Permanent tooth emergence in Gujjars of Punjab, India.

Patterns of permanent tooth emergence in Gujjars were studied in a cross-sectional sample of 483 children ranging in age from 6 to 13 years. Females were markedly advanced in permanent tooth emergence times over males, but no such sex differences were observed in sequence of emergence. Differences between median emergence times of right and left side antimers were significant for only 4 of 28 instances (14.29%), namely central incisors, mandibular first molars in males and lateral maxillary incisors in females. In general mandibular teeth except premolars tended to emerge earlier than their maxillary counterparts. The quiescent period between first and second tooth emergence stages was longer in males than in females. Mandibular depth and morphological facial length were very significantly correlated (p < 0.01) with the number of permanent teeth present in the oral cavity.     

Probit and survival analysis of tooth emergence ages in a mixed-longitudinal sample of chimpanzees (Pan troglodytes).

Tooth emergence data from a mixed-longitudinal sample of 58 chimpanzees of known age were analyzed using probit and survival techniques to produce median emergence ages, ranges of variability, and emergence sequences for primary and permanent teeth. Between-group comparisons were made to test for statistically significant differences in emergence ages. No such differences were found between right and left sides, or between maxilla and mandible, for any primary or permanent teeth. Male-female comparisons did demonstrate significant emergence-age differences for some teeth, although they were not always bilaterally symmetrical. More complete data are required to further clarify the nature of sex differences in tooth emergence in chimpanzees. Regression models for age prediction from the number of emerged teeth were generated and indicate that males achieve a given number of emerged teeth at a significantly later age than females. However, when fewer than five teeth have emerged, males are predicted to be younger than females. The sizable root mean square error values for these models suggest that this method of age prediction has limited usefulness owing to the amount of variability in timing of tooth emergence in chimpanzees. The implications of these data for studies on tooth emergence in early hominids are addressed.     

Genetic determinants and dynamics of permanent teeth emergence in Northwest Indian twins: A chronogenetic study

The understanding of the role of genetic factors in phenotypic variation in the emergence of secondary teeth in humans remains is incomplete. Dental emergence data based on a mixed longitudinal study were collected on 111 twin pairs from an urban population of Chandigarh. The observations over time on a single individual varied from one to nine, thus giving a total of 595 entities. Female twins manifested emergence priority over males. The differences between zygosities in mean emergence ages were significant for only 6 of 16 (37%) instances. Magnitude of variations seen between twins and singletons in their mean emergence timings and duration of the hiatus between two dental phases of emergence were of the order observed among different samples from the same population/ethnic group. Heritability estimates for the specified number of the teeth emerged showed age variations. These estimates were highest in the first two age groups (from 5 to 7 years), when the first molars and incisors emerged. Maxilla-mandible differences were seen for tooth emergence timings and sequence patterns. Heritability for tooth emergence timings was higher in maxilla than in mandible. Multifactorial model of inheritance was the best fit model to explain variations observed in dental emergence timings and dental sequence pattern polymorphisms and there were significant genetic components of variation for both of these. There were sex differences in heritability; females had higher estimates than males. Genetic factors accounted for about 60% of the total phenotypic variation in the length of hiatus interval between two active stages of permanent teeth emergence.     

Associations in emergence age among permenent teeth

Associations in the timing of emergence among the permanent teeth of Boston children were obtained from a mixed longitudinal growth study of 414 Caucasian twin pairs examined annually. Correlations were estimated by the method of maximum likelihood for corresponding left-right teeth, upper-lower teeth, and all paired combinations from central incisor to second molar in a jaw quadrant of each sex. Strong positive correlations in emergence timing prevailed throughout the dentition. Principal component analyses on correlation matrices of jaw quadrant relations for boys and girls in the maxilla and mandible showed that three components effectively explained the emergence associations among the seven permanent teeth in each jaw quadrant. Factor analytic techniques further illustrated the nature of the three components and showed the emergence relations to be essentially the same in the maxilla and mandible for both sexes. The first component was a general maturation factor influencing all of an individual's teeth to be simultaneously early or late in emerging. The remaining two components were a molar factor, affecting almost exclusively the emergence timing of the permanent first and second molars, and a duration factor that affected the duration of the emergence process for non-molar teeth, contrasting particularly the incisors and premolars.     

