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The mandibular second premolar can be considered one of the most challenging teeth to treat endodontically; due to the complexity of its root canal morphology and increased incidence of multiple canals. The knowledge of internal anatomy of root canals and their possible variations as well as use of magnification, e.g. operating microscope, radiographic examination and illumination, can increase the chances of finding additional canals and contribute to the success of endodontic treatment. The purpose of the current investigation is to report the successful endodontic treatment of a mandibular second premolar with 4 canals; all of them in one single root. [ABSTRACT FROM AUTHOR]

Introduction: In order to successfully perform root canal treatment, thorough knowledge of the root canal anatomy is essential. Cone-beam computed tomography (CBCT) has the ability to improve our understanding of the root canal system. The goal of the present study was to compare the accuracy of CBCT in revealing the number and form of the root canals of different maxillary and mandibular teeth with clearing and staining method. Methods and Materials: CBCT images were taken from 80 extracted human teeth fixed in agar arch models. The number and configuration of the root canals of each tooth were determined by the two observers. Then the teeth were cleared and stained. Two endodontists evaluated the number and forms of the root canals. The accuracy of CBCT was determined and compared with clearing and staining by Fisher's exact test. The agreement of two methods in detection of the number and form of the root canals were evaluated by Kappa test, P<0.05. Results: CBCT accurately detected the number of root canals in 129 (92.1%) of 140 roots and the form of the canals in 119 (85%) of the roots. There was no significant difference between the accuracy of CBCT in the detection of the number (P=0.13) and forms (P=0.4) of root canals of maxillary and mandibular teeth. The agreement between CBCT, and tooth clearing and staining in detection of the number of root canals was excellent in the maxilla (kappa=0.88±0.05) and good in the mandible (kappa=0.720±0.097). The agreement between the two methods in demonstration of the form of root canals was good in both maxillary (kappa=0.73±0.07) and mandibular (kappa=0.67±0.09) teeth. Conclusion: CBCT provides accurate information about root canal morphology. Application of this technique could result in more successful endodontic treatment. [ABSTRACT FROM AUTHOR]

Introduction: The present study was conducted to assess the morphology of mandibular canines using cone-beam computed tomography (CBCT) in a north Iranian population. Methods and Materials: For the morphological assessment of mandibular canines, 150 CBCT images taken from patients for different reasons were used. The mandibular canines were examined in sagittal, coronal and axial dimensions. The canal pattern, number of roots/canals, the tooth length, the orientation of the roots and the position of the apical foramina were evaluated and the effect of gender on each variable was assessed. The obtained data were analyzed using the Chi-square and student’s t-tests. Results: According to the Vertucci’s criteria, the most common pattern was type I morphology (89.7%), followed by types III (5.7%), II (3.7%) and V (1%). No significant differences were observed between the male and female patients in terms of canal type (P>0.05). Gender difference is a factor which affected the root length and the number of mandibular canine root and root canal. There were 296 single-root and four double-root canines. The double-root canines and mandibular canine with two canals were significantly more common among men than women (P=0.00). The apical foramen was laterally positioned in 68.3% and centrally in 31.7% of the cases, and the root curvatures were mostly oriented toward the buccal region. No significant statistical difference was observed for mentioned parameters in right and left half of the jaw. Conclusion: Due the diverse morphology and the potential presence of a second mandibular canine among Iranians, dentists should perform endodontic treatments with greater care. CBCT is an accurate tool for the morphological assessment of root canals. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Many studies have been performed to evaluate the stress distribution around endodontic posts; those which compared posts composed of different materials are rare. The aim of this study was to compare stresses induced in dentin by three structurally different posts using photoelasticity method. MATERIALS AND METHODS: Nine blocks of PSM-5 Photoelastic material with 45×45×10 mm dimension were prepared. In each block, a canal 9 mm in length and 0.8 mm in width was drilled. Blocks were divided into 3 groups of three each. In the first group, the canals were prepared for insertion of Fiber Post with 1.25 mm width. In the second group, the canals were prepared for insertion of ParaPost with 1.25 mm width and the canals in the third group were prepared for casting post similar to the above samples. Casting Post pattern was made by Duralay resin and casted by Ni-Cr alloy. All posts were cemented in canals with Panavia cement. The stresses were evaluated in the polariscope under three different conditions: 1) without load, 2) with 135 N vertical load, and 3) with 90 N oblique load (26° inclination to post long axis). The fringe orders in the cervical, middle and apical regions of the posts were evaluated and compared with each other.RESULTS: Application of the vertical load induced a high stress concentration (FO=4) in the apical region of the ParaPost, while lower stress was observed in the middle (FO=2) and cervical region (FO=2+). Fiber Post and Casting Post showed even stress distribution (FO=2+). High stress concentration was detected with the application of oblique force in the cervical region of ParaPost (FO=5) and Casting Post (FO=3+). Fiber Posts fractured before reaching 90-N loading force. CONCLUSION: The stress distribution around Fiber Post and Casting Post were constant in comparison with ParaPost. Fiber Post with 1.25 mm width was not recommended in situations with high oblique stresses.

Introduction: Relining fiber posts using composite resins helps the posts adapt to the anatomical space of the root canals. The aim of this study was to evaluate the effect of composite resin type on the push-out bond strength of anatomical fiber posts to intra canal dentin., Methods and Materials: Forty-eight bovine upper incisors were prepared for post space after root canal therapy and randomly divided in to six groups. Five different types of composite resin (GrandioSO, GrandioSO Heavy Flow, X-tra Fil, X-tra base and everX Posterior) were used for relining the prepared fiber posts. In the control group, the prepared post was cemented into the post space without relining. Cervical, middle and apical cross-sections were achieved from each root and push-out test was conducted at a crosshead speed of 0.5 mm/min. One sample from each group was scanned using a micro-CT scanner which provided views from the apical, middle and coronal thirds. Data were analyzed using Kolmogorov-Smirnov test, repeated measures ANOVA and post hoc tests using SPSS 17 ( P <0.05)., Results: Statistical analysis showed significant differences in terms of mean push-out bond strengths between different composite resin types and cross-sections ( P <0.001). The mean push-out bond strength of the samples relined with Grandio SO composite resin (15.48±2.32) and X-tra Fil Bulk-fill composite resin (14.09±1.98) were significantly higher than that of other groups ( P <0.05). The unrelined group had a mean push-out bond strength (5.94±1.45) which was significantly lower than that in other groups ( P <0.05). In addition, there was a relationship between cross-sections and composite resin types ( P <0.05)., Conclusion: This in vitro study showed that the composite resins used for relining can affect the push-out bond strength to intra canal dentin based on their physical and mechanical properties., Competing Interests: ‘None declared’.