The role of occlusal discrepancies in the long-term stability of the mandibular arch.

To assess the influence of occlusal discrepancies on the long-term stability of orthodontic treatment, the dental casts, and cephalometric records of 40 patients were evaluated, pretreatment, post-treatment, and at least 9 years post-retention. Post-treatment and post-retention casts were mounted in a semi-adjustable articulator in RCP. In addition to arch dimension measurements, discrepancies between RCP and ICP were measured in three spatial planes using a condymeter. Arch width and length decreased significantly after retention. The position of the lower incisors was relatively stable, whereas the lower molars moved forward substantially. Lower anterior irregularity increased after treatment. As a consequence, 60% of the cases had unsatisfactory lower anterior alignment after retention. The long-term records generally showed a trend towards moderate crowding. The amount of slide decreased over time and had a statistically significant, though clinically only moderate, influence on the increase in lower anterior irregularity.