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The success of root canal therapy is fully predicated upon a complete understanding of root and canal morphology and all the anatomical variations that can complicate the endodontic treatment. Of these morphological variations, taurodontism, RGs, and C-shaped canals are of note due to their implications on diagnosis, treatment planning, and endodontic success. This study aimed to investigate the prevalence and regional variations of C-shaped canals, RGs, and taurodontism across 20 countries using CBCT imaging and meta-analytic methods. A multicenter, cross-sectional study analyzed CBCT datasets from 6,000 participants (12,000 teeth) distributed equally across 20 countries. Standardized evaluation arrangements were utilized to identify RGs (RG), taurodontism, and C-shaped canals with their prevalence stratified by region, gender, and age. Statistical analyses cover subgroup comparisons, correlation studies, and sensitivity analysis using Cramer’s V. RGs had a pooled global prevalence of 20%, with high-rised rates in Africa. C-shaped canals reported a 10% global prevalence, mainly in Asia, On the Other hand taurodontism was lowest prevalent at 7%, with markable regional variability. Prominent bilateral symmetry was noticed for all features, and taurodontism showed the highest rate (98.33%). Important correlations existed among C-shaped canals, grooves, and taurodontism showing shared developmental pathways. The current study points out the significant prevalence, including anatomical variations of RGs, taurodontism, and C-shaped canals in mandibular 1st premolars, with substantial demographic and regional differences. The findings highlight the importance of perception of these features’ morphological interrelationships along with bilateral symmetry to increase diagnostic accuracy, clinical outcomes, and treatment planning.

A thorough assessment of complex canals in any tooth is a crucial prerequisite for the success of the treatment. The radicular space is often complex, and the canals might also additionally separate at all levels of the root canals, which poses a great challenge to the treating clinician. The mandibular premolars often have variations and complexity in the canal system. The abnormal morphology of these mandibular premolars makes it inaccessible to find and negotiate the additional canals; failure to identify other canals often leads to unsuccessful root canal treatment. This case series reports five successful nonsurgical root canal treatments in mandibular premolars.

Background Mandibular premolars are complicated teeth to endodontically treat due to the anatomical variations that can present. The purpose of this study was to determine the presence of C-shaped configurations in mandibular premolars by cone-beam computed tomography (CBCT). Methods 380 mandibular first premolars and 308 mandibular second premolars cone-beam computed tomographic images were obtained from 292 patients (175 female and 117 male). Tooth position, number of roots, root canals, C-shaped root canal system configuration, level of canal bifurcation and radicular grooves were evaluated by two endodontists trained in CBCT evaluation; previously calibrated between them, and a radiologist with endodontic experience. Data were statistically compared by The Chi-square test (α = 0.05) to examine any significant difference between gender and C-shaped root canal system and any significant difference between C-shaped configuration according to Fan criteria and gender. Results Overall 100% (n = 688) teeth examined, 19.2% (n = 132) had a C-shaped root canals system. 9.16% (n = 63) in male patients and 10.03% (n = 69) in female patients. The prevalence of C-shaped root canal system in mandibular first premolar was 83.33 and 16.66% in mandibular second premolars. According to Fan classification, the mandibular first premolars showed 3.63% as C1, 9.09% C2, 59.09% C3, 21.81% C4a, 1.8% C4b. Mandibular second premolars showed 13.63% as C1, 18.18% C2, 13.63% C3, 27.27% C4a, 9.09% C4b. Male patients showed 4.54% as C1, 3.78% C2, 22.72% C3, 11.36% C4a, 0.75% C4b, and 4.54% out of classification. Female patients showed 0.75% as C1, 6.81% C2, 30.03% C3, 9.84 C4a, 2.27% C4b, and 2.27% out of classification. The 53.36% canal bifurcation in mandibular first premolars and 50.09% in mandibular second premolars were in the middle third. No statistical differences were found between C-shaped root canal system and gender or C-shaped configuration according to Fan criteria and gender. P was < 0.05. Conclusions Within the limitation of this study, the presence of C-shaped anatomical system is relatively low in mandibular second premolars than in mandibular first premolars.

[This corrects the article DOI: 10.1371/journal.pone.0193894.].

ObjectivesThis study aimed to investigate the effectiveness of deep convolutional neural network (CNN) in the diagnosis of interproximal caries lesions in digital bitewing radiographs.Methods and materialsA total of 1,000 digital bitewing radiographs were randomly selected from the database. Of these, 800 were augmented and annotated as “decay” by two experienced dentists using a labeling tool developed in Python programming language. The 800 radiographs were consisted of 11,521 approximal surfaces of which 1,847 were decayed (lesion prevalence for train data was 16.03%). A CNN model known as you only look once (YOLO) was modified and trained to detect caries lesions in bitewing radiographs. After using the other 200 radiographs to test the effectiveness of the proposed CNN model, the accuracy, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the receiver operating characteristic curve (AUC) were calculated.ResultsThe lesion prevalence for test data was 13.89%. The overall accuracy of the CNN model was 94.59% (94.19% for premolars, 94.97% for molars), sensitivity was 72.26% (75.51% for premolars, 68.71% for molars), specificity was 98.19% (97.43% for premolars, 98.91% for molars), PPV was 86.58% (83.61% for premolars, 90.44% for molars), and NPV was 95.64% (95.82% for premolars, 95.47% for molars). The overall AUC was measured as 87.19%.ConclusionsThe proposed CNN model showed good performance with high accuracy scores demonstrating that it could be used in the diagnosis of caries lesions in bitewing radiographs.Clinical significanceCorrect diagnosis of dental caries is essential for a correct treatment procedure. CNNs can assist dentists in diagnosing approximal caries lesions in bitewing radiographs.