Canadian Eskimo permanent tooth emergence timing

To identify the times of emergence of the permanent teeth of Canadian Eskimos (Inuit), 368 children and adolescents were examined. The presence or absence of all permanent teeth except the third molars was recorded and these data subjected to probit analysis. Female emergence times were advanced over males. Generally, the Inuit of both sexes showed statistically significant earlier emergence times than Montreal children, except for the incisors. The present results do not support hypotheses indicating that premature extraction of the deciduous teeth advances the emergence of their succedaneous counterparts. There is some indication the controls of deciduous tooth emergence continue to play some part in emergence of the permanent dentition, especially the first permanent teeth that emerge.     

Studies on agenesis in the permanent dentition

Tooth dimensions in 104 males and females with agenesis of one or more permanent teeth, other than third molars, have been examined. The amounts of size reduction from normal in mesiodistal and buccolingual tooth diameters appear to be independent. Also some apparent differences from normal tooth size variability were noted. Interestingly, first molars and canines, both considered to be stable components of the dentition, showed significant variability in tooth size. In addition the incidence of individual tooth agenesis within this sample was noted and maxillary lateral incisor was most frequently absent in both sexes.     

Data on morphometric analysis of anterior teeth from Hazaribag College of Dental Sciences and Hospital,jharkhand

It is of interest to document data on morphometric (measurement of external form) analysis of maxillary and mandibular anterior teeth collected from a dental set up using mesio-distal (MD) dimension. The mesiodistal dimensions of all permanent anterior teeth (central incisor, lateral incisor and canine) of 25 males and 25 females patients were recorded using digital vernier calipers. Data were charted and statistical analysis was done using Mann Whitney U test. Data shows sexual dimorphism for every tooth between males and females. However, dimorphism was exhibited only in maxillary and mandibular canine, mandibular central incisors, and lateral incisor. Hence,odontometric parameters offer simple, reliable and cost-effective in forensic investigation for recording gender discrimination.     

Allometric relations of teeth and jaws in man

Static adult intraspecific allometry of jaws and teeth was investigated in a sample of 100 Negro crania. The relations between tooth area, postcanine surface, incisor surface, and four viscerocranial measures were examined separately for males and females. Our results indicate a marked lack of morphological integration between P-sets within the orofacial subregion and a similar lack of correspondence between jaw size and tooth size. Allometric analyses indicate that mandibular length scales negatively allometric to maxilloalveolar length and to bigonial width, that canine base area scales positively to upper and lower jaw length, and that all the other teeth scale negatively to jaw length. The postcanine surface area was found to be negatively allometric to the canine base area, which in turn scaled isometrically to incisor surface. Hence, any lengthening of the mandible will tend to be associated with a relative shortening of the maxilla, with relatively larger canines and a relative reduction of the cheek teeth.     

Interrelation between fusions in the primary dentition and agenesis in the succedaneous permanent dentition seen from an embryological point of view

The purpose of the present study was to elucidate the relationship between fusions in the primary dentition and the occurrence of agenesis in the succedaneous permanent dentition in a Danish child population and to elucidate this relationship from the recently described normal embryological development of the anterior parts of the human maxilla and mandible. The material included radiographs, either as intraoral film or as orthopantomograms from a total of 19 primary dentitions with a total of 21 fusions. Radiographs of the permanent dentition in the fusion regions were available for all 19 dentitions. Of 21 fusions, a total of 20 were in the mandible and one in the maxilla. In 15 cases, the fusions were between primary incisors and in six cases between lateral incisors and canines. Agenesis of a permanent lateral incisor always occurred when there had been fusion of a primary lateral incisor and a canine in the primary dentition. When fusion had been between primary incisors, there was only agenesis of an incisor in the permanent dentition in a few cases. The degree of fusion between the involved teeth was not related to the occurrence of agenesis. It is suggested that the intra-jaw differences are related to the recently reported prenatal developmental patterns of the alveoli of the incisors and canines. Moreover, it is suggested that neural crest developmental field differences between the developing maxilla and mandible may explain the inter-jaw differences in phenotypic abnormalities.     

