Giuseppe Cantatore

Alternating versus Continuous Rotation: A Comparative Study of the Effect on Instrument Life

INTRODUCTION Rotary nickel-titanium instruments have multiple advantages but with the risk of more fractures because of flexure or torsion. Alternating rotation appears to be an alternative to continuous rotary movement. The objective of this study was to determine the influence of the type of instrument rotation on the frequency of fractures or deformation. METHODS Instrumentation was performed on 120 molar root canals with an angle of curvature greater than 30 degrees using alternating rotation (group A: 60 degrees clockwise, 45 degrees counterclockwise) and continuous rotation (group B). RESULTS The results indicate that instruments used with alternating rotation have a higher mean number of uses (13.0) compared with the continuous rotation group (10.05); this difference was statistically significant (p < 0.05). CONCLUSIONS The ProTaper shaping instruments (S1 and S2) are those that achieved the greatest difference in use with alternating rotation, with S2 being the most resistant to fracture or deformation with the two types of movement used.

Canal Shaping with WaveOne Primary Reciprocating Files and ProTaper System: A Comparative Study

INTRODUCTION This study compared the canal curvature and axis modification after instrumentation with WaveOne Primary reciprocating files (Dentsply Maillefer, Ballaigues, Switzerland) and nickel-titanium (NiTi) rotary ProTaper (Dentsply Maillefer). METHODS Thirty ISO 15, 0.02 taper, Endo Training Blocks (Dentsply Maillefer) were used. In all specimens, the glide path was achieved with PathFile 1, 2, and 3 (Dentsply Maillefer) at the working length (WL). Specimens were then assigned to 1 of 2 groups for shaping: specimens in group 1 were shaped with ProTaper S1-S2-F1-F2 at the WL and specimens in group 2 were shaped with WaveOne Primary reciprocating files at the WL. Pre- and postinstrumentation digital images were superimposed and processed with Matlab r2010b (The MathWorks Inc, Natick, MA) software to analyze the curvature-radius ratio (CRr) and the relative axis error (rAe), representing canal curvature modification. Data were analyzed with one-way balanced analyses of variance at 2 levels (P < .05). RESULTS The instrument factor was extremely significant for both the CRr parameter (F(1) = 9.59, P = .004) and the rAe parameter (F(1) = 13.55, P = .001). CONCLUSIONS Canal modifications are reduced when the new WaveOne NiTi single-file system is used.

Use of Nickel-Titanium Rotary PathFile to Create the Glide Path: Comparison With Manual Preflaring in Simulated Root Canals

The study compared changes to canal curvature and incidence of canal aberrations after preflaring with hand K-files or with nickel-titanium rotary PathFile in S-shape Endo Training Blocks. The influence of the operators expertise was also investigated. One hundred training blocks were colored with ink, and preinstrumentation images were acquired digitally. Preflaring was performed by an endodontist with PathFile (group 1) and hand stainless steel K-files #10-15-20 (group 2); an inexpert clinician performed preflaring with PathFile (group 3) and hand stainless steel K-files (group 4). Preinstrumentation and postinstrumentation images were superimposed to evaluate the outcomes investigated. Differences in canal curvature modification and incidence of canal aberration were analyzed with the Kruskall-Wallis plus post hoc tests and by the Monte Carlo method, respectively, (P < .05). The PathFile groups demonstrated significantly less modification of curvature (P < .001) and fewer canal aberrations (P < .001). No expertise-related difference was found within instrument groups (P > .05), whereas the inexpert clinician produced more conservative shaping with Pathfiles than did the expert with manual preflaring (P < .01).

Root Canal Anatomy Preservation of WaveOne Reciprocating Files with or without Glide Path

INTRODUCTION This study evaluated the influence of glide path on canal curvature and axis modification after instrumentation with WaveOne Primary reciprocating files. METHODS Thirty ISO 15, 0.02 taper Endo Training Blocks were used. In group 1, glide path was created with PathFile 1, 2, and 3 at working length, whereas in group 2, glide path was not performed. In both groups, canals were shaped with WaveOne Primary reciprocating files at working length. Preinstrumentation and postinstrumentation digital images were superimposed and processed with Matlab r2010b software to analyze the curvature radius ratio (CRr) and the relative axis error (rAe), representing canal curvature modification. Data were analyzed with 1-way balanced analyses of variance at 2 levels (P < .05). RESULTS Glide path was found to be extremely significant for both CRr parameter (F = 9.59; df = 1; P = .004) and rAe parameter (F = 13.55; df = 1; P = .001). CONCLUSIONS Canal modifications seem to be significantly reduced when previous glide path is performed by using the new WaveOne nickel-titanium single-file system.

