Change in Anterior Crowding over 20 Years from Third Decade of Life in Untreated Angle Class I Crowding

Many studies have investigated age-related change in normal occlusion and during the post-retention phase of orthodontic treatment. None, however, have investigated such change in malocclusion. The purpose of this study was to compare age-related change in Angle Class I crowding with that in normal occlusion. Dental casts obtained from 10 men and 2 women in their 20s and then again in their 40s were digitized with a 3-dimensional laser scanner to measure anterior crowding, angulation, inclination, andarch width and length. A paired t -test was used to evaluate change in these values betweenthe two sets of casts. A student's t -test was used to compare values between the crowdingand normal groups. The casts obtained from individuals with untreated Angle Class Icrowding revealed that anterior crowding increased with age due to a decrease in thelength of the maxillary arch. Clear lingual inclination of the maxillary incisors and mesiolingual inclination of the maxillary canines were also observed. A decrease was observedin the anterior arch width and an increase in crowding due to lingual inclination of themandibular canines in the mandible. The space between the mandibular central incisors and between the mandibular lateral incisors and canines was particularly associated withan increase in crowding, suggesting that this was age-related. A comparison betweenpatients in their 40s with Angle Class I crowding and those with normal occlusion revealedthat the increase in maxillary anterior crowding was greater in the former. Mandibularanterior crowding increased at around the same rate, however.