Masculinization of the eruption pattern of permanent mandibular canines in opposite sex twin girls

The aim of this study is to explore the effect of prenatal androgenization on the clinical eruption of permanent teeth expressing dimorphism and bimaturism. The eruption curves of permanent teeth (except third molars), including those that make up the canine complex (permanent canines, lower first premolars), are compared among opposite sex twins (OS twins) relative to single‐born boys and girls. The comparisons are made with regard to three phases of eruption (pierced mucosa, half‐ erupted, and completely erupted) from a cross‐sectional sample of dental casts, using Kaplan–Meier survival and Cox regression analyzes. The casts were collected from 2159 school children from the US Collaborative Perinatal Project, including 39 pairs of OS‐twins, of which 12 pairs (30.8%) were Euro‐Americans and 27 pairs (69.2%) were of African‐American ancestry. The eruption patterns of the incisors, upper first molars, and lower canines were found to be significantly masculinized (delayed) among OS twin girls. The differences in most other teeth were either not significant, or the number of observations of active eruption phases were too few, such as in the upper first molars and incisors, to yield strong evidence and meaningful results. The masculinization of the tooth eruption pattern in OS twin girls is intriguing because of the lower canine responses during puberty, as well as canine primordial formation during early fetal androgenization of their co‐twin during the 8th to 14th gestational weeks. The present results offer a challenge for future research exploring tooth eruption mechanisms, and may also highlight some cases of delayed or ectopic canines, which are biased toward females. Am J Phys Anthropol 151:566–572, 2013. © 2013 Wiley Periodicals, Inc.     

Age and wisdom teeth in Nigeria

An attempt has been made to estimate the eruption age of wisdom teeth in the North Nigerian population. The present study was carried out on 654 boys and 584 girls of age groups ranging from 11-23 years. From the data collected estimates have been provided for the eruption age of the third molar. In general, teeth of the lower jaw erupt before those of the upper jaw. The teeth on the left side erupt earlier than those on the right side. The wisdom teeth erupt little earlier amongst boys (18 years) as compared with girls (18.5 years). In general, the wisdom teeth erupt in Nigerians with some constancy between the age of 15 and 21. The wisdom teeth fail to erupt in 5% of the individuals.     

Developmental stage of the dentition and speech sound production in a series of first-grade schoolchildren.

This study was undertaken to investigate the effect of developmental stage of the dentition on speech sound production in children with and without articulatory speech disorders. In the whole sample, there were 281 subjects, mean age 7.5 years (SD 0.4). The stage of the eruption of the permanent incisors was calculated as the percentage height of each tooth of the mean crown height of the corresponding tooth in a group of 252 young adults. Eruptional stage of the first permanent molars was classified into three categories. Articulatory disorders were diagnosed by one experienced speech therapist and phoniatrician using the Remes Articulation Test [Remes, 1975] for the Finnish language. The results showed a wide interindividual variation in developmental stage of the dentition in a group of 7-year-old children with a tendency of the first permanent molars but not the incisors to erupt earlier in girls than in boys. Boys had a higher frequency of misarticulations estimated to need treatment than did girls. The present results indicate that during eruption of permanent teeth it is more important to draw attention to symmetrical eruption and to individual timing pattern rather than to the mean values of tooth eruption in subjects of the same age. The findings also suggest a decreasing risk of faulty speech sound production with advancing eruption of some permanent teeth still present in 7-year-old children.     

Chronology, dynamics and period of permanent tooth eruption in Zagreb children (Part II)

The aim of the present paper is to determine the beginning, order, median time, termination, dynamics, continuity and intensity of the permanent tooth eruption, as well as its calendar, in a sample of Zagreb children. The study included 2768 children (1398 boys and 1370 girls). All subjects were classified in one-year age groups. The continuity of tooth eruption occurs from 5.1 years to 14.97 years, i.e., for a period of 9.87 years. Each particular tooth has its own dynamics of eruption (V5-V95) which on the average amounts to 4.25 years. The continuity of eruption is 10.1 years in boys and 9.8 years in girls. The dynamics of eruption is 4.15 years in boys and 4.35 years in girls. A certain asymmetry in eruption has been described.     