Shaping Ability of Four Nickel-Titanium Rotary Instruments in Simulated S-Shaped Canals

INTRODUCTION The purpose of this study was to compare the shaping ability of ProTaper, Mtwo, BioRaCe, and BioRaCe + S-Apex instruments in simulated canals with an S-shaped curvature. METHODS Canal transportation and aberrations were assessed by comparing the preinstrumentation and postinstrumentation images under a stereomicroscope. Analysis of variance and post hoc Student-Newman-Keuls test were used for statistical analysis. RESULTS ProTaper instruments caused more pronounced canal transportation in the apical curvature (P < .01) than all other instruments. The use of ProTaper, Mtwo, and BioRaCe instruments resulted in more canal aberrations compared with BioRaCe + S-Apex (P < .05). CONCLUSIONS NiTi systems including less tapered and more flexible instruments like S-Apex seem to be favorable when preparing S-shaped canals.

Computed micro-tomographic evaluation of glide path with nickel-titanium rotary pathfile in maxillary first molars curved canals

INTRODUCTION X-ray computed micro-tomography scanning allows high-resolution 3-dimensional imaging of small objects. In this study, micro-CT scanning was used to compare the ability of manual and mechanical glide path to maintain the original root canal anatomy. METHODS Eight extracted upper first permanent molars were scanned at the TOMOLAB station at ELETTRA Synchrotron Light Laboratory in Trieste, Italy, with a microfocus cone-beam geometry system. A total of 2,400 projections on 360° have been acquired at 100 kV and 80 μA, with a focal spot size of 8 μm. Buccal root canals of each specimen (n = 16) were randomly assigned to PathFile (P) or stainless-steel K-file (K) to perform glide path at the full working length. Specimens were then microscanned at the apical level (A) and at the point of the maximum curvature level (C) for post-treatment analyses. Curvatures of root canals were classified as moderate (≤35°) or severe (≥40°). The ratio of diameter ratios (RDRs) and the ratio of cross-sectional areas (RAs) were assessed. For each level of analysis (A and C), 2 balanced 2-way factorial analyses of variance (P < .05) were performed to evaluate the significance of the instrument factor and of canal curvature factor as well as the interactions of the factors both with RDRs and RAs. RESULTS Specimens in the K group had a mean curvature of 35.4° ± 11.5°; those in the P group had a curvature of 38° ± 9.9°. The instrument factor (P and K) was extremely significant (P < .001) for both the RDR and RA parameters, regardless of the point of analysis. CONCLUSIONS Micro-CT scanning confirmed that NiTi rotary PathFile instruments preserve the original canal anatomy and cause less canal aberrations.

Postoperative Pain after Manual and Mechanical Glide Path: A Randomized Clinical Trial

INTRODUCTION This prospective randomized clinical trial evaluated the incidence of postoperative pain after glide path performed with PathFile (PF) (Dentsply Maillefer, Ballaigues, Switzerland) versus stainless-steel K-file (KF). METHODS In 149 subjects, the mechanical glide path was performed with nickel-titanium (NiTi) rotary PF; in 146 subjects, the manual glide path was performed with stainless-steel KFs. Postoperative pain, analgesics consumption, and the number of days to complete pain resolution were evaluated in the following 7 days. An analysis of variance model for repeated measures was used to compare the variation of pain-scale values (P < .05). The Students t test for continuous variables normally distributed, the nonparametric Mann-Whitney U test for the nonnormally distributed variables, and the chi-square test for dichotomous variables were used (P < .05). Despite homogeneous baseline conditions at diagnosis, tooth type, pain prevalence, and scores, the postoperative pain prevalence curves in PF group evidenced a more favorable trend in terms of time to pain resolution compared with the KF group (P = .004). The difference was also evident in the model adjusted for analgesics consumption in both groups (P = .012). The mean analgesics intake per subject was significantly higher in the KF group (3.7 ± 2.2) compared with the PF group (2 ± 1.7) (P < .001). Mean pain stop values were also significantly higher in the KF group (2.7) compared with the PF group (1.7) (P = .001). CONCLUSIONS The glide path with NiTi Rotary PF leads to less postoperative pain and faster symptom resolution.

