Does initial malocclusion predict the outcome of orthodontic treatment?

Keyvan Sohrabi

Introduction: The assessment of orthodontic treatment outcomes and clinical performance are important goals in orthodontics. This study assessed the improvement of malocclusion in patients treated in University of Washington Graduate Orthodontic Clinic. The relationships between initial severity of the malocclusion, duration of treatment, and final treatment outcomes were also determined.

Methods: Patients who completed treatment during years 2012-2013 were included in this study. Exclusion criteria included complex multidisciplinary patients, phase 1 treatment procedures, and patients with craniofacial problems. PAR index scoring was performed on initial and final models and ABO Cast-Radiographic evaluation on final records. Patient data collected included treatment duration, Angle classification, type of appliances used, treatment strategy, and cephalometric analysis. Data were analyzed with t-test, ANOVA, and multiple linear regression models.

Results: Records from 102 different patients were included in this study. The mean age ± SD of subjects was 16.4 yrs ±9.9 mos. The following types of malocclusion were included: 43% Class I, 33% Class II, and 24% Class III. Average treatment duration for these patients was 23.2 ±5.5 months. Results showed an overall 80 ±23% improvement in PAR. Of all patients treated, 48% were greatly improved, 46% improved, and 6% of the patients did not improve. The analysis showed that the average ABO score for patients after completion of treatment was 19.5 ±8.8. The ABO component garnering the greatest points was occlusal relationship (3.8 ±2.9) and lowest scoring area was found to be interproximal contacts (0.5±1.2). A positive and significant (P<0.0001) relationship was found between initial and final PAR score and the ABO score. A trend was noted for the lower mean final PAR and ABO scores in the extraction group, but this difference between extraction and non-extraction treatments did not reach statistical significance. The mean ABO score for Class I patients was the lowest compared to other categories. The regression model indicated that the initial PAR score and duration of treatment were associated with the ABO score however, age, ANB and SN-MP were not significantly associated with the outcome of treatment.

Conclusion: The majority of patients were treated satisfactorily in the graduate orthodontic clinic. Initial severity of patients and duration of treatment were significantly associated with for the final outcome of treatment.