Abstract
The purpose of this study was to examine the effects of lower infraocclusal first deciduous molars on the dental occlusal relationship. The occlusal relationship, length of the dental arch, width of the dental arch, and the occlusal curvature of lower dentition were discussed in accordance with Hellman's dental age using 29 study casts.
The results of this study were as follows:
I. Concerning the anterior occlusal relationship, the anterior crossbite was found to occur with high frequently.
2. Concerning the occlusal relationship of the first molars in materials of dental age III A and dental age III B, Angle's class III was the most common.3. For the dentition with lower infraocclusal first deciduous molars on both sides, the width of the dental arch between the second deciduous molars was small, and the length of the dental arch was large in both maxilla and mandible.4. The occlusal curvature of the dentition with lower infraocclusal first deciduous molars on both sides was larger than the standard value of the lower occlusal curvature of the normal occlusion.5. The occlusal curvature of the dentition when one side has no lower infraocclusal first deciduous molar was close to the standard value. On the other hand, the side with the infraocclusal first deciduous molar was larger than the standard value and dissymmetrical with respect to the side with the infraocclusal first deciduous molar.6. The subjects of dental age III A showed a larger curve than those of dental age II C, showing a tendency of toward infraocclusal first deciduous molars.
