Dental Dimensions Research Articles

Tooth size and arcadal length correlates in man

Intra-arcadal mesiodistal and buccolingual tooth size correlations were evaluated in a sample of 125 caucasoids with ideal occlusion. Dental dimensions were corrected for arcade mength (as a measure of jaw size) by a series of regression analyses of each mesiodistal dimension on the sum of the mesiodistal dimensions within each arcade. Regression coefficients of tooth dimension on arcade length were calculated to gain an insight into the dimensional sensitivity of individual teeth to arcade length variation. The data presented here suggest a strong association between arcadal length (jaw size) dependence, and the dimensional stability of individual teeth. When corrected for arcade length, a definite pattern of tooth size correlation emerges: postcanine maxillary and mandibular teeth are negatively correlated to the anterior teeth and are positively correlated to one another. The hypothesis is developed that anterior and postcanine teeth should be viewed as two separate and negatively size-correlated units, beyond the boundaries of the four morphological tooth classes. Recognition of this basic dichotomous size arrangement within each jaw allows for a reassessment of some of the problems associated with hominid dental evolution.

Genetic variance in dental dimensions of Punjabi twins.

Genetic variance analysis of 56 tooth size traits was based on a sample of 58 pairs of twins (23 MZ and 35 DZ) from Chandigarh, India. Results of a t-test for equality of means showed no association of zygosity with any of the traits. Heterogeneity of total variance was found in 18 traits, which invalidates conventional genetic variance estimates and reveals considerable hidden environmental determinance. In contrast to other studies, Indian MZ twins had higher variance than did DZ twins, in most instances. There was also evidence of stronger environmental covariance for MZ and DZ twins. The study revealed substantial, complex environmental determination for some dental dimensions, especially of incisors and second molars.

Sexual dimorphisms in dental dimensions of higher primates.

Dental dimensions and distributions of dental dimensions of males and females were compared for great apes (Pan, Gorilla, and Pongo, and humans (Homo). The results were examined and discussed with reference to fossil primates Sivapithecus and Ramapithecus. The analyses focused on patterns of sexual dimorphism, both with regard to mean dimensions and the distribution of those dimensions. Sex differences in mean canine dimensions were large and significant for Gorilla and Pongo, significant but smaller for Pan, and small but occasionally significant for Homo. The dispersions of measures were greater for males than for females in Gorilla and Pan but did not differ significantly for Pongo or Homo. Examination of the noncanine teeth revealed complex sex differences. In the anterior teeth, sex differences in mean dimensions were generally apparent for Gorilla and Pongo, less so for Pan, and least of all in Homo. The patterns of dispersion of measures of anterior teeth differed markedly from those of the canines. Pan exhibited the same pattern for anterior and canine teeth. Gorilla showed the opposite pattern. Pongo and Homo showed similar dispersions for males and females in many cases. Sex differences in posterior teeth followed the pattern of the canines for Gorilla and were absent for Pan. Pongo exhibited mean differences in dimensions across sex, but dispersions were similar. The pattern for Homo was most like that of Pongo, but with fewer significant differences. The genera differed with regard to the number of significant differences in means or dispersions along the tooth row. It is clear that the patterns of dimorphism differ qualitatively across all extant genera of great apes and humans. It appears that the pattern for Homo most closely resembles that of Ramapithecus, whereas Pongo most closely resembles Sivapithecus. The patterns for Gorilla and Pan appear to be unlike either of the fossil forms. It is suggested that the qualitatively distinct patterns of dental sexual dimorphism indicate substantial flexibility during recent primate evolution and that the degree of structural flexibility demonstrated provides a basis for appreciating potential for plasticity of gender differences in behavioral, social, and cultural systems.

Dental sexual dimorphisms in some extant hominoids and ramapithecines from China: A quantitative approach.

AbstractStudies of sexual dimorphism in the dental dimensions of some extant and fossil hominoids have been carried out by means of univariate statistical methods [Oxnard et al., 1985]. The study reported here extended these studies with multivariate statistical methods (canonical variates analyses). The extant genera studied were Gorilla, Pan, Pongo, and Homo. The fossil teeth interpolated were those of the recently discovered ramapithecines from Yunnan Province, China. For both extant and fossil species, the lengths and breadths of all maxillary and mandibular teeth were used except for the third molar, which was excluded because of its absence in so many human subjects. The nature of sexual dimorphism in the dentition of extant apes and humans was assessed, and the positions of the fossil teeth within the multivariate results for the extant forms was examined. Among the apes, the greatest sexual dimorphism was seen in Gorilla; the least was seen in Pan. Three different patterns of sexual dimorphism were apparent among the three ape species. The maxillary and mandibular patterns were different in Gorilla and Pan but more similar in Pongo. The African apes showed greater differences between variances for each sex and of each jaw; these features may have evolved most recently. The conventional notion that sexual dimorphism is mainly due to size and size‐related shape effects along a single continuum or axis was rejected. The interpolation of the fossil data placed Sivapithecus close to each of the more dimorphic apes, especially Pongo, but also showed that it had higher order differences from the extant forms studied. Ramapithecus was most similar to Homo. These results have implications both for the role of sexual dimorphism in the evolution of higher primates and for the phylogenetic relationships among them.

