ENDO, 04/2017

Pain in the dentoalveolar region is a common symptom. This usually involves acute pain, meaning the correct treatment can be rapidly applied. However, for certain types of persistent pain in this region, the aetiology is difficult to determine. Previously, there has been confusion regarding the diagnosis and classification of this type of persistent pain, which was often designated under different terms, such as atypical odontalgia, phantom pain or deafferentation pain. Recently, a classification system was developed for these types of conditions and the following term was agreed: persistent dentoalveolar pain. This new term was the first step in arriving at an improvement in the taxonomy: three criteria were established to lead to advancements in the fields of clinical research and treatment. Keywords: neuropathic pain, non-odontogenic pain

Objective: To compare the effect of glide path established by size 20/0.02 taper hand K-file and size 20/0.04 taper rotary file, on the amount of debris extruded apically during root canal instrumentation by rotary ProTaper Universal (S1-F2) and reciprocating WaveOne (Primary) file systems. Materials and methods: Eighty mandibular molars with curved mesial roots and two separate canals were selected and randomly divided into two groups (n = 40) for glide path preparation using either size 20/0.02 taper hand K-files and size 20/0.04 taper rotary files. These groups were further divided into two (n = 20) for root canal instrumentation by ProTaper Universal and WaveOne files; Group 1: 20/0.02 + ProTaper, Group 2: 20/0.02 + WaveOne, Group 3: 20/0.04 + ProTaper, and Group 4: 20/0.04 + WaveOne. The debris extruded during instrumentation was collected in pre-weighed Eppendorf tubes and stored in an incubator at 70°C for 5 days. Tubes containing the dry, extruded debris were then weighed. One-way analysis of variance was applied to the weights obtained followed by Tukey's post hoc test for multiple comparison. Results: All the groups resulted in debris extrusion. Establishing a glide path with size 20/0.04 taper rotary files, resulted in less debris extrusion, compared to a glide path prepared by size 20/0.02 taper hand K-files (P 0.001). Conclusion: Creating a glide path with size 20/0.04 rotary file, reduced the debris extrusion in curved root canals during instrumentation by ProTaper Universal and WaveOne. Keywords: apical extrusion, glide path, instrumentation, ProTaper Universal, WaveOne

Objective: The aim of this study was to compare the effect of four instruments used as orifice openers on the cervical dentine thickness of human mandibular first molars, using cone beam computed tomography (CBCT). Materials and methods: Forty human permanent mandibular first molars were decoronated and sectioned using a water-cooled safe sided diamond disc. The mesial roots were vertically mounted in a transparent acrylic resin box before CBCT scanning. Sections were scanned at 2.0, 3.0 and 4.0 mm below the cervical line. The samples were randomly divided into four equal groups according to the orifice opener used (n = 10). The canals were instrumented using Sendoline, Pre-RaCe, Hyflex and ProTaper files. The root canals were scanned after the cervical flaring using the same pre-flaring scanning protocol; cervical dentine thickness was measured before and after flaring. One way analysis of variance ANOVA was used to compare between the tested groups and each thickness. Tukey's post hoc test was used for pairwise comparison between the means. A dependent t-test was used for intra-group comparison (P ≤ 0.05). Results: For the Hyflex group, the percentage change in distal cervical thickness was significantly higher than the mesial one at the level of 2.0 mm below the cervical line. At the level of 3.0 mm and 4.0 mm for the Sendoline group, the percentage change in distal cervical thickness was significantly higher than the mesial one. Conclusion: None of the rotary instruments used in this study caused any damage to the root canal walls. Keywords: cervical flaring, cone-beam computed tomography (CBCT), dentine thickness, orifice opener, root canal instruments

Objective: The purpose of this study was to evaluate the ability of a solution containing fluoride to dissolve rotary instrument fragments in a simulated root canal within a maximum of 60 min. Material and methods: Eighteen M-Wire alloy rotary instruments were divided into three experimental groups according to length. An electrochemical cell was prepared in the canals with three electrodes, and file fragments were immersed in fluoride solution. A constant anodic potential of 800 mV was applied. Statistical analysis was performed using the non-parametric Wilcoxon test for paired data. Group means were compared by ANOVA for normally distributed variables, and with the Kruskal-Wallis and Jonckheere-Terpstraen tendency tests for variables that were not normally distributed. The level of statistical significance was set at P 0.005. Results: A significant loss of weight was observed, which increased with initial fragment weight (P 0.001). Complete (n = 3) or almost complete dissolution of 5.0 mm and 10.0 mm file fragments was achieved. The average weight reduction was 36% for 17.0 mm file fragments. The anodic potential was correlated positively with the degree of weight loss (r = 0.85, P 0.001). Conclusion: The electrochemical method enabled significant dissolution of NiTi instrument fragments within a maximum of 60 min. Keywords: active dissolution, endodontic instruments, fracture, nickel-titanium

Objective: This study aimed to evaluate and compare the mechanical behaviour of four brands of engine-driven NiTi endodontic instruments: HyFlex CM, made of controlled memory NiTi wire; Twisted File, made of R-phase NiTi; ProFile Vortex, manufactured from M-wire NiTi and RaCe, made of conventional NiTi. Materials and methods: Instruments were tested for bending resistance, cyclic fatigue, torsional resistance, Vickers hardness and toughness. Data obtained were statistically tested by analysis of variance and Student Newman-Keuls (SNK) multiple comparison tests. Results: The mechanical tests showed that instruments have different mechanical properties and performance. Conclusions: The results from this study showed that HyFlex CM files had the highest bending resistance, cyclic fatigue life and toughness. Keywords: cyclic fatigue, endodontic instruments, flexibility, nickel-titanium alloy, torsional resistance Conflict of interest statement: The authors deny any conflicts of interest related to this study.