昆明市儿童恒牙萌出时间及恒牙萌出与生长发育关系的调查研究

本文报道了昆明市8148例儿童恒牙（第三磨牙除外）萌出时间的横断面调查，对恒牙萌出与年龄、身高、体重和月经初潮的关系进行了探讨。经相关分析，恒牙萌出数与年龄高度相关，与身高和体重低度相关，并建立了由年龄、身高或体重推算萌牙数的回归方程。还发现恒牙萌出与青少年性成熟也有一定的联系。提示恒牙萌出也能反映儿童的生长发育状况，故可作为衡量儿童生长发育的一项指标。     

Dental developmental status of southern Chinese girls in Hong Kong

Dental developmental status of the permanent canines, premolars and second molars were studied in one hundred and two twelve-year-old Southern Chinese girls born and brought up in Hong Kong. Eruption of these teeth were defined as gingival emergence during the clinical examination while the root development was assessed from orthopantomographs. Root resorption pattern of the primary canines and molars were also studied with the aid of the orthopantomographs. Two-thirds of girls presented with permanent dentition stage. The root resorption patterns of the primary teeth were different from their order of exfoliation. The mandibular permanent teeth were in advanced in both eruption and root development than the corresponding maxillary teeth, except the first premolars.     

Teeth eruption in children with normal occlusion and malocclusion

The aim of this study was to assess the differences in eruption of permanent teeth (C, P1, P2 and M2) in a group of children with and without malocclusion. A sample of 1758 children (921 boys and 837 girls), aged 8-13 was randomly selected. The subjects were grouped by chronological age (11 groups) and by presence of malocclusion. Statistically significant differences were found for both, upper and lower canines in the age group 11 (p<0.01). Statistically significant difference was found in the age group 8.5 for upper first (p<0.05), upper second premolars (p<0.01) in the age group 10, and the lower second premolars in the age group 11 (p<0.05). Premature loss of deciduous teeth caused early eruption of succedaneus permanent teeth, possibly leading to development of a malocclusion.     

Maxillary volume growth in childhood

Nasomaxillary abnormalities in form, position, and development in children are often prominent features of craniosynostosis, and in particular, craniofacial dysostosis. While attempting to quantitatively assess the volumetric maxillary deficiency in these patients, it became apparent that there was no "normal" reference range for maxillary volumes throughout childhood that could be used for comparison. The aim of this study was to generate a model for measuring maxillary volume and subsequent changes throughout childhood. The technique of segmentation was applied to magnetic resonance images obtained in 55 healthy children (30 boys, 25 girls), aged 1 month to 184 months (15.33 years). Maxillary volumes were plotted against age for boys and girls to create a model for normal maxillary growth during the first 15 years of life. Maxillary volumes were larger in boys at all ages. However, the pattern of maxillary growth in boys and girls was similar and could be divided into three periods, each lasting approximately 5 years. During the first 5 years of life, there is a steady increase in maxillary volume, at the end of which the maxilla has reached 53 percent of the volume recorded at 15 years. There is an accelerated rate of growth between 5 and 11 years, which corresponds to the development and eruption of the permanent dentition. Thereafter, until the age of 15 years, the rate of growth of the maxilla plateaus. Maxillary volume in the first 12 months of life is, on average, 29 cm3 in boys and 25 cm3 in girls. By 15 years of age, it has increased to an average of 73.0 cm3 in boys and 59.4 cm3 in girls (an increase by a factor of 2.5 in boys and 2.4 in girls). The difference between the two sexes is statistically significant for the entire series (boys: mean maxillary volume = 56.55 cm3, SD = 24.61; girls: mean maxillary volume = 40.68, SD = 17.69, p = 0.009, one-way analysis of variance).     

