One of the most complexes in root and canal anatomy is the maxillary first permanent molar. This study aimed to analyze the frequency of mesiobuccal (MB2) canal and its apical portals of exit, in patients belonging to different gender-age groups and determine the possible relation with sex and age. A CBCT scan images were accessed from a documented database of 343 patients (178 male, 165 female), who had an oral and maxillofacial examination. The age of the patients ranging from 12 to 63 years. The frequency of the MB2 canal and its portals of exit apically were observed. Age and gender correlation were calculated using the χ2 test. P < 0.05 was considered significant. A total of 634 maxillary first molars (335 male, 299 female) were included. The MB2 canal was found in 53.78% of the cases. A significantly higher incidence of the MB2 canal was detected in males than in females. No correlation in the presence and/or absence of the MB2 canal in terms of age. When MB2 canal present, a single apical foramen was observed in 66.28% of the cases, two apical foramina were present in 33.72% of the cases. MB2 canals may be present in approximately half of the cases, from which one third of the cases have their own apical portal of exit.

It is impossible to remove tooth-colored restorations by mechanical means without unnecessary damage to the adjacent sound tooth structure. This study is aimed at investigating erbium-doped yttrium aluminum garnet (Er: YAG) laser (Hoya ConBio, VersaWave, CA, USA) in removing composite resin restorations and assessing the change in morphology of bonding surfaces using a scanning electron microscope (EDX, CAMSCANNER, 3200LV, UK). The investigators collected thirty extracted sound human premolar teeth for this investigation, and the conventional design class V cavity was prepared on the buccal surface of each specimen. The specimens were allocated randomly into three groups, according to the procedure used for the ablation of the composite restoration: group A (high-speed diamond fissure bur), group B, and group C (Er: YAG laser) using a different pulse repetition rate of 20 Hz (group B) and 25 Hz (group C). The AutoCAD software program (Autodesk, Inc., 2016) was used to calculate the surface area and the resulting dimensional change of the cavities after restoration removal. The cavities were filled with composite resin and randomly assigned into two groups conforming to the methods applied to eliminate the restoration; diamond turbine fissure bur and laser. In each group, two specimens were selected randomly for scanning electron microscope analysis of bonding surfaces. The least meantime for the composite resin removal was observed in the high-speed diamond bur, significantly less than both Er-YAG laser groups ( $p<0.001$ ). However, at a higher pulse repetition rate, time-consuming decreased. The results showed that laser is more conservative in removing composite resin restoration as the change was most remarkable in group A (0.800 mm), then group C (0.466 mm), and the slightest change is in group B (0.372 mm) ( $p=0.014$ ). The dentin surface of group A showed a smooth surface with no opened dentinal tubule and intact smear layer. In groups B and C, dentin surfaces were irregular, scaly, or flaky, and dentinal tubules were opened without a smear layer. Therefore, Er: YAG laser is effective for composite resin removal considering the parameters chosen in this study with fewer changes in cavity surface area and better microretentive features.

(1) Background: Accurate diagnosis and treatment plans in orthodontics were facilitated by novel technologies. The prediction of occlusal problems is of utmost importance for clinicians. This present study aimed to find any possible correlation between unilateral and bilateral palatally impacted maxillary canine, palatal dimensions, and maxillary arch perimeter using digital measurements and determine the factors that could be used as predictors for maxillary palatal canine impaction. (2) Method: A cross-sectional study was conducted on cone-beam computed tomography images of orthodontic patients aged 15 to 25. Palatal dimensions and maxillary arch perimeter were digitally measured using Materialize Interactive Medical Image Control System. (3) Results: A significant difference was found between the case and the study groups regarding palatal depth, length, and arch perimeter, except for the palatal width. A weak correlation was reported in palatal depth and length with canine impaction, whereas the correlation was moderate concerning the arch perimeter. They can be used as predictors for palatal canine impaction. (4) Conclusion: Palatal dimensions and dental arch perimeter affect maxillary palatal canine impaction. Deficient arch perimeter, palatal depth, and length could be helpful in the prediction of maxillary palatal canine impaction.

