Mechanical properties and metallurgical features of new and ex vivo used Reciproc Blue and Reciproc.

AIM: To compare the mechanical properties and metallurgic features of new and used Reciproc Blue and Reciproc instruments. METHODOLOGY: A total of 120 R25 Reciproc Blue and R25 Reciproc instruments were used. The morphological, chemical, mechanical, thermal and phase composition characteristics of new and ex vivo used files were investigated by scanning electron microscopy (FEG-SEM) with energy dispersive X-ray spectroscopy (EDS), focused ion beam analysis (FIB), micro-Raman spectroscopy, FEG-SEM metallography, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and indentation tests. Usage-induce degradation was evaluated. Ten new and ten used instruments per type were run until fracture occurred in a stainless steel artificial canal (60° angle of curvature, 4-mm radius). Time to fracture and the length of the fractured fragment were recorded. Torque and angle of rotation at failure of ten new and ten used instruments for each type were measured according to ISO 3630-1. The fracture surface of each fragment was examined. Two-way analyses of variance was used to analyse the data statistically (α-level 0.05). RESULTS: SEM analysis revealed microcracks near the tip on both files after ex vivo usage tests. FIB imaging and micro-Raman spectroscopy confirmed the presence of an oxide layer on the Reciproc Blue surface. There was no thinning of the coating after use. XRD revealed a reduction of martensite and R-phase in Reciproc Blue after use. DSC analysis revealed different transformation temperatures for the instruments analysed. Reciproc Blue was significantly more flexible than Reciproc for both new and used samples (P < 0.05), and they were significantly more resistant to cyclic fatigue than Reciproc (P < 0.05). Ex vivo usage reduced the fatigue resistance of both files. Torsional resistance of Reciproc and Reciproc Blue was not reduced by simulated use (P > 0.05). CONCLUSIONS: The thermal treatment of Reciproc Blue was associated with a finer structure with smaller grains than Reciproc, which increased its fracture resistance and was also responsible for its reduced hardness and lower elastic modulus. Both files were safe during ex vivo usage in severely curved canals.

Cutting efficiency of conventional and heat-treated nickel-titanium rotary or reciprocating glide path instruments.

AIM: To compare the cutting efficiency of several glide path files: HyFlex EDM Glidepath File (HEGF), One G (OG), R-Pilot (RP) and WaveOne Gold Glider (WOGG) at different cutting inclinations. METHODOLOGY: Cutting efficiency of 120 new HEGF, OG, RP and WOGG was tested at 90°, 70° and 45° inclination in relation to the sample. Depending on manufacturer instructions, instruments were tested in continuous rotation or reciprocating motion against standardized gypsum samples for 120 s using a customized apparatus. Cutting efficiency was determined by measuring the weight loss and the length of the sample cut. Data were analysed using two-way analysis of variance and Tukey t-test (P < 0.05). RESULTS: RP and WOGG had greater cutting ability than HEGF and OG in all tested angles. RP tested at 45° had significantly greater cutting efficiency than when tested at 90° and 70° (P < 0.05). OG was not significantly different in terms of cutting ability at 90°, 70° and 45° (P > 0.05). HEGF and WOGG had significantly greater cutting efficiency at 45° and 70° compared to 90° (P < 0.05), with no significant difference between 45° and 70° (P > 0.05). RP had the greatest cutting ability at all tested angles. CONCLUSIONS: Reciprocating glide path instruments had greater cutting efficiency compared to those in continuous rotation. An inclined insertion (45° or 70°) increased the cutting ability of glide path files except for One G conventional NiTi files.

Colorimetric study about the stratification's effect on colour perception of resin composites.

To evaluate the influence of a different order of dentin and enamel layers on stratification appearance of different resin composites. 144 Dentin (D) and Enamel (E) composite samples (Clearfil Majesty ES-2 Premium, Brilliant EverGlow, Estelite Asteria), 1 mm thick, were divided into 12 configurations for each composite, with Enamel-Dentin-Dentin-Enamel (EDDE) assumed as target. The colour specification was conducted using a spectrophotometer, elaborating the results with the CIE L*a*b* colour coordinates and calculating the colour difference in terms of [Formula: see text] quantity. A value of this last major of 3.3 was considered not clinically acceptable. Moreover, data were analyzed using two-way analysis of variance and Tukey post hoc test (P < 0.05). For Clearfil Majesty ES-2 Premium and Brilliant EverGlow, six configurations showed [Formula: see text] > 3.3 compared to gold standard EDDE. [Formula: see text] was influenced especially by b* and L* coordinates (P < 0.05). EDED showed no visual difference (0 < [Formula: see text] < 1.1) for both composites. For Estelite Asteria, two configurations reported [Formula: see text] > 3.3 compared to EDDE. In particular, the L* coordinate influenced [Formula: see text] results (P < 0.05). EDDD was the best configuration (0 < [Formula: see text] < 1.1). Within the limits of a vitro study, Brilliant EG showed more dependence from order and thickness of stratification (resulting more similar to Clearfil Majesty ES-2 Premium); therefore, it could be indicated for more complex aesthetic restorations. Estelite Asteria seems to be able to balance small differences in thickness of dentin and enamel layers, and consequently, it is more indicated to different clinical situations.

