Late development of multiple supernumerary teeth in a patient with hypodontia

Introduction

The reported prevalence of supernumerary teeth in the permanent dentition ranges from 0.15% to 3.9% [8]. They are conveniently classified according to their location (mesiodens, paramolar, distomolar) or morphology (conical, tuberculate, supplemental, odontomes). The most common are maxillary midline supernumeraries. While single supernumerary tooth usually occur in isolation, multiple supernumerary teeth are typically associated with a congenital syndrome or a cleft palate. In non-syndromic patients, multiple supernumerary teeth usually have been found in the mandibular premolar area [4, 7, 13].
Late-developing supernumeraries are those extra teeth that form after normal corresponding teeth of the same region have completed their root formation [7]. In a several reports of late-developing supernumerary teeth, they were mostly found in the mandibular premolar region [2, 5, 6, 9, 11, 14, 17]. Their prevalence in an orthodontic population has been reported to be 0.64% [10].
Hypo-hyperdontia is a very rare condition in which dental agenesis (excluding third permanent molars) and a supernumerary tooth or teeth occur concomitantly. The prevalence of non-syndromic hypo-hyperdontia ranges from 0.33% [15] to 0.73% [3] in the orthodontic population and could be below 0.1% when the general population is considered [1]. The condition was reported more commonly in males than in females with a 1.4 : 1 ratio [8, 16]. Hypo-hyperdontia can affect either one or both jaws. To date, approximately 200 patients with hypo- hyperdontia have been reported in the English literature since 1932 [1, 8, 16]. In most of them, the anomaly was bimaxillary or involved only the anterior maxillary region [8, 16].
The aim of this report is to present for the first time a case of hypo-hyperdontia involving multiple late-developing supernumerary teeth and mandibular incisor hypodontia.

Case presentation

A 9-year-old Caucasian boy was referred to the Clinic of Orthodontics at the Academic Centre for Dentistry in mixed dentition stage with a missing mandibular permanent central incisor and class I malocclusion. Extraoral examination and functional analysis showed no relevant alterations. Medical and dental history was noncontributory with no previous tooth extractions, facial trauma, premature birth, neonatal teeth, or numerical anomalies of the primary dentition. Family members had neither congenitally missing nor supernumerary teeth. The initial panoramic radiograph (Figure 1) confirmed the congenital absence of one mandibular incisor and showed normally developing other teeth, including third molars. No radiographic evidence of other pathology was noted. Orthodontic treatment with fixed appliances commenced after the eruption of second molars and progressed uneventfully for 26 months. A second panoramic radiograph (Figure 2) was taken shortly after debonding at the age of 15 to assess the third molars and an unexpected finding was the presence of developing supernumerary teeth in all four quadrants. It was decided to perform cone beam computed tomography (CBCT) to determine the exact location of the supernumeraries relative to normal dentition and identify possible root resorption (Figure 3). The teeth were not associated with cyst formation or root resorption of adjacent teeth. Given the close proximity of the inferior alveolar nerve and the evidence that further extra teeth may be developing, the patient is being monitored. Surgical intervention will be contemplated in the future.

Discussion

Based on the published case reports it has been noted that patients with a previous history of supernumerary teeth in the anterior maxillary region have a greater possibility of developing supernumerary premolars at a later age [13]. They start calcifying around 10-15 years of age at the lingual site of the dental arch. They are thought to represent a part of the post-permanent dentition type of supernumerary tooth as they develop from an extension of the dental lamina after the permanent follicles have been formed and resemble normal premolar teeth [13].
Orthodontists may diagnose late-developing supernumerary teeth more often as panoramic radiographs are taken periodically during orthodontic treatment [7]. However, the supernumerary crypt and early stage of mineralization can be easily overlooked due to the lingual position relative to the normal premolar roots. Moreover, supernumerary premolars may interfere with orthodontic space closure and affect the stability of ortho­dontic treatment [7, 10, 15].
Controversy exists regarding the timing for surgical removal of supernumerary premolars. To avoid the risk of damage to the roots and adjacent nerves some authors recommend leaving and monitoring them in situ until further development enables safer surgery. As the recurrence rate of supernumerary premolars has been reported to be 8% [13], the patient requires further regular and careful clinical and radiographic monitoring even after supernumerary premolars are surgically removed.
In the present case, late development of the supernumerary teeth was even more surprising as the patient had already been diagnosed with mandibular incisor hypodontia. To our best knowledge, this is the first report of multiple late-developing supernumerary teeth being a part of this unique numerical combination.

Conclusions

This is the only known documented case of late development of multiple supernumerary teeth in a patient with hypodontia. Dentists who treat children and young adolescents should take into consideration the rare possibility that a generally healthy individual despite the initial diagnosis of hypodontia is still capable of forming a supernumerary teeth.

CONFLICT OF INTEREST

The authors declare no potential conflicts of interest with respect to the research, authorship, and/or publica­tion of this article.

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