Enameloid-bound δ15 N reveals large trophic separation among Late Cretaceous sharks in the northern Gulf of Mexico.

The nitrogen isotopic composition (15 N/14 N ratio, or δ15 N) of enameloid-bound organic matter (δ15 NEB ) in shark teeth was recently developed to investigate the biogeochemistry and trophic structures (i.e., food webs) of the ancient ocean. Using δ15 NEB , we present the first nitrogen isotopic evidence for trophic differences between shark taxa from a single fossil locality. We analyze the teeth of four taxa (Meristodonoides, Ptychodus, Scapanorhynchus, and Squalicorax) from the Late Cretaceous (83-84 Ma) Trussells Creek site in Alabama, USA, and compare the N isotopic findings with predictions from tooth morphology, the traditional method for inferring shark paleo-diets. Our δ15 NEB data indicate two distinct trophic groups, with averages separated by 6.1 ± 2.1‰. The lower group consists of Meristodonoides and Ptychodus, and the higher group consists of Scapanorhynchus and Squalicorax (i.e., lamniforms). This δ15 NEB difference indicates a 1.5 ± 0.5 trophic-level separation between the two groups, a finding that is in line with paleontological predictions of a higher trophic level for these lamniforms over Meristodonoides and Ptychodus. However, the δ15 NEB of Meristodonoides is lower than suggested by tooth morphology, although consistent with mechanical tests suggesting that higher trophic-level bony fishes were not a major component of their diet. Further, δ15 NEB indicates that the two sampled lamniform taxa fed at similar trophic levels despite their different inferred tooth functions. These two findings suggest that tooth morphology alone may not always be a sufficient indicator of dietary niche. The large trophic separation revealed by the δ15 NEB offset leaves open the possibility that higher trophic-level lamniforms, such as those measured here, preyed upon smaller, lower trophic-level sharks like Meristodonoides.

On the dentition, tooth replacement, and taxonomic status of Charruodon tetracuspidatus Abdala & Ribeiro, 2000: A bizarre cynodont from the middle upper Triassic of southern Brazil.

Among the living tetrapods, mammals present a unique tooth replacement pattern, diphyodonty. Therefore, studying the dentition of mammalian ancestors is relevant to a better understanding of how this remarkable feature evolved. However, little is known about the postcanine tooth replacement pattern among Triassic cynodonts. Here, we applied the nondestructive method of microcomputed tomography (microCT) to analyze the dentition of the enigmatic Upper Triassic sectorial-toothed cynodont Charruodon tetracuspidatus (MCP 3934 PV, holotype) from the Candelaria Sequence, Santa Maria Supersequence, Brazil. The microCT-scan data allowed visualization of the replacement dentition and roots of the functional teeth, which provided information to inform interpretations of the ontogenetic stage and taxonomy of the species. A combination of dental and mandibular traits, as well as the small size of the specimen MCP 3934 PV, suggest an early ontogenetic stage. Additionally, the specimen could potentially be an ontogenetically immature form of another taxon, or a yet unknown species of probainognathian cynodont. Therefore, Charruodon tetracuspidatus is here designated as a nomen dubium, given the challenges of maintaining the species as valid.

Effect of Dental Course Cycle on Anatomical Knowledge and Dental Carving Ability of Dental Students.

This study assessed the effect of the course cycle on theoretical knowledge of dental morphology and the dental carving ability of dental students. Thirty-two dental students from the third semester (initial cycle) and 30 students from the eighth and tenth semesters of the dental course (end cycle) had their theoretical knowledge on dental morphology assessed using a questionnaire with ten closed questions. Their dental carving ability was also assessed using wax carvings in macro models of plaster (for the third [S3] and eight [S8] semesters) and natural-sized artificial teeth (for the tenth [S10] semester). The teeth chosen for the dental carving activity were #16 and #47. The scores were statistically analyzed using the t-test, Kruskal-Wallis test, and Mann-Whitney test (α = 0.05). Students from the initial cycle presented better theoretical knowledge than the other groups did (P < 0.007). No significant differences in carving score were found between the initial and end cycles (P > 0.05), although S10 students obtained a higher score for teeth #16 and #47 (P < 0.05). Natural-sized artificial teeth received a higher evaluation score in dental carvings than the macro models (P < 0.001). Within the limits of this study, it was possible to conclude that students from the initial cycle (S3) presented higher theoretical knowledge, whereas no difference in carving ability was observed between the initial and end cycles. The tenth semester (S10) students performed dental carvings with better quality. Furthermore, carvings in natural-sized artificial teeth presented better quality compared with the macro models.

Estrogen deficiency affects tooth formation and gene expression in the odontogenic region of female rats.

