Morphology and classification of the second mesiobuccal canal in maxillary first molars: a cone-beam computed tomography analysis in a Chinese population.

BACKGROUND: Understanding the tooth anatomy is crucial for ensuring effective endodontic treatment. This study investigated the root canal morphology of the second mesiobuccal (MB2) canal in maxillary first molars (MFMs) in a Chinese population using cone-beam computed tomography (CBCT). METHODS: This study evaluated 486 MFMs with MB2 canals from 285 participants undergoing CBCT examination and determined the Vertucci's classification and position of the MB2 canal orifice. The prevalence of the MB2 canal was correlated with the sex, age, and tooth side. The correlations between the prevalence of the MB2 canal and sex and tooth side were assessed using the Fisher's exact test. The chi-square test was used for evaluating the correlation between the prevalence of the MB2 canal and age. RESULTS: The number of type II, III, IV, V, VI, VII, and other root canals in the MFMs was 30.9%, 0.6%, 65.0%, 1.2%, 1.2%, 0.4%, and 0.6%, respectively. Among the 201 cases with bilateral inclusion, 87.6% showed consistent canal configuration. Results of the first clear apparent position (FCAP) of the MB2 canals showed that 434, 44, and 3 teeth had FCAP at the upper, middle, and bottom one-third of the root, respectively. The FCAPs of the MB2 canal in the MFMs with types II, IV, and VI, as well as types III and V canals showed significant differences (p<0.05). The horizontal distance between the MB1 and MB2 canal orifices in the type II canals of MFMs was significantly lesser than those in the type IV canals of MFMs (p < 0.01). The longitudinal distance between the pulp chamber floor plane and MB2 canal orifice significantly correlated with age (p < 0.05). CONCLUSIONS: The morphology of the mesiobuccal root canal in the MFMs is complex. Complete understanding of the anatomical morphology of the root canal combined with the CBCT and dental operating microscope is necessary for the accurate detection of the MB2 canal and consequently improved success rate of root canal treatment. Our study findings can help endodontists improve endodontic treatment outcomes.

Chewing asymmetry in dogs: Exploring the importance of the fossa masseterica and first molar teeth morphology.

Dogs are animals with strong bite force. This strong bite mechanism has led to significant changes in the skeletal system such as fossa masseterica. It can be thought that one side is used more than the other side in chewing and is related to the preference of using the same side's hand, eye and foot. In the study, directional asymmetry and fluctuating asymmetry, which occurs as a result of chewing asymmetry, were examined on the first molar teeth and the fossa masseterica in 85 dog mandibles including a wide diversity of morphotypes. The association of high PC1 values for directional asymmetry with a pronounced cranial index, as evident in breeds like Pekingese, Pomeranian and Bulldog, indicates a potential evolutionary or selective breeding trend favouring brachycephaly. On the contrary, guardian breeds like the German shepherd and Bernese mountain dog, which typically require strong jaws for their roles, showcased reduced PC1 values, which might be related to their functional morphology. Similarly, the PCA results for the first molar teeth shape variations also highlighted the influence of cranial shape, with boxer dogs displaying notably higher PC1 values. The fluctuating asymmetrical distributions provided valuable insights into individualistic variations. Interestingly, no specific breed distribution trend was observed for these asymmetries, indicating a more individual-based variation rather than breed-based. It is essential to note that while these results provide valuable insights, further studies are required to understand the underlying causes better. Factors like genetic variations, developmental processes, dietary habits and external environmental factors could play pivotal roles in these observed morphological differences.

Biometric analysis of furcation area of molar teeth and its relationship with instrumentation.

The anatomy of furcation favours the bacterial retention and makes periodontal debridement as well as oral hygiene procedures difficult. Teeth that have lost attachment to a level of the furcation are said to have a furcal invasion or furcation involved.Involvement of furcation in a multi-rooted tooth poses a very different type of clinical situation in terms of establishment of diagnosis, determination of prognosis and of course planning the treatment modality.The present study was carried out on 200 selected extracted human first and second permanent molar teeth based on a predefined criteria. Teeth with prosthetic crowns, fused or fractured roots, those not fully developed, grossly carious or heavily restored at the cementoenamel junction (CEJ) were excluded from the study. The morphology of the root trunk was recorded by measuring various dimensions of the root trunk,including furcal angle and root trunk volume was calculated by using a custom made special apparatus. The furcation areas were debrided with different types of curettes in the market in order to see how best the instrument could be maneuvered in the furcation area. The data so obtained was statistically analysed using SPSS version 22. The highest root trunk volume and the longest root trunk length were found to be in the maxillary second molar. 48.60% furcations didn't allow instrument engagementof furcation area with standard area specific curettes. The proposal of inclusion of root trunk length (mm) is suggested in addition to classification of FI to have assess prognosis and appropriate treatment for of the involved tooth.

