RESUMO
Background: A successful endodontic treatment requires a comprehensive knowledge of the root canal morphology. This study compared the diagnostic accuracy of cone-beam computed tomography (CBCT) and the sectioning technique for the assessment of mandibular first molar (MFM) root canal morphology. Materials and Methods: In this in vitro, experimental study, 48 eligible MFMs were mounted in 12 blocks (groups of 4) made of acrylic resin and sheep bone powder and underwent CBCT. Next, the teeth were mounted in transparent self-cure acrylic blocks, and their roots were sectioned at three points with 3 mm intervals. Images underwent multiplanar reconstruction in NNT Viewer software and were analyzed by one radiologist with the cooperation of an endodontist. The sections were also evaluated by an endodontist under a stereomicroscope (gold standard). The frequency and percentage of single-canal, and two-canal roots were determined by each technique. The agreement between CBCT and the Gold standard was analyzed by calculating the kappa coefficient (P < 0.05). Results: The diagnostic accuracy of CBCT for the assessment of the MFM root canal morphology was 80% on the mesial surface, 99% in the distal surface, and 96% in total. In the mesial surface, 94.2% of two-canal roots and 66.7% of single-canal roots were correctly detected by CBCT. These values were 100% and 97.4% in the distal surface, and 95.2% and 95.8% in total, respectively. A significant agreement was noted between CBCT and the Gold standard with κ =0.412 for the mesial, 0.939 for the distal, and 0.907 for the total surfaces (P < 0.001). Conclusion: CBCT can be reliably used for the assessment of the complex root canal morphology of MFMs when other modalities fall short.
RESUMO
Background: The literature on the effect of bleaching on stainability and color stability of any composites is scarce and controversial. In the case of some composites and/or bleaching agents or staining solutions, there is no previous study. Therefore, this rather large study was conducted for the first time to examine simultaneously the effects of bleaching and 3 staining solutions on 3 composite types. Materials and Methods: This 3-phase experimental in vitro study was performed on 18 groups of 5 specimens each: 90 composite discs with 10 mm diameter and 1 mm thickness were fabricated from 3 resin composites (microhybrid, nanohybrid, and nanofilled). Forty-five discs underwent bleaching with 15% carbamide peroxide, and the remaining 45 were immersed in distilled water at room temperature. The color assessment was performed before and after this step, and Δa, Δb, and ΔL color parameters were calculated for each specimen. The specimens were then immersed in coffee, cola, and red grape juice for 2 weeks, and underwent colorimetry again. The simultaneous effects of bleaching and staining agents and composite types on ΔE (color changes) of composite specimens were analyzed using an independent-samples t-test, a Mann-Whitney U-test, and two-way and one-way analysis of variances followed by a Tukey and a Dunnett's T3 tests (α = 0.05). Results: Bleaching had no significant effect on color changes of microhybrid, nanohybrid, or nanofilled composites (P > 0.05). The stainability of composites did not increase after bleaching (P > 0.05). Regardless of the composite type and the presence of bleaching, coffee had the worst effect on color of composite specimens, while cola had the smallest staining effect (P < 0.05). Conclusion: Stainability of microhybrid/nanohybrid/nanofilled composites did not increase after bleaching with 15% carbamide peroxide. Coffee should be consumed with care, as far as composite coloring is a concern, regardless of the type of composite in use or its bleaching history. Cola was the weakest stainer. Coffee always caused perceptible staining (ΔE >3.7), regardless of the composite in use or its bleaching history. Red grape juice caused such perceptible colorations in most cases. Cola did not cause any perceptible discoloration in most cases.
RESUMO
Background: Cone-beam computed tomography (CBCT) has the highest sensitivity and specificity for the detection of vertical root fractures (VRFs). This study aimed to compare the diagnostic accuracy of CBCT with different gamma values for the detection of VRFs. Materials and Methods: In this in vitro, experimental study, multiplanar CBCT scans were obtained from 61 extracted premolars with prefabricated titanium posts using NewTom CBCT scanner. Next, VRFs were artificially induced in all teeth with a mallet, and the teeth underwent CBCT with three different gamma values. The images were evaluated by two observers twice with a 2-week interval for the presence/absence of VRFs. Data were analyzed using the kappa coefficient, McNemar test, and Chi-square test. The sensitivity, specificity, and overall accuracy of CBCT with different gamma values for the detection of VRFs were assessed by receiver operating characteristic curve. The level of significance was lesser than 0.05 (P < 0.05). Results: Changing the gamma value did not change the sensitivity, specificity, or accuracy of CBCT for the detection of VRFs. No significant difference was noted between the two observers in the detection of VRFs on CBCT scans taken with different gamma grades. The inter- and intra-observer agreement were excellent for all gamma grades. Conclusion: Any gamma value preferred by the observer can be used for the detection of VRFs on CBCT scans.
