An eight-year-old male was referred to a clinic with a diagnosis of transposition of a central and lateral incisor. Radiographs revealed what appeared to be transposition of teeth 1.2 and 1,1 complicated by a supernumerary tooth. Further investigation and literature review suggested that the child had a mesiodens and an ectopically erupting central incisor. The mesiodens was extracted and the incisors brought into alignment. The orthodontic management of the case is discussed.

An eight-year-old American Caucasian male was referred to a university dental clinic with a diagnosis of transposition of the maxillary right central and lateral incisors and a supernumerary tooth present in the area [Fig. 11.

The child's medical history was non-contributory for pertinent findings. The child's father reported that the child's paternal grandfather had "an extra top front tooth"; the remaining dental history was unremarkable except for a history of routine dental care. A Class I skeletal pattern with no vertical dysplasia was confirmed by routine cephalometric analysis; there were no transverse problems noted during the oral examination. Tooth 2.1 was present in the oral cavity and 2.2 was partially erupted. Teeth 1.2 and 1.1 were unerupted and radiographi-cally superimposed upon one another; the tooth occupying the space of tooth 1.1 was diagnosed as a mesiodens instead of the referred diagnosis of a transposed maxillary lateral incisor 1.2 [Fig. 11.

Transposition of teeth occurs infrequently and most often involves the maxillary canine.¹"-⁵ Most reports of transposition have not been quantitative, rather case reports. Ruprecht and colleagues reported two cases of transposition out of 1,581 sets of dental patients records evaluated in a Middle Eastern dental school patient population.⁶ The cause of transposition is unknown.¹ Among the theories of the etiology of this condition are large stage development disturbances,⁷ migration of teeth within the jaws^s and heredity.⁹'¹⁰

The incidence of supernumerary teeth has been reported in various populations including Hawaiian (0.3%), Western Canadian (%3.1), Danish (%1.7) and Saudi Arabian (2.3%).'^M4 Profitt¹⁵ states "Supernumerary or extra teeth also result from disturbances during the initiation and proliferation stages of dental development. The most common supernumerary tooth appears in the maxillary midline and is called a mesiodens. Supernumerary lateral incisors also occur." Heredity appears to play a role in the development of some supernumerary teeth.¹⁶'¹⁷ Moyers¹⁶ summarizes the etiology of supernumerary teeth as "The principle causative factors are said to be (1) heredity, (2) epithelial remnants and (3) gross aberrations in development, such as the supernumeraries seen with the cleft palate.¹¹

Although the mesiodens, in this patient, anatomically appeared to be a lateral incisor, the literature does not support the conclusion that the left side maxillary central and the lateral incisors were transposed with an unerupted supernumerary tooth present. ^,"'^T5 On the contrary, only one report was found describing central-lateral transposition and the authors claimed it was the first and only report of central-lateral transposition in the literature.¹⁹

Since the radiographic appearance of the submerged teeth suggested fusion, the mesiodens was not initially extracted until the status of the two unerupted teeth could be determined.

The treatment plan called for orthodontically banding and bonding the following maxillary teeth: first permanent molars, primary canines, the mesiodens and the left central incisor. Standard Edgewise appliances (0.022" slot) were to be used. The molars were to be banded and the anterior teeth bonded. A light nickel-titanium wire (0.014" or 0.016" round) was to be placed. The plan called for surgically uncovering the central incisor (1.1) and the lateral incisor (1.2) and evaluating if they were fused. If not fused the plan called ' for extracting the mesiodens and orthodontically bonding to the submerged teeth and subsequently attaching them to the archwire via stainless steel ligatures. If the teeth were fused, the plan called for extracting both, keeping the mesiodens. The mesiodens would then be orthodontically repositioned into the lateral incisor position and at the appropriate time a resin bonded bridge would be constructed to replace 1.1. The anatomy of the mesiodens was favorable as an adequate substitution for 1.2.

The orthodontic appliances were placed according to the plan. An initial 0.014" nickel-titanium arch wire* was ligated into place. The distal ends of the wire were annealed prior to final ligation and were turned down in the conventional manner, in order to prevent the wire from dislodging. The buccal mucosa was protected from irritation from the long span of unbracketed wire (space from the tube of the upper molar to the primary canine, right and left) by threading measured lengths of 1.7 mm diameter plastic tubing* over the wire. The oral surgery was scheduled.

Fortunately, the surgery was delayed for two months. When the child presented to the clinic for follow-up, the right central incisor was partially erupted. Upon clinical examination, it was apparent (local anesthetic was administered and an instrument was placed between the teeth; they moved independently) that the two teeth (1.1 and 1.2) were not fused. The mesiodens was extracted that day under local anesthesia. The central incisor (1.1) was buccal to the lateral incisor (1.2).

Approximately two months after the extraction of the mesiodens tooth 1.1 was erupted far enough to be bonded, more incisal than conventional [Fig. 2]. Tooth 1,2, although unerupted at that time, was essentially in its proper mesial-distal-axial position in Ihe arch |Fig. 1|; tooth 1.1 was repositioned mesially by using a .008 X .030 inch open coil spring compressed over a light 0.01 h" round steel archwire. The archwire was "stepped" in order for the incisal edges of the central incisors to be at the same vertical position. The coil was compressed (approximately 0.25") between the right maxillary primary canine (5.3) and the right maxillary incisor (1.1). Plastic tubes were threaded over the buccal segments of the archwire for mucosal protection and distal ends of the archwire were secured as previously described. The boy was seen for routine orthodontic adjustment visits every 4 to 6 weeks. New lengths of coil were placed as needed to maintain a light force.

After six months of those mechanics, tooth 1.1 was repositioned (tipped) into a more normal position and # 1.2 had partially erupted. Teeth 1.2 and 2.2 were then bonded and brought into position over a period of approximately two months. The appliances were then removed (orthodontic treatment time: 10 months). Tooth 5.3 did not prematurely exfoliate nor did it move distally as a result of the reciprocal forces placed upon it. At the time of appliance removal the child's radiographic and intraoral appearance was consistent with what one would normally find in a child of his age¹⁵

Based on the dental literature and the child's history the initial diagnosis of central-lateral incisor transposition was incorrect. The child presented with a mesiodens that looked anatomically like a lateral incisor. The orthodontic management of the problem was discussed. IFigs. 2,3]. (Please note that the Panorex was exposed prior to appliance removal but on the same day the appliances were removed.) Although the Panorex showed that the roots of 1.1 and 1.2 were in close approximation, the teeth were debanded/bonded as there was a concern that continued orthodontic treatment might be injurious to the root of 1.2, due to the position of 1.3. The child was lost to follow-up after appliance removal.

The author is grateful to Drs. James Shupe and Philip O'Rourke of the Department of Pediatric Dentistry, College of Dentistry, University of Kentucky for their assistance in preparing the manuscript. Thanks is also extended to Misses Marzi Andaya and Marian Nicolas of the Department of Dentistry at King Faisal Specialist Hospital   and   Research   Center   for   their   secretarial support.