The relationship between organ weights and body weights, facial dimensions, and dental dimensions in a population of olive baboons (Papio cynocephalus anubis).

AbstractQuestions concerned with the relationship between organ weights and body weight on an intraspecific level are best answered by using a sample of animals collected in the wild from a single locale during a single season. The organ weights and body weights for this study were obtained from the necropsy reports prepared in the field (Athi Plain, Kenya) by H. C. McGill, Jr. on 36 adult animals (18 males and 18 females). Dental and facial measurements were taken by M.I. Siegel.In order to avoid erroneous results produced by statistical treatment of combined sex samples of sexually dimorphic species, data on the sexes were analyzed separately. Means and standard deviations are reported for selected organ weights and body dimensions (heart, lung, liver, spleen, kidney, adrenal, brain, and pancreas weights, crown–rump length, crown–heel length, head circumference, chest circumference, and body weight). All of the above measures were significantly (p<0.05) different between the sexes. Logarithms of these measures were significantly correlated with the logarithm of body weight in males for heart, lung, liver, spleen, kidney, and adrenal weights, crown–heel length, and head and chest circumference, and in females for crown–heel length, heart, liver, and kidney weights. Partial correlational analysis, removing the effects of body size (weight), showed mostly negative correlational relationships between dental and visceral dimensions. Most of the correlations between facial and visceral dimensions were negative. Allometric equations were calculated for the dental, facial, and visceral dimensions versus body weight, and are compared with prior published results.

Variation and dynamics of a fossil antelope population

656 mandibles and isolated teeth of the bovid Pachytragus solignaci Robinson from two localities in the Miocene Beglia Formation, Gafsa, Tunisia, have been individually aged on the basis of ontogenetic development and state of dental wear. The sample probably represents normal but seasonally restricted mortality. Life table analysis indicates an annual mortality rate of 25–30%, increasing in old animals. Dental dimensions are affected by stabilizing selection which sets in as the tooth comes into function, earlier mortality being nonselective in that respect.

Ramapithecus and Sivapithecus from China: Some implications for higher primate evolution.

The pattern of overall dental dimensions in over 900 teeth of ramapithecines from Lufeng in China is examined using frequency distribution histograms and fitted normal curves, and compared with data for extant hominoids. A prior study has demonstrated unequivocally that at least two groups of animals must have existed at Lufeng [Wu and Oxnard, 1983; Oxnard, 1983a]. The present investigation confirms this finding in more detail. In addition it shows that one fossil group possesses smaller teeth with a lesser degree of sexual dimorphism and approximately equal numbers of adult males and females, and the other possesses larger teeth with a rather larger degree of sexual dimorphism and a female-male ratio that may have approximated from as low as 2:1 to as high as 4:1. Comparisons of patterns of difference along the tooth row demonstrate that both these forms differ from modern apes in their sexual dimorphism, the smaller form being more like humans than the larger, which is more like apes, especially orangutans. Comparisons of the areas of the canine teeth with each of the other functional segments of the tooth row again show that the smaller form is basically similar to modern humans and that the larger resembles extant great apes. Comparisons of other functional dental areas seem to relate to dietary and masticatory functions. Thus the cutting areas are large relative to the chewing areas in omnivorous humans, whereas in the essentially vegetarian great apes this ratio is smaller. The smaller fossil resembles the human condition and may have been somewhat omnivorous; the larger one more resembles the apes and may have been somewhat more vegetarian. However, these comparisons also show that the way in which the larger form resembles the apes is associated with special development of the canines, which is different from that in any modern ape. Comparisons show that the canines in the larger form project far beyond the normal line of tooth crowns. Finally, comparisons show that canine sexual dimorphism in height is marked in the larger form. Neither of these last two features is true of the smaller fossil. These findings have implications for our understanding of the evolution of early pongids and hominids, and for the evolution of primate sexual dimorphisms and dental mechanisms.

Deciduous tooth dimensions in fetal rhesus monkeys from mothers with induced diabetes.

Thirty-four measurements of the deciduous dentition in 21 fetal rhesus monkeys from diabetic mothers (FDM) and 36 nondiabetic fetuses were compared in order to assess the effects of induced maternal diabetes on the teeth of third-trimester fetuses. After exclusion of 14 variates due to significant age-related variation, univariate statistical analysis suggested a trend toward smaller teeth in the FDMs. Multivariate discriminant function analysis indicated not only a clear separation between the two groups, with molar breadths and some incisor length and breadths serving as the best discriminators, but also that the deciduous dental dimensions in FDMs are smaller than in nondiabetic fetuses.

