Long-term stability of dental arch form in normal occlusion from 13 to 31 years of age

Based on observations of longitudinal changes in dental arch dimensions, it has been stated that an individuality of arch form and an integrity of thi s form exists. However, longitudinal studies evaluating arch form changes h ave rarely been reported in the literature. The purpose of this investigati on was to use a computer-assisted method for the description and analysis o f maxillary and mandibular arch form in a sample of normal occlusion subjec ts, and to evaluate the long-term stability in dental arch form from the ag e of 13-31 years. The study was carried out on 30 subjects of Scandinavian origin with normal occlusion, recorded at a mean age of 13.6 years and at follow-up at 31.1 y ea rs. Arch form analysis was based on a standardized photographic procedur e, digitization of morphological landmarks, and a computerized form analysi s in which arch form was described using eccentricity values of conics. No specific arch form could be found to represent the sample. Age changes occu rred in arch form, although with large individual variations. For the mandi ble, a significant change to a more rounded arch form with age was found, w hich in males was accompanied by a significant increase in inter-molar dist ance and reduction in arch depth. There was also a significant correlation between change in mandibular arch form and increased irregularity of the lo wer incisors. These findings of lack of stability in arch form in normal oc clusion subjects, when passing from adolescence into adulthood, further que stion the possibility of achieving stability post-orthodontically.