Ecological factors affecting eruption timing of mandibular teeth in roe deer

Increasing evidence suggests that conditions in early life have important consequences for body size and fitness in mammals. As regards herbivores, teeth play a central role in the long-term performance of individuals. So far, however, patterns of teeth eruption have been scarcely investigated in relation to environmental and climatic factors experienced by herbivores. We described the eruption timing of mandibular teeth in a population of roe deer (Capreolus capreolus) located in the Apennines (Central Italy), through the analysis of 2161 jaws of fawns (1176 females and 985 males) shot in their first winter of life over three hunting seasons (2013–2015). Results showed that the percentage of juveniles exhibiting permanent teeth depends on the cohort. Among the factors that may affect both incisiviform and molariform teeth replacement timing, our findings include body mass and population density. Additional factors determining the relative speed of teeth replacement are (1) food availability for the mother during the last part of gestation, the birth period and the lactation, (2) winter temperature experienced by the mother, and (3) temperature experienced by fawns during their first summer and autumn. Besides, for the first time in literature, elevation was reported to delay front teeth replacement. A greater number of climatic factors were found to shape the eruption timing of the third molar (M₃) in comparison to that of incisiviform teeth. Also, a different pattern was found in males and females. The eruption of M₃ is, indeed, a costly and long-lasting process requesting optimal nutritional conditions and the meeting of a threshold jaw size. Our results indicate a strong correlation between environmental conditions and eruption process, i.e., between resource availability during the gestation and rearing periods and eruption timing.     

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.     

Eruption of permanent teeth in Brazilian Whites and Blacks

A total of 302 White and 904 Black children six, nine and 12 years of age were studied for the eruption of their permanent teeth. Differences between the two ethnic groups were not large, but the Black subjects were generally more precocious at the beginning of the process (especially the girls, both in the upper and lower incisors). At nine and 12 years of age, however, these dissimilarities disappear. The latter do not seem to be related to distinct rates of extraction or agenesis of deciduous teeth. No significant differences were observed in the degree of asymmetry present in the permanent dentition of the White and Black individuals studied.     

Economic impact on tooth emergence

As shown in nearly 10,000 Negro and White boys and girls between 4.5 and 16.5 years of age, poverty-level children (with an income-to-needs ratio of 1.0) tend to be delayed in permanent tooth emergence as compared with those approximating median per-capita income. For boys, a per-capita income difference of $2200 was associated with a 0.15 standard deviation difference in emergence timiing of 28 permanent teeth.     

Genome-wide association study identifies four loci associated with eruption of permanent teeth

The sequence and timing of permanent tooth eruption is thought to be highly heritable and can have important implications for the risk of malocclusion, crowding, and periodontal disease. We conducted a genome-wide association study of number of permanent teeth erupted between age 6 and 14 years, analyzed as age-adjusted standard deviation score averaged over multiple time points, based on childhood records for 5,104 women from the Danish National Birth Cohort. Four loci showed association at P<5×10(-8) and were replicated in four independent study groups from the United States and Denmark with a total of 3,762 individuals; all combined P-values were below 10(-11). Two loci agreed with previous findings in primary tooth eruption and were also known to influence height and breast cancer, respectively. The two other loci pointed to genomic regions without any previous significant genome-wide association study results. The intronic SNP rs7924176 in ADK could be linked to gene expression in monocytes. The combined effect of the four genetic variants was most pronounced between age 10 and 12 years, where children with 6 to 8 delayed tooth eruption alleles had on average 3.5 (95% confidence interval: 2.9-4.1) fewer permanent teeth than children with 0 or 1 of these alleles.     

Sex differences in HDL ApoC-III in American Indian youth

ABSTRACT: BACKGROUND: Since American Indians are predisposed to type 2 diabetes (DM2) and associated cardiovascular risk, Cherokee boys and girls (n = 917) were studied to determine whether BMI Z (body mass index Z score) is associated with the apoC-III (apolipoprotein C-III) content of HDL (high density lipoprotein), a previously reported predictor of DM2. METHODS: An ad hoc cross-sectional analysis was conducted on a previously studied cohort. Participants were grouped by gender-specific age groups (5 to 9, 10 to 14 and 15 to 19 years). ApoA-I (apolipoprotein A-I) and HDL apoC-III were assayed by immunoturbidimitry. ApoC-III was measured in whole plasma, and in HDL to determine the molar proportion to apoA-I. General linear models were used to assess association. RESULTS: The HDL apoC-III to apoA-I molar ratio increased by BMI Z quartile in girls aged 10--14 years (p < 0.05 for linear trend, p < 0.05 for difference in BMI Z quartile IV vs. I to III) and aged 15--19 years (p < 0.05 for trend). In boys the increase by BMI Z occurred only at ages 15--19 years (p < 0.01 for trend and for quartile difference). CONCLUSIONS: ApoC-III showed an obesity-related increase relative to apoA-I during adolescence beginning in girls aged 10 to 14 years and in boys aged 15 to 19 years. The earlier changes in girls may alter HDL's protective properties on the beta-cell and contribute to their increased risk for DM2.     

