Department of Orthodontics, Dental School, Federal University of Pará, Belem, Brasil.
PLoS One. 2011;6(12):e28387. doi: 10.1371/journal.pone.0028387. Epub 2011 Dec 22.
Studies examining human and nonhuman primates have supported the hypothesis that the recent increase in the occurrence of misalignment of teeth and/or incorrect relation of dental arches, named dental malocclusion, is mainly attributed to the availability of a more processed diet and the reduced need for powerful masticatory action. For the first time on live human populations, genetic and tooth wear influences on occlusal variation were examined in a split indigenous population. The Arara-Iriri people are descendants of a single couple expelled from a larger village. In the resultant village, expansion occurred through the mating of close relatives, resulting in marked genetic cohesion with substantial genetic differences.
METHODOLOGY/PRINCIPAL FINDINGS: Dental malocclusion, tooth wear and inbreeding coefficient were evaluated. The sample examined was composed of 176 individuals from both villages. Prevalence Ratio and descriptive differences in the outcomes frequency for each developmental stage of the dentition were considered. Statistical differences between the villages were examined using the chi-square test or Fisher's exact statistic. Tooth wear and the inbreeding coefficient (F) between the villages was tested with Mann-Whitney statistics. All the statistics were performed using two-tailed distribution at p≤0.05. The coefficient inbreeding (F) confirmed the frequent incestuous unions among the Arara-Iriri indigenous group. Despite the tooth wear similarities, we found a striking difference in occlusal patterns between the two Arara villages. In the original village, dental malocclusion was present in about one third of the population; whilst in the resultant village, the occurrence was almost doubled. Furthermore, the morphological characteristics of malocclusion were strongly different between the groups.
CONCLUSIONS/SIGNIFICANCE: Our findings downplay the widespread influence of tooth wear, a direct evidence of what an individual ate in the past, on occlusal variation of living human populations. They also suggest that genetics plays the most important role on dental malocclusion etiology.
研究表明，人类和灵长类动物牙齿排列不齐和/或牙弓关系不正确的情况（称为牙齿错颌畸形）最近有所增加，这主要归因于更精细加工的饮食的出现和对强大咀嚼作用的需求减少。首次在活人群中，在一个分裂的土著人群中研究了遗传和牙齿磨损对咬合变化的影响。阿拉拉-伊里里人是一对被逐出一个更大村庄的夫妇的后代。在这个小村庄里，通过近亲交配来扩张，导致了显著的遗传凝聚和大量的遗传差异。
方法/主要发现：评估了牙齿错颌畸形、牙齿磨损和近亲繁殖系数。检查的样本由来自两个村庄的 176 人组成。考虑了每个牙列发育阶段的结果频率的患病率比和描述性差异。使用卡方检验或 Fisher 精确检验检验两个村庄之间的统计学差异。使用 Mann-Whitney 统计检验村庄之间的牙齿磨损和近亲繁殖系数（F）。所有统计均在 p≤0.05 时使用双侧分布进行。近亲繁殖系数（F）证实了阿拉拉-伊里里土著群体中频繁的近亲通婚。尽管牙齿磨损相似，但我们发现两个阿拉拉村庄之间的咬合模式存在显著差异。在原始村庄，大约三分之一的人口存在牙齿错颌畸形；而在衍生村庄，这种情况几乎翻了一番。此外，错颌畸形的形态特征在两组之间也有很大的不同。
结论/意义：我们的研究结果淡化了牙齿磨损对活人群体咬合变化的广泛影响，这直接证明了一个人过去吃了什么。这也表明遗传在牙齿错颌畸形的病因中起着最重要的作用。