Objective: To compare the effect on human gingival cell proliferation (HGC) exposed to an epoxy resin-based sealer at different temperatures. Materials and methods: Human gingival fibroblasts (HGFs) were established from explants of healthy gingival tissue, exposed to heat-treated sealer (150°C) and at room temperature (14°C). Cellular responses were recorded using flow cytometry at different times of assessment - 12 h, 24 h, 48 h and 72 h. Results: Cells exposed to room temperature sealer showed an increase proliferation at 12 h and 24 h. However, at both experimental temperatures there was not a significant difference in cellular response at 72 h, but there was a decrease proliferation compared to the control group. At both experimental conditions there was a significant increase in the rate of cell death, compared with the control group at 72 h. Conclusions: In vitro experimental assay showed a cytotoxic effect on HGFs after being exposed to resin epoxy sealer at 72 h. Clinical Significance: Elevated temperature changes in root canal sealers during warm vertical compaction techniques should not impact periapical cellular responses adversely, if any sealer is inadvertently expressed beyond the confines of the root canal system. Keywords: cell proliferation, fibroblasts, flow cytometry, root canal sealer, warm vertical compaction Conflict of interest statement: All the authors have contributed significantly on this work research and in writing this article; and all are in agreement with the manuscript in form and content. The authors deny any conflicts of interest related to this study.

Objectives: Despite the variety of root canal sealers on the market, an ideal root canal sealer has not been developed. A new epoxy resin sealer, BJM Root Canal Sealer, contains a quaternary amine macromolecule, Biosafe, which provides anti-biofilm features. The aim of the present study was to perform an in vitro evaluation and comparison of the physical properties of this novel endodontic epoxy resin-based sealer (BJM Root Canal Sealer) with those of AH Plus and MM-Seal. Materials and methods: Flow, working time and solubility were evaluated based on the ISO 6876/2012 standards. Dimensional change was assessed based on the ISO 6876/2001 standards. The physical properties were analysed using one-way analysis of variance (ANOVA). Results: The tested sealer flows were consistent with the ISO 6876/2012 recommendations. The dimensional changes of the tested sealers were inconsistent with the ISO 6876/2001 recommendations. The AH Plus sealer exhibited a lower flow than the other sealers (P 0.05). The MM-Seal sample featured the lowest working time and highest dimensional change compared with the other sealers (P 0.05). Solubility tests showed that AH Plus and BJM Root Canal Sealer have solubilities within the limit allowed by the ISO 6876/2012 recommendations (3% mass fraction). Conclusions: BJM Root Canal Sealer presented physicochemical properties that were similar to the AH Plus sealer. The physicochemical properties of BJM Root Canal Sealer conformed to the ISO 6876/2012 recommendations, except for the dimensional change, which did not fulfil the ISO 6876/2001 recommendations, as seen in all tested sealers. Keywords: epoxy sealer, physical properties, root canal sealer

Purpose: The objective of this study was to compare engine-driven instrumentation methods in relation to the appearance of defects in the walls of the root canal. Materials and methods: In total, 60 single-rooted human teeth, extracted for periodontal reasons, were conserved in Deltalab Eurotubo sterile A with 2% thymol until use. The teeth were decoronated and randomly divided into three groups (n = 20). In Group 1, canal negotiation was achieved with a size 10 K-file, followed by rotary pre-instrumentation with Pathfiles. Instrumentation with the ProTaper Universal system was carried through to a final file F4. In Group 2, the teeth were instrumented with the WaveOne Gold system according to the manufacturer's instructions. In Group 3, the teeth were left unprepared as control. After this, the canals were irrigated with 2 ml of distilled water and the teeth were conserved in distilled water. The samples were sectioned transversely before subsequent analysis on three levels. Defects were scored: 0 for no defects, 1 for cracks. Results: Reciprocating instrumentation with the WaveOne Gold Large instrument reduced by 30% the frequency of occurrence of cracks in the root canal walls in the coronal and apical thirds with respect to ProTaper F4 instrumentation (P 0.05). There were no statistically significant differences between the systems in the incidence of cracks in the middle third. Conclusions: Instrumentation with WaveOne Gold generated fewer cracks in the coronal and apical thirds of the root canal compared with the ProTaper system. Keywords: cracks, ProTaper Universal, WaveOne Gold