Gender-specific growth patterns for stature,sitting height and limbs length in Croatian children and youth (3 to 18 years of age)

In a cross-sectional study of growth, 5,155 children (2,591 females, 2,564 males) from the town of Zagreb (Croatia) were measured. Four traits of linear dimensionality (stature, sitting height, arm and leg lengths) were studied in the age span of 3 to 18 years. A significant average annual increase of all four anthropometric parameters were observed up to 14 and 15 years of age in girls and 16 years of age in boys, showing that girls had a shorter growing period. In the prepubertal period until 9 years of age, gender differences were negligible. At the age of 10, boys were overgrown by girls in all parameters due to the earlier onset of puberty in girls. The growth gains for girls, when compared with those for boys, show a different pattern across variables. The female growth advantage remained in a two years period for the limbs length, but in a three year period for stature and the longest, for 4 years, for sitting height. The male predominance in size had an onset at the age of 13 for the limbs and in the age of 14 for stature and sitting height. The patterns of sexual dimorphism in stature and sitting height during growing years are similar to those observed in other populations of Europe. Growth of Croatian children and youth is very similar to that of the tallest European populations.     

Features of the circadian rhythm of temperature of the skin at children of 8-9 years and young men and girls

Problem of the present work was studying age features circadian rhythm of temperature of a skin with application of a method "Termochron iButton". Day-night rhythm of a skin temperature at two age-grades was investigated: boys and girls of 8-9 years and young men and girls of 20-22 years. For this purpose monitoring temperature during 48 hours with an interval of registration 10 minutes has been lead. Are revealed authentic chronobiological differences: mesor temperatures above at girls, than at boys, and at young men, above, than at girls. Amplitude of a circadian rhythm is above at boys and at girls. Researches chronobiological parameters in the different terms of day have shown, that an average level of temperature at night below at all examinees. The amplitude at adult people in the different terms of day does not differ, while at children it above in the night term.     

Activity pattern, smoking habits, and somatometric variables of the Czechoslovakian population

A total of 3762 subjects of both sexes, natives of Czechoslovakia, ranging in age from 12--55 years, were examined. Both anamnestic data and selected anthropometric variables were evaluated. The proportion of non-smokers for adult males was 47--56%, and for adult females was 54--74% of the population. The proportion of subjects not engaged in any type of physical activity decreases in boys between 12 and 18 years from 28 to 16%, in girls between 12 and 15 years from 25 to 22%; from then on the trend reverses and the percentages rises up to 42% in men and 65% in women. The number of subjects participating in competitive sporting activity reaches its peak at 18 years, when 46% of boys annd 43% of girls compete, but then decreases quickly. 12 year old girls are taller and heavier than boys but at 15 years the relationship is reversed. The LBM at the age of 12 is equal in boys and girls, but from then till 18 years the increase is larger in boys. The LBM weight in adults remains steady, women attaining 77% of the value found in men. The skinfold increases with age similarly in both sexes, except for an interval between 12 and 18 years, when girls show a steeper increase. Adult women attain 121--160% of the values characteristic for men. The grip strength of the right hand equals about 50 kp in adult men and 30 kp in adult women. Within the age range followed, it remains unaffected by age.     

