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Crenulated occlusal surfaces have previously been described on maxillary and mandibular molars; however, the occurrence of crenulations on premolars is only anecdotally supported. This study applies a modified version of a recordation scale developed for molar crenulations to record the frequency of crenulated premolars on the maxillary and mandibular premolars of modern individuals from a variety of populations: African, African American, Asian, Australian, European American, Latino, and Malay (n = 1238). Crenulations on the molars of the same individuals were also recorded to assess the relationship between occurrences on premolars and molars. Observations were compiled into frequency tables and analyzed using chi-square tests and correspondence analysis; relationships among teeth were quantified with polychoric correlation coefficients. Although crenulated premolars are observed rarely overall, the frequency of occurrence is significantly associated with group membership. Crenulated premolars occur most frequently in African, African American, and Australian samples and are observed least often among European American and Malay samples. Additionally, there is a strong relationship between third and fourth premolars, particularly within a jaw, and between fourth premolars and the molars in the same jaw. Interestingly, crenulations in premolars are most strongly associated with Grade 2 crenulations on molars. The observed differences between populations, and the associations between crenulated premolars and molars are evaluated with respect to function, tooth size, and dental development. Based on the results presented here, we recommend the addition of premolar crenulations to existing dental morphological traits used to study human population variation.

Developing morphological diagnoses for fossil mammals requires an understanding of intraspecific variation in the anatomical elements under study. Dental traits along with tooth size can be informative of taxonomic identify for extinct species. However, it is unclear what selective or developmental processes are responsible for documented patterns in tooth-size variation making application to the fossil record difficult. We assessed combined species tooth-type variation and intraspecific tooth-size variation for 19 species to evaluate whether developmental controls or occlusion-driven functional demands influence carnivoran tooth-size variation. We also estimated phylogenetic signal for the coefficient of variation (CV). Combined species tooth-size variation separated by tooth type shows that canines are more variable than molars and lower premolars. We found intraspecific tooth-size variation patterns differ between species. However, comparisons of the CVs did not support the hypotheses that developmental controls or functional demands of occlusion constrain size variation in mammal teeth. Our results suggest that a combination of factors influence carnivoran tooth-size variation, such as differences in ontogeny, diet, sexual dimorphism, and evolutionary history. Patterns of carnivoran intraspecific tooth-size variation suggest a better understanding of dental size variation in extant species is essential for accurate morphological studies of fossil taxa.

Objective: The present study was undertaken to assess whether Boltons ratio can be applied to Chattisgarhi population and if values obtained are significantly different from that of Boltons established values, then to establish Boltons standards for the Chhattisgarhi population and also to determine if sexual dimorphism exists in overall and anterior ratios. Study Design: 120 subjects (60 male and 60 female) between 17-25 years of age having normal occlusion were selected. Boltons anterior and overall ratio was calculated on study models and values obtained were statistically analyzed for co-efficient of variation, standard deviation and mean values. This data was compared with standard Bolton’s values. Results: The combined anterior and overall ratios of Chhattisgarhi population did not differ significantly from that of Boltons sample, however significant sexual dimorphism was noted both in anterior and overall ratios among males and females. Conclusion: Boltons anterior and overall tooth size ratios can be applied to Chhattisgarhi population. Keywords: Bolton ratio, Chhattisgarhi population.

Objective:To evaluate if genetic polymorphisms in the oestrogen receptor 1 ( ESR1) and oestrogen receptor 2 ( ESR2) genes encoded for oestrogen receptors alpha (ERα) and beta (ERβ) are involved in permanent tooth size.Design:Cross-sectional study.Setting:Orthodontic Clinic at School of Dentistry of Ribeirão Preto, University of São Paulo.Participants:A total of 108 orthodontic patients.Materials and Methods:Pre-treatment orthodontic records were evaluated. Dental casts were used to determine the maximum crown measurements of fully erupted permanent teeth in the mesiodistal dimensions. Second and third molars were not included in the analysis. Genomic DNA samples were used for the genotyping of four genetic polymorphisms: ESR1 (rs9340799 and rs2234693) and ESR2 (rs1256049 and rs4986938). The associations between tooth size and sex were evaluated using t test. The associations between tooth size and genotype were analysed with linear regression and adjusted by sex at an alpha of P⩽0.05.Results:Female patients presented smaller tooth size than male patients. A statistically significant difference was observed in almost all teeth ( PConclusion:This study provides evidence that genetic polymorphisms in ESR1 and ESR2 could be associated with tooth size in permanent teeth.

Form of expressions of dental microwear and mesovear of small mammals depends on abrasiveness, hardness and a number of other characteristics of the feed. Analysis of micro- and mesorelief is used on paleontological materials for the reconstruction of some parameters of the animals diet. Small mammals move a hard way from objects of biocenoses to fossils. Bone remains are modified in the process of accumulation and fossilization. In particular, bone remains from ornithogenous deposits were influenced to the substances of the digestive system of birds. In this work, an experimental estimation was made of the degree of changes in a number of characteristics of narrow-headed vole molars (Microtus gregalis) from the pellets of two species of owls. On the same samples before and after exposure to substances of the digestive system of a Polar Owl (Nyctea scandiaca) and Eagle Owl (Bubo bubo), it was shown that the microrelief of the tooth enamel undergoes serious changes and haven't information about the in vivo diet of the voles. A different degree of preservation of the mesoreliefs characteristic was shown. An assessment of their applicability for paleoreconstructions depending on this was given.

