John T. Mayhall

Developmental patterns of human dental morphological traits

A longitudinal series of casts of the deciduous and permanent dentitions of 827 children from Burlington Growth Centre study was examined for 5 traits: shovel-shape of the incisors, cusp six, cusp seven and protostylid of the mandibular molars, and Carabelli trait of the maxillary molars. The changing trait frequencies found support the concept of morphogenetic gradients of expression for non-metric traits from deciduous to permanent teeth. Tests of association showed that if shovelling was present on the deciduous incisors it would usually appear on the permanent successors. Tests of association between the other 4 traits on deciduous second molars and the permanent molars support the view that the second deciduous molar belongs to the total molar tooth district. This gradient expression of morphological traits would fit either the field or clone concepts, but it, and the intra-individual discordances for trait presence, probably reflects the great temporal spacing of dental development seen in man.

Part one: Patterns of health and disease among the Waorani Indians of Eastern Ecuador

Abstract The Waorani Indians, who live south of the Rio Napo in eastern Ecuador, are beginning to experience the effects of contact with the outside world. Synthesis of biomedical information with an understanding of cultural practices related to health provides insight into changing patterns of health and disease during the process of acculturation. The perspective gained from these multidisciplinary studies will aid in providing health care in the future and will increase appreciation of the ecology of health of these Amerindians in the past.

Dental morphology of 45,XO human females: Molar cusp area, volume, shape and linear measurements

A three-dimensional analysis of the maxillary first molars of five 45,XO females and comparison with normal females and males demonstrated a reduction of cusp areas and volumes in the 45,XO females. Mesiodistal and faciolingual dimensions were also reduced. The reductions in basal area and volume were greater in the later developing, distal cusps. In normal females the second X chromosome apparently does not exert an effect on the cusp height but increases the basal area. The results further indicate that the Y chromosome in normal males increases both cusp height and basal area. The steepest cusps were found in 45,XO females while the shallowest were in the control males. Both sex chromosomes thus seem to affect the shape of the cusp but the resulting phenotypes differ.

A new, three-dimensional method for determining tooth wear

A new technique combining moiré contourography and digital image analysis allows the three-dimensional description of molar wear. It is possible to describe the amount of tooth material lost in a given time, e.g. mm3/year, and the differing amounts of wear on individual cusps. The moiré technique can be used in conjunction with more conventional quantitative techniques or by itself to assist in age determination in a population. It can be used to describe small amounts of wear that hitherto were difficult to quantify. It is not recommended where the wear includes the greatest convexity of the crown (height of contour) or affects the central fossa.

Tooth crown size in 46, X, i (Xq) human females

Permanent tooth crown sizes of six Finnish females with a 46, X, i(Xq) chromosome constitution (isochromosome for the long arm of the X chromosome) were measured from dental casts and compared with those of normal women, first-degree female relatives and 45, X females. Crown diameters of the 46, X, i(Xq) females were not only smaller than in the normal women but even smaller than the 45, X females. These findings can be considered indirect evidence that X chromosome gene(s) for tooth crown growth are most probably located on the short arm.

Torus mandibularis in 45,X females (Turner syndrome)

Ninety-three Finnish females with a 45,X chromosome constitution, 78 first-degree female, and 37 first-degree male relatives were examined to determine the frequency and expression of torus mandibularis. The results indicate that among adults the frequency of the trait was significantly lower and the expression weaker in the 45,X females than in male control relatives. A similar trend was observed in comparison to normal females. In juveniles the trend was reversed. Our findings suggest that the sex chromosomes may have an influence on the occurrence, expression, and timing of development of the mandibular torus. Sexual dimorphism in the manifestation of torus mandibularis may result particularly from the effect of the Y chromosome on growth.

Canadian Inuit Caries Experience 1969-1973

man Adaptability Section. The dental study collected results each year from 1969 through 1973 in the two Foxe Basin, Northwest Territories communities of Igloolik and Hall Beach. These communities have a combined resident population of approximately 800. In 1969 and again in 1973, all available residents were examined for dental caries by the same investigator, who used a mirror and explorer and a high-intensity light. No radiographs were available. Each person was questioned about the general composition of his daily diet. These re-

Sucrose Taste Sensitivity in Canadian Inuit and Its Relationship to Dental Caries

Zengo and Mandel (Arch Oral Biol 17: 605-607, 1972) have shown recently that New York adults who are caries resistant require greater concentrations of sucrose to perceive a sweet taste than do those who are caries prone. Their findings were not consistent with the theory that an elevated sucrose taste threshold should contribute to an increase in sucrose intake in order to perceive the sweet taste, with a resultant increase in caries susceptibility. They postulated that since taste acuity may be determined genetically, the taste sensitivity differences might indicate a genetic difference between the resistant and susceptible groups. To test this possibility on a genetically and culturally unrelated group, adult Inuit (Eskimo) of Igloolik, Northwest Territories were used in a test that was modified because of shipping, weather, and language problems. The procedure used in Igloolik was the same as that developed by E. Freeman in a teaching laboratory situation at the University of Toronto (personal communication, 1973). Four sucrose dilutions (0.1, 0.25, 0.5, and 1.0%) were made daily and were used at room temperature. Each individual was given a small amount of the 0.1% dilution in a paper cup and was told to hold the solution in his mouth before swallowing. Then, he was asked if he detected any sweetness. If the answer was negative, the procedure was repeated with the 0.25%o dilution. This technique was continued until a positive answer was recorded. If the patient could detect no sweetness in any of the four solutions, he was recorded as having a threshold greater than the 1.0% solution. Chi-square tests were performed by treating