Jurassic shuotheriids show earliest dental diversification of mammaliaforms.

Shuotheriids are Jurassic mammaliaforms that possess pseudotribosphenic teeth in which a pseudotalonid is anterior to the trigonid in the lower molar, contrasting with the tribosphenic pattern of therian mammals (placentals, marsupials and kin) in which the talonid is posterior to the trigonid1-4. The origin of the pseudotribosphenic teeth remains unclear, obscuring our perception of shuotheriid affinities and the early evolution of mammaliaforms1,5-9. Here we report a new Jurassic shuotheriid represented by two skeletal specimens. Their complete pseudotribosphenic dentitions allow reidentification of dental structures using serial homology and the tooth occlusal relationship. Contrary to the conventional view1,2,6,10,11, our findings show that dental structures of shuotheriids can be homologized to those of docodontans and partly support homologous statements for some dental structures between docodontans and other mammaliaforms6,12. The phylogenetic analysis based on new evidence removes shuotheriids from the tribosphenic ausktribosphenids (including monotremes) and clusters them with docodontans to form a new clade, Docodontiformes, that is characterized by pseudotribosphenic features. In the phylogeny, docodontiforms and 'holotherians' (Kuehneotherium, monotremes and therians)13 evolve independently from a Morganucodon-like ancestor with triconodont molars by labio-lingual widening their posterior teeth for more efficient food processing. The pseudotribosphenic pattern passed a cusp semitriangulation stage9, whereas the tribosphenic pattern and its precursor went through a stage of cusp triangulation. The two different processes resulted in complex tooth structures and occlusal patterns that elucidate the earliest diversification of mammaliaforms.

Influence of crown shade, translucency, and scan powder application on the trueness of intraoral scanners.

OBJECTIVES: Natural teeth and dental restorations present with various shades and levels of translucency. This study aimed to determine whether these variations in ceramic crowns and scan powder application affect the trueness of intraoral scanners. METHODS: Eight identical premade resin typodonts, each prepared for a crown on the maxillary right second molar, were used. Eight lithium disilicate crowns, distinguished by two levels of translucency (high and low) and four shades (BL1, A2, A3, and A4), were fabricated to an identical design and cemented onto each typodont, providing eight distinct experimental groups (2 levels of translucency × 4 shades). Reference scans were acquired using a desktop scanner. Test scans were performed ten times for each experimental group using two different intraoral scanners (Medit i700 and CEREC Primescan AC), with and without the application of scan powder (n = 10). Three-dimensional metrology software was used to assess the trueness of the intraoral scan datasets. Statistical analysis involved the Kruskal-Wallis H test, Mann-Whitney U test, and independent t-test (α=0.05). RESULTS: For powder-free intraoral scan datasets, the crown shade did not significantly affect trueness within each translucency group (P = 1.000). For both intraoral scanners, compared with low translucency groups, higher marked deviations were exhibited by high translucency groups (P<.001). Scan powder use largely mitigated these differences (P>.05) and enhanced the trueness of the intraoral scan (P<.01). CONCLUSIONS: Shade did not significantly influence the trueness of intraoral scans. High-translucency crowns were scanned with less accuracy than were low-translucency crowns. CLINICAL SIGNIFICANCE: Unlike tooth shade, translucency significantly affected the accuracy of intraoral scans. Therefore, considering the use of scan powder when scanning objects with high translucency may be beneficial.

Facial soft-tissue thickness in children: A study of a CTBC Brazilian sample.

As an auxiliary method in the process of human identification, forensic facial approximation (FFA) is an important tool for identifying unknown human bodies whose remains do not present the necessary traceability to any antemortem data collection. Specific characteristics are necessary when addressing children aged between 6 and 10 years, who have little sexual differentiation and a mixed dentition. Due to the chronology of eruption of the permanent second molars in this population, it is not possible to measure facial soft-tissue thickness (FSTT) from specific landmarks such as supra and infra M2. The objective of this research was to report the method for measuring the average FSTT of 32 landmarks adapting the method for adults replacing the landmarks at the upper and lower second molars (Supra M2 and Infra M2) in children up to 10 years of age for a measurement using the deciduous second molars as reference. We found statistical differences for some points, considering the variables of age and sex, but with a maximum difference of 2 mm, which allows the use of a single FSTT table. The deciduous teeth can replace the reference of the thicknesses at the supra and infra M2 landmarks. In addition to the new FSTT data for children in Brazil, we concluded that the proposed adaptation to the deciduous M2 points can be applied to obtain soft-tissue data for 32 facial points.

Age estimation by pulp canal/root ratio in Yorkshire terrier dogs.