Morphological and morphometric bone variation between archaeological wolves and the oldest domestic dogs commonly are used to define species differences. However, reference data often have been based on small numbers, without robust statistical support. We consulted the literature on these matters in all possible languages and tested many of the proposed species differences by examining wolf and dog skeletons from several collections, accompanied by an extensive synthesis of existing literature. We thus created large reference groups, assessing data distributions and variability. We examined mandible height, width, length, and convexity; contact points of the skull on a horizontal plane; caudal shifting of the border of the hard palate; skull size; carnassials tooth size reduction; micro-anatomical differences in teeth, snout, and skull height; and snout length and width. Our results show that skull length and related size; skull height; snout width; orbital angle; P4 and M1 mesio-distal diameter can help (albeit to a limited extent) to distinguish the oldest archaeological dogs from wolves. Based on our observations, we re-evaluated recent large Pleistocene canids reported as Paleolithic dogs and concluded instead that they fit well within the morphomentric distributions seen with Pleistocene wolves. The research presented here reflects the recent trend to critically re-evaluate axiomatic assumptions about wolf-dog differences, and to rephrase the morphological and morphometric definition of an early archaeological dog in a more suitable manner. These results are important to the international archaeological community because they place historical reports in a newer context, and create a robust (although narrow) framework for further evaluation of archaeological dogs and wolves.

The obligatory use of cooking by the Mousterian occupants of the north temperate zone relaxed the forces of selection maintaining archaic tooth size and led to the reductions that shaped modern human face form from the Middle East to the Atlantic coast. The delay in the spread of cooking techniques accounts for the later onset of dental reduction to the south. The development and use of projectiles in the African Middle Stone Age led to gracilization and the earlier appearance of "modern" post-cranial and reflected cranial form in Africa. The subsequent adoption of the use of projectiles elsewhere was followed by gracilization and the appearance of "modern" post-cranial morphology. The craniofacial form of Cro-Magnon allies it with the living populations of northwestern Europe, specifically with the fringes in Scandinavia and England, but not with the European continent. Qafzeh represents the pattern still found in sub-Saharan Africa, particularly West Africa. Although the craniofacial configuration in both is "modern," the dentition of Qafzeh is archaic in size and form. Qafzeh is a logical representative of the ancestral form for sub-Saharan Africans but not for Cro-Magnon and subsequent Europeans.

Objective Anthropological studies have reported that tooth size decreases in the context of diet changes. Some investigations have found a reverse trend in tooth size from the prehistoric to the modern times. The aims of this study were to analyze tooth size in skeletal samples from Mesolithic–Neolithic Age, Bronze Age, and Roman to Medieval times to determine sex differences and establish a temporal trend in tooth size in the aforementioned periods. Design Well-preserved permanent teeth were included in the investigation. The mesiodistal (MD) diameter of all teeth and buccolingual (BL) diameter of the molars were measured. Effects of sex and site were tested by one-way ANOVA, and the combined effect of these factors was analyzed by UNIANOVA. Results Sexual dimorphism was present in the BL diameters of all molars and MD diameters of the upper first and the lower third molar. The lower canine was the most dimorphic tooth in the anterior region. The MD diameter of most teeth showed no significant difference between the groups, (sample from: Mesolithic–Neolithic Age-group 1; Bronze Age-group 2; Roman times-group 3; Medieval times-group 4), whereas the BL diameters of the upper second and the lower first molar were the largest in the first group. Multiple comparisons revealed a decrease in the BL diameter of the upper second and the lower first molar from the first to the later groups. Lower canine MD diameter exhibited an increase in the fourth group compared to the second group. Conclusion On the basis of the MD diameter, a temporal trend could not be observed for most of the teeth. The lower canine exhibited an increase in the MD diameter from the prehistoric to the Medieval times. Changes of BL diameter were more homogeneous, suggesting that the temporal trend of molar size decreased from the Mesolithic–Neolithic to Medieval times in Serbia.

Theropods have fascinated both paleontologists and the general public due to their large diversity of sizes and morphologies. They also present a large variation in tooth morphologies. Previous studies have estimated the bite force of several specimens. The goal of this study is to determine if there is a correlation between the tooth size, shape and position on the skull and mandible and the bite force of these dinosaurs. Measurements were made on several theropods, including the bending strength of the teeth on the anterior-posterior and the mediolateral axes of the jaws, as well as the bending strength of the mandible, and were compared to fossil and modern Crocodylia. We observed that several bending strength maxima of the teeth trends were aligned with key areas of the mandible, and that the size, shape as well as the position of the teeth on the jaws were correlated with the bite force of both Crocodylia and theropods, which can be related to their diet and feeding habits.

Background: The relationship between tooth size and stature has been analysed extensively at the interspecies level but has received less attention at the intraspecies level. The relationship between these two parameters does not seem to be the same among modern human populations. Aim: The aim of this study is to analyse the relationship between tooth dimensions and body measurements in the Baka Pygmies. Subjects and methods: Height, weight, and tooth dimensions were obtained for 45 adult Baka females and 17 males from Le Bosquet (Cameroon). Correlations were obtained between the variables and compared to results for other human populations. Results: The Baka population is distinctive in the small number of significant correlations. Only two buccolingual diameters among Baka females show any significant correlation with height. The lack of significant correlations between tooth dimensions and body dimensions among the Baka means that changes in body size are accompanied by random variations in tooth dimensions. Conclusion: The absence of correlations may be accounted for by the impact of environmental effects on the somatic growth of the Baka producing a Pygmy phenotype adapted to live in the forest. It is worth noting that many correlations become significant when sexes are pooled. This research was funded by PICS 07492 MAMIBAKA, Wenner-Gren Foundation [grant No. 7819], National Geographic Society [grant No. 8863-10], and Agence National de la Recherche [ANR-11-BSV7-0011] to F.V.R.R. and Spanish Ministerio de Economía y Competitividad [grant Nos. CGL2011-22999 and CGL2014-52611-C2-1-P] to A.R.

