Morphological characteristics on the mandibular fused deciduous anterior teeth with Micro-CT

This study aimed to clarify the morphological characteristics of the fused portion in the mandibular fused deciduous anterior teeth using microfocus x-ray computerized tomography, a method which allows nondestructive three-dimensional observation at high resolution in any direction. The specimens consisted of five mandibular deciduous central/lateral incisor fused teeth, and four lateral incisor/canine fused teeth. These specimens were scanned using x-ray micro-CT and three-dimensional images of anatomical features of the crowns were reconstructed. Two-dimensional sliced images were created and then, the morphology of the fused portions were examined by measuring angle of the fused portion, enamel and dentin thickness at the fused portion. Angles of lingual fused portion in deciduous central/lateral incisor fused teeth, and labial fused portion in deciduous lateral incisor/canine fused teeth are significantly smaller, and the enamel thickness at these fused portions are also thinner. The values of the dentin thickness in deciduous central/lateral incisors tended to be thinner than those of deciduous canine, which means dentin thickness of the deciduous central/lateral incisors are thinner than that of canine. The fused portions in the fused deciduous anterior teeth have the similar morphological features to those of pit and fissure of the occlusal surface in molars and are likely to be the initiation and predilection sites of dental caries. Therefore, it is considered to be preferable to apply pit and fissure sealant into the fused portions at an early time point of the treatment.