Background: The study of the morphological parameters of teeth on dental radiographic images, especially evaluation of the pulp canal/root ratio (PCRR), has been presented as a reliable method to estimate age both in humans and animals. Evaluating PCRR involves a simple, nondestructive procedure that can be used both in living individuals and in cadavers. There is a scarcity of studies assessing the relationship between PCRR and age in dogs (Canis lupus familiaris). Objective: The aim of this study was to evaluate the relationship between PCRR and age in Yorkshire terrier dogs. Animals and procedures: Dental radiographs of 53 Yorkshire terrier dogs from the database of the Odontovet Veterinary Dentistry Center (Brazil) were analyzed. Using ImageJ software, 3 consecutive measurements of the widths of 2 roots (mesial and distal) and their respective pulp canals were taken at both mandibular molar teeth (left, 309 and right, 409). The PCRR was then calculated using width means. Results: The PCRR decreased with increasing age in both mesial (0.21 ± 0.09 in animals aged < 24 mo, 0.12 ± 0.04 in animals aged between 25 and 96 mo, and 0.09 ± 0.03 in dogs aged > 96 mo) and distal (0.24 ± 0.11, 1.01 ± 0.03, and 0.09 ± 0.03, by the same order) roots. A statistically significant, moderate negative correlation was demonstrated between age and PCRR of the mesial [rs (97) = -0.545; P < 0.001] and distal [rs (98) = -0.578; P < 0.001] roots. Conclusion and clinical relevance: This work contributes to the knowledge of PCRR in dogs and its relationship with age, paving the way for further studies using larger samples in different canine breeds.

Estimation de l'âge par le rapport canal pulpaire/racine chez des chiens de race Yorkshire. Contexte: L'examen des paramètres morphologiques des dents sur des radiographies dentaires, particulièrement l'évaluation du rapport canal pulpaire/racine (PCRR), a été présenté comme une méthode fiable d'estimer l'âge chez les humains et les animaux. L'évaluation du PCRR est faite au moyen d'une procédure simple et non-destructive qui peut être utilisée autant chez les individus vivants que sur des cadavres. Il y a peu d'études évaluant la relation entre le PCRR et l'âge chez les chiens (Canis lupus familiaris). Objectif: L'objectif de la présente étude était d'évaluer la relation entre le PCRR et l'âge chez des chiens de race Yorkshire. Animaux et procédures: Les radiographies dentaires de 53 chiens de race Yorkshire provenant de la base de données du Centre de dentisterie vétérinaire Odontovet (Brésil) ont été analysées. À l'aide du logiciel ImageJ, 3 mesures consécutives de la largeur de 2 racines (mésiale et distale) et de leur canal pulpaire respectif ont été prises au niveau des dents molaires mandibulaires (gauche, 309 et droite, 409). Le PCRR a par la suite été calculé utilisant les moyennes des largeurs. Résultats: Le PCRR diminuait avec une augmentation de l'âge autant pour la racine mésiale (0,21 ± 0,09 chez les animaux âgés de < 24 mo, 0,12 ± 0,04 chez les animaux âgés entre 25 et 96 mo, et 0,09 ± 0,03 chez les chiens de > 96 mo) que pour la racine distale (0,24 ± 0,11, 1,01 ± 0,03, 0,09 ± 0,03, dans le même ordre d'âge). Une différence statistiquement significative, corrélation modérément négative a été mise en évidence entre l'âge et le PCRR pour la racine mésiale [rs (97) = −0,545; P < 0,001] et la racine distale [rs (98) = −0,578; P < 0,001]. Conclusion et pertinence clinique: Cette étude contribue à la connaissance du PCRR chez les chiens et sa relation avec l'âge, ouvrant la voie à des études ultérieures avec un échantillonnage plus grand et différentes races de chien.(Traduit par Dr Serge Messier).

Morphometric variations and nonmetric anatomical traits or anomalies of the primary molar teeth, plus the molars' size thresholds for sex identification.