Retreatability of two hydraulic calcium silicate-based root canal sealers using rotary instrumentation with supplementary irrigant agitation protocols: a laboratory-based micro-computed tomographic analysis.

AIM: To investigate the retreatability of two calcium silicate-based materials (BioRoot RCS, Septodont, Saint-Maur-des-Fossés, France and GuttaFlow Bioseal, Colténe/Whaledent AG, Langenau, Germany) using rotary instrumentation combined with supplementary irrigant agitation techniques using extracted teeth in a laboratory setting. METHODOLOGY: The root canals of extracted single-rooted mandibular premolars were prepared to size 40, .04 taper and randomly divided into two experimental groups (n = 36) depending on the root filling material. Root canals were filled with gutta-percha and GuttaFlow Bioseal (GB, group 1) or BioRoot RCS (BR, group 2), scanned using a micro-CT scanner and stored in phosphate-buffered saline for 4 months. Removal of root filling was performed with rotary instruments, and specimens were randomly allocated to one of the subgroups for supplementary irrigant agitation (n = 12): subgroup A, syringe irrigation (control); subgroup B, Tornado Brush (M.I.B, Suresnes, France) and subgroup C, ultrasonically activated irrigation. Specimens were re-scanned with micro-CT to calculate the volume of remnant root filling material. Data were analysed statistically by two-way ANOVA and post hoc Tukey's tests (P = 0.05). RESULTS: Specimens filled with GuttaFlow Bioseal were associated with a significantly smaller volume of root filling remnants compared with BioRoot RCS (P < 0.05). There was no significant difference between the supplementary irrigant agitation subgroups in the removal of GB (P > 0.05). In group 2 (BioRoot RCS), subgroups B (Tornado Brush) and C (ultrasonically activated irrigation) were associated with a significantly smaller volume of root filling remnants compared with subgroup A (syringe irrigation) (P < 0.05). There was no significant difference between subgroups B and C (P > 0.05). CONCLUSIONS: Significantly smaller volumes of root filling remnants of GuttaFlow Bioseal, than BioRoot RCS, were present after their removal with rotary instruments and irrigation. Supplementary irrigant agitation techniques were associated with smaller volumes of remnants during the removal of BioRoot RCS but not that of GuttaFlow Bioseal.

Influence of continuous rotation or reciprocation of Optimum Torque Reverse motion on cyclic fatigue resistance of nickel-titanium rotary instruments.

AIM: To evaluate the resistance to cyclic fatigue of ProTaper Next (PTN; Dentsply Sirona, Ballaigues, Switzerland), Revo-S (Micro-Mega, Besançon, France), Mtwo (Sweden & Martina, Padova, Italy), Twisted Files (TF, SybronEndo, Orange, CA, USA) and EndoWave (J Morita Corporation, Osaka, Japan) used in continuous rotation or in reciprocation of Optimum Torque Reverse motion (OTR). METHODOLOGY: A total of 120 nickel-titanium files were tested. Twenty-four instruments for each brand were divided into two groups (n = 12) on the basis of the motion tested: continuous rotation (Group 1) or reciprocation of OTR motion (Group 2). Resistance to cyclic fatigue was determined by recording time to fracture (TtF) in a stainless steel artificial canal with a 60° angle of curvature and 5 mm radius of curvature. The TtF data were analysed by using two-way analysis of variance (anova) and Bonferroni's post hoc tests at 0.05. RESULTS: Mtwo and TF had significantly higher TtF when compared with all other instruments, both in continuous rotation and in reciprocation of OTR motion (P < 0.0001 and P < 0.05, respectively). No difference was observed between Mtwo and TF (P > 0.05), in both motions. PTN was associated with higher cyclic fatigue resistance than Revo-S and EndoWave, both in continuous rotation and in reciprocation of OTR motions (P < 0.0001). No difference was observed between Revo-S and EndoWave, in both motions (P > 0.05). Reciprocating OTR motion improved TtF of all instruments (P < 0.0001). CONCLUSIONS: Reciprocation of OTR motion improved significantly cyclic fatigue resistance of all instruments tested compared with continuous rotation. Mtwo and TF had significantly higher cyclic fatigue than the other instruments, in both continuous rotation and reciprocation of OTR motion.