Teeth are thought to be less affected than post-cranial elements by factors such as age, region, sex, and post-Pleistocene climate change, making changes in tooth size a better gage of domestication-induced morphological change in Sus scrofa. Rigorous empirical evaluation of this assumption, however, has been lacking. Here we examine the impact of multiple factors on molar size in an assemblage of modern wild boar from Southwest Asia, as well as a large assemblage of ancient S. scrofa from an archaeological site in southeastern Turkey dated to 11,600 cal. BP. We find that age related interstitial wear has a profound impact on molar lengths. Comparisons of length measurements of S. scrofa molars should only be made if one strictly controls for the state of wear, as well as the stage of crown development and eruption in third molars. Breadth measurements, on the other hand, are little affected by progressive wear and, as a result, are preferable to length measurements in the analysis of molar size in S. scrofa. We also evaluate the impact of logarithm size index (LSI) scaling on molar dimensions. Molar lengths are subject to a number of factors that distort meaningful patterning rendering LSI values of length dimensions of little utility in the evaluation of molar size in S. scrofa. With the exception of the upper first molar, LSI values of molar breadths appear to both capture and amplify patterns seen among unconverted measurements of individual teeth. Our evaluation also confirms the assumption that the size of post-cranial elements is more profoundly affected than molars by factors such as region and Post-Pleistocene climate change. While sexual dimorphism also has a greater impact on the size of post-crania than on molars, the degree of sexual dimorphism in molar breadths, as well as in M3 lengths, is still substantial and must be taken into account in any study of S. scrofa molar size. Before interpreting downward shifts in molar size as an indicator of domestic status, archaeozoologists need to first to consider the possible impact of differences in the proportions of males and females in archaeological assemblages. We conclude with a number of recommendations for new protocols for the analysis of S. scrofa dental metrics. We also offer observations about the impacts of factors like region, sex, and change over time on the size of the molars of this species that may open up new areas of research.

In order to explore temporal trends of morphological variation in the narrow-headed vole ( Microtus gregalis ) traditional morphometric methods were used to quantify enamel differentiation quotient (SDQ), tooth size (L) and tooth proportion (A/L) in over 800 first lower molars from two sites in Central Europe. Our results suggest that SDQ values in late Middle Pleistocene assemblages are significantly lower than those in Late Pleistocene populations. A greater chronostratigraphic variation in SDQ occurs across the Late Pleistocene compared to the late Middle Pleistocene. This probably indicates repeated extinctions and re-colonisations, most likely from Eastern Europe or Asia, during MIS 3 and MIS 2. However, it is unclear whether this pattern represents a local phenomenon or whether the SDQ changes took place across a large geographical scale. Further studies on fossil and recent populations of the species are necessary to identify the determinants of SDQ variation in Microtus gregalis and to confirm the usefulness of the index for the Pleistocene stratigraphy.

SUMMARY: The principal orthodontic problems observed in the mixed dentition phase are related to arch length and tooth size discrepancy. In order to identify such space discrepancies different methods of mixed dentition space analyses have been introduced. For this reason the purpose of this study is to generate a new regressive equation to predict the diameter of cuspid and bicuspid teeth through mesiodistal widths of lower incisors in a Chilean population sample between native and non-native population. The study was conducted at the Araucania Dental Clinic in Temuco, and the sample comprised of historical dental casts from 200 school children (93 boys and 107 girls) from Temuco, Chile, between 13-16 years of age. The native Mapuche population consisted of 107 students and the non-native of 93 students. Measurements of the mesiodistal widths of mandibular incisors, maxillary and mandibular canines and premolars were carried out with the help of Vernier gauge calipers calibrated to 0.01 of a millimeter. The results show that there are differences in the mesiodistal diameter size of incisors, and canines and premolars in the two studied groups. There is a low correlation of the variables studied. In conclusion, significant sexual dimorphism in tooth sizes exists in the native sample, and there is no difference in non-native population. It is necessary to develop a predictive formula that is greater than 70 % of accuracy for clinical application. Resonance imaging (MRI).

Background: Intercellular communication by the hedgehog cell signaling pathway is necessary for tooth development throughout the vertebrates, but it remains unclear which specific developmental signals control cell behavior at different stages of odontogenesis. To address this issue, we have manipulated hedgehog activity during zebrafish tooth development and visualized the results using confocal microscopy. Results: We first established that reporter lines for dlx2b, fli1, NF-κB, and prdm1a are markers for specific subsets of tooth germ tissues. We then blocked hedgehog signaling with cyclopamine and observed a reduction or elimination of the cranial neural crest derived dental papilla, which normally contains the cells that later give rise to dentin-producing odontoblasts. Upon further investigation, we observed that the dental papilla begins to form and then regresses in the absence of hedgehog signaling, through a mechanism unrelated to cell proliferation or apoptosis. We also found evidence of an isometric reduction in tooth size that correlates with the time of earliest hedgehog inhibition. Conclusions: We hypothesize that these results reveal a previously uncharacterized function of hedgehog signaling during tooth morphogenesis, regulating the number of cells in the dental papilla and thereby controlling tooth size. Developmental Dynamics 244:577–590, 2015. © 2015 Wiley Periodicals, Inc.

Objective: The aim of this study was to determine if Bolton’s tooth size ratios can be applied to Mediterranean, Japanese and Japanese-Brazilian populations. Materials and methods: The sample comprised 90 pairs of dental casts of untreated individuals with normal occlusion, divided into 3 groups according to ethnical characteristics: White (30 Mediterranean descendant subjects, with a mean age of 13.64 years), Japanese (30 subjects with Japanese ancestry, with a mean age of 15.63 years) and Japanese-Brazilian (30 Japanese-Brazilian subjects, with a mean age of 13.96 years). A digital caliper was used to measure the maxillary and mandibular mesiodistal widths from first molar to first molar on each dental cast. The anterior and overall tooth size ratios were calculated. T test was applied for comparisons between Bolton standards and the ethnical groups for anterior and overall ratios. Results: Only the Japanese-Brazilian group showed significantly greater ratios than Bolton standards. Conclusion: It was concluded that Bolton’s ratios are not applicable to the Japanese-Brazilian population. Therefore, it is suggested that Bolton’s ratios may not be suitable for different populations.

