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Al-Ani A H, Antoun JS et al. J Dent Res 2017;96: 1014–1019

On one hand, mutations in the genes MSX1, PAX9, AXIN2, and EDA have been identified in familial forms of nonsyndromic hypodontia, yet environmental factors such as trauma, and children with thalidomide embryopathy for example, also show hypodontia. When odds ratios were adjusted for possible confounders, if the mother smoked ten or more cigarettes each day during pregnancy, there was increased odds that the child would have hypodontia (adjusted OR, 4.18; 95% CI, 1.48–11.80; P = 0.007). In this case-control study that recruited mothers of 89 children with hypodontia with a 1:3 case-control ratio, the number of cigarettes smoked each day, alcohol consumed and caffeine intake was ascertained using a questionnaire. There would appear to a biological gradient, one of Hill's criteria for causation, with increased odds of children with hypodontia with increased maternal cigarette smoking.