A longitudinal study of the development of crowded dental arch.

It is important to determine both where and when in the process of dental arch development crowding occurs. The authors investigated 81 children (boys/37, girls/44). These children were developing permanent dentition without early loss of deciduous or permanent teeth, which is considered to be one of the causes of malocclusion. Impressions were taken from subjects who had normal, spaced, or crowded permanent dental arch, and longitudinal casts made every two months from three years of age. In both the maxilla and the mandible, the transition to the crowded condition most often occurred (maxillary: 84.6%, mandibular: 64.5%) at the time of eruption. Crowding condition was also caused by the eruption of other teeth; however, this was rare. The maxillary and mandibular crowding mostly occurred (maxillary: 69.2%, mandibular: 77.4%) in the anterior teeth. It was seldom observed in the premolar and first molar regions.