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An Analysis of the Skeletal Relationships in a Group of Young People with Hypodontia

Hypodontia is the developmental absence of one or more teeth, excluding the third molars (Goodman et al., 1994). The prevalence in the general population is between 3·5 and 6·5 per cent (Brook, 1974), whilst a survey of 6000 orthodontic patients gave a prevalence of 4·3 per cent, with the lower second premolar followed by the upper lateral incisor being the most frequently missing teeth (Rose, 1966). The absence of one or two teeth is relatively common, but severe hypodontia (six or more missing teeth) is rarer and may be associated with a syndrome such as ectodermal dysplasia (Hobkirk and Brook, 1980). Previous cephalometric studies of these patients have shown a reduced lower face height and increased overbite (Woodworth et al., 1985; Dermaut et al., 1986), together with a number of other dentofacial features, some agreeing and some contradictory. Whilst Woodworth et al. (1985) found a reduced lower face height, Roald et al. (1982) found that the lower face height was normal. Direct comparisons between studies is complicated by the varying severity of hypodontia of the sample groups, in addition to the cephalometric analysis used (Sarnas and Rune, 1983; Woodworth et al., 1985;Yuksel and Ucem, 1997). A recent study (Yuksel and Ucem, 1997) subdivided their group of patients according to the location of the absent tooth and investigated the effect of the site of location of hypodontia on dentofacial features. Comprehensive management of hypodontia is best undertaken in interdisciplinary clinics, and these have been established in a number of centres for diagnosis, treatment planning and co-ordination of treatment (Hobkirk et al., 1994). A dedicated clinic for patients with hypodontia has run for 5 years at Newcastle Dental Hospital, with over 150 new patients seen. The most significant presenting complaints were poor appearance and lack of function. On clinical examination, in addition to the expected reduction in tooth number and variations in tooth morphology, there was a clinical perception that patients had a reduced lower face height and increased overbite. The objectives of the present study were thus to examine the dentofacial features of a group of patients with hypodontia, in particular whether cephalometric analysis confirmed the clinical perception of reduced lower face height and to determine the relationship of these facial features with different numbers of missing teeth.