes and systemic steroid therapy. Significant pre-operative factors included narrow but deep periodontal probing depth; pain; discharging sinus; and iatrogenic perforation (for 2 degrees RCTx cases only). Significant intra-operative factors included iatrogenic perforation; patency at apical terminus; and extrusion of root fillings. Significant post-operative restorative factors included presence of cast restoration versus temporary restoration; presence of cast post and core; proximal contacts with both mesial and distal adjacent teeth; and terminal location of the tooth. The presence of pre-operative pain had a profound effect on tooth loss within the first 22 months after treatment [hazard ratio (HR) = 3.1; P = 0.001] with a lesser effect beyond 22 months (HR = 2.4; P = 0.01). Patency at the apical terminus reduced tooth loss (HR = 0.3; P < 0.01) within the first 22 months after treatment but had no significant effect on tooth survival beyond 22 months. Extrusion of gutta-percha root filling did not have any effect on tooth survival (HR = 1.1; P = 0.2) within the first 22 months but significantly increased the hazard of tooth loss beyond 22 months (HR = 3.0; P = 0.003). Conclusions The 4-year tooth survival following primary or secondary root canal treatment was 95%, with thirteen prognostic factors common to both.
AimTo assess in a laboratory setting the amount of apically extruded debris associated with different single-file nickel-titanium instrumentation systems compared to one multiple-file rotary system. MethodologyEighty human mandibular central incisors were randomly assigned to four groups (n=20 teeth per group). The root canals were instrumented according to the manufacturers' instructions using the reciprocating single-file system Reciproc, the single-file rotary systems F360 and OneShape and the multiple-file rotary Mtwo instruments. The apically extruded debris was collected and dried in pre-weighed glass vials. The amount of debris was assessed with a micro balance and statistically analysed using anova and post hoc Student-Newman-Keuls test. The time required to prepare the canals with the different instruments was also recorded. ResultsReciproc produced significantly more debris compared to all other systems (P0.05). Instrumentation with the three single-file systems was significantly faster than with Mtwo (P<0.05). ConclusionsUnder the condition of this study, all systems caused apical debris extrusion. Rotary instrumentation was associated with less debris extrusion compared to reciprocal instrumentation.
Aim To compare white ProRoot MTA (WMTA), EndoSequence BC sealer (BC sealer) and Biodentine with regard to their ability to produce apatites and cause Ca and Si incorporation in adjacent human root canal dentine after immersion in phosphate-buffered saline (PBS). Methodology Root sections of human single-rooted teeth were filled with one of the materials and immersed in PBS for 1, 7, 30 or 90days (n=5 each). Morphology and elemental composition of surface precipitates and interfacial dentine were analysed using a wavelength-dispersive X-ray spectroscopy electron probe microanalyser with image observation function. Ca- and Si-incorporation depths in the interfacial dentine were measured. In addition, the amount of Ca ions released from the test materials was measured by EDTA titration. Results All materials produced surface precipitates of acicular or lath-like morphology with Ca/P ratio of 1.6 : 2.0. Within dentinal tubules, the three materials formed tag-like structures that were frequently composed of Ca- and P-rich and Si-poor materials, suggesting intratubular precipitation. Ca- and Si-incorporation depths were in the order of Biodentine>WMTA>BC sealer, with a significant difference between BC sealer and the others at several time-points (PWMTA>BC sealer with significant differences between the materials (P<0.05). Conclusions Compared with Biodentine and WMTA, BC sealer showed less Ca ion release and did not show Ca and Si incorporation as deeply in human root canal dentine when immersed in PBS for up to 90days.
AimTo evaluate the surface and microstructural alterations of new and used HyFlex EDM prototypes and to test their fatigue resistance. MethodologyFifteen HyFlex EDM prototypes were used for invitro instrumentation of severely curved root canals. Surface and microstructural characteristics of new and used files were compared by ESEM analysis equipped with energy dispersive X-ray spectrophotometry (EDS) and optical metallographic imaging. Usage-induced degradation was assessed. Thirty additional HyFlex EDM prototypes and 20 standard manufactured HyFlex CM files were subjected to cyclic fatigue tests. Time to fracture was recorded, and results were validated using the Kruskal-Wallis test (-level 0.05). Fatigued files were analysed by ESEM for fractographic evaluation. ResultsSurface and microstructural characterization of EDM prototypes revealed the typical spark-machined surface of a NiTi EDM alloy. No fractures were registered during root canal instrumentation. No evident surface alterations and minor degradation were observed between new and used instruments. The metallographic analysis of new and used files disclosed a homogeneous structure, mostly composed of lenticular martensite grains, and some residual austenite. The cyclic fatigue test showed an increase of fatigue resistance up to 700% on the EDM compared to CM files. ConclusionsSpark-machined peculiar surface is the main feature of HyFlex EDM. Low degradation was observed after multiple canal instrumentations. Prototypes exhibited surprising high values of cyclic fatigue resistance and a safe invitro use in severely curved canals.
Aim To compare the shaping ability of three different single-file systems with Mtwo rotary instruments during the preparation of curved root canals in extracted teeth. Methodology A total of 80 root canals with curvatures ranging between 25 degrees and 35 degrees were divided into four groups of 20 canals. Based on radiographs taken prior to instrumentation, the groups were balanced with respect to the angle and the radius of canal curvature. Canals were prepared to the following apical sizes: Mtwo: size 30 using the single-length technique; Reciproc, F360, and OneShape: size 25. Using pre- and post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis programme. Preparation time, changes in working length, and instrument failures were also recorded. These data were analysed statistically using anova and StudentNewmanKeuls test. Results During preparation, no file fractured. All instruments maintained the original canal curvature well with no significant differences between the instrument systems (P=0.792). Instrumentation with Reciproc and OneShape was significantly faster than with F360 and Mtwo (P<0.05), while F360 was significantly faster than Mtwo (P<0.05). No significant differences were obtained regarding changes in working length during instrumentation with the different instruments (P=0.784). Conclusions Under the conditions of this study, all instruments respected the original canal curvature well and were safe to use. The use of Reciproc and OneShape instruments required less time to prepare the curved canals compared with Mtwo and F360.