OBJECTIVES Dental eruption schedules have been closely linked to life history variables. Here we examine a sample of 50 perinatal primates (28 species) to determine whether life history traits correlate with relative tooth size at birth. MATERIALS AND METHODS Newborn primates were studied using serial histological sectioning. Volumes of deciduous premolars (dp2 -dp4 ), replacement teeth (if any), and permanent molars (M1-2/3 ) of the upper jaw were measured and residuals from cranial length were calculated with least squares regressions to obtain relative dental volumes (RDVs). RESULTS Relative dental volumes of deciduous or permanent teeth have an unclear relationship with relative neonatal mass in all primates. Relative palatal length (RPL), used as a proxy for midfacial size, is significantly, positively correlated with larger deciduous and permanent postcanine teeth. However, when strepsirrhines alone are examined, larger RPL is correlated with smaller RDV of permanent teeth. In the full sample, RDVs of deciduous premolars are significantly negatively correlated with relative gestation length (RGL), but have no clear relationship with relative weaning age. RDVs of molars lack a clear relationship with RGL; later weaning is associated with larger molar RDV, although correlations are not significant. When strepsirrhines alone are analyzed, clearer trends are present: longer gestations or later weaning are associated with smaller deciduous and larger permanent postcanine teeth (only gestational length correlations are significant). DISCUSSION Our results indicate a broad trend that primates with the shortest RGLs precociously develop deciduous teeth; in strepsirrhines, the opposite trend is seen for permanent molars. Anthropoids delay growth of permanent teeth, while strepsirrhines with short RGLs are growing replacement teeth concurrently. A comparison of neonatal volumes with existing information on extent of cusp mineralization indicates that growth of tooth germs and cusp mineralization may be selected for independently.

International audience; Objective: Accurate sex estimation is an essential step for the reconstruction of the biological profile of human remains. Earlier studies have shown that elements of the human permanent dentition are sexually dimorphic. The aims of this study are to determine the degree of sexual dimorphism in the dental tissue volumes and surface areas of mandibular canines and to explore its potential for reliable sex determination.Method The teeth included in this study (n = 69) were selected from anthropological collections from Spain, South Africa and Sudan. In all cases, the sex of the individuals was known. The teeth were scanned and three-dimensional (3D) measurements (volumes and surfaces areas) were obtained. Finally, a dsicriminant function analysis was applied.Results Our results showed that sexual dimorphism in canine size is due to males having greater amounts of dentine, whereas enamel volume does not contribute significantly to overall tooth size dimorphism. Classification accuracy of the multivariable equations tested on slightly worn teeth ranged from 78 to 90.2% for the crossvalidation, and from 71.43 to 84.62% for the hold-out sample validation. When all functions were applied together, the sex was correctly assigned 92.30% of the time.Conclusions Our results suggest that the 3D variables from mandibular canine dental tissues are useful for sex determination as they present a high degree of dimorphism. The results obtained show the importance of 3D dental tissue measurements as a methodology in sex determination, which application should be considered as a supplemental method to others.

Previous results regarding human sex chromosome aneuploidies have shown that the X and Y chromosomes affect tooth size and morphology. This study looked for the effect of sex chromosome deficiency on permanent tooth crown heights.The material, from the Finnish KVANTTI Research Project, consisted of 97 45,X females and 15 45,X/46,XX females. The controls were 32 sisters and 28 mothers of the 45,X females, eight sisters and two mothers of the 45,X/46,XX females and 35 female population controls. Crown heights of all the available teeth except third molars on both sides of the jaws were measured from panoramic radiographs with a digital calliper according to the defined procedure.The tooth crown heights were significantly smaller in the 45,X females than in the female population controls, except for the incisors and one canine in the maxilla, whereas the tooth crown heights of the 45,X/46,XX females were close to those of the normal control females. The differences between the 45,X and 45,X/46,XX females were statistically significant, excluding the upper incisor area and a few teeth in the mandible.The effect of the sex chromosome deficiency on permanent tooth crown height is due to the magnitude of lacking sex chromosome material. The present results regarding the 45,X females are parallel to previous findings in Turner patients regarding reduced mesiodistal and labiolingual dimensions and tooth crown heights in the permanent dentition.

House mice from 24 Scottish and Faroese islands show positive correlation of skeletal size with island area, conforming to a model of resource limitation in very small islands. Molar size is not correlated with island size, suggesting greater genetic canalization; smaller individuals have larger tooth to body size ratio. The size variation may have a simple genetic basis or may be ecophenotypic. The offset between skeletal and molar size has potential use in the fossil record as a marker for these rapid effects, while longer-term evolutionary change reverts to approximate tooth—body size isometry. Collation of related studies indicates frequently deterministic relationships of small-mammal body size to island size. The parameters of the relationship (positive, negative or parabolic) vary widely with case study according to biotic and abiotic factors. In the present study there was no relationship of mouse size to any variable (e.g. presence of competitors) except island area.

Kleiber suggested that mammalian metabolic rate scales with body mass at Mb3/4. Bigger animals use relatively less energy. Gould reasoned that teeth should scale the same way given caloric need. In many cases though, cheek tooth occlusal area increases isometrically, one-to-one with body mass (i.e., Mb2/3). Fortelius reconciled the discrepancy by noting that larger mammals also chew slower, so a given amount of food per bite but few bites per unit time could still mean metabolic scaling of energy consumed in a day. Here I revisit dental allometry, referencing new studies of tooth size, muscle mass, chewing rate, and food fracture scaling. Early predictions have held up reasonably well through the decades, though many more factors involved have emerged. These can be difficult to parse for intepreting deviations from expected tooth size in fossil mammals, including early hominins. Still, relative tooth size variation can help us generate dietary hypotheses.

Forty-eight dental casts (37 males, 11 females) of Uva Bintenna Veddas were the population. Mesiodistal (MD) and buccolingual (BL) diameters were measured and analyzed for sexual dimorphism and size variation. In males, MD of maxillary canines and mandibular first molars were significantly greater at p p p p p 1, P1, and M1 showed least variability in both arches and in both sexes. In males, both MD and BL showed high variability in maxillary lateral incisors and mandibular second premolars.

