Certain teeth have an increased tendency to be congenitally missing more often than the others. The rarest and least reported as missing are the mandibular canines. In this paper, we report a case of missing mandibular canines and the presence of a supplementary mandibular incisor.
 

The size, shape and number of teeth are under genetic control. In humans, changes in these dental morphological characteristics are not uncommon. Hypodontia (oligodontia) is a genetically caused anomaly although neither the genetic mechanism nor mode of genetic transfer of the anomaly is clear.¹ The anomaly is however associated with known syndromes such as ectodermal dysplasia and Down's syndrome.² Hypodontia affects females more than males²³ and its prevalence is 0.1 -0.9% in primary dentition and 3.5-6.5% in permanent dentition.² Although any tooth may be congenitally missing, there is a greater tendency for certain teeth to be missing more frequently than others. The most frequently missing teeth are the third molars, upper lateral incisors, second premo- lars and lower central incisors.⁴ Missing canines are rare, this is particularly so of the mandibular canine.⁵

A review of the English literature disclosed a report on congenitally missing maxillary canines in two cases.⁶ In this paper, we report a case of con- genitally missing bilateral mandibular canines and the presence of one supplementary lower incisor.
 

A 14-year-old female [Fig. 1], with a chief com- plaint of proclination of upper incisors that com- promised her aesthetics, was referred to our Orthodontics Clinic by a dentist. She appeared healthy with no evidence of obvious systemic or oral diseases. She gave a history of one admission to a hospital for tonsillectomy. She had no previous dental treatment of any sort before she saw the dentist who referred her to our Orthodontics Clinic. The information was confirmed by her mother.

Clinical Examination

Extraoral examination showed a true lateral con- vex profile suggestive of a mild Class II skeletal pat- tern with slightly increased lower facial height [Fig. 2]. Intraoral examination revealed missing 18, 28, 33, 38, 43, 48 and the presence of a supernumer- ary lower incisor [Figs. 3,4]. Intraoral soft tissues appeared normal. She had a Class II molar relation and Class II Division 1 incisal relation with a 10 mm overjet [Figs. 4,5,6].

Radiographic Examination

Routine panoramic view [Fig.7] revealed unerupted third molars, missing lower canines and a supernumerary lower incisor. It was confirmed from the patient's record at her health center that she had no previous dental extractions.

Supernumerary teeth, hypodontia, megadontia and microdontia have all been associated with genetic and environmental etiological factors. It is rare to see congenitally missing mandibular canines. This case which was associated with the presence of a supplementary mandibular incisor was equally a rare case.

The incidence of congenitally missing teeth have been reported in various populations (Table 1). Similar information on Bahrain had not been pub- lished. In the orthodontics records of our clinic, the case described in this paper was the first case of congenitally missing mandibular canines. The case might encourage a future study in the incidence of congenitally missing teeth in Bahrain.