The eruption times of permanent teeth in boys and girls in the Stormarn District, Schleswig-Holstein (Germany)

In a longitudinal study in two small towns in southern Schleswig-Holstein (Ammersbek and Ahrensburg, District Stormarn; 9155 inhabitants) we investigated 2832 oral findings of 1396 patients (711 males, 685 females). The minimum age was 1.51 years, and the maximum age was 25.50 years. The dental findings were collected over a period of about 20 years (1982-2002). The oral findings per child were assessed between one and eight times. The eruption times of teeth in females are earlier than those for the same teeth in males. Further, the permanent dentition in females is completed earlier than in males. In both sexes the tooth eruption occurs symmetrically in both jaws. The comparison of both jaws revealed a slightly advanced eruption of the lower jaw teeth in both sexes. There is a noteworthy change in the eruption sequence of the teeth. In contrast to other reports we observed that the eruption of the canine proceeds the eruption of the second molar. We found no acceleration of the dentition when compared with other reports and could confirm the rules of tooth eruption in man. Conclusion: Oral examination of teeth is a simple tool to calculate tooth eruption intervals. This first investigation on a population of Schleswig-Holstein revealed a change in the eruption sequence of permanent teeth. These findings are relevant for dental treatment planning and should be reconfirmed at certain intervals.     

Sequences and timing of dental eruption in semi-free-ranging mandrills (Mandrillus sphinx)

The chronology of tooth emergence is often used to examine the growth and development of individuals and to compare life histories across species. Emergence patterns are also used to age animals and to infer life history influences for extinct species. However, comparative studies of primates are hindered by a lack of dental development data for many species. Here we describe the sequences and timing of tooth emergence for a large sample of semi-free-ranging mandrills (Mandrillus sphinx) and compare this with other life history variables for this species. Deciduous dentition emerged in the sequence i1 i2 c p3 p4. The augmented sequence (including information about variability in emergence sequence) was i1 i2 [c p3] p4 for the female maxilla and the male mandible, and i1 i2 c p3 p4 for the female mandible and the male maxilla. Deciduous dentition was complete by 5.0 months in females and 6.4 months in males. The permanent dentition began to emerge at 26 months, and complete adult dentition had emerged by 68 months for males and 85 months for females. Sex differences occurred in the augmented eruption sequences: females M1 I1 I2 [M2 C] P3 P4 M3, males M1 I1 [I2 M2] [P4 = P3 = C] M3. The order of tooth eruption and the occurrence of sequence polymorphisms were very similar to those observed for baboons and macaques. Comparison with life history variables showed that mandrills have complete deciduous dentition at weaning, females possess both adult incisors and M1 when they first reproduce, but still have deciduous canines and premolars, and that both sexes have full adult dentition before they attain their full adult stature and mass.     

Coronal breadth of human primary anterior teeth

Original data for mesiodistal diameter of deciduous anterior teeth on 180 White children show: (1) mean size is smallest for the lower central incisor and largest for the upper canine, (2) means from combining widths on the left anterior teeth of each arch are larger in the maxilla than the mandible by 4.0 mm, (3) individual differences for widths of the upper central and lateral incisors extend from one child with these teeth of similar size to another child with the central incisor larger than the lateral by 2.3 mm, and (4) anterior tooth correlations are positive, varying from r = 0.4 for upper canine width with width of lower central incisor, to r = 0.8 for combined widths of left anterior teeth in the maxilla with combined widths of their antagonists. Comparative findings are drawn from investigations on Australian aborigines, South African Bushmen, Liberian Negroes, Tristan da Cunha islanders, Japanese, Japanese-Negro admixtures, Japanese-White admixtures, White groups living in several parts of Europe, and North American Whites. Among these ethnic groups, Australian aborigines have the largest deciduous anterior teeth. Composite means on each sex for North American Whites show boys to have slightly larger anterior deciduous teeth than girls.     

Sex-specific strategies of dentine depletion in red deer

Worn teeth in herbivore ungulates may be related to lower efficiency in mastication and hence lower performance. However, selection should favour maximal performance in terms of body mass and reproductive capacity during reproductive lifespan, when permanent teeth are already partially worn. We hypothesize that wear rate may respond to a strategy of use of tooth materials (notably dentine), which balances instantaneous wear rate and performance against tooth preservation for future performance and reproduction. In the present study, we investigated 4151 carcasses of Iberian red deer Cervus elaphus hispanicus and show that more worn molars were not related to lower performance throughout age. By comparing between sexes, tooth wear rates were smaller in females than in males, but the relationship between tooth wear and body performance also differed between the sexes: females did not show a significant relationship between tooth wear and performance but males with more worn teeth were in general heavier and had larger antlers until senile age, when more depleted teeth were related to smaller antlers. These results reveal, for the first time, sex-specific lifetime strategies of dentine expenditure: maintenance of performance ability throughout a longer reproductive lifespan in females, compared with maximizing current performance by depleting dentine reserves within a shorter lifespan in males.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 487–497.     