Introduction: Tooth developmental disturbances may occur by anomalies in position, number, shape and tooth size [1], and is genetic-related [2–4]. Transposition is an unique and extreme form of ectopic eruption in which a permanent tooth develops and erupts in the position normally occupied by another [5]. Although transpositions are quite common in canines [6–8], this condition rarely occurs with incisors or premolars [6,9]. On the other hand, pathologic root resorption can be observed during eruption of permanent dentition [10], but is very unusual in maxillary first molar. Materials and methods: A 12-year-old male was referred to the Orthodontics Department of Egas Moniz Dental Clinic complaining with severe pain on the left side of the maxillary and premolars transposition on the right side. After clinical and radiographic examination, through orthopantomography and cone-beam computerized tomography (CBCT) severe root resorption of the left maxillary first molar caused by abnormal eruption of the second premolar was diagnosed. Futhermore, the transposition of the upper right premolars was confirmed and severe transversal collapses (Pont’s Premolar Index: -13,5 mm; Pont’s Molar Index: -14,4 mm), ectopic upper canines, maxillary compression, crossbite between 1.6 and 4.6, skeletal Class I and unilateral Angle Class II, diagnosed. Discussion and conclusions: According to the literature, the frequency of tooth transposition is less than 0.4% [7,8,11,12]. In most cases they are more common with unilateral occurrence [4,8,9], on the left side as opposed to the right side [7,8], and have been found more often in the maxilla [4,7]. Our case is significant because this patient is male and typically this has been found more often in females [4,6,7] and tooth transpositions in premolars and pressure root resorption of the maxillary first molar are extremely rare [6,9,10].

Introduction : Determination of the actual level of genetic determinance of occlusal variation could have a significant effect on prognosis and treatment planning. Aim: The objective of this study was to evaluate the hereditary variations occurring among the members within monozygotic and dizygotic twin pairs based on widest mesiodistal measurements in relation to the posterior permanent dentition. Materials and methods: Twenty-eight adult twin pairs (16 monozygotic pairs, 12 dizygotic pairs) in the age group of 14 to 55 years were used for the study. Mesiodistal measurements of maxillary and mandibular permanent posterior teeth at their maximum width were considered. Intrapair differences were calculated, the differences in the two groups were compared and the level of significance was tested. Results: Significant differences between the twin groups was found in relation to all the teeth studied except the maxillary and mandibular second molars. Conclusion: Genetically conditioned variations of highly significant nature were seen in 12 of the 16 posterior teeth studied, thereby confirming the evidence that size of teeth is under genetic control.

The reconstruction of diet is important for understanding the paleoecology and evolution of early hominins. This paper reviews and colligates the fossil evidence for diets of early Homo (Homo habilis, Homo rudolfensis, Homo erectus), particularly that related to tooth size, shape, structure, and wear. Technological innovations and new finds have led to improved understandings of feeding adaptations and food preferences in the earliest members of our genus. Differences in dental topography between these species and the australopiths, for example, have been documented, as have differences in microwear textures between H. habilis and H. erectus. These and other lines of evidence suggest a probable shift in diet in early Homo, and especially H. erectus, compared with their australopith forebears, with a broadened subsistence base to include foods with a wider range of fracture properties. Studies to date also make clear that while much remains to be done, early hominin teeth hold the potential to provide more...

Background Wnt5a and Mrfzb1 genes are involved in the regulation of tooth size, and their expression levels are similar to that of Bmp7 during morphogenesis, including during the cap and early bell stages of tooth formation. We previously reported that Usag-1-deficient mice form supernumerary maxillary incisors. Thus, we hypothesized that BMP7 and USAG-1 signaling molecules may play important roles in tooth morphogenesis. In this study, we established double genetically modified mice to examine the in vivo inter-relationships between Bmp7 and Usag-1. Results We measured the volume and cross-sectional areas of the mandibular incisors using micro-computed tomography (micro-CT) in adult Bmp7- and Usag-1-LacZ knock-in mice and their F2 generation upon interbreeding. The mandibular incisors of adult Bmp7+/− mice were significantly larger than those of wild-type (WT) mice. The mandibular incisors of adult Usag-1−/− mice were the largest of all genotypes examined. In the F2 generation, the effects of these genes were additive; Bmp7+/− was most strongly associated with the increase in tooth size using generalized linear models, and the total area of mandibular supernumerary incisors of Usag-1−/−Bmp7+/− mice was significantly larger than that of Usag-1−/−Bmp7 +/+ mice. At embryonic day 15 (E15), BrdU assays demonstrated that the labeling index of Bmp7+/− embryos was significantly higher than that of WT embryos in the cervical loop. Additionally, the labeling index of Usag-1−/− embryos was significantly the highest of all genotypes examined in dental papilla. Conclusions Bmp7 heterozygous mice exhibited significantly increased tooth sizes, suggesting that tooth size was controlled by specific gene expression. Our findings may be useful in applications of regenerative medicine and dentistry.

The utility of dental metric data in both a forensic anthropological and a bioarchaeological setting is surveyed. This review involves a discussion of data collection methods and statistical treatment, as well as the effects of sex, age, biological stress, and development on tooth size. Heritability rates are also explored, as are general trends in hominin evolution and among modern human populations. The authors highlight the importance of understanding biological data in order to employ appropriate statistical analyses.

It is suggested with increasing frequency that rather than the industry standard of 1/4 inch mesh, zooarchaeologists use 1/8 inch or even 1/16 inch mesh to insure more complete recovery. These suggestions are based on the implicit assumption that the body size of a taxon and the probability that the remains of that taxon will be recovered are positively correlated. Size of skeletal specimens provides a more direct measure of recovery probability and accounts for the fact that not all skeletal elements in a body are the same size. Frequencies of eight kinds of rodent teeth representing three genera recovered from the Marmes archaeological site in southeastern Washington State, USA, correlate strongly with tooth size despite the use of 1/25 inch mesh screens. Shape of tooth types measured is insufficiently varied to reveal more than a general relationship between shape and recovery frequency. Choice of an appropriate screen mesh should consider the nature of a deposit, research goals, and cost efficiency.