Cyclic fatigue resistance of two nickel-titanium rotary instruments in interrupted rotation.

AIM: To investigate the influence of interrupted rotation on cyclic fatigue of two nickel-titanium rotary instruments. METHODOLOGY: Cyclic fatigue of 300 new ProTaper Next size X1; X2 and Mtwo size 10, .04 taper; size 15, .05 taper; size 20, .06 taper and size 25, .06 taper instruments was tested in continuous or interrupted rotation. Fifty files of the same brand and size were randomly assigned to five groups (n = 10). Group 1 instruments were tested in continuous rotation; groups 2 and 3 in paused rotation for 1 s every 10 or 20 s, respectively; groups 4 and 5 in interrupted rotation for 5 s every 10 or 20 s, respectively. Cyclic fatigue was expressed in time to fracture (TtF) in an artificial canal with 60° angle and 5 mm radius of curvature. The fracture surface was examined with a scanning electron microscope (SEM). Data were evaluated by two-way analysis of variance. RESULTS: Cyclic fatigue of groups 2 and 4 of ProTaper Next X2 and Mtwo size 25, .06 taper was significantly lower than that of group 1 of the same instruments (P < 0.01). ProTaper Next X2 had significantly reduced cyclic fatigue in groups 3 and 5 (P < 0.05). No differences were found by interrupting the rotation for 1 or 5 s in all instruments (P > 0.05). Fatigue of other instruments was not affected by interrupted rotation (P > 0.05). CONCLUSIONS: Interrupted rotation reduced cyclic fatigue resistance of ProTaper Next X2 and Mtwo size 25, .06 taper, especially when a higher number of interruptions was performed.

Shaping ability of two nickel-titanium instruments activated by continuous rotation or adaptive motion: a micro-computed tomography study.

OBJECTIVES: The objective of the study was to evaluate the shaping ability of curved root canals using Twisted File Adaptive (TFA) files (SybronEndo, Orange, CA) and Mtwo (Sweden & Martina, Padova, Italy) activated by continuous rotation or adaptive motion. MATERIALS AND METHODS: Thirty-two mandibular molars with two separate mesial canals and severe angles of curvature were selected. Each canal was randomly assigned to one of the four experimental groups (n = 16): TFA and Mtwo files used in continuous rotation (groups 1 and 3) or in adaptive motion (groups 2 and 4). Root canals before and after preparation were assessed by micro-computed tomography. Volume, surface area, canal transportation, and centering ability were recorded and analyzed using two-way analyses of variance. RESULTS: Volume and surface area increased less with TFA files in continuous rotation than in other groups (P < 0.001 and P < 0.01, respectively, for each comparison) that were not different (P > 0.05). TFA files had significantly less transportation and higher centering ability than Mtwo both in continuous and adaptive motion (P < 0.0001). Centering ratio, but not canal transportation, was improved by adaptive motion compared with continuous rotation for both instruments (P < 0.01). However, no differences were found in canal transportation and centering ability in the apical third for both instruments and motions (P > 0.05). CONCLUSIONS: No difference between the devices and kinematics was found in the apical third; TFA performed significantly better in the middle and coronal parts of the root canal. CLINICAL RELEVANCE: The use of NiTi files made by heat-treated alloy and/or adaptive motion could improve the qualities of root canal shaping rather than the use of conventional NiTi instruments and/or continuous rotation in the coronal and middle thirds of the root canals, but not in the apical one. Moreover, these findings encourage the use of adaptive motion with conventional NiTi files to improve centering ability without affecting other preparation qualities of root canals.

Influence of cyclic torsional preloading on cyclic fatigue resistance of nickel - titanium instruments.