In vitro comparison of passive and continuous ultrasonic irrigation in simulated lateral canals of extracted teeth

INTRODUCTION Complete endodontic system disinfection requires the removal of vital and necrotic pulp tissue, microorganisms, and toxins. The purpose of this study was to compare the effects of 2 ultrasonic irrigation techniques on the penetration of sodium hypochlorite into the main canal and simulated lateral canals of extracted teeth. METHODS Two simulated lateral canals each were created 2, 4, and 6 mm from the working length in 60 single-rooted teeth (6 canals/tooth, n = 360). To resemble the clinical situation, a closed system was created in each tooth. The teeth were randomly assigned to 3 experimental irrigation groups: group 1 (n = 20), positive pressure irrigation (PPI); group 2 (n = 20), passive ultrasonic irrigation (PUI); and group 3 (n = 20), continuous ultrasonic irrigation (CUI). Samples were evaluated by direct observation of still images recorded under a dental operating microscope. To examine irrigating solution penetration, 20% Chinese ink (Sanford Rotring GmbH, Hamburg, Germany) was added to a 5% sodium hypochlorite solution and delivered into the root canals. RESULTS The results showed a significantly higher (P < .05) penetration of irrigant into the lateral canals in the CUI group. PUI and CUI did not differ significantly in solution penetration into the apical thirds of the main canals. The PPI group showed a significantly lower penetration of sodium hypochlorite into the main and lateral canals compared with the CUI and PUI groups. CONCLUSIONS CUI as a final rinse significantly increased the penetration of irrigating solution into simulated lateral canals.

Improvement of the fatigue resistance of NiTi endodontic files by surface and bulk modifications

AIM To assess the failure mechanism of rotary NiTi instruments by chemical, structural and morphological analyses to provide a rational explanation of the effects of surface and bulk treatments on their resistance to fatigue fracture. METHODOLOGY Thermal treatment (350-500 °C) was performed on electropolished (EP) and non-electropolished (Non-EP) NiTi endodontic instruments. Bulk and surface chemical composition and crystallographic structures were determined by energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) to evaluate the effects of thermal treatment and electropolishing on the NiTi alloy. Fatigue tests of all instruments were performed. Surface morphology before and after the tests, and fractured section were analysed using scanning electron microscopy to determine crack extensions. Results were analysed statistically using analysis of variance (anova) and post hoc Student-Newman-Keuls test. RESULTS Before thermal treatment, significant differences (P < 0.05) in fatigue resistance between EP and Non-EP instruments (the number of revolutions to failure, N(f) , was 385 and 160, respectively) were attributed to differences in the surface morphology of the instruments. SEM analysis of the fracture surfaces indicated that flexural fatigue fractures occurred in two steps: first by a slow growth of initial cracks and then rapid rupture of the remaining material. Thermal treatment did not affect the surface morphology but resulted in significant changes in the instrument bulk with the appearance of an R-phase and an improved fatigue resistance; indeed after treatment at 500 °C, N(f) increased up to 829 and 474 for EP and Non-EP instruments, respectively. CONCLUSIONS Both thermal treatment and electropolishing improved the resistance of NiTi rotary instruments against fatigue fracture.

Pitting Corrosion Resistance of Nickel–Titanium Rotary Instruments with Different Surface Treatments in Seventeen Percent Ethylenediaminetetraacetic Acid and Sodium Chloride Solutions

This study evaluated the pitting corrosion resistance of nickel-titanium (NiTi) rotary instruments with different surface treatments in 17% ethylenediaminetetraacetic acid (EDTA) and NaCl solutions. Electropolished RaCe instruments were allocated to group A, non-electropolished RaCe instruments to group B, and physical vapor deposition (PVD)-coated Alpha files to group C (10 instruments per group). Electrochemical measurements were carried out by using a potentiostat for galvanic current measurements. On the basis of electrochemical tests, no localized corrosion problems are to be expected in EDTA. In NaCl, pitting potential occurred at higher values for the electropolished and PVD instruments, indicating an increased corrosion resistance. There appears to be a risk of corrosion for NiTi instruments without surface treatments in contact with NaCl. NiTi files with PVD and electropolishing surface treatments showed an increase corrosion resistance.