Most methods of dietary reconstruction are limited in their applicability to either extant or extinct taxa. We apply and discuss a method in which dietary information can be reconstructed from chips in the tooth enamel of both living and fossil primates. Such chips can be used to indicate the presence of large hard foods in the diet, and also to provide an estimate of the bite force that was used when the chip was created. Furthermore, the equations derived from this method allow an estimate of maximum bite force to be obtained from a simple measurement of tooth size. We use this method to investigate dietary differences in nonhuman great apes (Pongo, Gorilla, Pan). The high frequency of chips on teeth of Pongo indicate that they frequently use high forces to process hard foods such as seeds and nuts. Gorilla can generate even higher bite forces, but their low incidence of tooth chips suggests that they do so when consuming soft but tough foods. Tooth chips provide a lasting dietary signal that is not easily masked or erased, making them particularly useful for the study of rarely eaten items such as some fallback foods.

Mesozoic tooth marks on bone surfaces directly link consumers to fossil assemblage formation. Striated tooth marks are believed to form by theropod denticle contact, and attempts have been made to identify theropod consumers by comparing these striations with denticle widths of contemporaneous taxa. The purpose of this study is to test whether ziphodont theropod consumer characteristics can be accurately identified from striated tooth marks on fossil surfaces. We had three major objectives (1) to experimentally produce striated tooth marks and explain how they form; (2) to determine whether body size characteristics are reflected in denticle widths; and (3) to determine whether denticle characters are accurately transcribed onto bone surfaces in the form of striated tooth marks. We conducted controlled feeding trials with the dental analogue Varanus komodoensis (the Komodo monitor). Goat (Capra hircus) carcasses were introduced to captive, isolated individuals. Striated tooth marks were then identified, and striation width, number, and degree of convergence were recorded for each. Denticle widths and tooth/body size characters were taken from photographs and published accounts of both theropod and V. komodoensis skeletal material, and regressions were compared among and between the two groups. Striated marks tend to be regularly striated with a variable degree of branching, and may co-occur with scores. Striation morphology directly reflects contact between the mesial carina and bone surfaces during the rostral reorientation when defleshing. Denticle width is influenced primarily by tooth size, and correlates well with body size, displaying negative allometry in both groups regardless of taxon or position. When compared, striation widths fall within or below the range of denticle widths extrapolated for similar-sized V. komodoensis individuals. Striation width is directly influenced by the orientation of the carina during feeding, and may underestimate but cannot overestimate denticle width. Although body size can theoretically be estimated solely by a striated tooth mark under ideal circumstances, many caveats should be considered. These include the influence of negative allometry across taxa and throughout ontogeny, the existence of theropods with extreme denticle widths, and the potential for striations to underestimate denticle widths. This method may be useful under specific circumstances, especially for establishing a lower limit body size for potential consumers.

Diet changes are considered key events in human evolution. Most studies of early hominin diets focused on tooth size, shape, and craniomandibular morphology, as well as stone tools and butchered animal bones. However, in recent years, dental microwear and stable isotope analyses have hinted at unexpected diversity and complexity in early hominin diets. Some traditional ideas have held; others, such as an increasing reliance on hard-object feeding and a dichotomy between Australopithecus and Paranthropus , have been challenged. The first known evidence of C 4 plant (tropical grasses and sedges) and hard-object (e.g., seeds and nuts) consumption dates to millions of years after the appearance of the earliest probable hominins, and there are no consistent trends in diet change among these species through time.

In a seminal paper in 1975, Gould proposed that postcanine occlusal area (PCOA) should scale metabolically (0.75) with body mass across mammals. By regressing PCOA against skull length in a small sample of large-bodied herbivorous mammals, Gould provided some marginal support for this hypothesis, which he then extrapolated as a universal scaling law for Mammalia. Since then, many studies have sought to confirm this scaling relationship within a single order and have found equivocal support for Gould's assertion. In part, this may be related to the use of proxies for both PCOA and body mass, small sample sizes, or the influence of a “taxon-level effect,” rendering Gould's scaling “universal” problematic.Our goal was to test the universality of Gould's prediction and the impact of the taxon-level effect on regressions of tooth size on body mass in a large extant mammalian sample (683 species spanning 14 orders). We tested for the presence of two types of taxon-level effect that may influence the acceptance or rejection of hypothesized scaling coefficients. The hypotheses of both metabolic and isometric scaling can be rejected in Mammalia, but not in all sub-groups therein. The level of data aggregation also influences the interpretation of the scaling relationship. Because the scaling relationship of tooth size to body mass is highly dependent on both the taxonomic level of analysis and the mathematical methods used to organize the data, paleontologists attempting to retrodict body mass from fossilized dental remains must be aware of the effect that sample composition may have on their results.

Aims: As part of ongoing studies of the aetiology of dental anomalies the aims of this study were to identify multiple components of tooth size of the upper permanent incisors in 34 patients with supernumerary teeth and to compare them with those in a control group to determine whether the presence of a supernumerary tooth has a local effect on the size of the surrounding dentition. Methods and results: The labial and occlusal aspects of the clinical crowns of the upper permanent central and lateral incisors on the study models of 74 subjects were digitally imaged and measured using an image analysis system and automated macro (34 patients with supernumerary in the upper incisor region: 17 males and 17 females and 40 controls: 20 males and 20 females). The macro-defined 17 variables from each view. From the labial view these were: the mesio-distal and occluso-gingival length and additional measurements along 25 and 75% of the mesio-distal line and at 25, 50 and 75% along the occluso-gingival line such that all these sub-divisions extended to the periphery of the tooth. From the occlusal view these were: the mesio-distal and labio-lingual lengths, and additional variables that sub-divided the mesio-distal again at 25 and 75% along the length and at 25, 50 and 75% along the labio-lingual dimension. Principal component analysis (PCA) was used to identify the key factors with the most random variability. Comparisons were then carried out between the supernumerary cases and control group using 2-way ANOVA. Seven factors of tooth size for the upper central incisors and eight factors for the upper lateral incisors were extracted. Most of these variables were found to be larger in the supernumerary group than in the control. Statistically significant differences were found for 5 out of 7 and 4 out of 8 for the upper central and lateral incisors respectively. Conclusions: A number of factors of tooth size were identified and found to be larger in the supernumerary group compared to the control (7 for upper central and 8 for upper lateral incisors); the majority reached the 0.05 significance level. Tooth crown size of the upper central incisor was affected more than that of the upper lateral incisor, supporting a local field effect. (C) 2008 Elsevier Ltd. All rights reserved.

