Laila Gonzales Freire

A micro-computed tomography evaluation of long-oval canal preparation using reciprocating or rotary systems.

AIM To evaluate, using micro-computed tomography, the preparation of long-oval root canals using a single reciprocating system versus a multiple-file rotary system. METHODOLOGY Distal canals of thirty mandibular molars were selected and randomly assigned to one of two instrument groups (n = 15): Reciproc 40 (VDW, Munich, Germany) or BioRaCe system (FKG Dentaire, La Chaux-de-Fonds, Switzerland). The teeth were scanned before and after preparation of the canal by a SkyScan 1172 micro-computed tomography scanner at 11-μm resolution. Morphometric variations were measured by volume increases and by the remaining untreated canal surface area in the entire canal and as well as in each third of the canal. Data were compared using the Mann-Whitney test. RESULTS The Reciproc system left significantly more areas untouched (P < 0.001) in the cervical and middle thirds (18.14% and 21.82%) as compared to BioRaCe (8.14% and 11.35%). The Reciproc system had the greatest increase in volume of both the entire canal and the apical third (P < 0.5). CONCLUSIONS Neither technique was able to completely prepare the outline of long-oval canals. The Reciproc system removed more tooth structure. The BioRaCe left fewer untouched dentine walls in the more coronal thirds of the canal, whilst Reciproc left fewer in the apical third.

Microscopic computerized tomographic evaluation of root canal transportation prepared with twisted or ground nickel-titanium rotary instruments

OBJECTIVE The aim of this study was to evaluate, ex vivo, canal transportation and the centering ability of nickel-titanium rotary instruments manufactured by twisting and by traditional grinding, with the use of microscopic computerized tomography (μCT). STUDY DESIGN Fifteen mandibular molars were embedded in a rubber-based impression material and submitted to μCT before and after instrumentation. Images were reconstructed, and cross-sections corresponding to distances 1, 2, 3, 4, 5, 6, and 7 mm from the anatomic apex were selected for analysis. Statistical analysis was performed with Mann-Whitney test. RESULTS Canal transportation and centering ability results were similar for both instruments. Statistically significant differences (P < .05) were observed only at the 3 and 4 mm cross-sections, with lower levels of apical transportation and a better centering ratio associated with twisted instruments than with ground instruments. CONCLUSIONS Our findings showed that twisted and ground instruments behaved similarly, allowing the preparation of curved canals with little transportation, which occurred in both mesial and distal directions.

Influence of dentin on pH of 2% chlorhexidine gel and calcium hydroxide alone or in combination

The aims of endodontic treatment in cases of apical periodontitis are to reduce as much as possible the number of microorganisms inside the root canal system and to inactivate toxins produced by them. Most of the times, these objectives are not achieved solely by chemomechanical preparation, and intracanal dressing may be necessary. In these cases, calcium hydroxide is used as a root canal dressing due to its well-known and recognized antimicrobial activity. Chlorhexidine has a wide spectrum of antimicrobial activity and its association with calcium hydroxide has been recommended in an attempt to amplify antimicrobial effects of calcium hydroxide. It is also known that dentin exerts a buffering effect under wide pH variations, and may be responsible for decreasing the antimicrobial activity of drugs inside the root canal. The objectives of this study were to assess the pH of 2% chlorhexidine gel and calcium hydroxide alone or in combination, as well as the influence of dentin on the pH of these compounds. Dentin powder was obtained from bovine teeth and added as 1.8% to the volume of the medications. All substances were individually stored in plastic flasks, in triplicate. A pH meter was used at five different moments to assess pH in viscous medium: immediately after preparation and after 24 h, and 7, 14, and 21 days. Results were analyzed by paired Students t-test. Statistically significant differences were observed in the 2% chlorhexidine gel group alone or associated with calcium hydroxide and added of dentin powder (P < 0.05). Mean pH values indicated the influence of dentin powder because of a significant increase in pH. Calcium hydroxide with propylene glycol as the vehicle always showed high pH, demonstrating that this compound was not affected by the presence of dentin.