An accurate estimation of the working canal length is essential for successful root canal treatment. This study is aimed at investigating the diagnostic accuracy of root canal length estimation on cone‐beam computed tomography (CBCT) scans and digital paralleling radiographs (PAs), using the real canal length as a gold standard, and at evaluating the influence of canal curvature on this estimation. Sixty extracted human premolar teeth were selected for this study. Root canal length measurement was performed on CBCT scans (NewTom, Giano, Verona, Italy) and digital paralleling radiography (EzRay Air W; Vatech, Korea). The real working length was established by subtracting 0.5 mm from the actual canal length. No significant difference was found between CBCT and digital paralleling radiography. There was a tendency for underestimation of the root canal length measured on the CBCT images in 52 (86.7%) of the examined teeth and overestimation in 5 teeth (8.3%). All the digital radiographs slightly overestimated the real canal length. The analysis revealed a strong correlation between the estimation from moderate to severe curvature for digital radiography and CBCT images. Preoperative working length estimation can be made closest to its real clinical canal length on the standardized paralleling technique, using a long (16‐inch) target‐receptor distance.

Background: A thorough understanding of the original root and canal anatomy is a critical technical prerequisite for performing cleaning and shaping treatments. Therefore, this research aimed to characterize maxillary first premolar teeth' root morphology and canal architecture. Methods: One hundred forty-two extracted human adult maxillary first premolar teeth have been retrieved. The extracted teeth were thoroughly cleaned and irrigated to eliminate any remaining debris or blood. They were then preserved in formalin solution until they were eligible for screening. To begin, a visual examination was employed to ascertain the number of roots and their geometry in each sample. Then, utilizing digital radiography in two plains, mesiodistal and distomesial, to further determine those parameters. Finally, a sectioning technique had been used to have the samples cut mesiodistally into slices to validate the internal root canal architecture and identify the number of root canals and their varieties in accordance with Vertucci's categorization system. The canal layout, the pulp chamber, and the root canals were all highlighted (marked) using a fine tip marker in a permanent orange hue to make the canal features more accessible and accurate to visualize. All of the processes were conducted by two highly qualified dentists. The sample size was estimated statistically using the Sealed Envelope program, and the percentage of each configuration was derived in proportion to the overall sample size in order to establish the percentage of each type in each configuration. Results: From the 142 teeth examined, 42 (29.57%) had one root, 97 (68.31%) had two roots, and only three premolars (2.12%) had three roots. Concerning canal configurations, 100 teeth (70.43%) had type (IV) canal configuration, followed by 37 teeth (26.05%) had types (V), three teeth (2.12%) had type (VIII), and one tooth (0.70%) for each of type (I) and type (II). Conclusions: The anatomical pattern of inspected maxillary first premolars are mainly two rooted and predominantly have a type (IV) canal morphology.

Background: Radiographic analysis of tooth morphology is mandatory for accurate calibration of the degree of canal curvature angle and radiographic working length to its real dimensions in case difficulty assessment protocols. This study aimed to determine the impact of the degree of root canal curvature angle on maintaining the real working length and the original canal axis of prepared root canals using a reciprocating rotary instrumentation technique. Methods: Radiographic image analysis was performed on 60 extracted single-rooted human premolar teeth with a moderate canal curvature (10°–25°) and severe canal curvature (26°–70°). Working length and longitudinal canal axis were determined using cone-beam computed tomography (CBCT) and digital periapical radiography. The real canal length was determined by subtracting 0.5 mm from the actual canal length. Root canals were prepared using the WaveOne Gold reciprocating file (Dentsply Maillefer, Ballaigues, Switzerland). Results: There was no significant relation of the degree of canal curvature angle to the accuracy of radiographic working length estimated on CBCT and digital periapical radiographic techniques (P > 0.05). Postinstrumentation changes in the original canal axis between moderate and severe canal curvature angles, assessed on CBCT and periapical digital radiographic images were statistically non-significant (P > 0.05). Conclusions: A standardized digital periapical radiographic method performed similarly to the CBCT technique near to its true working length. No significant interaction exists between the diagnostic working length estimation, postoperative root canal axis modification, and the degree of canal curvature angle, using reciprocating rotary instrumentation technique.