Gustavo De-Deus

Lack of correlation between sealer penetration into dentinal tubules and sealability in nonbonded root fillings

AIM To determine the correlation between leakage and sealer penetration into dentinal tubule. METHODOLOGY The root canal of 60 mandibular central incisor teeth were prepared and filled under standardized conditions. Teeth were placed into a device to assess glucose penetration using 15 psi pressure application. After 1 h, glucose concentrations in the lower chamber were measured using an enzymatic reaction. Each specimen was then sectioned horizontally at 3, 6 and 8 mm from the apex, and a standard metallographic preparation was performed. The coronally facing surface of each slice was examined in a high-resolution stereomicroscope and under Confocal Laser Scanning Microscope. For each slice, the external outline of the root canal, the internal circumference of the root canal walls and the areas along the canal walls where the sealer had penetrated into the dentinal tubules (sealer tags) were outlined and measured. Afterwards, the percentage of the sealer penetration in each section was calculated. The Spearman correlation test was used to verify the correlation between the variables studied (glucose leakage and sealer penetration into dentinal tubules). RESULTS The means and standard deviations of glucose leakage were 0.744 g L(-1) (±0.5), and the percentage of the dentinal tubule sealer penetration varied between teeth from 5.6% to 42.21%, with an average of 13.7 ± 17.2%. The Spearman correlation test revealed no significant correlation between the two factors analysed (P = 0.082). The r(2) value was equal to 0.12. CONCLUSIONS There was no significant correlation between sealability sealer penetration into dentinal tubules. The lack of correlation reported is of relevance as sealer penetration into dentinal tubules has been used as an advantageous property during the launch of new root filling materials and techniques.

Cytocompatibility of the ready-to-use bioceramic putty repair cement iRoot BP Plus with primary human osteoblasts

AIM To verify the in vitro cytocompatibility of iRoot BP Plus (iRoot) and to compare it with White ProRoot MTA (MTA). METHODOLOGY Thirty-six human maxillary incisor root canals were prepared using a step-back flaring technique. The apical 3 mm was resected perpendicular to the long axis at the roots, and root-end cavities were prepared with the aid of an ultrasonic device plus a diamond retrotip with continuous irrigation using water, producing standardized preparations. After that, the root-end cavities were filled with iRoot or MTA, and each root was exposed to cell culture media for 24 or 48 h. Human osteoblast cells were exposed to the extracts thus obtained, and a multiparametric cell viability assay was performed, evaluating mitochondrial activity, membrane integrity and cell density. The results were analysed by one-way analysis of variance, complemented with the Duncan post-test (P < 0.05). RESULTS Cells exposed to MTA revealed a cytocompatibility pattern similar to the untreated cells (negative control), at both experimental times (P > 0.05). iRoot, however, promoted a significantly poorer viability than MTA and the control, after 48 h of exposure (P < 0.001). Nevertheless, iRoot did not induce critical cytotoxic effects because cell viability remained higher than 70% of the control group in most tests performed. CONCLUSION iRoot and MTA were biocompatible and did not induce critical cytotoxic effects.

Blue Thermomechanical Treatment Optimizes Fatigue Resistance and Flexibility of the Reciproc Files

Introduction: The aim of the present study was to evaluate the influence of Blue thermal treatment on the bending resistance and cyclic fatigue of conventional M‐Wire Reciproc files (VDW, Munich, Germany). The roughness pattern and the microhardness of the files were also assessed. Methods: Flexibility of standard Reciproc R25 files and the corresponding Blue prototypes was determined by 45° bending tests according to the ISO 3630‐1 specification. Instruments were also subjected to cyclic fatigue resistance, measuring the time to fracture in an artificial stainless steel canal with a 60° angle and a 5‐mm radius of curvature. The fracture surface of all fragments was examined with a scanning electron microscope. The roughness of the working parts was quantified by using a profilometer, and the microhardness test was performed using the Vickers hardness tester. Results were statistically analyzed using the Student t test with a level of significance set at P < .05. Results: Reciproc Blue instruments presented a significantly longer cyclic fatigue life and significantly lower bending resistance than the original Reciproc instrument (P < .05). Regarding the roughness pattern, there was no significant difference between Reciproc Blue and the original Reciproc instruments (P > .05), whereas Reciproc Blue revealed significantly lower microhardness than the original Reciproc instrument (P < .05). Conclusions: Reciproc Blue nickel‐titanium showed improved all‐around performance when compared with conventional M‐Wire superelastic nickel‐titanium, demonstrating improved flexibility and fatigue resistance, and reduced microhardness while maintaining similar characteristics of the surface. HighlightsSo far, Blue thermal treatment was not assessed regarding cyclic fatigue and other mechanical features.Reciproc Blue showed overall improved performances when compared with conventional Reciproc, demonstrating improved flexibility and fatigue resistance, and reduced microhardness while maintaining similar characteristics of the surface.

