Finishing occlusion, degree of stability and the PAR index

The occlusions of sixty-five patients, treated by one private specialist orthodontist with consistent philosophy and goals, were assessed according to the PAR Index. For each patient, pre-treatment, post-treatment and follow-up study models were assessed. Follow-up models were taken at least 6.5 years following the removal of all retention appliances. Mean-weighted PAR scores were calculated for the total sample and various sub-groups at each stage. Mean percentage changes in weighted PAR scores were also calculated. The relationships between the occlusal standards at the end of active treatment and at the end of the follow-up period, and specific diagnostic and treatment factors were then investigated to search for any factors that might be predictive of long-term post-treatment occlusal stability or instability. The overall mean-weighted pre-treatment, post-treatment and follow-up PAR scores were 25.5, 3.0 and 7.0, respectively. There was an 85.6 per cent decrease with treatment in the overall mean-weighted PAR score. This was followed by a 15.2 per cent increase in that overall mean during the follow-up period. In this introductory study, neither the PAR score at the end of active treatment, nor the amounts of occlusal change occurring during or after active treatment, were found to be predictive of the amount of post-treatment occlusal change.