Abstract
Relatively many case reports on a geminate or fused tooth were found in the literature, but those on a three-fusion tooth were rare. Two cases of a three-fusion tooth, containing supernumeraries, were found in a boy and a girl, patients at Nihon University Dental Hospital at Matsudo. The boy was 2.8 years old (Case I), and the girl was 4.7 years old (Case II) at the time of the treatment.
From examining the history and clinical observations, the following findings were obtained.
(1) Family history: Abnormalities in the form of the tooth crowns were found among the family members with both Cases I and II.
(2) Medical history: Mother of Case II failed to take enough food during her early pregnancy.
(3) Intraoral findings: The three-fusion tooth of Case I consisted of the maxillary right deciduous central and lateral incisors and a supernumerary tooth. Lingual version was observed with the mandibular right deciduous lateral incisor of Case I, and the crowding of teeth was observed around the anterior portion of the same subject. The three-fusion tooth of Case II consisted of the mandibular right deciduous lateral incisor, canine, and a supernumerary tooth. The fusion of the mandibular left deciduous lateral incisor and canine and a serious overbite were also observed with Case II.
(4) Radiographic findings: The permanent successor was observed at the deciduous central incisor with Case I, and at the deciduous canine with Case II. The permanent successor at the fused tooth of the mandibular left was also recognized with Case II.
The two cases are being clinically observed at present. Further morphological and histological investigations will be made after these fused teeth fall off.
