Background The aim of this study was to analyze the root and canal morphology of the maxillary permanent first molars in an Emirati population using cone-beam computed tomography (CBCT). Methods Two hundred and sixty-one CBCT scans were acquired. The data were extracted and anonymized to remove all patient identifiers. Two observers (an endodontic resident and an endodontist) evaluated all scans on diagnostic quality monitors. Results The prevalence of a second mesiobuccal canal (MB2) was 80.1% in all examined samples. Type II Vertucci classification, was the most common canal configuration (59%) in the mesiobuccal root, followed by Types I (19.9%) and IV (15.3%), while Type III was the least common (5.7%). Types I, II, and IV were significantly more common in the 21–40-year age group (P < 0.001), while Type III was observed significantly more often in the < 20-year age group (P < 0.001). No significant effect of gender on the prevalence of Vertucci classification in the mesiobuccal root of maxillary first molars (P = 0.74) was found. Analysis of bilateral symmetry showed that 80% teeth had perfect bilateral symmetry, whereas 20% were asymmetrical. Type II canal configuration showed the highest prevalence of bilateral symmetry (48.7%), followed by Type I (15%) and Type IV (10%), while Type III showed the least prevalence of symmetry (3%). Conclusions This was the first study to analyze the prevalence of MB2 canal in an Emirati population. Our results indicate high prevalence of MB2 (80.1%) and emphasize the importance of using advanced techniques to locate the MB2 canal.

The aim of this study was to investigate the possible relationship between interfacial forces, duration of instrumentation and effectiveness of root canal shaping by filing. All factors were standardised except the manner of manipulation of the files and the dependent variables (interfacial force and duration of filing). The outcome measured was the final prepared canal shape. The study tested the hypothesis that if interfacial forces and duration of filing had predictive value for effective canal shaping, a relationship between them should be apparent. If it was not, it could be inferred that the remaining uncontrollable variable, "manner of file manipulation" had a dominating influence. 18 operators used a standard filing technique to instrument a root canal each in single rooted teeth matched for anatomy. The teeth were mounted in a custom-made transducer designed to measure laterally applied interfacial forces between file and dentine. The length of time taken with each instrument in the series was measured giving a total duration of instrumentation. The final canal shape measured by standardised "before" and "after" radiographic images of the roots was judged against an "ideal" canal shape calculated from the size of instruments used and based on the preliminary canal shape. Although some trends were revealed, no obvious relationship was demonstrated between interfacial force, duration of filing and final canal shape. Operators clearly used a range of interfacial forces characteristic for each individual and for the different file sizes. Both light and heavy forces could produce a satisfactory canal shape. Use of light or heavy forces did not obviously affect speed of preparation. Tactile discrimination was not dependent on use of light or heavy forces. It was inferred that the "manner of file manipulation" remained undefined and was probably the dominant factor influencing outcome of canal shaping.

Objective The aim of this study was to determine the effect of a Nd:YAG laser on enamel surface morphology and hardness using different energies and pulses. Materials and Methods Twenty freshly extracted mature teeth were collected and sectioned. An Nd:YAG laser operating at 1,064 nm wavelength and providing up to 9 nanosecond laser pulses (1 J), with a laser spot diameter of 0.8 mm and irradiated surface area of 3 × 3 mm2, was applied to carbon black-coated teeth. The samples were randomly divided into two main groups; each group comprised 20 samples, according to the treatment parameters. The first group was further divided into subgroups A, B1, C1, and D1 using the different energies of 0, 350, 450, and 550 mJ, respectively, with 1 pulse for B1, C1, and D1. The second group was subdivided into A, B2, C2, and D2 and treated with 200 mJ, 3, 4, and 6 pulses for subgroups B2, C2 and D2, respectively. Subgroup A was the same sample for both groups as control with 0 pulses and 0 energy. Morphological features and microhardness were evaluated after laser exposure. Statistical Analysis Analysis of variance (Kruskal–Wallis test) was used to compare all subgroups, followed by the Scheefy significant difference post hoc test to determine the highest significance of the subgroups. Alpha < 0.05 was set as significant. Results The changes in the surface morphology of the enamel included increased crystal sizes, cracks, fissures, and voids with increasing energies and pulses. In group 1, the microhardness was 405.6, 562.7, 612, and 637 for energies of 0, 350, 450, and 550 mJ, respectively. In group 2, the microhardness was 405.6, 673, 866, and 1,050 for 0, 3, 4, and 6 pulses, respectively. Conclusion The Nd:YAG laser is efficient for increasing the microhardness of the enamel surface with minimum morphological damage by applying low energy with more pulses.