The aim of this case series is to contribute to the better knowledge and management of the complex anatomical configurations of maxillary premolars with four canals. The paper explains the endodontic treatment of five maxillary premolars with four canals, with three buccal and one palatal orifices, in different patients. The cases report several approaches in the treatment of four-canal maxillary premolars including a conservative canal preparation with a hybrid shaping technique, endodontic microsurgery and the application of biomaterials. The use of an operating dental microscope, different operating strategies and the critical evaluation of radiographs are all necessary steps for the correct and safe endodontic management of these teeth.

Background The aim of this study was to evaluate the predictability of F22 aligners (Sweden & Martina, Due Carrare, Italy) in guiding teeth into the positions planned using digital orthodontic setup. Methods Sixteen adult patients (6 males and 10 females, mean age 28 years 7 months) were selected, and a total of 345 teeth were analysed. Pre-treatment, ideal post-treatment—as planned on digital setup—and real post-treatment models were analysed using VAM software (Vectra, Canfield Scientific, Fairfield, NJ, USA). Prescribed and real rotation, mesiodistal tip and vestibulolingual tip were calculated for each tooth and, subsequently, analysed by tooth type (right and left upper and lower incisors, canines, premolars and molars) to identify the mean error and accuracy of each type of movement achieved with the aligner with respect to those planned using the setup. Results The mean predictability of movements achieved using F22 aligners was 73.6%. Mesiodistal tipping showed the most predictability, at 82.5% with respect to the ideal; this was followed by vestibulolingual tipping (72.9%) and finally rotation (66.8%). In particular, mesiodistal tip on the upper molars and lower premolars were achieved with the most predictability (93.4 and 96.7%, respectively), while rotation on the lower canines was the least efficaciously achieved (54.2%). Conclusions Without the use of auxiliaries, orthodontic aligners are unable to achieve programmed movement with 100% predictability. In particular, although tipping movements were efficaciously achieved, especially at the molars and premolars, rotation of the lower canines was an extremely unpredictable movement.

Objectives This in vitro study aims to compare the fracture resistance of three CAD/CAM materials used in endocrown restoration of interproximal defects in maxillary premolars. Materials and methods 45 maxillary premolars extracted as part of orthodontic treatment were included. Following standardized root canal treatment, all teeth were prepared into Mesial-Occlusal (MO) cavity types. The samples were then randomly divided into three groups: LD [repaired with lithium disilicate glass ceramics (IPS e.max CAD)], VE [treated with polymer-infiltrated ceramics (Vita Enamic)], and LU [repaired with resin-based nanoceramics (Lava Ultimate)]. Axial static loading was applied using a universal testing machine at 1 mm/min until fracture, and fracture resistance and failure modes were recorded. Results Regarding Fracture Resistance Values (FRVs), the LD group exhibited significantly higher values than the other two groups, VE ( P  = 0.028) and LU ( P  = 0.005), which showed no significant difference ( P  = 0.778). On the other hand, regarding failure modes, the LD group had a higher prevalence of irreparable fractures compared to the other two groups, VE ( P  < 0.001) and LU ( P  < 0.001), which showed no significant difference. Conclusions Although lithium disilicate glass ceramics exhibited higher FRVs, they had a lower repair probability. In contrast, polymer-infiltrated ceramics and resin-based nanoceramics contributed to tooth structure preservation. Clinical relevance For maxillary premolars with interproximal defects following root canal treatment, resin ceramic composites are recommended for restoration to enhance abutment teeth protection.

Successful root canal treatment requires a thorough understanding of root canal morphology. This study investigated the root canal morphology and the fine anatomical characteristics of maxillary first premolars in an Iraqi sub-population using micro-computed tomography (micro-CT) and classified using Vertucci and Ahmed et al. systems. A total of 151 extracted maxillary first premolars were collected, cleaned and disinfected. The collected teeth were scanned using a micro-CT system. The images were segmented and three-dimensionally (3D) reconstructed using Mimics research software, for the evaluation of root canal morphology, isthmuses and accessory canals. The data were analysed using the Monte Carlo simulations for Chi-Square test with a significance level of 0.05. Results showed that out of the 151 maxillary first premolars, 82 (54.3%) were double-rooted and 69 (45.7%) were single-rooted. The most common root canal configuration in the single-rooted teeth was Vertucci Type VII (Ahmed et al. code 1 MaxP 1–2−1–2 ), and Vertucci Type IV (Ahmed et al. code 2 MaxP B 1 P 1 ) was the most common type in the double-rooted teeth. About 15.2% of the samples could not be classified by Vertucci system and were classified using Ahmed et al. system. Isthmuses were observed in 28.5% of the samples with the middle root third was the most common location. Isthmus prevalence was significantly higher in single-rooted teeth (50.7%) compared to the double-rooted teeth (9.8%) ( P  < 0.001). The accessory canals were found in 77.5% of the samples, mostly in the apical third of the root, as classified by Ahmed et al. coding system for accessory canals. Accessory canal location varied more in the buccal root compared to the palatal root and single-rooted teeth ( P  < 0.05). Maxillary first premolars showed wide variations in root canal morphology and fine anatomical features such as isthmuses and accessory canals in the studied Iraqi population. Ahmed et al. system appeared to be more reliable in characterizing the root canal morphology compared to Vertucci classification. Clinicians need to consider utilising advanced imaging techniques, such as CBCT, to provide a clearer visualization of root canals. This allows them to plan disinfection protocols, ensuring thorough cleaning of the entire canal system.