Mathematical modeling for explanation and prediction of treatment outcome in growing patients with anterior open bite malocclusion treated with rapid molar intruder and posterior bite blocks

Abstract

Purpose

Rapid molar intruder (RMI) is a non-compliant treatment modality for correction of anterior open bite (AOB) in growing patients. The aim of this study is to explain the main treatment outcome (increase in overbite) by the other morphological changes after treatment with RMI and posterior bite blocks (PBBs). We also investigated the baseline characteristics that may help predict the treatment outcome.

Subjects and methods

Fourteen patients (mean age ± SD = 10.7 ± 1.7 year) with AOB malocclusion were treated with RMI springs and PBBs fixed on posterior teeth for 4 months. Patients were assessed before and after treatment using cephalometric radiographs. Multivariable regression model was developed to explain overbite change by the other morphological components. Single regressions of overbite change on baseline variables were conducted to determine best predictor of treatment outcome.

Results

Treatment produced significant increase in overbite. The change in overbite was best explained by the changes in facial axis angle, upper anterior dental heights and upper posterior dental heights. The best predictor for treatment outcome was the facial axis angle before treatment.

Conclusion

The correction of AOB by the RMI may be explained by orthopedic and dental changes resulting from growth and treatment. The orthopedic changes consisting of counterclockwise mandibular true rotation is the strongest contributor to overbite increase. Patients with severe vertical growth pattern tend to have greater closure rate of open bite.

Keywords:

• Anterior open bite
• Rapid molar intruder
• Posterior bite blocks
• Early treatment