Background: Studies examining human and nonhuman primates have supported the hypothesis that the recent increase in\r\nthe occurrence of misalignment of teeth and/or incorrect relation of dental arches, named dental malocclusion, is mainly\r\nattributed to the availability of a more processed diet and the reduced need for powerful masticatory action. For the first\r\ntime on live human populations, genetic and tooth wear influences on occlusal variation were examined in a split\r\nindigenous population. The Arara-Iriri people are descendants of a single couple expelled from a larger village. In the\r\nresultant village, expansion occurred through the mating of close relatives, resulting in marked genetic cohesion with\r\nsubstantial genetic differences.\r\nMethodology/Principal Findings: Dental malocclusion, tooth wear and inbreeding coefficient were evaluated. The sample\r\nexamined was composed of 176 individuals from both villages. Prevalence Ratio and descriptive differences in the\r\noutcomes frequency for each developmental stage of the dentition were considered. Statistical differences between the\r\nvillages were examined using the chi-square test or Fisher�s exact statistic. Tooth wear and the inbreeding coefficient (F)\r\nbetween the villages was tested with Mann-Whitney statistics. All the statistics were performed using two-tailed distribution\r\nat p#0.05. The coefficient inbreeding (F) confirmed the frequent incestuous unions among the Arara-Iriri indigenous group.\r\nDespite the tooth wear similarities, we found a striking difference in occlusal patterns between the two Arara villages. In the\r\noriginal village, dental malocclusion was present in about one third of the population; whilst in the resultant village, the\r\noccurrence was almost doubled. Furthermore, the morphological characteristics of malocclusion were strongly different\r\nbetween the groups.\r\nConclusions/Significance: Our findings downplay the widespread influence of tooth wear, a direct evidence of what an\r\nindividual ate in the past, on occlusal variation of living human populations. They also suggest that genetics plays the most\r\nimportant role on dental malocclusion etiology.
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