BACKGROUND: There is some evidence that estrogen regulates the expression of several genes in different cells, including dental cells. Therefore, the aim of this study was to investigate the role of estrogen deficiency during tooth development regarding tooth structure morphology and its impact on the expression of odontogenesis-related genes. METHODS: A total of 40 female Wistar rats was divided into OVX (estrogen deficiency) and Sham (control) groups. Bilateral ovariectomy was performed in the OVX group, while Sham surgery was performed in the control group at the age of 21 days. At an age of 56 days, 16 rats were euthanized for gene expression analyses of Bmp4, Smad6, Tgfb1 and Runx2. At the age of 63 days, the remaining rats were euthanized for histological and morphometric analyses of teeth. The mandibles of the rats were submitted to µCT analysis. Tooth structures (enamel, dentin and dental pulp) were analyzed. T test was used to compare the mean differences between groups (p<0.05). RESULTS: In the µCT analysis, enamel and dentin thickness were significantly increased in the control group (p<0.0001). Pulp dimensions were significantly larger in the OVX group (p<0.0001). A reduction of tooth structures in the OVX group was confirmed in HE staining. Smad6 was differentially expressed in the OVX group (p=0.04). CONCLUSION: Estrogen deficiency affects gene expression in the odontogenic region and tooth structure morphology.

Educational Interventions to Improve Dental Anatomy Carving Ability of Dental Students: A Systematic Review.

This systematic review aimed to identify the level of impact of educational strategies for teaching tooth carving on the carving ability of undergraduate dental students. The PubMed-NCBI, Cochrane-CENTRAL, LILACS, Ibecs, BBO, Web of Science, and Scopus databases were searched in May 2019, for randomized controlled trials (RCTs) and two-arm non-randomized studies of interventions (NRSI) addressing educational interventions toward the dental carving of undergraduate students. Studies from the year 2000 until the search date, written in English, Portuguese, and Spanish were included. Study screening and data extraction were performed in duplicate and blinded. The data were presented narratively, considering the dental carving ability of students the primary outcome. The risk of bias was assessed using the RoB tool 2.0 and ROBINS-I, and the level of evidence was determined with GRADE. Of 3,574 studies, 6 were included, with 3 RCTs and 3 NRSIs. Very low level of evidence was provided from the NRSIs that flipped classroom (1 study; n = 140) and a student-driven revised module (1 study; n = 264) improved the carving ability of students. Additionally, there was moderate evidence of online complementary material (1 RCT; n = 30) and reinforcement class improving the carving ability of students (1 RCT; n = 29). The replacement of traditional classes by an instructional DVD (1 RCT; n = 73) and assessment of carving projects through digital systems (1 NRSI; n = 79) did not enhance the carving ability of students. Study design, risk of bias, and imprecision downgraded the level of evidence. There was a very low to moderate evidence on the effectiveness of student-driven educational approaches and complementary classes of dental anatomy in improving the dental carving ability of students.

Optimizing quality of dental carving by preclinical dental students through anatomy theory reinforcement.

Knowledge of dental anatomy is of great importance in the practice of dentistry, especially in oral rehabilitation, because without this knowledge, professional practice is not possible. Dental carving plays a major role in training dental students as it develops their manual dexterity. This randomized controlled trial aimed to evaluate the influence of didactic-theoretical reinforcement on the theoretical and practical knowledge of dental anatomy of preclinical students by examining the quality of the anatomical restorations performed by these students before and after a didactic-theoretical reinforcement. For the evaluation of theoretical knowledge, a questionnaire with closed questions about dental anatomy was used. To evaluate the effect of didactic reinforcement on dental carvings, two groups of 15 preclinical students were assessed. Experimental group (G1) received a three-hour theoretical tutoring on dental anatomy, while the control group (G2) did not. The dental carving scores obtained by the two different groups were compared using Student's t-test. Cohen's d was used to estimate the effect sizes between groups. The frequency of correct answers given for each theoretical knowledge question was compared in each group using Fisher's exact test. T-test was also used to compare the means of the two groups' final scores of theoretical evaluations. To compare these final scores obtained in both carving and theoretical tests, a principal component analysis was performed with different items assessed in each test to obtain factor loading scores and a final weighted score, where factor loadings were considered for each item. Weighted scores were compared using t-test. Also, scores obtained during the head and neck course were assessed and compared using t-test. Spearman's correlation test was used to assess the correlation between scores obtained prior to the anatomy course and scores obtained in the dental carving exercise. The theoretical evaluation revealed no significant difference between the grades (mean ± SD) of G1 (85.1 ± 6.6%) and G2 (86.2 ± 9.1%) with the grades of a baseline test that was previously obtained when students submitted to the study (P = 0.725). Regarding the tooth carving assessment, the dental carving quality by students of G1 has significantly improved, except for tooth #23 (P = 0.096). Theoretical reinforcement of dental anatomy seems to improve the students' carving performance but does not enhance their knowledge about dental anatomy. Anat Sci Educ 11: 377-384. © 2017 American Association of Anatomists.

