Genetic and Environmental Factors

The advances in human genetics and gene expression have contributed to the identification of genetic markers associated with certain skeletal malocclusions and dental malformations. Genetic factors, demonstrated in family and twin studies, consistently show that malocclusion patterns cluster in families, specifically in craniofacial structures such as the jaw size and shape, facial growth patterns, and tooth size and numbers.⁵

Malocclusion is typically polygenic, involving multiple genes, such as DUSP6 and ADAMTS, causing mandibular prognathism, Class II and III skeletal malocclusion. These gene expressions provide the baseline craniofacial blueprint.⁶

Environmental factors, mainly postnatally, such as thumb sucking, pacifier use, tongue thrusting, and mouth breathing, provide strong evidence links to malocclusion. The table below provides a baseline distribution of oral habits and malocclusion outcomes.⁷

Systemic and lifestyle influences, such as nutrition and feeding patterns, socioeconomic status and access to care, as well as disease, trauma and endocrine disorders, contribute to the severity of malocclusion. The interaction between genetics, which provide the baseline craniofacial blueprint and environmental factors, which modify growth expression, along with timing, the prenatal phase, mainly genetic control, and postnatal growth, strongly influenced by environmental factors, demonstrates the multifactorial relationship of malocclusion.

Malocclusion is not purely genetic or environmental. Genetics dominates the skeletal discrepancies, specifically in Class II and III occlusion. The environment strongly affects dental alignment and severity.⁶