Research on Dental Arch Size and Occlusion in Primary Dentition Based on a Large-scale Survey

Abstract

This research aimed to clarify the dental arch size and the prevalence of malocclusions in primary dentition. The width and length of the dental arch and the presence of malocclusion were examined using dental models obtained from 1,702 children aged from 3 years and 0 months to 6 years and 6 months registered at nursery schools during the period of 2013 to 2018. The findings were as follows.

1. The width of the primary dental arch in the maxilla and mandible was significantly larger in boys than girls at each age.

2. Regarding the prevalence of malocclusions evaluated based on the criteria for the dental health survey of 3-year-old children by the Japanese Society of Pediatric Dentistry, crowding teeth were seen most frequently and anterior cross-bite ranked second. The prevalence of maxillary protrusion and open bite tended to decrease with age, while deep bite tended to increase with age.

3. Compared to the crowding teeth group, the dental arch widths were significantly larger at multiple measuring points in the normal (without any types of malocclusion) groups of both boys and girls. When the dental arch lengths were compared between the two groups, neither boys nor girls showed differences in the maxilla, while the values in the mandible were significantly larger in the normal group with boys and girls combined.

4. The diameters of the crown of the incisors in both the maxilla and mandible were significantly larger in the crowding teeth group compared to the normal group. Overbites were significantly larger in the crowding teeth group at the ages of 3, 4, and 5.

This study revealed the characteristics of the size of the primary dental arch and the occlusal conditions in children today, and the values at some measuring points were found to be highly relevant to crowding of teeth.