INTRODUCTION: Morphological and morphometric features of the teeth are of interest to various clinical and academic dental and medical fields including prosthodontics, orthodontics, anatomy and anthropology, pathology, archeology, and forensic dentistry. These have been more or less researched in the case of the permanent dentition. However when it comes to the primary dentition, the literature is scarce and controversial. No study worldwide exists on the cutoff points (thresholds) for sex identification; no study exists on metric or nonmetric traits of deciduous teeth in Iranians. Hence, the aim of the study was to assess both the metric and nonmetric traits of primary molars, as well as their cut-off points for sex identification. METHODS: In this epidemiological cross-sectional study, pretreatment casts of 110 children (51 boys and 59 girls) aged 6 to 12 years were collected. Maxillary and mandibular first and second primary molars were evaluated regarding their metric traits (mesiodistal and buccolingual widths) and 9 nonmetric traits (Accessory cusp on the upper D, Accessory cusp on the lower D, Fifth cusp on the upper E, Carabelli's cusp on the upper E, Protostylid on the lower E, Fifth cusp on the lower E, Sixth cusp on the lower E, Tuberculum intermedium [metaconulid] on the lower E, and Deflecting wrinkle on the lower E). ROC curves were used to identify cut-off points for sex determination as well as the usefulness of metric measurements for this purpose. Data were analyzed using independent-samples and paired-samples t-tests, McNemar, Fisher, and chi-square tests, plus Pearson and Spearman correlation coefficients (α = 0.05). RESULTS: All the primary molars' coronal dimensions (both mesiodistal and buccolingual) were extremely useful for sex identification (ROC curves, all P values ≤ 0.0000099). Especially, the mandibular primary molars (areas under ROC curves [AUCs] between 85.6 and 90.4%, P values ≤ 0.0000006) were more useful than the maxillary ones (AUCs between 80.4 and 83.1%, P values ≤ 0. 0000099). In the mandible, the first primary molar (maximum AUC = 90.4%) was better than the second molar (maximum AUC = 86.0%). The optimum thresholds for sex determination were reported. Sex dimorphism was significant in buccolingual and mesiodistal crown widths of all the primary molars (all P values ≤ 0.000132), but it was seen only in the case of 2 nonmetric traits: Deflecting wrinkle (P = 0.001) and Tuberculum intermedium (metaconulid, P = 0.029) on the lower Es, taking into account the unilateral and bilateral cases. The occurrence of nonmetric traits was symmetrical between the right and left sides (all P values ≥ 0.250). All mesiodistal and two buccolingual molar measurements were as well symmetrical (P > 0.1); however, two buccolingual measurements were asymmetrical: in the case of the maxillary E (P = 0.0002) and mandibular D (P = 0.019). There were three weak-to-moderate correlations between the nonmetric traits of the mandibular second molars (Spearman correlations between 22.7 and 37.5%, P values ≤ 0.045). Up to 6 concurrent nonmetric traits were observed in the sample, with 53.6% of the sample showing at least 2 concurrent nonmetric traits at the same time, without any sex dimorphism (P = 0.658). CONCLUSION: Sex dimorphism exists considerably in primary molars' sizes, but it is not as prevalent in their nonmetric traits or abnormalities. Primary molars' crown sizes are useful for sex identification; we calculated optimum cut-off points for this purpose, for the first time.

Retrospective study of the morphology of third maxillary molars among the population of Lower Silesia based on analysis of cone beam computed tomography.

INTRODUCTION: Understanding the anatomy of root canal systems and being aware of their variations is crucial for successful endodontic treatment. Specifically, the intricate and diverse nature of the root anatomy in maxillary third molars poses a significant challenge for dental clinicians. The study analyzed the morphology of the root canal system in maxillary third molars among residents of the Lower Silesia region in Poland using cone beam computed tomography (CBCT). MATERIAL AND METHODS: This retrospective cross-sectional imaging study was conducted at the X-Ray Diagnostics Laboratory of the Academic Dental Polyclinic of Wroclaw Medical University, Poland. The study evaluated 316 CBCT scans and included 196 maxillary third molars. They were obtained from 118 females and 78 males over the age of 18, in the period from January to April 2022 (three consecutive months). The number of roots, root canals, and root canal configurations according to Vertucci's classification were analyzed. RESULTS: Three-rooted maxillary molars were found most often (64.29%), followed by single-rooted (24.49%), two-rooted (7.65%), and four-rooted (3.57%) teeth. Among all the roots examined, Vertucci Type I root canals were the most prevalent. Our research found that single-rooted forms (40 teeth, 33.89% vs. 8 teeth, 10.26%, p = 0.0013) of maxillary third molars were significantly more common in females than in males. However, three-rooted forms (62 teeth, 79.49% vs. 64 teeth, 54.24%, p = 0.0013) of maxillary third molars were significantly more common in males than in females. DISCUSSION: In the Lower Silesia region, the typical maxillary third molar in the Polish population has a three-rooted structure with Vertucci Type I root canal configuration. We noted a sex-dependent correlation in maxillary third molar morphology, with single-rooted forms more prevalent in women and three-rooted forms in men.

New craniodental fossils of Paranthropus robustus from Kromdraai, South Africa (2014-2017 excavations).

