Albert A. Dahlberg

ANALYSIS OF THE AMERICAN INDIAN DENTITION

Publisher Summary This chapter presents an analysis of the American Indian dentition on the evolutionary and functional basis, following the consideration of its morphology and comparative aspects. Many elements of form and size in the American Indian dentition suggest the existence of some selective evolutionary advantage. It also appears that certain attributes have not necessarily been incidental acquisitions in the process of drift peculiar to the individuals of a particular geographic area. Pursuit of this problem includes inquiry into the environmental complex, the evidences of function in the teeth, the structural potentials of the teeth, and ideas relating to survival of an organism. The dentition of the American Indian is not a homogeneous representation of a homogeneous people. Subsequently, a comparison of measurements and traits of the teeth between several Indian tribes and with other ethnic and geographic groups provides some perspective of the Indian dentition. Size of the teeth is quite basic and gives a means of description of some importance. The means of the Indian groups vary widely but none as much as two standard deviations. The standard errors of the means set them off quite firmly. The American Indians display markedly stronger tooth and a larger unit of functional capacity. Also, Carabellis cusp plays little part in the American Indian dentition.

Relationship of Tooth Size to Cusp Number and Groove Conformation of Occlusal Surface Patterns of Lower Molar Teeth

Lower molar occlusal surface pattern variation has always been assumed to be correlated with size, particularly the aspect concerning the number of cusps. Although it is not necessary to show a statistically significant relationship in every instance of comparison, such a consideration of size and pattern is helpful in clarifying and evaluating the general evolutionary trends occurring in the permanent lower molar teeth of modern hominid populations.

Anomalous morphologic formation of deciduous and permanent teeth in a 5-year-old 15th century child: A variant of the Ekman-Westborg-Julin syndrome

A gross morphologic anomaly affecting both the primary and secondary teeth of unknown cause is presented. A 5-year-old American Indian child exhibited macrodontia, extreme shovel-shaping, agenesis, three-rooted deciduous molars, dens invaginatus, and other less striking dental features. This case represents the earliest example of a variant of the Ekman-Westborg-Julin syndrome reported in the New World.

The influence of crown size dimorphism on sex differences in the Carabelli trait and the canine distal accessory ridge in man

When the two sexes were contrasted, Pima Indian males showed larger crown dimensions and more pronounced expressions of two morphologic variables, the Carabelli trait and the lower canine distal accessory ridge. In addition, a significant positive relationship was found between crown size and degree of expression of the morphologic traits. When regression analysis was utilized to control for male-female tooth size differences, the moderate dimorphism shown by Carabelli trait was reduced by about half. The more dimorphic distal accessory ridge, related primarily to mesio-distal diameter, also showed a lesser sex difference when crown size effects were held constant. While size dimorphism does contribute to morphologic dimorphism, factors unrelated to crown size still contribute the majority of variance present in trait expression both within and between sexes.

Inherited Congenital Absence of Six Incisors, Deciduous and Permanent

Congenital absence of teeth is not of general occurrence, nor is it extremely rare. Much discussion has been advanced in recent years as to the etiology of the abnormality. Endocrine glands, syphilis, diet and heredity all have been discussed in this connection, and no doubt all are correct to a certain extent. It appears, however, that the hereditary factor is responsible for a large percentage of these conditions. Since early in the nineteenth century reports have appeared tracing dental anomalies through several generations. Some of these family histories have been dependable; others, unfortunately, have not. A case was referred to the author following through at least four generations of the patients family. There were forty-six members, eighteen of whom had at least six anterior teeth missing congenitally in both dentitions. (Chart I.) The patient (D 18), a twin, was a white male twelve years of age, of average height and weight, intelligent and in good health. Examinations by a pediatrician and endocrinologist were entirely negative. Wassermann and Kahn tests were negative. A clinical examination of the child revealed the following teeth to be caries free and firmly fixed in the jaws:

Interaction between Relative Molar Size and Relative Number of Cusps

M1>M2 ........... 2 M2>Ml orM2=M1. 0 imber of cusps have been in whom the mesiodistal crown diameter of the manjiables in both sexes and dibular first molar exceeded that of the mandibular ions (A. A. DAHLBERG, second molar, the number of cusps on Ml exceed61; S. M. GARN, A. A. ed the number of cusps on M2 in 86 individuals and R. S. KEREWSKY, (79 per cent). Only 23 of these subjects, or 21 per 6; S. M. GARN, A. A. cent, were characterized by an equal number of and R. S. KEREWSKY, cusps on both mandibular molars. However, in 13 night therefore postulate additional subjects, in whom the second molar ive crown size of the first equaled or exceeded the first molar in crown size, relative number of cusps the relative number of cusps was reversed; four subjects had more cusps on the first molar than on the Ls of European ancestry second, and nine (69 per cent) had an equal number of cusps on the two molars. This difference in cusp part by USPHS grant DEnumber was significant by stochastic x2 test both for tute of Dental Research, Nathe number of sides that could be studied (N = 224, B. Lewis and morphological X2 = 52.2) and for the total number of subjects (N = 122, x2 = 15.6). The degree of association beable on request to the authors. tween relative molar size and relative cusp num-

Ontogeny and dental genetics in forensic problems

Teeth are an excellent and reliable source of information useful in establishing identities in the absence of dental records providing that matching dental casts or teeth of other possibly related family members are available and that information on dental trait frequencies can be obtained. Such demographic data is generally available from physical or odontological anthropology departments in universities or museums. The data collected is subjected to statistical scrutiny and treatment of probability methodology.

Dental Caries in the Eskimos of Wainwright, Alaska

The caries rates reported for Alaskan natives have had wide variances. Rosebury et ai noted a low prevalence of dental caries in the Kuskokwim Delta area (T. ROSEBURY and L. M. WAUGH, Amer J Dis Child 57:871-893, 1939; T. ROSEBuRY and K. MAXWELL, Amer J Dis Child 57:1343-1362, 1939). A more recent study (A. L. RUSSELL, C. F. CONSOLAZIO, and C. L. WHITE, J Dent Res 40:594-603, 1961) showed that there was a reduction in the DMFT rate with increasing age for males between the ages of 17 and 54. The younger group (17 to 19 years) had a DMFT rate of 10.2; the rate for the 45 and older age group was 6.8. The Division of Indian Health of the USPHS report for the fiscal year 1967 showed that the mean DMFT rate for Alaskan beneficiaries was 13.62. This study of the Eskimos of Wainwright, Alaska, was conducted during July 1968 and included 244 males and females. Examination was accomplished by one investigator using a mirror and explorer without the aid of X rays. Rather than the decreasing DMFT rate noted by Russell et al, there is a steady upward trend of the rate with a leveling off at approximately age 25. The rates noted in the table are not actually the DMFT rates, but rather the rates for decayed, missing, and filled permanent and deciduous teeth present at the time of examination, which expresses total caries experience. A great number of individ-