Rare Condition of Dens Invaginatus in a Maxillary Primary Molar and a Birooted Maxillary Primary Canine diagnosed during Routine Examination.

Congenital morphological dental alterations are related to the physiological phase of tooth development. Since the etiology of the dens invaginatus and supernumerary roots has yet to be fully determined, a rare presentation of dens invaginatus in a primary molar and a birooted deciduous maxillary canine were incidentally detected in routine radiographic examinations. Essential clinical considerations and treatment options are presented. CLINICAL SIGNIFICANCE: This study highlights the importance of a deep and comprehensive anamnesis and clinical examination, with radiographs taken when necessary. The negligence of these stages in an initial consultation could cause irreversible future damage to the patient, since rare dental anomalies or other lesions that require treatment may not be detected. HOW TO CITE THIS ARTICLE: Brandão ECB, Ribeiro AAA, Seabra LMA. Rare Condition of Dens Invaginatus in a Maxillary Primary Molar and a Birooted Maxillary Primary Canine diagnosed during Routine Examination. Int J Clin Pediatr Dent 2017;10(2): 193-195.

Description and quantitative analysis of the dentition of the southern thorny skate Amblyraja doellojuradoi.

A description of the tooth morphology of 234 jaws from the southern thorny skate Amblyraja doellojuradoi in the south-west Atlantic Ocean is given. Seven rows of teeth were selected and length and width of each tooth in these rows were measured. It was found that functional series corresponds to the third teeth and the average width and length of these teeth were compared among jaws, maturity stages, sexes and rows. Generalized linear models were used to determine the subset of measures that most contribute to explain the variability between groups. It was observed that males have longer teeth than females, but the teeth of females are wider. These differences are attributed to reproductive behaviour, in which males bite females to hold them during copulation. This study provides a description of the teeth of A. doellojuradoi, supplying a valuable tool for identification of species. In addition, the establishment of the main variations observed in the dentition, improves the understanding of the species' biology.

Mestizo anterior teeth's proportions / Proporciones de los dientes anteriores en una población mestiza

Teeth proportions relate to beauty and harmony but aesthetic dental ideal proportion models show inconsistent results. Golden Proportion´s, Preston's, Fayyad's, Snow's, and Ward's models where characterized for best fit in a Colombian mestizo population anterior teeth. Models of teeth´s beauty proportions (Golden Proportion´s, Preston's, Fayyad's, Snow's, and Ward') are analyzed for best fit in a mestizo (mixed race) Colombian population and variables as sex, aesthetic balance or history of previous orthodontic treatments were also analyzed for their probable impact on the distribution of the dental proportions. It was used standardized photographs of anterior teeth on 351 individuals of both sexes with complete erupted and healthy teeth. The measurements were done by calibrated computer software (error of 0.05 mm). A Chi squared test was used to check whether sex, aesthetic balance and previous orthodontic treatment had an impact on the distribution of the dental proportions. Also a nonparametric Wilcoxon test was used to analysis the null hypothesis. A cluster analysis using k means was carried out to search for subgroups, which better explain the distribution of anterior dental proportions in the sample. For the considered results the null hypothesis of the mean equaling to the Golden Proportion was rejected (Wilcoxon test p value <0.001). For the whole population, the Chi squared test did not reject the null hypothesis of equal proportions among the groups with respect to the sex (p value= 0.56), aesthetic balance (p value= 0.98) and history of previous orthodontic treatments (p value= 0.67) variables. For the aesthetically balanced individuals, the Chi squared test also failed to reject the null hypothesis of equal proportions among the groups with respect to the sex (p value= 0.63) and history of previous orthodontic treatments (p value= 0.93) variables. Two Gaussian distributions were found for RED models fitting well in 58 % for RED 70 % (0.7 SD 0.03) and 42 % for RED 75 (0.75 SD 0.025). From the cluster analysis using k means, two groups were identified in the whole sample. No universal model can describe the whole population but is possible to find a set of models for the different population subgroups. Aesthetically ideals are open to interpretation. Clinical aesthetically standards for ideal teeth proportions are open to interpretation in a mestizo (mixed raced) population.