Assessing apical transportation in curved canals: comparison between cross-sections and micro-computed tomography

The aim of this study was to compare two methods of assessing apical transportation in curved canals after rotary instrumentation, namely, cross-sections and micro-computed tomography (µCT). Thirty mandibular molars were divided into two groups and prepared according to the requirements of each method. In G1 (cross-sections), teeth were embedded in resin blocks and sectioned at 2.0, 3.5, and 5.0 mm from the anatomic apex. Pre- and postoperative sections were photographed and analyzed. In G2 (µCT), teeth were embedded in a rubber-base impression material and scanned before and after instrumentation. Mesiobuccal canals were instrumented with the Twisted File (TF) system (SybronEndo, Orange, USA), and mesiolingual canals, with the EndoSequence (ES) system (Brasseler, Savannah, USA). Images were reconstructed, and sections corresponding to distances 2.0, 3.5, and 5.0 mm from the anatomic apex were selected for comparison. Data were analyzed using Mann-Whitneys test at a 5% significance level. The TF and ES instruments produced little deviation from the root canal center, with no statistical difference between them (P > 0.05). The canal transportation results were significantly lower (0.056 mm) in G2 than in G1 (0.089 mm) (p = 0.0012). The µCT method was superior to the cross-section method, especially in view of its ability to preserve specimens and provide results that are more closely related to clinical situations.

Presence of Voids after Continuous Wave of Condensation and Single-Cone Obturation in Mandibular Molars: A Micro-Computed Tomography Analysis

Introduction The objective of this study was to assess the presence of voids in mesial root canals of mandibular molar teeth obturated by using the single‐cone (SC) and continuous wave of condensation (CWC) obturation techniques, and results were analyzed by using micro–computed tomography. Methods Twenty‐four mandibular molars with fully developed roots and mesial root curvature ranging from 25° to 35° were instrumented by using Reciproc R25 files, and then they were obturated by using the SC and CWC techniques. Specimens were scanned before and after obturation for micro–computed tomography analysis (voxel size, 17.42 &mgr;m). After volumetric analysis and tridimensional reconstruction of the root canals, data were analyzed by using analysis of variance and the Tukey test. Results No significant differences were observed between the 2 techniques in terms of total percentage volume of voids: CWC = 3.91% ± 0.72%; SC = 6.52% ± 1.16% (P > .05). Only in the cervical third, CWC showed a significantly lower percentage of voids when compared with SC, namely 2.86% ± 0.94% vs 8.00% ± 1.86%, respectively (P < .05). Conclusions The percentage volume of voids was similar in the 2 groups and was influenced by the obturation technique only in the cervical third. HighlightsWe assessed the presence of voids in mesial root canals of mandibular molars after obturation.We compared the single‐cone and the continuous wave of condensation obturation techniques.Total percentage volume of voids was similar in the 2 groups.In the cervical third, CWC performed better.

Ions Release and pH of Calcium Hydroxide-, Chlorhexidine- and Bioactive Glass-Based Endodontic Medicaments

This study evaluated pH and release of calcium, sodium and phosphate ions from different medications in human dentin. Fifty premolars were prepared and randomly divided into groups: (CHX) - 2% chlorhexidine gel; (CHX + CH) - CHX + calcium hydroxide PA; (CH) - CH + propylene glycol 600; (NPBG) - experimental niobium phosphate bioactive glass + distilled water; (BG) - bioactive glass (Bio-Gran) + distilled water. The specimens were immersed in deionized water and the pH variations were measured. The quantification of ions in the solutions was made by inductively coupled plasma - atomic emission spectroscopy (ICP/AES) at 10 min, 24 h, 7, 14, 21 and 30 days. The results were analyzed by ANOVA and Tukey`s test, with a significance level of 5%. CH had the highest level of calcium ions release at 30 days, while CHX and BG released more sodium ions. BG, NPBG and CHX released a higher amount of phosphate ions. The pH of CH was significantly higher compared with the other groups. CH favored the greatest increase of pH and calcium ions release. The bioactive glasses released more sodium and phosphate ions and presented an alkaline pH immediately and after 30 days.

Photobiomodulation of mesenchymal stem cells encapsulated in an injectable rhBMP4-loaded hydrogel directs hard tissue bioengineering

Photobiomodulation (PBM) therapy displays relevant properties for tissue healing and regeneration, which may be of interest for the tissue engineering field. Here, we show that PBM is able to improve cell survival and to interact with recombinant human Bone Morphogenetic Protein 4 (rhBMP4) to direct and accelerate odonto/osteogenic differentiation of dental derived mesenchymal stem cells (MSCs). MSCs were encapsulated in an injectable and thermo‐responsive cell carrier (Pluronic® F‐127) loaded with rhBMP4 and then photoactivated. PBM improved MSCs self‐renewal and survival upon encapsulation in the Pluronic® F‐127. In the presence of rhBMP4, cell odonto/osteogenic differentiation was premature and markedly improved in the photoactivated MSCs. An in vivo calvarial critical sized defect model demonstrated significant increase in bone formation after PBM treatment. Finally, a balance in the reactive oxygen species levels may be related to the favorable results of PBM and rhBMP4 association. PBM may act in synergism with rhBMP4 and is a promise candidate to direct and accelerate hard tissue bioengineering.