Since the initial discovery of Paranthropus robustus at the site of Kromdraai in 1938, the hypodigm of this species has been expanded by subsequent work at the localities of Swartkrans and Drimolen, with a few fossils also known from Cooper's D, Gondolin and Sterkfontein Member 5. Beginning in 2014, systematic excavations at Kromdraai uncovered a large and previously unknown fossiliferous area, shedding light on Units O and P in the earliest part of the site's stratigraphic sequence. The aim of this paper is to provide detailed descriptions and illustrations of 30 P. robustus craniodental specimens recovered between 2014 and 2017 within the Unit P deposits at Kromdraai. This new sample predates all prior conspecific specimens found at this site (including the holotype of P. robustus from Kromdraai, TM 1517). Its basic dental morphology dimensions and cranial features are compared in a preliminary analysis with other P. robustus samples. The P. robustus sample from Kromdraai Unit P documents previously unknown portions of the P. robustus juvenile cranium. The new dental and cranial remains aid in the exploration of potential morphological distinctions between site-specific P. robustus samples and are compared favorably in size and morphology with the small P. robustus specimens from Drimolen (e.g., DNH 7). These findings do not support the hypothesis that the specimens from Drimolen belong to a different taxonomic group. Instead, they reinforce the presence of a significant degree of sexual dimorphism within P. robustus. The Kromdraai Unit P specimens also contribute to the biodemographic profile of P. robustus. The notable prevalence of infants (i.e., juvenile individuals before the emergence of their first permanent molars) mirrors the natural mortality profiles observed in wild chimpanzees. This suggests a closer resemblance in the processes of accumulation in Kromdraai Unit P and Drimolen than at Swartkrans.

External Validation of the Effect of the Combined Use of Object Detection for the Classification of the C-Shaped Canal Configuration of the Mandibular Second Molar in Panoramic Radiographs: A Multicenter Study.

INTRODUCTION: The purposes of this study were to evaluate the effect of the combined use of object detection for the classification of the C-shaped canal anatomy of the mandibular second molar in panoramic radiographs and to perform an external validation on a multicenter dataset. METHODS: The panoramic radiographs of 805 patients were collected from 4 institutes across two countries. The CBCT data of the same patients were used as "Ground-truth". Five datasets were generated: one for training and validation, and 4 as external validation datasets. Workflow 1 used manual cropping to prepare the image patches of mandibular second molars, and then classification was performed using EfficientNet. Workflow 2 used two combined methods with a preceding object detection (YOLOv7) performed for automated image patch formation, followed by classification using EfficientNet. Workflow 3 directly classified the root canal anatomy from the panoramic radiographs using the YOLOv7 prediction outcomes. The classification performance of the 3 workflows was evaluated and compared across 4 external validation datasets. RESULTS: For Workflows 1, 2, and 3, the area under the receiver operating characteristic curve (AUC) values were 0.863, 0.861, and 0.876, respectively, for the AGU dataset; 0.935, 0.945, and 0.863, respectively, for the ASU dataset; 0.854, 0.857, and 0.849, respectively, for the ODU dataset; and 0.821, 0.797, and 0.831, respectively, for the ODU low-resolution dataset. No significant differences existed between the AUC values of Workflows 1, 2, and 3 across the 4 datasets. CONCLUSIONS: The deep learning systems of the 3 workflows achieved significant accuracy in predicting the C-shaped canal in mandibular second molars across all test datasets.

Microcomputed-Tomographic Analysis of the Root Canal Morphology of the Mandibular First Molars in a Malaysian Subpopulation Using Two Classification Systems / Análisis por Tomografía Microcomputada de la Morfología del Conducto Radicular de los Primeros Molares Mandibulares en una Subpoblación de Malasia Utilizando dos Sistemas de Clasificación

SUMMARY: This work investigated the morphology of the root canal system of the mandibular first molar in a Malaysian subpopulation. Using micro-computed tomography with an isotropic resolution of 22 µm, 140 mandibular first molars were scanned. MIMICS software was used for segmentation, 3-D reconstruction and analysis of the acquired images. The canal configuration was described using Vertucci [supported by the supplementary configurations proposed by Sert & Bayirli (2004)] and Ahmed et al. (2027), coding systems. The chi-square test was used to assess the association between qualitative variables. By non-considering intercanal communications, Vertucci types IV (17.1%) and I (76.4%) were the most frequently reported configurations in the mesial and distal roots, respectively. Of the reported configurations, 24.3% and 4.3% were non-classifiable by Vertucci system in the mesial and distal roots, respectively. Up to 63.6% and 9.3% of the reported configurations were non- classifiable, and type I was the most frequent when considering intercanal communications (7.1% and 76.4% in the mesial and distal roots, respectively). According to Ahmed et al., system, almost half of the sample had more than four digits (47.9%), followed by the 3-digits category (20.71%). In both systems, a significant association was found between the canal configuration and the root type (p<0.001). The mandibular first molar of this Malaysian subpopulation demonstrated a wide range of root canal morphology. When compared to the Vertucci system, the system developed by Ahmed et al., successfully classified all molars configurations despite their level of complexity. The complex canal anatomy of mandibular first molars in this subpopulation warrants special attention during root canal treatment procedures.

