Genetics analysis has been used to evaluate the heritability of numerous orofacial traits and features, including malocclusions. The dental arch is an important structure to assess before diagnosing a malocclusion and planning for orthodontic treatment. The eruptive paths of the teeth, jaw development, and dental movement after eruption will contribute to the dental arch details that form under the influence of genetic, epigenetic, and environmental factors. The genetic factors influence the dental arch variation from the early stage of organ development from initiation to terminal differentiation. The dental arch development involves a series of interactions between epithelium and adjacent mesenchymal tissues, mediated by signaling pathways. Disturbances in the interactions will result in abnormalities or variations of dental arch shape and size. Such influence can arise even from single nucleotide polymorphisms (SNPs) associated with the dental arch phenotype. Epigenetic mechanisms can also play a role. For example, some enzymes can change gene expression through histone modifications resulting in phenotypic variation. Furthermore, environmental factors such as unbalanced circum-oral muscular pressure are able to affect dental arch shape and size.