A Review of Hypodontia: Classification, Prevalence, Etiology, Associated Anomalies, Clinical Implications and Treatment Options

Abstract

A retrospective review of literature was carried out to determine the classification, prevalence, etiology, associated anomalies, clinical implications and treatment options for hypodontia. Many methods of classification have been reported in the literature. Some researchers have classified hypodontia as isolated family form or as an inherited form; others have defined the congenital absence of teeth according to the number of missing teeth and yet classified hypodontia according to the severity of the condition. The prevalence of hypodontia in the primary dentition is found to be very low whereas the occurrence of tooth agenesis varies in the permanent dentition based on ethnic and sex differences. The tooth most commonly found to be missing is the third molar. With regard to the remaining 28 teeth, metaanalysis has revealed that the teeth most commonly affected are the mandibular second premolars, maxillary lateral incisors, maxillary second premolars and the mandibular incisors. From the literature it is evident that the etiology of hypodontia is varied and that genetic, epigenetic and environmental factors may be contributory factors. Tooth anomalies reported in the literature to be associated with hypodontia, include microdontia, canine impaction, taurodontism, transposition and rotation of teeth, and hypoplastic alveolar bone. Researchers have suggested that clinical management of hypodontia requires careful multidisciplinary planning and has financial implications. The suggested members of the team should include general dental practitioners, dental nurses, orthodontists, pediatric dentists, prosthodontists, oral and maxillofacial surgeons, specialist laboratory technicians, clinical psychologists, clinical geneticists, dermatologists, speech and language therapists.

Variations in dental arch morphology are outcomes of the complex adaptive system associated with the developmental variation of hypodontia

“…It forms part of the complex adaptive system (CAS) of oro-facial development whereby epithelial tissues and neural crest mesenchyme are involved in delicate signalling pathways with multiple molecular events that overlap each other [1][2][3][4]. For a system to be considered as complex and adaptive, it should exhibit the principles of self-organisation and self-adaptation.…”

Variation in tooth crown size and shape are outcomes of the complex adaptive system associated with the tooth number variation of hypodontia

“…When a specific tooth does not form this is known as tooth agenesis; the most frequently affected teeth are the third molars [1]. The dentition may be affected in varying numbers of missing teeth; hypodontia, which is the absence of one or up to five teeth, oligodontia, which involves six teeth or more and anodontia, which is the total absence of teeth [1]. Oligodontia and anodontia occur infrequently in a population and are commonly associated with syndromes such as ectodermal dysplasia [2].…”

Congenitally Missing Mandibular Second Premolars: A Case Report

“…3 Multifactorial etiology combining genetics, epigenetic and environmental factors has been suggested by Al Shahrani et al and Larmour et al 5,6 Regulatory homeobox genes found to be associated with tooth agenesis consist of MSX-1, PAX-9, EDA and AXIN-2. 7 It may also be associated with some environmental insult during development.…”