A differential environmental effect on human anterior tooth size.

Factor-analytic studies of human tooth size routinely exhibit separate factors for the mesiodistal and buccolingual dimensions of anterior teeth but a single factor each for premolar and molar size. This observed independence within the anterior field is shown to be attributable to a much larger effect of environmental factors on the buccolingual vs. the mesiodistal diameters, a significant cause of which may be calculus accumulation hitherto unrecognized in the relevant literature. The heritability of dental dimensions is also discussed.

Sexual dimorphism and human tooth size differences

Current male/female differences in tooth size are due to the male/female differences in body bulk that exist in any given human population. These differences are residues of the sexual dimorphism that was maintained for adaptive reasons during the Middle Pleistocene. Late in the Pleistocene the development of food processing techniques led to the reduction of both male and female dental dimensions. Dental sexual dimorphism, however, was maintained until the very end of the Pleistocene when the hunting of large game animals by crude techniques was replaced by a focus on great numbers of small game caught by more sophisticated means and by an increasing utilization of plant foods. The subsequent reduction in dimorphism represents the actions of the Probable Mutation Effect operating under conditions of relaxed selection. The conclusion offered is that the smallest degree of sexual dimorphism visible in the modern world is to be found among those populations that are separated by the greatest interval of time from precursors who depended for their survival on a Pleistocene big game hunting mode of subsistence.

The relationship between body weight, facial, and dental dimensions in a population of olive baboons ( Papio cynocephalus anubis)

Correlation coefficients between dental dimensions, facial dimensions, and body weights for the adult males of a homogeneous troop of baboons were calculated. No significant correlations were found between mesial-distal tooth diameters and body weight. Facial dimensions also were generally not significantly correlated with body weight.

Functional implications of primate enamel thickness

Recent evolutionary interpretations of Hominoidea have postulated functional relationships between tooth form, diet and masticatory biomechanics. A major consideration is the durability of the tooth under certain dietary conditions. Teeth with low cusps and thicker enamel are able to withstand heavy mastication of abrasive food bolus for a longer period. When comparisons are made between species of higher primates the variables of tooth size, cusp morphology, and enamel thickness appear to be related but until now no systematic analysis has been made to determine the functional relevance of several dental dimensions. This study provides data gained from comparisons of dentition of nine species of primates. Histological sections were made of the post canine teeth and 21 dimensions were compared. The relevant dimensions identified serve to withstand dental wear. The distribution of thicker enamel corresponded to the observed wear planes. Humans had thicker enamel than pongids while the macaque had the thinnest. These preliminary results tend to support theories which explain low, thick, enameled cusps in hominids.

Heat stress, fluctuating asymmetry and prenatal selection in the laboratory rat.

Recent studies have demonstrated that stress may increase the fluctuating asymmetry of teeth and limbs in laboratory animals. The present study investigates the effects of heat on such parameters. Pregnant laboratory rats are exposed to temperatures of 33 degrees C during gestation. Increases in fluctuating asymmetry of dental dimensions as well as bone density are found for the pups of such females when compared to unstressed controls. A general increase in limb lengths is also reported for young of heat stressed animals. Prenatal selection with differential survival is suggested as a possible explanation for differences found between the experimental and control animals.

A twin study of dental dimension. I. Discordance, asymmetry, and mirror imagery

Bilateral tooth measurements in twins are partitioned into three orthogonal contrasts, each associated with one degree of freedom, to estimate three parameters: discordance, asymmetry, and mirror imagery. The probability levels of the within-pair variance ratios were used to test for significance of these estimates. The results provided strong evidences for the existence of significant genetic determinants of almost all of the individual tooth dimensions, but little or no evidence for a genetic basis of asymmetry. The analysis gave no indication that monozygotic twinning was associated with an increased degree of either fluctuating asymmetry or mirror imagery, when compared to dizygotic twins. The data on monozygotic twins further suggested that for most variables examined, the increment of environmental discordance resulting from the twinning phenomena was greater than the developmental noise that caused asymmetry within individual cotwins.

Dental and other bodily dimensions in different orthodontic categories.

Dental and other bodily dimensions in different orthodontic categories.

A factor analysis of morphogenetic fields in the human dentition

The traditional morphogenetic fields of the human dentition were evaluated by means of factor analysis of dental dimensions taken from a series of human crania. When crown length, crown width and crown index were considered separately, factors emerged which could be identified with the tooth group fields. But a combined crown length-crown width analysis generated factors which extended beyond the regional tooth groups. Crown width itself was revealed to be an important axis of morphologic intergration. It was concluded that univariate methods are not adequate for identifying morphogenetic fields; the teeth must be treated as multidimensional units where the correlation among dimensions is accounted for.