AIM: To evaluate the effect of different torsional preloads on cyclic fatigue resistance of endodontic rotary instruments constructed from conventional nickel-titanium (NiTi), M-Wire or CM-Wire. METHODOLOGY: Eighty new size 25, 0.06 taper Mtwo instruments (Sweden & Martina), size 25, 0.06 taper HyFlex CM (Coltene/Whaledent, Inc) and X2 ProTaper Next (Dentsply Maillefer) were used. The Torque and distortion angles at failure of new instruments (n = 10) were measured, and 0% (n = 10), 25%, 50% and 75% (n = 20) of the mean ultimate torsional strength as preloading condition were applied according to ISO 3630-1 for each brand. The twenty files tested for every extent of preload were subjected to 20 or 40 torsional cycles (n = 10). After torsional preloading, the number of cycles to failure was evaluated in a simulated canal with 60° angle of curvature and 5 mm of radius of curvature. Data were analysed using two-way analysis of variance. The fracture surface of each fragment was examined with a scanning electron microscope (SEM). Data were analysed by two-way analyses of variance. RESULTS: Preload repetitions did not influence the cyclic fatigue of the three brands; however, the 25%, 50% and 75% torsional preloading significantly reduced the fatigue resistance of all instruments tested (P < 0.01, P < 0.001 and P < 0.0001, respectively) except for the HyFlex CM preloaded with 25% of the maximum torsional strength (P > 0.05). CONCLUSIONS: Torsional preloads reduced the cyclic fatigue resistance of conventional and treated (M-wire and CM-wire) NiTi rotary instruments except for size 25, 0.06 taper HyFlex CM instruments with a 25% of torsional preloading.

Influence of rotational speed on the cyclic fatigue of Mtwo instruments.

AIM: To evaluate the effect of rotational speed on cyclic fatigue of Mtwo nickel-titanium files. METHODOLOGY: A total of 120 new Mtwo rotary instruments sizes 10, 0.04 taper; 15, 0.05 taper; 20, 0.05 taper; and 25, 0.06 taper were randomly divided into three groups on the basis of the rotational speed used to shape nine standardized simulated canals: group A = 350 rpm; group B = 250 rpm; group C = 150 rpm. Each group consisted of 40 instruments, 10 for every size. The average preparation time (in seconds) and the average correlated numbers of cycles to instrument (NCI) the nine standardized canals were recorded for each file. The resistance to cyclic fatigue was determined by counting numbers of cycles to failure (NCF) with a rotational speed of 300 rpm in a 60° curve with a 5-mm radius. Data were analysed by two-way anova. RESULTS: Preparation time was significantly longer at 150 rpm than at 250 or 350 rpm. The average number of cycles needed for each file to instrument nine standardized canals was significantly higher at 350 and 250 rpm, than at 150 rpm. There were no significant differences in the NCF (P > 0.05) between A, B and C groups for instruments of the same size. CONCLUSIONS: Speed did not affect the cyclic fatigue of Mtwo instruments with the same size and taper. Preparation time was shorter at 350 or 250 rpm rather than at 150 rpm. However, there was no significant difference between 350 and 250 rpm rotational speed, neither in the preparation time of simulated canals nor in the resistance to fatigue fracture.

Cyclic fatigue resistance of two reciprocating nickel-titanium instruments after immersion in sodium hypochlorite.

AIM: To assess resistance to cyclic fatigue of reciprocating nickel-titanium ( NiTi ) files (Reciproc and WaveOne) after immersion in NaOCl solution over several time periods. METHODOLOGY: A total of 90 new Reciproc R25 and WaveOne Primary were tested. The 45 files of the same brand were randomly assigned to three groups (n = 15) and submitted to the following immersion protocol in 5% NaOCl at 37 °C for 16 mm: no immersion (control), 1 or 5 min dynamically. The dynamic immersion and the following cyclic fatigue tests were performed using the appropriate preset reciprocation modes ('RECIPROC ALL' or 'WAVEONE ALL') in a specially designed endodontic motor. Resistance to cyclic fatigue was determined by recording time to fracture (TtF) in a stainless steel artificial canal with a 60° angle of curvature and 5 mm radius of curvature. The artificial canal was manufactured reproducing the instrument's size and taper. Data were analysed by 2-way analyses of variance. RESULTS: Resistance to cyclic fatigue of the same NiTi file was not significantly affected by immersion in NaOCl . Reciproc R25 was associated with a higher cyclic fatigue resistance in all groups compared to WaveOne Primary (P < 0.0001). CONCLUSIONS: Reciprocating dynamic immersion in NaOCl for 1 or 5 min did not reduce the cyclic fatigue resistance of NiTi files significantly. However, the type of reciprocating instrument influenced cyclic fatigue resistance with Reciproc R25 being more resistant than WaveOne Primary.

Decontamination efficacy of photon-initiated photoacoustic streaming (PIPS) of irrigants using low-energy laser settings: an ex vivo study.

