A Fused Maxillary Central Incisor and Its Multidisciplinary Treatment: An 18-Year Follow-Up

Fused teeth may cause aesthetic, spacing, periodontal, eruption, and caries problems. The present case report describes a 7-year-old boy patient with a chief complaint of unerupted maxillary incisor. Radiographic examination indicated a fused tooth which had two fused roots but two independent root canals. A complex management of a fused tooth is really difficult to standardize. In this case an orthodontic, endodontic, and surgical treatment (intentional replantation) allowed the tooth to be retained until 18 years following intervention. Maintenance of the root and alveolar bone in young adults at least until full skeletal maturation should be the main treatment objective. 1. Introduction Dentition development is a very complex process either in the primary or in the permanent tooth. Some authors have proposed a model of genetic network regulation in tooth formation; it seems obvious that most human congenital malformations and dental defects are caused by mutations in developmental regulatory genes. There would be a molecular basis of dental defects [1]. Fusion and gemination are considered abnormalities in tooth development. It is often difficult to differentiate between gemination and fusion and it was common to refer to these anomalies as “double teeth,” “double formations,” “joined teeth,” “fused teeth” or “dental twinning” [2–5]. In gemination the subdivision of the tooth bud is incomplete, giving rise to two dental units, the width of which in the mesiodistal dimension can be twice the dimensions of a single dental unit usually sharing a single root, pulp chamber and root canal. This bifid tooth is considered as a single tooth [6, 7]. By contrast, in fusion the originally separate tooth buds unite at the crown level (enamel) or at the crown and root levels (enamel and dentine), yielding a single large tooth during the odontogenesis, when the crown is not yet mineralized [8, 9]. Both anomalies occur more frequently in the primary dentition, particularly in the canine-incisor region, involving maxillary central and lateral incisors and mandibular lateral incisors and canines [2]. The incidence of unilateral occurrence is estimated in the literature to be 0.5% in the deciduous and 0.1% in the permanent dentition. There seems to be an overall lower incidence of double teeth in Caucasians than in Asians [10]. The aetiology of fusion is still unknown, but the influence of pressure or physical forces producing close contact between two developing teeth was reported as a possible cause. Gemination can be interpreted as an attempt of a supernumerary