En este trabajo se investigó la morfología del sistema de conductos radiculares del primer molar mandibular en una subpoblación de Malasia. Utilizando tomografía microcomputada con una resolución isotrópica de 22 µm, se escanearon 140 primeros molares mandibulares. Se utilizó el software MIMICS para segmentar (enmascarar), reconstruir en 3D, visualizar y analizar las imágenes adquiridas. La configuración del canal se describió utilizando Vertucci respaldado por las configuraciones complementarias propuestas por Sert & Bayirli (2004)] y Ahmed et al. (2017, 2020), sistemas de codificación. Se utilizó la prueba de chi-cuadrado para evaluar la asociación entre variables cualitativas. Sin considerar las comunicaciones intercanales, los tipos Vertucci IV (17,1%) y I (76,4%) fueron las configuraciones reportadas con mayor frecuencia en las raíces mesiales y distales, respectivamente. De las configuraciones reportadas, el 24,3 % y el 4,3 % fueron no clasificables por el sistema de Vertucci en las raíces mesial y distal, respectivamente. Hasta el 63,6 % y el 9,3 % de las configuraciones reportadas fueron no clasificables, siendo la tipo I la más frecuente al considerar las comunicaciones intercanales (7,1 % y 76,4 % en las raíces mesiales y distales, respectivamente). Según Ahmed et al. (2017, 2020) en el sistema, casi la mitad de la muestra tenía más de cuatro dígitos (47,9 %), seguido por la categoría de 3 dígitos (20,71 %). En ambos sistemas se encontró una asociación significativa entre la configuración del canal y el tipo de raíz (p<0,001). El primer molar mandibular de esta subpoblación de Malasia demostró una amplia gama morfológica del conducto radicular. En comparación con el sistema Vertucci, el sistema desarrollado por Ahmed et al. (2017, 2020) clasificaron con éxito todas las configuraciones de los molares a pesar de su nivel de complejidad. La compleja anatomía del canal de los primeros molares mandibulares en esta subpoblación merece una atención especial durante los procedimientos de tratamiento de conducto.

[Root canal therapy of maxillary molars with atypical canals: A report of three cases].

Maxillary molar with three roots and 3 to 4 canals is a common occurrence. However, in addition to common root canal anatomy, there may be significant differences in the number, distribution, and morphological structure of root canals. The success of root canal treatment is dependent on ensuring that all the intricate details associated with it are meticulously followed. Failure to locate all canals could have a negative effect on the treatment as it may lead to initiation or continuation of periapical pathology. Missed canals were the main reason for patients reporting back for nonsurgical root canal retreatment. Moreover, the bacteria residing in such canals could also result in persistence of symptoms. Root canal anatomy is complex, and the recognition of anatomic variations could be a challenge for clinicians. This article presents three cases of endodontic management of maxillary molars with atypical canal morphology. In the three cases of this study, the patients underwent cone beam computed tomographic (CBCT) examination before root canal treatment. The CBCT images revealed that the maxillary molars in case 1 and case 2 had 5 canals. Case 1: 2 mesiobuccal (MB, MB2), two distobuccal (DB and DB2), and one palatal canal. Case 2: 2 mesiobuccal (MB, MB2), one distobuccal (DB), and two palatal canals (MP and DP). In case 3, CBCT scan slices showed that the maxillary first molar presented as a C-shaped root canal with a rare tooth anomaly of taurodontism. Although C-shaped root canals were most frequently seen in the mandibular second molar, they might also appear in maxillary molars. A literature search revealed only a few case reports of C-shaped root canal systems in maxillary molars. Case 3 described the fusion between mesiobuccal and palatal roots of the maxillary first molar, forming a C-shaped mesiopalatal root canal. The above cases suggest that endodontists should always be aware of aberrancies in root canal system apart from the knowledge of normal root canal anatomy. CBCT as a means of diagnosis can be helpful for identifying and managing these complex root canal systems. This case series also highlights the importance of magnification and illumination. Through using an endodontic microscope, clinicians can identify root canals that are difficult to locate or overlooked with normal vision. A correct access opening is a most important step to locate and negotiate the orifices of root canals. The use of ultrasonic tips can refine the access cavity and allow controlled and delicate removal of calcifications and other interferences to the canal orifices, thereby helping to locate the extra orifices.

Objective evaluation of tooth carving using homologous models.