Primate origins and evolution. By R. D. Martin. Princeton,NJ: Princeton University Press. 1990. ISBN 0-691-08565-X. xiv + 840 pp. $125 (cloth)

Dental emergence ages are examined for a mixed longitudinal sample of 58 chimpanzees of known age and sex (22 males, 36 females) followed over the past 10 years. This study provides the most complete data set currently available on dental emergence in chimpanzees of known age and sex. Summary statistics and cumulative frequency percentiles of emergence ages are presented for both the permanent and the primary teeth. Male and female percentiles are also compared and reveal a number of cases of sexual dimorphism in emergence ages. Comparisons of emergence means reveal some statistically significant differences between upper and lower teeth but not between antimeres in the upper or lower dentition. Kendall's rank correlation coefficient (tau) suggests a correlation in timing between first molar and incisor emergence within individuals. In addition, a significant time lag was observed between first molar and central incisor emergence. A number of emergence sequence polymorphisms are presented as well. These findings provide important baseline information for future studies of chimpanzee growth, development, and demography and also contribute to several current issues in paleoanthropology relating to dental maturation patterns in early hominids.     

An adolescent female Neanderthal mandible from Montgaudier Cave,Charente, France

In 1974, an incomplete human mandible was discovered in the site of Montgaudier Cave, along the Tardoire (Charente), France. The mandible was found in association with stone tools and animal bones in geological deposits referable to the very end of the Middle Pleistocene or the beginning of the Upper Pleistocene. The mandible preserves much of the anterior part of the body and three permanent teeth: left lateral incisor, canine and first molar. Estimates based on tooth eruption of modern humans, as well as occlusal wear and root development, suggest an age at death of between 12.5 and 14.5 years. Morphologically, the fossil possesses features, such as a lack of a chin and multiple mental foramina, which have been observed on immature Neanderthal mandibular specimens from Europe. Comparison with these immature European Neanderthals indicates that the jaw and teeth of the Montgaudier mandible are small for its chronological age, suggesting it was that of a female. Am J Phys Anthropol 103:507–527, 1997 © 1997 Wiley-Liss, Inc.     

Wear Fast,Die Young: More Worn Teeth and Shorter Lives in Iberian Compared to Scottish Red Deer

Teeth in Cervidae are permanent structures that are not replaceable or repairable; consequently their rate of wear, due to the grinding effect of food and dental attrition, affects their duration and can determine an animal''s lifespan. Tooth wear is also a useful indicator of accumulative life energy investment in intake and mastication and their interactions with diet. Little is known regarding how natural and sexual selection operate on dental structures within a species in contrasting environments and how these relate to life history traits to explain differences in population rates of tooth wear and longevity. We hypothesised that populations under harsh environmental conditions should be selected for more hypsodont teeth while sexual selection may maintain similar sex differences within different populations. We investigated the patterns of tooth wear in males and females of Iberian red deer (Cervus elaphus hispanicus) in Southern Spain and Scottish red deer (C. e. scoticus) across Scotland, that occur in very different environments, using 10343 samples from legal hunting activities. We found higher rates of both incisor and molar wear in the Spanish compared to Scottish populations. However, Scottish red deer had larger incisors at emergence than Iberian red deer, whilst molars emerged at a similar size in both populations and sexes. Iberian and Scottish males had earlier tooth depletion than females, in support of a similar sexual selection process in both populations. However, whilst average lifespan for Iberian males was 4 years shorter than that for Iberian females and Scottish males, Scottish males only showed a reduction of 1 year in average lifespan with respect to Scottish females. More worn molars were associated with larger mandibles in both populations, suggesting that higher intake and/or greater investment in food comminution may have favoured increased body growth, before later loss of tooth efficiency due to severe wear. These results illustrate how independent selection in both subspecies, that diverged 11,700 years BP, has resulted in the evolution of different longevity, although sexual selection has maintained a similar pattern of relative sex differences in tooth depletion. This study opens interesting questions on optimal allocation in life history trade-offs and the independent evolution of allopatric populations.     

