Biomedical subjects
Publications and source records attributed to R S Corruccini.
Village-dwelling Punjabi youths show significantly better dental occlusion and less chronic respiratory allergy than their city-dwelling counterparts. Field diagnosis finds posterior crossbite the only occlusal condition correlated with mouth breathing in the samples studied.
Cross-cultural comparison of twin variances reveals widespread heterogeneity among zygosities for dental occlusal traits, implying various biases in calculation of genetic variance or heritability estimates. These estimates are fairly robust for dental size traits, however. Differences in pattern between Punjabi (Northwest Indian) and American twins highlight the environmental differences that affect heritability determinations.
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.
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Occlusal variations of immigrant Chinese parents, raised in less developed areas, were compared with their children who were born and bred in the United Kingdom. Of 11 occlusal traits, nine were significantly more variable or less well developed in the offspring. Because genetic factors were unchanged, the deterioration in occlusion in the offspring indicates environmental influences such as dietary consistency, premature deciduous tooth loss from caries and oral respiration.
An epidemiologic transition to high prevalence of such diseases as diabetes and coronary heart disease accompanies the process of modernization/industrialization. I suggest that an equally clearly defined epidemiologic transition characterizes malaligned and discrepant dental occlusal relations in western societies, and others undergoing urbanization, and that the rapidity of the transition is proportional to the rapidity of urbanizational change. This phenomenon rather throws the weight of suspicion toward environmental, not genetic, etiologic factors. The dental occlusal epidemiologic transition provides a model for developing further research into causes of malocclusion.
Of a sample of 40 baboons, 24 were given soft experimental diet, removing masticatory stress, for a 2-year period during growth. In oral-facial and dental occlusal structures, the experimental animals showed significantly elevated variability, reduced correlations, and some disruption of normal occlusion.
Logarithmic bivariate regression slopes and logarithmic principal component coefficient ratios are two methods for estimating allometry coefficients corresponding to a in the classic power formula Y = BXa. Both techniques depend on high correlation between variables. Interpretation is logically limited to the variables included in analysis. Principal components analysis depends also on relatively uniform intercorrelations; given this, it serves satisfactorily as a method for summarizing many bivariate combinations. Unmodified major principal component coefficients cannot represent scaling to body weight; rather, they represent scaling to a composite size vector which usually is highly correlated with body size or weight but has an unspecified allometry. Thus, the concepts of proportionality and of isometry must be kept distinct.
Occlusal variables and arch measurements have been recorded on 341 Pima Amerinds pertaining to two samples, one of older individuals raised on traditional diets, the other of younger individuals raised on refined commercial foods that are typical of modern urbanized people. Permanent dental occlusion is significantly more variable from defined ideals in the younger sample, despite their fewer deformities resulting from progressive aging. The youths had relatively narrower palates, correlating with a general trend among industrialized populations and also among experimental animals fed soft diets. Relative rate of deciduous tooth loss and replacement did not correlate with any occlusal variable.
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Forty-three squirrel monkeys were raised on either naturally tough or artificially softened foods. Significant differences were found in craniofacial and occlusal development between hard and soft diet animals: The latter exhibit maxillary arch narrowing, palatal arching, rotated and displaced teeth, crowded premolars, and retarded cranial bone mineralization. The correlates in results between soft diet squirrel monkeys and American children suggest that dietary consistency may be an important factor in human craniofacial growth.
Among 43 squirrel monkeys (Saimiri sciureus) raised either on naturally tough or on artificially soft foods, there are significant differences in occlusal features. Animals raised on soft foods show more rotated and displaced teeth, crowded premolars, and absolutely and relatively narrower dental arches. Dietary consistency may be a determinant of occlusal health.
A unique seventeenth-nineteenth century slave cemetery population from Newton plantation, Barbados, allows examination of craniodental characters in relation to ethnohistorical data. Age-at-death estimates suggest life expectancy at birth of 29 years and low infant mortality; historical demography, however, suggests life expectancy of 20 years and very high infant mortality. Tooth decay, bilateral tooth loss, periodontal disease, root hypercementosis, and severe enamel hypoplasia are high in frequency. The teeth yield evidence of such cultural practices as pipe-smoking and incisor mutilation. Several skeletal features reflect periodic near-starvation. Directional and fluctuating dental asymmetry, relative tooth size, and hypoplasia distribution suggest slaves experienced considerable weaning trauma; metabolic stress at this time exceeded that of prenatal and immediate postnatal periods. Odontometrics and dental and cranial nonmetric traits indicate that modern Blacks are intermediate between the ancestral slaves and modern Whites but more similar to the latter, suggesting effects of environmental covariance exceed those of genetic admixture. Nonmetric trait distributions show nonrandom patterns according to area of burial in the cemetery, a possible result of family segregation.
To improve our understanding of dental asymmetry, more anatomically discriminating measurements than maximum crown dimensions were used. The relation between antimeres and opponents in permanent first molar teeth of 192 twins were studied with respect to crown components measures. Several statistical methods were used to describe asymmetry and discrepancy of occluding units to correlate with developmental stress indicators such as zygosity, birth weight, and congenital disease. To varying degrees, developmental correlates are found to be associated with asymmetry. The amount of occlusal discrepancy seems to be a direct function of bilateral asymmetry. Heterogeneity of MZ-DZ total (among plus within pair) variances occurs fairly consistently for asymmetry but not for discrepancy, implying differential environmental influences between zygosities regarding asymmetry. Genetic variance estimates, designed to be unbiased by differences in environmental variances, are significant for cusp size but not for asymmetry. Our results suggest that asymmetry at the individual cusp level may be an indicator of developmental disruption and that environmental effects, particularly prenatal, may be greater for antimeric units than for occluding units.
Some major theories concerning the etiology of malocclusion and its modern increase in frequency include genetic explanations, such as inbreeding, racial crossing, and accumulation of mutations, as well as such environmental causes as "habits," allergies, and caries causing reduced arch space of premature deciduous tooth loss. Reduction of masticatory stress resulting from modern urbanism is less often considered as an agent. Many examples of acquisition of gross malocclusion in aboriginal peoples immediately following dietary "modernization" contradict the genetic explanations. A rural population from central Kentucky presents several propitious social characteristics for epidemiologic study of occlusion. They have experienced almost no professional dental care, they are highly inbred (but less so during the last 30 years), and their diet included many difficult-to-chew foods until the recent introduction of industry to the area. Occlusion was evaluated according to the criteria of the Treatment Priority Index. The temporal change and correlates of occlusal variation were assessed on wax-bite impressions of thirty-four persons, informant dietary histories, and other information. The older inhabitants raised on more traditional diets show significantly better occlusion. Dietary consistency provides the most powerful explanation for the transition in occlusal variation, through it was not conclusive in these data.
Moderate differences in the hardness of diet are related to significant differences in maxillary width and other measures of facial size. Probably even more important is a relationship to the coordination of growth of different parts of the dentofacial complex. Muscular stimulation mediated through occlusal function seems to play a significant role in the coordinated development of facial structures.