PURPOSE/OBJECTIVES: Tooth carvings are evaluated subjectively. However, subjective evaluations are associated with low intra- and inter-evaluator reliability in providing feedback for the fabrication of better tooth carvings. Therefore, this study aimed to analyze the relationship between subjective evaluation and the morphological characteristics of tooth carvings and their morphological characteristics using the feedback method in the low-scoring group. METHODS: Between April 2013 and September 2021, 120 maxillary left first molar carvings fabricated by undergraduate students were subjectively evaluated by an experienced instructor using a five-point scale. The tooth carvings were scanned to obtain three-dimensional shape data and divided into two groups, the high- and low-scoring groups, for principal component analysis. Homologous models with dimensions matching those of the average model were created, and principal component analysis was performed to evaluate the morphological characteristics of the tooth. RESULTS: Principal component analysis indicated that an objective evaluation was possible using homologous model. On increasing the subjective evaluation, the occlusal inclination angle and the cervical region of the tooth became steeper, and the shape of the occlusal surface resembled a parallelogram. In addition, large morphological differences were observed in the position of the cervical region of the tooth, height of contour, and shape of the occlusal surface in the low-scoring group, whereas no such difference was observed in the high-scoring group. CONCLUSION: Objective evaluation of tooth carving was possible using homologous model. The evaluation of tooth morphological characteristics could be effective in providing feedback to undergraduate students.

Developmental process of the modern house shrew's molars: implications for the evolution of the tribosphenic molar in Mesozoic mammals.

Phylogenetically, the tribosphenic molars-prototypes of multi-cusped cheek teeth in marsupial and placental mammals-are derived from the single-cusped conical teeth of reptiles through the addition of cusps. Ontogenetically, mammalian molars are formed through the interface between the dental epithelium and mesenchyme (future enamel-dentin junction), becoming geometrically complex by adding epithelial signaling centers, called enamel knots, which determine future cusp positions. To reevaluate cusp homologies in Mesozoic mammals from an ontogenetic perspective, this study tracked molar development in a living placental mammal species, the house shrew (Suncus murinus), whose molars are morphologically the least derived from tribosphenic prototypes. The development of shrew molars proceeded as if it replayed the evolutionary process of tribosphenic molars. The first formed enamel knots gave rise to the evolutionarily oldest cusps-upper paracone and lower protoconid. The order of formation of other enamel knots and their location in development seemed to trace the order of cusp appearance in evolution. The parallel relationship between ontogeny and phylogeny of mammalian molars, if any, suggests that a change in the timing between developmental events rather than a change in the morphogenetic mechanism itself, should have been a major causal factor for the evolutionary transformation of tooth morphology.

Geometric morphometrics and paleoproteomics enlighten the paleodiversity of Pongo.

Pleistocene Pongo teeth show substantial variation in size and morphology, fueling taxonomic debates about the paleodiversity of the genus. We investigated prominent features of the enamel-dentine-junction junction (EDJ)-phylogenetically informative internal structures-of 71 fossil Pongo lower molars from various sites by applying geometric morphometrics and conducted paleoproteomic analyses from enamel proteins to attempt to identify extinct orangutan species. Forty-three orangutan lower molars representing Pongo pygmaeus and Pongo abelii were included for comparison. The shape of the EDJ was analyzed by placing five landmarks on the tip of the main dentine horns, and 142 semilandmarks along the marginal ridges connecting the dentine horns. Paleoproteomic analyses were conducted on 15 teeth of Late Pleistocene Pongo using high-resolution tandem mass spectrometry. The geometric morphometric results show variations in EDJ shape regarding aspects of the height and position of the dentine horns and connecting ridges. Despite the issue of molar position and sample size, modern molars are distinguished from fossil counterparts by their elongated tooth outline and narrowly positioned dentine horns. Proteomic results show that neither a distinction of P. pygmaeus and P. abelii, nor a consistent allocation of fossil specimens to extant species is feasible. Based on the EDJ shape, the (late) Middle to Late Pleistocene Pongo samples from Vietnam share the same morphospace, supporting the previous allocation to P. devosi, although substantial overlap with Chinese fossils could also indicate close affinities with P. weidenreichi. The hypothesis that both species represent one chronospecies cannot be ruled out. Two fossil specimens, one from Tam Hay Marklot (Laos, Late Pleistocene), and another from Sangiran (Java, Early to Middle Pleistocene), along with some specimens within the Punung sample (Java), exhibit affinities with Pongo abelii. The Punung fossils might represent a mix of early Late Pleistocene and later specimens (terminal Pleistocene to Holocene) related to modern Pongo. The taxonomy and phylogeny of the complete Punung sample needs to be further investigated.

Association of root morphology of mandibular second molars on panoramic-like and axial views of cone-beam computed tomography.