Anomalous mitochondrial and nuclear gene sequences in individuals of the widely distributed tropical marine gastropod Conus ebraeus that were not distinguishable by shell shape and color pattern characters suggested the presence of a second, cryptic species. We tested this hypothesis by genetic, morphological, and ecological comparisons of additional individuals from the site in Okinawa where the two forms co-occurred. Radular tooth size and shape, prey type in nature, and microhabitats utilized differed markedly between the two forms. Adults with typical C. ebraeus DNA and radular teeth preyed primarily on errant polychaetes (Eunicidae); those with anomalous DNA and teeth ate mainly sedentary capitellids. Juveniles (shell length13 mm) had more similar teeth and ate primarily syllids. Radular teeth of the anomalous form agreed with those of Conus judaeus, distinguished from C. ebraeus by Rudolph Bergh in 1895 solely on tooth characters of one specimen from the Philippines. Samples from other widely scattered Pacific localities revealed only typical C. ebraeus gene sequences. Both forms occurred in Seychelles (western Indian Ocean), where their radular teeth and diets were consistent with the data from Okinawa, but DNA of available material was degraded. Although C. judaeus was long dismissed as an aberrant specimen and junior synonym of C. ebraeus, our results support its validity as a distinct species. These results highlight the importance of molecular and radular tooth characters relative to those of the shell. Moreover, cryptic species could well be important components of species richness in Conus specifically and marine molluscan biodiversity more generally.

Teeth are one of the best preserved and most commonly recovered elements in primate fossil assemblages. Taxonomic, functional, and phylogenetic hypotheses often rely on dental characters, despite considerable evidence of homoplasy in tooth form and large variation in tooth size within and among primates. 1,2 Recent studies have led to new areas of research centered on incremental tooth development, chemical composition, and internal structure. Due to rapid technological developments in imaging and elemental sampling, these new approaches have the potential to increase our understanding of developmental biology, including not only changes in the pace of growth and reproduction, but also our assessments of diets, migration patterns, environments, and taxonomy. The integration of these temporal, chemical, and structural approaches heralds a bright future for the role of dental tissue research in evolutionary anthropology.

Mice and rats, two species of rodents, show some dental similarities such as tooth number and cusp number, and differences such as tooth size and cusp size. In this study, the tooth size, tooth number, cusp size and cusp number, which are four major factors of the tooth patterning, were investigated by the heterospecific recombinations of tissues from the molar tooth germs of mice and rats. Our results suggest that the dental epithelium and mesenchyme determine the cusp size and tooth size respectively and the cusp number is co-regulated by the tooth size and cusp size. It is also suggested that the mesenchymal cell number regulates not the tooth size but the tooth number. The relationships among these factors in tooth patterning including micropatterning (cusp size and cusp number) and macropatterning (tooth size and tooth number) were analyzed in a reaction diffusion mechanism. Key molecules determining the patterning of teeth remains to be elucidated for controlling the tooth size and cusp size of bioengineered tooth.

Carabelli's trait is a morphological feature that can occur on the protocone of human maxillary molars. This study tests the hypothesis that Carabelli's trait is correlated statistically with the dimensions of the crown's four principal cusps or whether, as a cingular feature, the trait truly accretes onto an otherwise unaffected crown. Computer-assisted image analysis was used to measure the 6 intercusp distances and 12 angular relationships among cusp tips on the permanent first molar of 300 young adult American whites. Carabelli's complex was scored using an 8-grade ordinal scheme. Crown size was quantified in three ways, namely as 1) maximum mesiodistal and buccolingual diameters, 2) the 6 intercusp distances, and 3) the 12 angular cusp arrangements. There was no sex difference in the morphological expression of Carabelli's trait in this sample. Overall crown size and intercusp distances were significantly and progressively larger in molars with larger Carabelli's trait expressions. There are graded size responses between crown size (mesiodistal and buccolingual diameters), sizes of the four principal cusps, and morphological stage of Carabelli's complex, though the statistical relationships are appreciably stronger in males than females. Carabelli's trait occurs preferentially in larger molars. In contrast, angular (shape) relationships among cusp tips are not discernibly affected by trait size in either sex. There is the situation, then, that Carabelli's trait is developmentally correlated with crown size, but with no apparent alteration of cusp arrangements, suggesting that the increases are isometric across the occlusal table. Why the association is much weaker in females remains speculative, but these data provide yet another line of evidence that, within a population, tooth size is associated in a positive fashion with crown complexity.

This study investigates changes in past human and animal relationships by focusing on pig (Sus scrofa) remains excavated from archaeological sites in southern Kanto, Japan. Pigs and humans have had a close relationship since prehistoric times and the process of change in this relationship, including possible domestication, is one of the major issues in Japanese zooarchaeology. This study attempts to gain a better understanding of the nature of past interaction between humans and pigs by investigating their relative importance compared with other vertebrate remains, kill-off patterns, and changes in their size and shape at these sites. The materials used for this study date from the Earliest to Final Jomon (ca. 10,000–2500 BP), Yayoi (ca. 2500–1700 BP) and Kofun (ca. 1700–1300 BP) periods. The relative proportions of pigs were calculated to show the overall trend of pig exploitation in each site. Age at death was obtained based on the state of tooth eruption. Bucco-lingual crown measurements were taken on the third and fourth premolars and on each cusp of the first and second molars of the mandible, and the logarithmic ratio technique was then applied to these data. The age structure of Sus varies between different sites in the Jomon Period, and significant changes were observed in the Yayoi and Kofun Periods. A decrease in the relative proportion of pigs in the faunal assemblages was observed from Jomon to Kofun. Three major differences were observed in the size of pigs. The overall size of pigs significantly increased from Early to Middle Jomon, whilst a decrease in size occurred in the Yayoi Period. Finally, overall size increased significantly during the Kofun Period. Together with the archaeological evidence—such as the ritual burial of pigs accompanying human burial—we suggest that the interaction between pigs and humans became gradually stronger at some sites during the Late Jomon Period, and the relationship intensified in the Yayoi Period. Copyright © 2006 John Wiley & Sons, Ltd.

