Pordeus, Isabela Almeida; (1991) Intra-family patterns of dental health status and behaviours: A study of Brazilian families. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This study tested the hypothesis that because families shared similar patterns of behaviour, the children would reflect, in their own dental health status, the dental status of their parents. The sample consisted of 164 randomly selected Brazilian nuclear families, equally distributed in four social classes. All family members were clinically examined (861 subjects), and those at the age of 10 and above (717 subjects) were interviewed. Dental status (DMFS) and oral hygiene (ODI-S) were assessed, and information on dental health related behaviours (sugar consumption, oral hygiene habits, and pattern of dental attendance) was collected. Data analyses included one-way analysis of variance, Pearson's correlation coefficient, Kruskal-Wallis analysis of variance, rank correlation tests, and path analysis. Despite the homogeneous dental health status and related behaviours among families from different social backgrounds, statistically significant differences in dental health status and related behaviours were observed among the families from the four social classes. Strong intra-family patterns of dental health status and related behaviours emerged. Path analyses revealed that familial aggregation explained 71% of the phenotypic variance (DMFS) in children, of which 54% was determined by biological inheritance and 17% by family environment; while the remaining 29% of the phenotypic variance was explained by environmental factors outside the family environment. For parents, environmental factors outside the family environment accounted for 68% of the phenotypic variance; while familial aggregation explained 32% of the variance, of which 15% was determined by biological inheritance and 17% by family environment. It was concluded that dental caries experience fitted the liability and threshold model. For children, the environment had not had enough time to express itself, and the manifestation of dental caries was mainly determined by the biological factors. Since the environmental factors surrounding these children were fairly homogeneous, the biological determinant expressed itself more strongly. For parents, who have lived long enough in a 'hostile* environment above their threshold, environmental factors had enough time to manifest themselves, and the biological determinant became less important.

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