Eruption patterns of permanent front teeth as an indicator of performance in roe deer

In most species of vertebrates, teeth play a central role in the long-term performance of individuals. However, patterns of tooth development have been little investigated as an indicator of animal performance. We filled this gap using data collected during long-term capture-mark-recapture monitoring of 1152 roe deer fawns at Chizé, western France. This population fluctuated greatly in size during the 27 years of monitoring, offering a unique opportunity to assess how the eruption patterns of front teeth perform as indicator of animal performance. We used three indices of the eruption of permanent front teeth, the simplest being whether or not incisor I₂ has erupted, and the most complex being a 12-level factor distinguishing the different stages of tooth eruption. We also assessed the relevance of these indices as compared to fawn body mass, a widely used indicator of animal performance of deer populations. Dental indices and body mass were positively correlated (all r > 0.62). Similarly to body mass, all indices based on tooth eruption patterns responded to changes of population size and can be reliably used to assess the relationship between roe deer and their environment. We found a linear decrease in body mass with increasing population size (r² = 0.54) and a simultaneous delay in tooth development (r² = 0.48–0.55 from the least to the most accurate indicator). However, tooth development would be not further delayed in years with the highest densities (>15 adult roe deer/100 ha). A path analysis supported the population density effect on tooth eruption patterns being mainly determined by the effect of population size on body mass. Our study provides managers with simple indices (e.g., presence-absence of I₂) that provide a technically more easy way to standardize measurements of deer density-dependent responses over large geographical and temporal scales than would be possible with body mass.     

Brief communication: Emergence chronology of permanent teeth in Nigerian children

This study measured the mean age, duration, and sequence of the emergence of permanent dentition in Nigerian children and compared the findings with other population groups. The cross‐sectional study involved 1,078 Nigerian children, aged 4–16 years old, from selected primary and secondary schools in the Ife Central local government area in Ile‐Ife, Osun State. In general, compared to boys, girls had an earlier mean age of emergence of all the permanent teeth. Children from high socioeconomic class had an earlier mean age of emergence for the maxillary incisors (6.43 and 7.58 years) and mandibular incisors (5.28 and 6.44 years) compared to children from middle and low socioeconomic classes, although socioeconomic effects were more mixed for premolars and molars. Compared to their counterparts in the USA, Australia, Belgium, and Iran, Nigerian children showed an earlier mean age of emergence of all the permanent teeth studied except for Pakistani boys, who had an earlier mean age of emergence of the maxillary premolars and second molar. Poorer economic status has been associated with delayed dental development; however, when compared to other populations, the Nigerian children in this study have earlier mean emergence ages than children from wealthier countries such as the USA and Australia. Am J Phys Anthropol 153:506–511, 2014. © 2013 Wiley Periodicals, Inc.     

Evolutionary Implications of Dental Eruption in Dasypus (Xenarthra)

Late eruption of the permanent dentition was recently proposed as a shared anatomical feature of endemic African mammals (Afrotheria), with anecdotal reports indicating that it is also present in dasypodids (armadillos). In order to clarify this question, and address the possiblity that late eruption is shared by afrotherians and dasypodids, we quantified the eruption of permanent teeth in Dasypus, focusing on growth series of D. hybridus and D. novemcinctus. This genus is the only known xenarthran that retains two functional generations of teeth. Its adult dentition typically consists of eight upper and eight lower ever-growing (or euhypsodont) molariforms, with no premaxillary teeth. All but the posterior-most tooth are replaced, consistent with the identification of a single molar locus in each series. Comparison of dental replacement and skull metrics reveals that most specimens reach adult size with none or few erupted permanent teeth. This pattern of growth occurring prior to the full eruption of the dentition is similar to that observed in most afrotherians. The condition observed in Dasypus and many afrotherians differs from that of most other mammals, in which the permanent dentition erupts during (not after) growth, and is complete at or near the attainment of sexual maturity and adult body size. The suture closure sequence of basicranial and postcranial epiphyses does not correlate well with dental eruption. The basal phylogenetic position of the taxon within dasypodids suggests that diphyodonty and late dental replacement represent the condition of early xenarthrans. Additionally, the inferred reduction in the number of molars to a single locus and the multiplication of premolars represent rare features for any living mammal, but may represent apomorphic characters for Dasypus.