Incidence of Dentinal Crack Formation Using ProTaper Universal and WaveOne Systems in Straight and Curved Root Canals.

Introduction: This study aimed to compare dentinal micro crack formation following root canal instrumentation with ProTaper Universal (PTU) and WaveOne (WO) rotary systems in straight and curved root canals. Methods and Materials: One hundred mesiobuccal (MB) straight and curved canals of mandibular molars meeting inclusion criteria were divided into two control (n=10) and four experimental groups (n=20). After mounting the teeth and simulating the periodontal ligament, all the MB canals were coronally flared using Gates-Glidden drills #3 and 2 respectively. Then, in the experimental groups, the canals were instrumented with either PTU files (Sx, S1, S2, F1, F2), or Primary WO (25/0.08). Afterwards, roots were horizontally sectioned at 2, 4, and 6 mm from the apices, and evaluated under a microscope under 20× magnification. Data were analyzed with the Chi-Square and Kruskal-Wallis tests. The significance level was set at 0.05. Results: The control groups showed no cracks. There was no significant difference between the two systems in the straight root canals (P>0.05). But in the curved root canals, PTU produced significantly more cracks (P<0.05) with the complete crack type which was dominant (P=0.013) compared to WO. Conclusions: This in vitro study showed that in curved root canals, instrumentation with reciprocal WO system may be safer than full rotational PTU instruments regarding crack formation.

X-ray Diffraction Analysis of ProRoot Mineral Trioxide Aggregate Hydrated at Different pH Values.

INTRODUCTION: The aim of this study was to compare the chemical compounds of white ProRoot mineral trioxide aggregate (WMTA) hydrated at different pH environments. METHODS AND MATERIALS: Mixed samples of WMTA were kept in acidic (pH=5.4), neutral (pH=7.4) and alkaline (pH=9.4) environments for 48 h. Then, X-ray diffraction (XRD) analysis was performed for both hydrated and powder forms of WMTA. Portlandite crystalline structures of environments were compared from three aspects: intensity (height of the peak, corresponding to the concentration), crystallinity (peak area/total area) and crystal size (full-width at half-maximum of the peak). RESULTS: After matching the peaks of each sample with those of the International Center for Diffraction Data (ICDD) database, the main constituent of all set cements and powder form was found to be bismuth oxide. Acidic environment exhibited lower intensity and crystallinity of portlandite in comparison with neutral environment. CONCLUSION: The highest concentration and crystallinity of portlandite were observed in WMTA samples hydrated at neutral pH and the highest crystal size was detected after hydration in alkaline pH.

Effect of pH on physical properties of two endodontic biomaterials.

AIMS: To compare the surface microhardness, setting time, and elemental and topographic changes of mineral trioxide aggregate (MTA) and calcium-enriched mixture (CEM) in contact with acidic, neutral, and alkaline solutions. SUBJECTS AND METHODS: For evaluating 24-h and 28-day surface microhardness using Vickers test and initial setting time using Gillmore apparatus, glass molds were filled manually or ultrasonically, either with CEM or MTA and randomly immersed in solutions with acidic, neutral, and alkaline pH (5.4, 7.4, and 9.4, respectively). Topographic changes of the samples as well as energy dispersive X-ray spectra were examined using the scanning electron microscopy. STATISTICAL ANALYSIS USED: Data were analyzed using the Kruskal-Wallis, Mann-Whitney, Wilcoxon, one- and two-way ANOVA, Tukey's post hoc, and t-tests. RESULTS: After 28 days, there was an increase in the microhardness for all samples (without statistical significance [P > 0.05]), except for the samples of CEM in acidic environment (P > 0.05). The setting time of MTA samples was statistically higher than CEM samples (P ≤ 0.001). The setting time of both biomaterials was significantly higher in acidic pH than other groups (P ≤ 0.005). Surface topography and elemental constituents of biomaterials were altered in different solutions. CONCLUSION: The surface microhardness, setting time, and elemental and topographic properties of MTA and CEM were affected by different solutions. CEM exhibited quicker setting time than MTA; however, acidic solution negatively influenced both of them.

Tooth discoloration induced by calcium-silicate based materials: a literature review.

INTRODUCTION: Endodontic therapy may not focus only on biological and functional aspects, but should take esthetic considerations into account as well. It is common knowledge that calcium-silicate based materials may cause discoloration and thus impair the esthetic outcome of the treated tooth. The purpose of this review is to summarize the existing knowledge on the discoloration potential of these materials used for endodontic procedures. EVIDENCE ACQUISITION: A comprehensive literature search covering the period from 2000 to 2015 was conducted on PubMed and Google Scholar, using different keyword combinations including "tooth", "color", "discoloration", "staining", "endodontic", "root canal", "calcium silicate", "MTA", "portland cement", "Endocem" and "biodentine". Any relevant literature in the English language was considered for inclusion. In addition, previous review articles were hand-searched, and reference lists from endodontic textbooks were also reviewed. Articles were excluded if only single clinical reports or conference reports were included or if the topic was not related to the subject. EVIDENCE SYNTHESIS: For a wide range of these materials currently available in the market, only scarce or no evidence exist regarding their discoloration potential. CONCLUSIONS: The need for further research in this field and development of non-staining calcium silicate based materials is evident.

Efficacy of Two Rotary NiTi Instruments in Removal of Resilon/Epiphany Obturants.

INTRODUCTION: The success of endodontic retreatment is related to the complete removal of the obturation material from the root canal system. The aim of this study was to evaluate the efficacy of Mtwo R and ProTaper retreatment files in removing the Resilon/Epiphany system with or without chloroform during retreatment. MATERIALS AND METHODS: Sixty distal roots of first mandibular molars were prepared and laterally condensed with Resilon/Epiphany, then divided into four groups (15 each for retreatment): 1) Mtwo R/solvent; 2) Mtwo R; 3) ProTaper D/solvent; and 4) ProTaper D. The cleanliness of the canal walls was evaluated using radiography; a stereomicroscope and SEM. Data were subjected to ANOVA and Student's t-test. RESULTS: Neither rotary system performed better than the other when considering the whole root canal, with or without solvent. In the apical portion, ProTaper/solvent showed the best result (P<0.05). CONCLUSION: In Resilon/Epiphany retreatment cases, ProTaper/solvent was better in the apical portion; however when considering the whole canal, Mtwo R and the ProTaper D series had the same performance.