Dentine demineralization when subjected to EDTA with or without various wetting agents: a co-site digital optical microscopy study

AIM To analyse quantitatively the chelating ability of ethylenediaminetetraacetic acid (EDTA) and three common EDTA-based associations with wetting agents. METHODOLOGY Twelve maxillary human molars were selected, from which 3 mm thick discs were obtained from the cervical third of the root. Following the creation of standardized smear layer co-site microscopy image sequences of the dentine surface submitted to EDTA, EDTA plus 0.1% cetavlon (Sigma Chemical Co., St Louis, MO, USA), EDTA plus 1.25% sodium lauryl ether sulphate and SmearClear (Sybron Endo, Orange, CA, USA) were obtained after several cumulative demineralization times. Sixteen images were obtained of each dentine sample for each experimental time, at 1000 x magnification. An image processing and analysis sequence was used to measure the area of open tubules for each experimental time. Thus, it was possible to follow the demineralization process and quantitatively analyse the effect of the various substances. The Students t-test was used to assess differences between experimental groups. Results EDTA solution had the strongest effect at all experimental times whilst the association of EDTA with wetting agents showed a weaker chelating effect and this difference was statistically significant (P < 0.05). CONCLUSIONS (i) The EDTA solution had the strongest effect at all experimental times (P < 0.05); (ii) the association of EDTA with wetting agents did not improve the chelating power of the solution; (iii) co-site optical microscopy represents a powerful approach to compare directly, longitudinally and quantitatively the ability of the chelating solutions.

A new system for classifying root and root canal morphology.

Knowledge of root and root canal morphology is a prerequisite for effective nonsurgical and surgical endodontic treatments. The external and internal morphological features of roots are variable and complex, and several classifications have been proposed to define the various types of canal configurations that occur commonly. More recently, improvements in nondestructive digital image systems, such as cone-beam and micro-computed tomography, as well as the use of magnification in clinical practice, have increased the number of reports on complex root canal anatomy. Importantly, using these newer techniques, it has become apparent that it is not possible to classify many root canal configurations using the existing systems. The purpose of this article is to introduce a new classification system that can be adapted to categorize root and root canal configurations in an accurate, simple and reliable manner that can be used in research, clinical practice and training.

Exploiting the potential of free software to evaluate root canal biomechanical preparation outcomes through micro-CT images

AIM To propose an automated image processing routine based on free software to quantify root canal preparation outcomes in pairs of sound and instrumented roots after micro-CT scanning procedures. METHODOLOGY Seven mesial roots of human mandibular molars with different canal configuration systems were studied: (i) Vertuccis type 1, (ii) Vertuccis type 2, (iii) two individual canals, (iv) Vertuccis type 6, canals (v) with and (vi) without debris, and (vii) canal with visible pulp calcification. All teeth were instrumented with the BioRaCe system and scanned in a Skyscan 1173 micro-CT before and after canal preparation. After reconstruction, the instrumented stack of images (IS) was registered against the preoperative sound stack of images (SS). Image processing included contrast equalization and noise filtering. Sound canal volumes were obtained by a minimum threshold. For the IS, a fixed conservative threshold was chosen as the best compromise between instrumented canal and dentine whilst avoiding debris, resulting in instrumented canal plus empty spaces. Arithmetic and logical operations between sound and instrumented stacks were used to identify debris. Noninstrumented dentine was calculated using a minimum threshold in the IS and subtracting from the SS and total debris. Removed dentine volume was obtained by subtracting SS from IS. RESULTS Quantitative data on total debris present in the root canal space after instrumentation, noninstrumented areas and removed dentine volume were obtained for each test case, as well as three-dimensional volume renderings. CONCLUSION After standardization of acquisition, reconstruction and image processing micro-CT images, a quantitative approach for calculation of root canal biomechanical outcomes was achieved using free software.