AIM: To assess ex vivo, the antibacterial effectiveness of photon-initiated photoacoustic streaming (PIPS) of irrigants using an Er:YAG laser equipped with a newly designed, stripped and tapered tip in extracted teeth with infected root canals. METHODOLOGY: One hundred and forty-eight single-rooted extracted teeth were prepared to a size 25, 0.06 taper. The specimens were sterilized, and all teeth except ten (negative control group) were inoculated with Enterococcus faecalis and incubated in a CO(2) chamber at 37 °C for 15 days in Eppendorf tubes filled with trypticase soy broth medium changed every 2 days. Infected teeth were then randomly divided into four test groups (n = 32 for each): pulsed erbium/YAG laser at nonablative settings for 30 s with sterile bi-distilled water (Group A) or 5% sodium hypochlorite (NaOCl) (Group B); without laser-activated sterile bi-distilled water irrigation for 30 s (Group C) or 5% NaOCl irrigation for 30 s (Group D); the positive control group received no treatment in infected teeth (n = 10). Colony-forming units (CFUs) were counted from bacteriologic samples taken before (S1) and after treatment (S2). Data were analysed by Kruskal-Wallis and post hoc Dunn's multiple comparison tests. RESULTS: CFU counts were significantly lower in 5% NaOCl groups with or without laser activation than in sterile bi-distilled water without laser activation group (P < 0.001). Moreover, there was a significant difference between bi-distilled water groups with or without laser activation (P < 0.001). Sodium hypochlorite with laser activation group had the greatest CFU reduction, which was significantly greater than that evident in bi-distilled water groups with or without laser activation (P < 0.001). There were no significant differences between 5% NaOCl groups with or without laser activation (P > 0.05). None of the four groups generated negative samples predictably. CONCLUSIONS: Under the conditions of this ex vivo study, there were no significant differences in bacterial reduction between the laser and NaOCl or NaOCl alone groups. [Correction added after online publication, 18th April 2012: The following statement has been deleted: 'Thus, the use of a laser did not improve microbial killing over and above use of NaOCI alone.'].

Neuropathic pain in temporomandibular joint disorders: case-control analysis by MR imaging.

BACKGROUND AND PURPOSE: Temporomandibular joint disorders (TMJ-D) may be associated with the onset of neuropathic pain. The purpose of this study was to prospectively assess if, at the open-mouth position, the distance between the temporomandibular joint (TMJ) disk and the mandibular nerve is shorter in patients with TMJ-D and neuropathic pain vs patients with TMJ-D without neuropathic pain or in healthy people. MATERIALS AND METHODS: After ethical committee approval, we evaluated by MR imaging 16 TMJs with TMJ-D and neuropathic pain, 16 TMJs with TMJ-D without neuropathic pain, and 16 TMJs of healthy volunteers. All of the subjects were informed about the study procedure. We evaluated the distance between the TMJ disk and the mandibular nerve at the oval foramen level. Furthermore, the presence within the TMJs of internal derangement, osteoarthrosis, joint effusion, and bone marrow edema was evaluated. RESULTS: At the maximal open-mouth position, the distance between the TMJ disk and the mandibular nerve is shorter in patients with TMJ-D and neuropathic pain than in patients with TMJ-D without neuropathic pain or in healthy volunteers (P < .05). The imaging findings of TMJ internal derangement, effusion, osteoarthrosis, and bone marrow edema were present both in patients with TMJ-D without neuropathic pain and in patients with TMJ-D and neuropathic pain. CONCLUSIONS: We suggest that a closer proximity between the TMJ disk and the mandibular nerve could be one of the causes of the onset of neuropathic pain in patients with TMJ-D and neuropathic pain.

Morphometric evaluation of the temporomandibular joint and the masticatory spaces: the role of high-definition MRI.

AIM: The aim of this work was to describe the anatomy of the temporomandibular joint (TMJ), the masticator spaces and their possible variance by means of magnetic resonance imaging MRI. METHODS: We evaluated one TMJ in each of 28 volunteers (14 males and 14 females) without temporomandibular disorders. The TMJ with mouth closed was evaluated on axial, coronal and sagittal planes obtained with a 1.5 Tesla magnetic resonance scanner. MRI scans of the anatomic patterns of the temporomandibular region were analyzed and compared with the classical anatomy notions reported in the literature. Morphometric evaluation of the temporomandibular region and the medial and lateral pterygoid muscles was carried out. RESULTS: MRI anatomy of the TMJ, the masticator spaces and their possible variance were accurately described. In addition, morphometric evaluation of the TMJ and the masticator spaces was performed. Statistical analysis of the measurements showed that the length of the structures related to the glenoid fossa were usually longer in the female than in the males, whereas the condyle and masticator muscles were usually greater in the males than in the females. T-tests showed no significant differences (P > 0.05) between the measurements of the right and left TMJ. CONCLUSIONS: In preoperative maxillofacial surgery assessment, MRI is a useful tool to reduce operating time, avert surgical complications and improve patient outcome.