Las proporciones de los dientes se refieren a su belleza y armonía, pero los modelos de proporciones dentales estéticas ideales muestran resultados inconsistentes. La proporción Aurea y los modelos de Preston, Fayyad, Snow, y Ward fueron ajustados para caracterizar los dientes de una población colombiana mestiza. Modelos de proporciones de belleza de dientes (Proporción Aurea, Modelos de Preston, Fayyad, Snow y Ward) se analizaron para lograr alcanzar el mejor ajuste en una población colombiana mestiza (mezcla de razas), y también se analizaron las variables de sexo, equilibrio estético e historia de tratamientos de ortodoncia previos para evaluar su probable impacto sobre la distribución de las proporciones dentales consideradas. Fueron utilizadas fotografías estandarizadas de dientes anteriores de 351 individuos de ambos sexos con dientes completamente erupcionados y sanos. Las mediciones fueron realizadas con programas informáticos calibrados (error de 0,05 mm). Se utilizó la prueba Chi Cuadrado para comprobar si el sexo, el equilibrio estético y el tratamiento ortodóncico previo tuvieron un impacto en la distribución de las proporciones dentales. También se utilizó la prueba no paramétrica de Wilcoxon para el análisis de la hipótesis nula. Un análisis de conglomerados, utilizando la media k, se llevó a cabo para buscar subgrupos, que explicaron mejor la distribución de proporciones dentales anteriores en la muestra. Para que los resultados fueran considerados, la hipótesis nula de la media que equivale a la proporción áurea fue rechazada (Prueba de Wilcoxon, valor p <0,001). Para toda la población, la prueba de Chi Cuadrado no rechazó la hipótesis nula de proporciones iguales entre los grupos con respecto al sexo (valor de p= 0,56), equilibrio estético (valor de p= 0,98) y la historia de tratamientos de ortodoncia previos ( valor de p= 0,67). Para los individuos estéticamente balanceados, la prueba de Chi Cuadrado tampocó rechazó la hipótesis nula de proporciones iguales entre los grupos con respecto a las variables de sexo (valor p= 0,63) y la historia de los tratamientos de ortodoncia anteriores (valor p= 0,93). Se encontraron dos distribuciones gaussianas para los modelos RED que encajaron bien en el 58% para RED 70 % (0,7 DE 0,03) y el 42 % para RED 75 (0,75 DE 0,025). Con respecto al análisis de los conglomerados a través de las medias k, se identificaron dos grupos en toda la muestra. No hay un modelo universal que pueda describir toda la población, pero es posible encontrar un conjunto de modelos para los diferentes subgrupos de población. Los ideales estéticamente están abiertos a interpretación. Las normas clínicas de estética para dientes con proporciones ideales están abiertos a interpretación en una población mestiza.

Developmental anomalies affecting the morphology of teeth - a review

Introduction:The development of tooth is a complex process wherein there is series of interactions between the ectoderm and ectomesenchyme. The role of genes in determining the shape and form of a specific tooth has already been defined, the alterations in which can lead to a variety of anomalies in regards to number, size, form, shape, structure, etc. Objective: To review the literature on the developmental anomalies of teeth. Literature review: The developmental anomalies affecting the morphology exists in both deciduous & permanent dentition and shows various forms such as gemination, fusion, concrescence, dilacerations, dens evaginatus, dens invaginatus, enamel pearls, taurodontism or peg laterals. These anomalies have clinical significance concerning esthetics, malocclusion and more importantly predisposing the development of dental caries and periodontal diseases. Conclusion: Knowledge of various diagnostic criteria for identification of these developmental anomalies is significant for early diagnosis and pertinent treatment.

The C-shaped canal molar: an Endodontic-Archaeological study of the relationships between Mayan pre-Hispanic and contemporary population of Yucatán.

AIM: To assess the prevalence of C-shaped canal systems in mandibular second molars, in samples of modern and pre-Hispanic Mayan individuals in Yucatán, Mexico, and to analyse the trait through time and attempt to find new evidence of ethnical bonds between populations. METHODOLOGY: Three hundred and forty-one randomly selected patients were treated in the Endodontic Clinic at the Dental school of the Universidad Autónoma de Yucatán, and 48 mandibular second molars from pre-Hispanic Mayan collections were macroscopically and radiographically inspected. Statistical analysis was performed with a Fisher's exact test to compare the prevalence of C-shaped canal systems in modern and archaeological samples. RESULTS: In the clinical observation, 118 of 341 (35%) patients treated endodontically had C-shaped mandibular second molars. In the radiographical evaluation, 17 of 48 (35%) archaeological molars had fused roots and pulp chamber morphology categorized as C-shaped. There were no significant differences between the frequencies in both samples. CONCLUSION: This study highlighted that a one-rooted mandibular molar was likely to have a C-shaped canal. The similarity between ancient and modern samples indicates that the genetic make-up since the European conquest has not affected the expression of this trait. This study supports the theory that the Mayan population has a relationship with the Northeast Asian population.