Genetic Basis of Nonsyndromic and Syndromic Tooth Agenesis

Abstract

Human dentition development is a long and complex process which involves a series of reciprocal and sequential interactions between the embryonic stomodeal epithelium and the underlying neural crest-derived mesenchyme. Despite environment disturbances, tooth development is predominantly genetically controlled. To date, more than 200 genes have been identified in tooth development. These genes implied in various signaling pathways such as the bone morphogenetic protein, fibroblast growth factor, sonic hedgehog homolog, ectodysplasin A, wingless-type MMTV integration site family (Wnt), and transform growth factor pathways. Mutations in any of these strictly balanced signaling cascades may cause arrested odontogenesis and/or other dental defects. This article aims to review current knowledge about the genetic mechanisms responsible for selective nonsyndromic tooth agenesis in humans and to present a detailed summary of syndromes with hypodontia as regular features and their causative genes.

Keywords: genes; hypodontia; oligodontia; tooth agenesis.

Fig. 1

Clinical photographs and radiographs of a patient affecting with Weyers acrofacial dysostosis. (A and C) Bilateral postaxial polydactyly type A was removed at birth by surgical operations on both hands and feet, only scars (black arrows) were seen after amputation. (B and D) Apparent dysplastic fingernails and toenails. (D and E) Partial syndactyly at the second and third toes on both feet (black arrows). X-ray shows that the phalanges were not affected. (F) Oral examination of the upper lip reveals multiple oral frenula, diastemas, teeth which were abnormal in size and shape, delayed teeth eruption. (G) Panoramic radiographs showed the absence of permanent incisors (white arrows).

Fig. 2

Characterization of a patient with X-linked recessive isolated hypodontia. (A and B) The patient is a 13-year-old boy, who had fine scalp and body hair, nails, and no complaints about tolerance to heat. His facial features appeared normal, but dental examination revealed multiple missing and misshapen deciduous teeth. (C) A panoramic radiograph depicts the typical pattern of congenitally missing teeth and tooth buds.