Une reconstitution surprenante d’un fossile humain : la mandibule magdalénienne du crâne d’enfant Rochereil III

The fragmented pathological skull of a young child was discovered in a Magdalenian level in the Rochereil cave, Dordogne, France, in 1939. The bony fragments were extracted along with the surrounding soil, and completely cleaned in a laboratory. The mandible has been wrongly reconstructed. Among the nine teeth that are present on the mandible, three deciduous molars are human teeth at their correct places. Only one tooth in the incisor–canine block (the right deciduous lateral incisor) is a human tooth, but it is incorrectly positioned on the left side. The other incisors and canines implanted in this child's mandible originated from one or several young adult reindeer. These small animal teeth were probably mistaken for human pathological teeth because the child's skull and mandible showed several pathological lesions. The possibility of faulty reconstitution must be systematically considered when dealing with for all human fossils which have been discovered in the past.     

Age determination and body growth of the Common duiker Sylvicapra grimmia(Mammalia)

Age determination in the Common duiker Sylvicapra grimmia was investigated by analysis of tooth eruption and replacement sequence, incremental lines of tooth cementum and tooth wear in a unique collection of 48 known-age skulls, and also by analysis by post-natal body growth in known-age duiker. In both the mandible and maxilla, permanent molariform teeth were fully erupted and in wear by 26 months of age. There was little variation in the age of eruption and replacement of all molariform teeth, making this a particularly useful feature of the duiker for age determination purposes. In contrast, the variability in eruption of the incisiforms, coupled with the difficulty in distinguishing deciduous incisiforms from the permanent counterparts, placed an unexpected limitation on the use of these teeth. Although the apparent linear relationship between tooth attrition and age has potential for further investigation as an age determination technique, the cementum annuli were not correlated with chronological age. Theoretical Von Bertalanffy equations were used to analyse body growth with age. It was concluded that because the asymptote of growth was reached at such an early age, and because there is so much individual variation in growth, body growth, including horn growth, is of very limited value for age determination. Female duiker were significantly larger than males.     

Age assessment in infant crab-eating monkeys (Macaca fascicularis) based on tooth development

Tooth development was studied in 13 Macaca fascicularis monkeys with known dates of birth. Regular intra-oral examination was carried out and standardized lateral radiographs were collected from 27 until 150 weeks of age under general anaesthesia.
Three stages of tooth development were determined radiographically: onset of crypt formation, onset of mineralization, and crown completion. A fourth stage, the emergence, was determined clinically. Developmental stages were recorded for six mandibular and five maxillary teeth.
The ages of emergence of the permanent teeth and the developmental stages of the third molars showed the largest variation. A significant sex difference with earlier maturation in males was found for the start of crypt formation of the maxillary permanent canines and the maxillary second premolars, and for the start of mineralization of the maxillary permanent canines.
The data provide a tool by which chronological age can be assessed of Macaca fascicularis monkeys between 30 and 80 weeks of age. Owing to an interphase of about one year without significant developmental features in the dentition, age assessment based on tooth development cannot be performed from about 80 to 130 weeks of age. Age assessments are possible for the period between 130 and 150 weeks of age. However, in this period the reliability of the data is lower due to larger time intervals and standard deviations.     

The timing of eruption of the primary dentition in Nigerian children

The objectives of this study were to clarify the eruption time and sequence for primary teeth in Nigerian children. It also investigated the effect of sex and socioeconomic status on the timing and sequence of eruption. A random sample of 1,657 children from ages of 3-40 months were examined--921 (55.6%) males and 736 (44.4%) females. The age of eruption of the teeth was estimated using probit regression. The results show that there was no effect of sex, socioeconomic status or breastfeeding status on the timing of eruption and pattern of teeth eruption in Nigerian children. Left and right teeth had similar eruption times. Eruption times of the lateral incisor, canine, and molars were similar for upper and lower teeth. Interpopulation studies however showed that though the sequence of eruption of primary teeth in Nigerian population is similar to that of their peers in other compared populations, there are observable sex differences in the timing of tooth eruption.