BACKGROUND: Knowledge about the anatomy and morphology of the root canal system is essential for successful surgical and non-surgical root canal treatments. However, precise assessment of the root morphology and anatomy is not often possible on two-dimensional radiographs. This study aimed to investigate the association of root morphology of mandibular second molars on panoramic-like and axial views of cone-beam computed tomography (CBCT). METHODS: This cross-sectional study evaluated 1,231 CBCT scans of mandibular second molars obtained between October 2018 and February 2022 that were retrieved from the archives of a private radiology clinic. Panoramic-like images were reconstructed from the CBCT scans. The root morphology of mandibular second molars was classified on panoramic-like images as type 1, 2, 3, 4, or 5. The root pattern on axial CBCT images was classified into three types of single, double and C-shaped. The association of root morphology on panoramic-like and axial CBCT views was analyzed by the Chi-square test and Fisher's exact test at 0.05 level of significance. RESULTS: Of all, 62.7% of mandibular second molars were type 1; out of which, 97.3% had a double-root pattern on axial CBCT images. Also, 28.6% of them were type 2; of which, 92.6% had a double-root pattern. Moreover, 3.9% were type 3; of which, 47.9% had a C-shaped pattern; 0.9% were type 4, and 45.5% of them showed a single-root pattern; 3.8% were type 5 with 76.6% of them showing a single-root pattern. The prevalence of C-shaped canals was higher in females, and most C-shaped canals had a C3 pattern. CONCLUSION: Root morphology on panoramic-like CBCT views had a strong association with the root canal pattern on axial CBCT views. According to the results, mandibular second molars with a type 3 morphology on panoramic-like CBCT images are highly probable to have a C-shaped canal.

The Clinical and Radiological Evaluation of Impacted Third Molar Position, Crown and Root Morphology.

OBJECTIVE: This study aimed to analyze the crown and root morphology of maxillary and mandibular third molars, and assess their position in relation to adjacent anatomical structures using clinical examination and radiographic images. MATERIALS AND METHODS: A total of 176 extracted impacted or partially impacted third molars were included in this study. Orthopantomogram images (OPG) were used to evaluate the number of roots, position, depth of impaction relative to the occlusal plane of the second molar, and angulation of maxillary and mandibular third molars. The extracted teeth were examined to determine the actual number of roots. The root morphology was classified using the Alavi classification system for maxillary third molars and the Machado classification for mandibular third molars. Additionally, the number of cusps, crown dimensions, and morphology were analyzed using digital and dental calipers. RESULTS: The extracted samples exhibited a significantly higher number of roots compared to the number assessed on OPG images (P<0.001). The majority of mandibular third molars had two fused roots (37.39%) and a five-cuspid crown (48.70%), while maxillary third molars had three fused roots (26.23%) and four cusps (42.62%). Both maxillary (60.66%) and mandibular third molars (61.74%) were predominantly vertically positioned. Regarding the depth of impaction, maxillary third molars were primarily classified as Class C (65.57%), while mandibular third molars were classified as Class B (47.83%). Differences in crown shape were observed, with maxillary crowns being mostly triangular (36.07%) and mandibular crowns being oval (38.26%). Maxillary third molars had shorter crowns compared to mandibular third molars (P<0.05). CONCLUSION: The root morphology of maxillary and mandibular third molars in the population of Bosnia and Herzegovina displays variability. Orthopantomogram imaging was found to be inadequate for accurate determination of the number of roots in third molars. The number of cusps on third molars cannot be relied upon as a predictor of the number of roots. The study's findings will have implications for dental practice, particularly for oral surgeons and restorative dentists.

Endodontic management of an aberrant germinated composite odontome: A case report.

To describe the endodontic treatment of a germinated composite odontome with atypical internal anatomy. A 35-year-old male presented with pain in the left mandibular second molar region. Intraoral examination and Cone-Beam Computed Tomography (CBCT) revealed a rare case of a germinated composite odontome with a 3-2-1 Vertucci configuration in the mesial root. Occlusal morphology and mesial root configuration required modifications in methods of isolation and access cavity preparation. Contemporary tools like magnification, ultrasonics and controlled memory rotary files were essential for executing the treatment plan. The tooth was functional at 18 months follow up and radiographs revealed no abnormality.

An atypical anatomy of permanent mandibular second molar with five roots.

Especially in molars that may have sometimes aberrant additional root canals, the complexity of tooth internal morphology in individual cases sometimes does not match to admitted classification rules and underlines the risk of missed anatomy during the endodontic management. To our knowledge, a permanent mandibular second molar with independent five roots, three mesial and two distal, each of them harboring a single canal, was not yet reported. Despite the treatment difficulties this tooth could be successfully approached by using dental operative microscope and cone-beam computed tomography (CBCT) with small field of view. Though CBCT is not a routine imagistic examination, in case of atypical tooth anatomy aiming to establish adequate diagnosis and treatment plan, the successful clinical outcome prevails over the irradiation dose.