The Influence of Dentine on the pH of Calcium Hydroxide, Chlorhexidine Gel, and Experimental Bioactive Glass-Based Root Canal Medicament

Objectives. To evaluate the influence of dentine on the pH of different medications in standardized simulated canals. Materials and Methods. Forty resin blocks were divided into groups with and without dentine powder, as follows: 2% chlorhexidine gel; 2% chlorhexidine gel associated with calcium hydroxide PA; calcium hydroxide PA delivered in propylene glycol 600; and NPG delivered in distilled water. The dentine powder was obtained from the root dentine of bovine teeth and added to the medications. The simulated canals were placed in containers with 1.5 mL of deionized water and pH was monitored in multiple intervals, up to 30 days. The mean pH values were calculated and submitted to statistical analysis using paired Students t-test and ANOVA complemented by the Tukey test (p < 0.05). Results. There was no statistical difference between the groups with and without dentine powder (p > 0.05). The pH values of calcium hydroxide were significantly higher than those of NPG in the first 24 hours (p < 0.05). After 7 days, both behaved in a similar manner. Conclusion. The addition of dentine powder to the medications evaluated did not alter the pH of the external solution in any of the time points tested.

Micro–computed Tomography versus the Cross-sectioning Method to Evaluate Dentin Defects Induced by Different Mechanized Instrumentation Techniques

Introduction The objective of this study was to compare the methods of micro‐computed tomography (micro‐CT) and cross‐sectioning followed by stereomicroscopy in assessing dentinal defects after instrumentation with different mechanized systems. Methods Forty mesial roots of mandibular molars were scanned and divided into 4 groups (n = 10): Group R, Reciproc; Group PTN, ProTaper Next; Group WOG, WaveOne Gold; Group PDL, ProDesign Logic. After instrumentation, the roots were once again submitted to a micro‐CT scan, and then sectioned at 3, 6, and 9 mm from the apex, and assessed for the presence of complete and incomplete dentinal defects under a stereomicroscope. The nonparametric Kruskal‐Wallis, Friedman, and Wilcoxon tests were used in the statistical analysis. The study used a significance level of 5%. Results The total number of defects observed by cross‐sectioning followed by stereomicroscopy was significantly higher than that observed by micro‐CT, in all of the experimental groups (P ≤ .05). All of the defects identified in the postoperative period were already present in the corresponding preoperative period. There was no significant difference among the instrumentation systems as to the median numbers of defects, for either cross‐sectioning followed by stereomicroscopy or micro‐CT, at all the root levels (P > .05). In the micro‐CT analysis, no significant difference was found between the median numbers of pre‐ and postinstrumentation defects, regardless of the instrumentation system (P > .05). Conclusion None of the evaluated instrumentation systems led to the formation of new dentin defects. All of the defects identified in the stereomicroscopic analysis were already present before instrumentation, or were absent at both time points in the micro‐CT analysis, indicating that the formation of new defects resulted from the sectioning procedure performed before stereomicroscopy and not from instrumentation. HIGHLIGHTSMicro‐CT and the cross‐sectioning method were compared as to their ability to reveal dentinal defects after mechanized instrumentation.None of the evaluated instrumentation systems led to the formation of new dentin defects.The formation of new defects resulted from the sectioning procedure and not from instrumentation.

Nickel–titanium instruments in endodontics: a concise review of the state of the art

The introduction of automated instrumentation in endodontics represented a major advance in progress for this specialty, with improvements in the quality and predictability of root canal preparation and a significant reduction in procedural errors. In recent years, endodontic instruments have undergone a series of changes brought about by modifications in design, surface treatments, and thermal treatments. In addition, new movements have also been incorporated to offer greater safety and efficiency, optimizing the properties of the NiTi alloy, especially through eccentric rotary motion. An understanding of the mechanical properties of these new NiTi instruments and their effect on the clinical performance of root canal preparation is essential if dental practitioners are to select the instruments that provide optimal clinical outcomes, especially in curved or flattened canals. The objective of this literature review is to present and discuss the characteristics of the NiTi alloys used in the major instrumentation systems available in the market, as well as the influence of the metallurgical and mechanical properties of NiTi instruments and the movements that drive them, to enable more accurate and predictable planning of root canal preparation.