BackgroundThe aim of this study was to evaluate the effect of diode laser irradiation and bleaching materials on the dentinal tubule diameter after laser bleaching.Material and MethodsThe dentin discs of 40 extracted third molar were used in this experiment. Each disc surface was divided into two halves by grooving. Half of samples were laser bleached at different wavelengths with two different concentrations of hydrogen peroxide. Other half of each disc with no laser bleaching remained as a negative control. Dentin discs were assigned randomly into four groups (n=10) with following hydrogen peroxide and diode laser wavelength specifications; Group 1 (30% - 810 nm), group 2 (30% - 980 nm), group 3 (46% - 810 nm) and group 4 (46% - 980 nm). All specimens were sent for scanning electron microscopic (SEM) analysis in order to measure tubular diameter in laser treated and control halves. Data were analyzed by ANOVA and Tukey test (p<0.05).ResultsA significant reduction in dentin tubule diameter was observed in groups 1, 2 and 4. There was no significant difference between groups 1 and 2 and between groups 3 and 4 after bleaching.ConclusionsThe SEM results showed that diode laser was able to reduce dentin tubule diameter and its effect on dentin was dependent on chemical action of bleaching material. Key words:Laser, diode, dentin, tubule, diameter.

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Objectives  This study aimed to assess the effect of four intracanal medicaments on pull-out bond strength of fiber posts. Materials and Methods  A total of 65 single-rooted, single-canal teeth were selected and decoronated. Root canals were prepared and after rinsing were randomly divided into five groups ( n = 13). G 1 : calcium hydroxide (CH), G 2: CH plus chlorhexidine (CH+CHX), G 3 : triple antibiotic paste (TAP), G 4 : double antibiotic paste (DAP) were applied in the canals in the four groups. The control group (G 5 ) received no medicament. After 4 weeks, the medicaments were rinsed off and the canals were filled with gutta-percha. Post space was then prepared in root canals for the placement of glass fiber posts and self-adhesive cement (Panavia F2). After cementation, they were subjected to pull-out bond strength test. Statistical Analysis  Data were statistically analyzed using one-way analysis of variance and Tukey test.Results The pull-out bond strength values were significantly different in the groups ( p < 0.001). The highest values of bond strength were seen in G 2 , G 1 , and G 3 (359.97 ± 81.26, 333.79 ± 98.96, 309.27 ± 78.07), respectively. There was no significant difference between G 4 and G 5 ( p = 0.75). Conclusion  The results showed that CH, CH+CHX, and TAP enhanced the pull-out bond strength of fiber post to root canal wall as compared to the control group.

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Introduction: This study aimed to evaluate anatomy and morphology of mandibular permanent molars using cone-beam computed tomography (CBCT) in a selected Iranian population. Methods and Materials: CBCT images of 638 first and second mandibular molars (322 of males and 316 of females) were included in this in vitro study. Number of roots and root canals, Vertucci's configuration of each root, radix paramolaris (RP), radix entomolaris (RE), and C-shaped canals were determined in both genders. Data were analyzed by Pearson-Chi square test using SPSS (V.22) software (P = 0.05). Results:The most common configuration of distal roots were type I for both genders. Among 266 first molars, 97.3% teeth had two roots, 0.75% had RP and 1.87% had RE. All RP and RE were type I. Cshaped canals were found in 1.12% teeth and all were in male population, significantly at the left side (P=0.045). Among 372 second molars, 94.08% had two roots, 0.53% had RP and 0.26% had RE. The prevalent canal configuration of mesial roots was type III (52.96%) with significant difference between right (P=0.006) and left (P=0.049). C-shaped canals were found in 5.64% of second molars and more specifically detected in male group. Significant difference was observed between two genders in the right (P=0.024) and the left (P=0.009). Conclusion: Vertucci's type III and type II were the most prevalent configurations in mesial roots while for distal roots the predominant configuration was type I. RE, RP, and C-shaped channels were not common in mandibular molars between Iranian population and their prevalence were higher among male population.

Objective The aim of this study was to compare the fracture resistance of immature bovine roots when using ProRoot MTA, CEM Cement, and Biodentine as root filling materials. Materials and Methods An immature bovine tooth model was developed by removing the coronal and apical portions of 70 bovine incisors 8 mm above and 12 mm below the cementoenamel junction (CEJ). The specimens were then divided into five groups: ProRoot MTA, CEM Cement, Biodentine, gutta-percha/AH26 sealer, and control. All groups received a 5-mm apical plug with a temporary restorative material. Then, the remaining root canal space was filled with one of the afore-mentioned materials. After setting, the specimens were mounted in acrylic resin. Then, 3 mm coronal to the CEJ from the buccal side of the teeth and at a 135°angle to the long axis, the specimens were loaded until fracture. Results The specimens in the Biodentine (2196 N) and ProRoot MTA (2103 N) groups had significantly greater fracture resistance in comparison to the control group (p = 0.01). No significant difference was found between CEM Cement, gutta-percha and sealer AH26, and control groups. No significant differences occurred between the four experimental groups (p = 0.45). Conclusion Filling the root canal space with ProRoot MTA and Biodentine contributed to higher fracture resistance values.

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Objectives: This study aimed to compare the transportation of the mesiobuccal canal of maxillary molars following root canal preparation with HyFlex CM (HCM) and Edge Taper Platinum (ETP) rotary systems and stainless steel (SS) hand files using cone-beam computed tomography (CBCT). Materials and Methods: This in-vitro study was performed on 48 maxillary molars in three groups of 16. The teeth were mounted in acrylic blocks, and root canals were prepared using HCM in group 1 (up to #30/0.06), ETP in group 2 (up to F3/0.06), and SS hand files in group 3 (up to #30). CBCT scans were taken before and after root canal preparation. The amount of canal transportation was measured at 0, 3, 6, and 9mm from the apex. Data were analyzed using Kruskal-Wallis and Mann-Whitney tests. Results: The difference in canal transportation at 0 and 6mm from the apex was significant between the HCM and ETP groups (P=0.031 and 0.023) but none of the systems showed any significant difference with hand files at 0- and 6-mm levels (P=0.10, 0.56, 0.22, and 0.50), respectively. At 3mm from the apex, no significant difference was noted among the groups (P=0.30). At the 9-mm level, the amount of canal transportation was not significantly different between HCM and ETP (P=0.83) but they showed significant differences with hand files (P<0.001). Conclusion: ETP and HCM caused less canal transportation at the curvature of the mesiobuccal canal of maxillary molars compared to hand files. ETP showed superior efficacy in root canal preparation compared to HCM.