A simple framework is offered here for relating dental function, particularly the size of the dentition and its supporting skeleton, to the rest of the mammalian body. Built up from a simple understanding of the fracture properties of foods in mammalian diets, it predicts that mammals that reduce their body size rapidly will have jaws that become too small to house all their teeth. Dental overcrowding, with eventual reduction in tooth size or reduction in tooth number, is a logical result. The Flores finding shows a dentally crowded jaw entirely consistent with this theory. However, the theory also predicts that reduction in the values of certain mechanical properties of foods, particularly their toughness, will also bring about similar trends without changing body size. Dental crowding in modern humans is considered the combined result of tool use to comminute foods and cooking to modify their mechanical properties, such as toughness.

Chorion type is an important variable that can affect the prenatal environment of monozygotic (MZ) twin pairs, leading to differences in growth and development. In particular, vascular anastomoses between monochorionic (MC) MZ twin pairs can lead to an imbalance in nutrition between co-twins. One objective of this study was to determine whether maternal reports, hospital records or birthweight discordances found in MZ co-twins provide reliable indications of monochorionicity. The other objective was to test the hypotheses that in MZ twin pairs of known chorion type, MC twin pairs would show greater birthweight differences and greater within-pair variability in permanent tooth size than dichorionic (DC) twin pairs, reflecting greater differences in intrauterine environment between MC MZ pairs. Birthweights and tooth size data were recorded for 170 pairs of MZ Australian twins enrolled in an ongoing study of dentofacial growth and development. Chorion type based on maternal reports was compared with that based on hospital records for a subsample of 68 pairs of these MZ twins. Maternal reports were found to be unreliable for determining chorion type and hospital records often did not provide enough information to be certain about chorionicity. For 27 twin pairs with confirmed chorion type, associations were tested between birthweight discordances in MZ twin pairs and chorion type, and also between intrapair variances for tooth size and chorion type. A significant association was noted between birthweight discordance and chorion type (pp

The postcanine tooth crowns of late Early Pleistocene Homo erectus from Sangiran, Java, have been considered to be significantly smaller than those of older H. erectus remains of the same region. In this study, the degree of dental reduction in the former was examined by comparing their postcanine crown size with that of various regional groups of recent H. sapiens. The results show that overall crown size and degree of posterior molar reduction of Javanese H. erectus of the late Early Pleistocene was within the range of variation of recent H. sapiens. The position of this H. erectus group in the general trend of dental reduction in Early to Middle Pleistocene Asian archaic Homo is discussed. Implications for the phylogenetic discontinuity hypothesis between H. erectus and H. sapiens in Australasia are presented. In contrast to their reduced crown size, the Javanese H. erectus remains exhibit robust root systems, presumably a primitive retention. This observation indicates that reduction in crown size preceded reduction of the roots during evolution of Homo, at least in the Sunda region.

The aim of this study was to compare tooth size measurements between patients with supernumerary teeth and a control group.The supernumerary group consisted of 56 subjects (21 females and 35 males) and the control group of 40 subjects (20 females and 20 males). All available permanent teeth on the dental casts were imaged and measured from both buccal and occlusal views using an image analysis system. Mesio-distal, bucco-lingual or occluso-gingival dimensions, area and perimeter were measured from each view.Supernumerary tooth patients tended to have larger tooth size measurements for almost all variables than controls. Significant differences (p0.05) were found for the mesio-distal dimension of the upper and lower incisors and the bucco-lingual dimensions of the lower first premolars.The results are compatible with supernumerary teeth being a complex dental anomaly with a multifactorial aetiology in which both genetic and environmental factors are important. There is some evidence of a local effect with greater differences in tooth dimension adjacent to the site of the supernumeraries.

The relationship between the Yuanmou hominoid and the Lufeng hominoid (Lufengpithecus lufengensis), both from Yunnan Province, China, and among the most abundantly represented fossil hominoid of Eurasia, has been the subject of much debate. In the past 10 years, comparative studies of cranial and dental morphology of the Lufeng and Yuanmou hominoids indicate that the two hominoids resemble each other more than either of them resemble any other Miocene hominoid. In this paper, we summarize the dental differences seen between the Yuanmou and Lufeng hominoids, and discuss their implications. Our results show that the Lufeng hominoid has relatively smaller front teeth, smaller M-1, and higher SQ than the Yuanmou hominoid, indicating a more folivorous or soft diet, such as leaves and berries, in the former. Tooth wear analysis indicates that both upper and lower molars of the Yuanmou hominoid were more heavily worn than those of the Lufeng hominoid, offering additional support to the findings of tooth size proportion and shearing crest development. We propose that different diets might have characterized the two hominoid populations, the differences possibly related to the environment, behavior pattern, and population structure of the Yuanmou and Lufeng hominoids.

Summary Metric variability of the deciduous teeth of several Old World monkey taxa were examined at the intergeneric and interspecific taxonomic levels. In general, the deciduous teeth of these taxa lack significant size sexual dimorphism with the exception of Papio cynocephalus . The data clearly demonstrate that male dimensions are not consistently larger than those of the females, in fact, female dimensions are frequently larger than those of the male. Thus, negative percentage sexual dimorphism is present in all species except Papio cynocephalus . Tooth size differences are randomly distributed among these species and do not appear to have any anatomical significance with respect to the different diets of the colobine and cercopithecine monkeys. This odontometric analysis reveals that it would be problematical to use deciduous tooth size as a basis for species identification with the possible exception of Papio cynocephalus .

Models based on developmental mechanisms described in mice and shared by most mammals are shown to accurately predict tooth size in extinct hominins, and can explain the small third molars in our species. See Letter p.477