Some metric aspects of the permanent and deciduous dentition of the pygmy chimpanzee (Pan paniscus)

AbstractA search of the literature reveals that odontological data on the pygmy chimpanzee is almost completely lacking. The great usefulness of such data for the interpretation of fossil pongids is recognized.This investigation presents some basic descriptive statistics of five crown dimensions of the permanent and deciduous teeth of the pygmy chimpanzee. A sample of 140 individuals (composed of males and females of all ages) was investigated.No marked degree of sexual dimorphism was noted in any of the measurements of the deciduous dentition. Only the permanent canine exhibited a significant degree of sexual dimorphism. In individuals showing pronounced dental wear it was observed that mesiodistal tooth dimensions were reduced as a result of dental wear.Statistical comparisons of dental dimensions between Pan paniscus and Pan troglodytes suggest significantly larger teeth for the latter species.

The influence of geographic isolation on the skull of the green monkey ( Cercopithecus aethiops sabaeus ) V. The degree and pattern of differentiation in the cranial dimensions of the St Kitts green monkey

Some 300 years ago, free-ranging colonies of green monkeys from the West African species Cercopithecus aethiops sabaeus became established on the Caribbean island of St Kitts. Today, the cranium of the St Kitts monkey is, on an average, 4% bigger than in the present-day mainland descendants of the parent stock. This overall divergence has been compared on the one hand with the differences between C. aethiops sabaeus and each of two distinct sub­species of C. aethiops , and on the other with the divergence between C. aethiops sabaeus and representatives of each of two additional full species of Cercopithecus . The average difference between the cranial dimensions of the St Kitts green monkey and its parent species, C. aethiops sabaeus , is of approximately the same size as that between C. aethiops sabaeus and C. cephus cephus , (the moustached monkey) but is less than the difference between the cranial dimensions of C. aethiops sabaeus and those of either C. aethiops aethiops (the grivet) or C. nictitans nictitans (the white-nosed monkey). On the other hand, while in common with the St Kitts monkey, C. nictitans nictitans is, on an average, in its cranial dimensions, bigger than C. aethiops sabaeus , both C. cephus cephus and C. aethiops aethiops are smaller. The cranium of C. aethiops pygerythrus (the vervet) does not, on an average, differ in size from that of C. aethiops sabaeus . In both the St Kitts green monkey and in C. aethiops aethiops the most marked differences from C. aethiops sabaeus are in the transverse dimensions of the palate and mandible. In C. nictitans nictitans both the antero-posterior and transverse dimensions of the palate and mandible differ from C. aethiops sabaeus to a greater extent than do those of other cranial regions, while in C. cephus cephus , the antero-posterior dimensions of all parts of the skull differ from C. aethiops sabaeus to a greater extent than do the transverse dimensions. Many of these differences in overall cranial size contrast with those previously established for the teeth, and when cranial and dental dimensions are considered together, it is found that the subgroups of Cercopithecus cannot be readily separated on the basis of differences in size and general proportions. As the pelage of the St Kitts monkey is apparently indistinguishable from that of C. aethiops sabaeus , it would be inappropriate to assign the island monkey to a distinct taxonomic group.

Overall dental dimensions of hominoids.

Overall dental dimensions of hominoids.

The influence of geographic isolation on the skull of the green monkey (Cercopithecus aethiops sabaeus) IV. The degree and speed of dental differentiation in the St Kitts green monkey

The extent and character of dimensional differences between the teeth of the African and St Kitts green monkeys have been compared with corresponding differences between the African green on the one hand and its two fellow subspecies, the vervet and grivet, and its two fellow species, the white-nosed monkey and moustached monkey, on the other. Dimensions which tests showed to be highly correlated were grouped, and the means of the groups compared; dental dimensions were also analyzed by means of discriminant functions. The extent to which the permanent teeth of the St Kitts monkey now differ from the modern African descendant of its parent species is greater than, but in a direction opposite from, the difference which separates the white-nosed monkey from the African green. It is also approximately two-thirds the difference which separates the vervet from the African green, but considerably less than the difference which separates the grivet and moustached monkeys. The comparisons also showed that different teeth differed in the extent to which they diverged from those of the African green. The greatest divergence in the St Kitts, the white-nosed and the moustached monkeys was observed in the lateral dimensions of the canines; and in the vervet and grivet in the transverse dimensions of the incisors. The speed at which the changes in the St Kitts monkey have occurred appears to be from 5000 to 10,000 times the estimated rate of evolution in the teeth of horses over a period of from 5 to 16 million years.