Cyclic and Torsional Fatigue Resistance of XP-endo Shaper and TRUShape Instruments

Introduction: The purpose of this study was to evaluate the cyclic and torsional fatigue resistance of the XP‐endo Shaper (FKG Dentaire, La Chaux‐de‐Fonds, Switzerland) and TRUShape (Dentsply Tulsa Dental Specialties, Tulsa, OK) instruments. Methods: Twenty XP‐endo Shaper (30/0.01) instruments and 20 TRUShape (30/0.06v) instruments were used. Cyclic fatigue resistance was tested by measuring the number of cycles and time to fracture in an artificial stainless steel canal with a 60° angle and a 5‐mm radius of curvature (n = 10). The torque and angle of rotation at failure of new instruments (n = 10) were measured according to ISO 3630‐1. The fracture surface of all fragments was examined with a scanning electron microscope. Results were statistically analyzed using the Student t test at a significance level of P < .05. Results: The XP‐endo Shaper instruments showed a significantly longer number of cycles to fracture and time to failure in seconds than the TRUShape instruments (P < .05). The XP‐endo Shaper also presented a lower maximum torque load (P < .05) but a significantly higher angular rotation to fracture than TRUShape (P < .05). Conclusions: The XP‐endo Shaper instruments showed a higher cyclic fatigue resistance and angle of rotation to fracture but lower torque to failure than TRUShape instruments. HighlightsCyclic and torsional fatigue resistance of the newly launched XP‐endo Shaper and TRUShape instruments was assessed.The XP‐endo Shaper instruments showed a significantly longer cyclic fatigue life than TRUShape instruments.The XP‐endo Shaper presented a lower maximum torque load but a higher angular rotation to fracture than TRUShape.

Environmental Temperature Drastically Affects Flexural Fatigue Resistance of Nickel-titanium Rotary Files

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. HighlightsThe effect of a reduced environmental temperature (−20°C ± 2°C) on flexural fatigue resistance of NiTi instruments was tested and compared with room temperature (20°C ± 2°C).Fatigue resistance tested at a low environmental temperature was significantly higher for all the groups tested.No difference was observed between fragment length among the groups with the geometry of the curve maintained constant for all instruments tested.Environmental temperature is an important variable in determining the fatigue resistance of nickel‐titanium rotary files.

On the Causality Between Dentinal Defects and Root Canal Preparation: A Micro-CT Assessment

This study aimed to evaluate the cause-effect relationship between canal preparation with ProTaper Universal (PTU) system and dentinal defects formation using micro-computed tomography (micro-CT) analysis. Forty mesial canals of mandibular molars with a type II Vertuccis canal configuration were scanned at an isotropic resolution of 14.16 µm. The sample was assigned to an experimental (n = 30) and a control (n = 10) groups, and the mesial canals were prepared with PTU system up to F2 instrument. The specimens from the experimental group were scanned and the cross-section images of the mesial roots, before and after preparation, were screened to identify the presence of dentinal defects. In the control group, the specimens were sectioned perpendicularly to the long axis of the root into 1-mm-thick slices (n = 80) and examined under optical microscope. Once a dentinal defect was detected, the slice was scanned through micro-CT. In the experimental group, dentinal micro-cracks were observed in 4,828 slices (24.04%). In all cross-section images, dentinal defects identified in the postoperative images were already present in the corresponding preoperative image. In the control group, 13 out of 80 slices (16.25%) had at least one dentinal defect visualized under stereomicroscopy, which was identified after a further micro-CT scanning. Micro-CT showed reliability as similar as optical microscopy in detecting dentinal defects, adding the possibility of tracking the dentinal tissue, before and after canal preparation, and providing a clear visualization of micro-cracks. Root canal preparation with PTU system did not induce the formation of new dentinal defects.

Short‐Term Response of Human Osteoblast‐Like Cells on Titanium Surfaces With Micro‐ and Nano‐Sized Features

Since the way that human bone cells behave on contact with different surfaces topographies seems to be crucial to osseointegration, the aim of the present study is to evaluate the participation of some micro- and nanosized features of Ti surfaces in the short-term response of primary human osteoblast-like cells (HOC). Surfaces were prepared as ground (G-Ti), hydrofluoric acid etched (HF-Ti), and sandblasted/HF-etched (SLA-Ti), and analyzed using both three-dimensional (3D) profilometer and atomic force microscope (AFM). Cell morphology was assessed using scanning electron microscopy (SEM) after 4 and 24 h in culture. Cell viability, adhesion, and spreading were also evaluated 4 and 24 h after seeding over each surface. Data were compared by analysis of variance (ANOVA) complemented by Duncan test. Cell morphology, cell counting, and membrane integrity (Neutral Red, NR) were not affected by surface treatment at any time. However, HF-Ti presented the smallest surface area and did not increase tetrazolium hydroxide (XTT) reduction from 4 to 24 h. On the other hand, a higher level of spreading was only found on the rougher and isotropic SLA-Ti at 4 h. In conclusion, although all evaluated Ti surfaces allowed HOC short-term adhesion, the finer topography introduced by HF as single treatment did not favor HOC mitochondrial activity and spreading. The rougher and more complex SLA surface seems to provide a better substrate for HOC short-term response.