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Biomedical subjects

A Demirjian

Publications and source records attributed to A Demirjian.

At least 37 records · Page 2Linked to original sources
PubMed1986

Sexual dimorphism in the emergence of deciduous teeth: its relationship with growth components in height.

Sexual dimorphism in the emergence of the deciduous dentition of French-Canadian children may be explained by differences in recumbent length. Relative to the chronological age scale, boys are longer and their teeth emerge earlier than girls. Recumbent lengths attained at the exact age of emergence, as estimated by fifth-order polynomials fitted to each subject's serial data, are comparable between the sexes. Multi- and univariate analyses of variance show no significant sex differences in the lengths attained at the age of emergence of the deciduous teeth. These findings suggest that clinical standards for emergence of deciduous teeth scaled relative to length rather than chronological age are more accurate and efficient.

Age Factors↗
PubMed1986

Sexual dimorphism in mandibular growth of French-Canadian children 6 to 10 years of age.

Polynomial regression is used to model the mandibular growth of 28 girls and 26 boys who were followed longitudinally from 6 to 10 years of age. The pooled-within individual designs indicate that ramus height follows a linear pattern of size increase; corpus and total mandibular lengths display curvilineal, decelerating, patterns of growth over the age range. Multivariate analyses of variance reveal significant sex differences in size, favoring boys, for the two length measures at 6 years of age. Growth velocity for corpus length is also significantly greater in boys than in girls. Sexual dimorphism in the growth of total mandibular length is more complex, including differences in velocity and deceleration. Ramus height shows no significant pattern of variation between boys and girls for either size or growth velocity.

Aging↗
PubMed1986

A polynomial approach to craniofacial growth: description and comparison of adolescent males with normal occlusion and those with untreated Class II malocclusion.

Orthogonal polynomials are used to model the craniofacial growth of adolescent boys, aged 11 through 14 years, and to evaluate variation between normal occlusion and untreated Class II malocclusion. The results show linear growth (velocity) for the maxillary measures; their angular relationships to the cranial base remain stable throughout the age range. Mandibular measures show growth velocity and acceleration, indicating the adolescent growth spurt. For the majority (80%) of measures, boys with normal occlusion and those with Class II malocclusion were not significantly different. Mean growth velocity of basion-nasion is significantly greater for subjects with Class II, Division 1 malocclusion. Total mandibular length and the ANB angle display significant mean size (constant) differences between boys with normal occlusion and boys with untreated Class II malocclusion. The groups are comparable in growth velocity and acceleration, indicating that the size differences are established before 11 years of age and maintained during adolescence.

Adolescent↗
PubMed1985

Interrelationships among measures of somatic, skeletal, dental, and sexual maturity.

The interrelationships among five measures of physiologic maturity for 50 French-Canadian girls are evaluated--menarche, peak height velocity (PHV), 75% skeletal maturity, appearance of the ulnar sesamoid, and 90% dental development. The mean ages of occurrence of the events differed significantly (P less than 0.01). Menarche and 90% dental maturity showed the least variability. Ages of PHV, menarche, and 75% skeletal maturity were significantly correlated (P less than 0.05). Age of menarche was most closely associated with PHV. The appearance of the ulnar sesamoid was highly correlated with 75% skeletal maturity; both were equally related to the ages of PHV and menarche. The age at which French-Canadian girls attain 90% of their dental development showed no significant relationships with the other maturity indicators. The results imply that the mechanisms controlling dental development are independent of somatic and/or sexual maturity.

Adolescent↗
PubMed1985

Adjusting craniofacial correlations for technical error.

Reliability estimates provide a means of adjusting observed correlations for technical error. The results show that the true correlations among 11 craniofacial landmarks are consistently higher than observed values. Consequently, the regression slopes defining these relationships are also increased. The less reliable two measures are, and the closer their joint reliability approximates the observed correlation, the greater the expected change in true correlation. Adjusting craniofacial relationships for technical error may substantially increase the proportion of variation explained, and thereby alter statistical inferences drawn from results.

Cephalometry↗
PubMed1984

Effects of premature loss of deciduous molars.

A statistical exploration of space changes following early loss of deciduous molars, developing a picture of closure from both directions with district differences between upper and lower arch changes.

Age Factors↗
PubMed1984

Sexual dimorphism in the emergence of the deciduous teeth.

Exact ages of emergence of the twenty deciduous teeth have been investigated on a longitudinal sample of 195 French-Canadian children (113 boys and 82 girls). A multivariate analysis of variance yielded a significant overall sex difference (p less than 0.0001). It has been found that the emergence of the deciduous dentition in boys is more precocious than that in girls by about one month; this difference is present at the emergence of the upper central incisor and is maintained henceforth. The only notable exception to this pattern is the emergence of the first molars. Results of the present study, combined with those of previous research, suggest that sexual dimorphism in the emergence of the deciduous teeth could be mediated through ethnic factors.

Age Factors↗
PubMed1980

Sexual dimorphism in body composition changes during the pubertal period: as shown by French-Canadian children.

Size and velocity growth curves of stature to represent skeletal growth, lean arm circumference to represent muscle growth, and the sum of three skinfolds to represent fat tissue changes, are presented for a longitudinal study of Montreal school-age chidren. Both a chronological age scale, and one relative to the individual ages of peak growth velocity in stature, are used. Intercorrelations between the various components are tabulated for age groups based on the two scales. The three skinfolds are also analyzed separately. The results show that such simple anthropometric measures can be usefully taken to represent the growth of different body components. Longitudinal analysis reveals that, whereas the relationship of muscular to statural growth in boys is purely maturational, it is not so for girls, and that the different skinfolds show complex sexual differences in growth during the pubertal period.

Adipose Tissue↗
PubMed1980

Heritability estimates of somatotype components based upon familial data.

Somatotype components were obtained in 239 French-Canadian families from Montreal. Endomorphy, mesomorphy and ectomorphy were anthropometrically assessed in the Health and Carter system. All three components were available in 208 pairs of siblings, while only ectomorphy was estimated in 507 parent-child pairs. Sibling correlations reached 0.40 for endomorphy, 0.30 for mesomorphy, and 0.38 for ectomorphy. Partialling out the effects of 7 socioeconomic indicators permitted an estimate of common familial environment upon covariation between relatives. Residual sibling correlations yielded broad heritability estimates (HB) of 0.50 for endomorphy, 0.42 for mesomorphy and 0.54 for ectomorphy. Narrow heritability (HN) for ectomorphy, controlling for familial indicators, was approximately 0.36 including a positive contribution from assortative mating.

Adult↗
PubMed1980

Sexual differences in dental development and prediction of emergence.

The dental development of a genetically homogeneous French-Canadian group of children ranging in age from 2.5 to 19 years was evaluated from 5,437 panoramic radiographs by the method of Demirjian et al. The maturity of each mandibular tooth was evaluated individually. For each stage of each tooth, the developmental curves of boys and girls were compared. A common pattern was found for each tooth, namely the chronological similarity between boys and girls in the early stages of development and the advancement of girls over boys for the later stages. Development scores were given to the seven mandibular teeth. Up to five to six years of age, no difference was found in the timing of dental development between boys and girls, in contrast to the older ages where girls were always more developed than boys. When the emergence curve was plotted with developmental curves, a close relation was established between the stage of formation of all teeth and their emergence, hence the predictive value of the use of dental maturity curves in clinics.

Adolescent↗