This report presents a rare case of birooted bilateral maxillary primary canines. A Japanese girl aged 8 years 10 months was referred to the Pediatric Dentistry Clinic of Osaka University Dental Hospital by an orthodontic dentist to extract maxillary bilateral primary canines. The canines appeared to be birooted in panoramic radiography and were extracted under infiltration anesthesia. Both visual observation and computed tomography findings revealed that the birooted primary canine had 2 roots for each root canal. In spite of the rareness of this condition, it should be kept in mind because of potential problems in affected patients.
Permanent canines generally have a single root with a single root canal , while birooted canines are rare with a reported occurrence rate of 1.5% . Furthermore, the rate of permanent canines without a single root canal has been found to be 2.3% . On the other hand, the occurrence rate of birooted primary canines has not been reported, though several case reports have been presented with radiography images, but without morphological evaluation or internal structure analysis results . Here, we describe a rare case of birooted primary canines along with detailed findings.
A 6-year-6-month-old girl visited the Orthodontic Clinic of Osaka University Dental Hospital with a chief complaint of malocclusion. Following diagnosis, orthodontic treatment using a maxillary protraction headgear appliance was initiated. At the age of 8 years 10 months, the patient was referred by her orthodontist to our clinic for consultation regarding extraction of bilateral maxillary primary teeth as part of the orthodontic treatment plan.
An oral examination did not find mobility of the bilateral maxillary primary teeth. As for family history, her mother had 10 congenital missing teeth, while there was no other exceptional medical or dental history. Panoramic radiography revealed 6 congenital missing permanent teeth, the maxillary right second premolar, maxillary left first and second premolars, mandibular left second premolar, and mandibular bilateral central incisor ( Fig. 1 ). Additionally, the bilateral maxillary primary canines appeared to be birooted, with mesial and distal roots, and a single pulp chamber. Under infiltration anesthesia, we extracted the bilateral maxillary primary canines and the birooted maxillary left primary canine was subjected to detailed analysis.
Morphological evaluation findings revealed that the crown shape was similar to that of a common primary canine, while tooth attrition was observed in the cusp ( Fig. 2 ). The birooted primary canine had both mesial and distal roots, with furcation located at the lower third of the roots. It was assumed that one-third of the distal root had already been absorbed due to the maxillary left permanent canine, while the mesial root had not yet been absorbed. Each root was clearly shown to have its own canal. Measurements of the birooted canine are shown in Table 1 . When compared to the average size of a single root maxillary primary canine , labiolingual diameter of crown was thought to be within a normal range, whereas the mesiodistal diameter of the crown was considered to be longer. On the other hand, the overall length, crown and root lengths were thought to be reduced as compared to normal.