Abstract

The Role of Mandibular Morphology in the Prediction of Individual Treatment Response

by Franchi Lorenzo

In order to improve the efficacy of Class II and Class III treatment in growing patients, the clinician could benefit from the detection of pretreatment individual craniofacial features that could help in the identification of ideal candidates to growth modification procedures. Prediction models for individual patient responsiveness to orthopedic treatment of Class II and Class III malocclusion will be illustrated. As for Class II treatment a study was performed on a sample of 39 pubertal patients (21 females, 18 males) treated with the Twin Block appliance. Lateral cephalograms were available at the start of the treatment (T1) and at the end of functional therapy (T2). The outcome variable was the T2–T1 change in the sagittal position of the soft tissue Pogonion with respect to the vertical line perpendicular to the Frankfort plane and passing through point Subnasale. The predictive variables were age, gender at T1, and all the cephalometric parameters measured T1. Forward stepwise linear regression with P value to enter 0.05 and P value to leave 0.10 was applied. The only significant predictive variable that was selected was the mandibular angle (Co–Go–Me angle) (P = 0.000). In particular, a greater advancement of the soft tissue chin on the profile can be expected with smaller pretreatment values of Co–Go–Me angle. As for Class III treatment a prediction model to forecast long-term stability of early treatment with rapid maxillary expansion and facemask was developed. Seventy-three consecutively treated Caucasian Class III patients (41 females and 32 males) with a mean age at T1 (before treatment) of 7.1 years, was re-evaluated for the assessment of long-term success or failure of treatment at T2 (mean age 21.8 years). Gender and cephalometric variables, chronologic age, and dentition phase at T1 were used as predictors for long-term unsuccessful treatment at T2. A mixed stepwise logistic regression with P = 0.05 to enter and to leave was applied. The prediction model consisted of only one cephalometric variable: the angle between the Condylar Axis and the Mandibular Plane (CondAx-MP) (odds ratio: 1.52, 95% confidence interval: 1.25-1.85, P < 0.0001). Unsuccessful treatment at T2 was predicted for values of CondAx-MP at T1 greater than the cut-off value of 147.8 degrees. Interestingly, mandibular morphology proved to be a reliable indicator of individual response to both Class II and Class III treatment in the growing patient.

Learning Objectives

After this lecture, you will be able to recognize the importance of evaluating mandibular morphology to predict individual patient responsiveness to treatment
After this lecture, you will be able to evaluate the mandibular morphology and apply the predictive model to predict individual patient responsiveness to Class II treatment with the Twin Block
After this lecture, you will be able to evaluate the mandibular morphology and apply the predictive model to predict individual patient responsiveness to Class III treatment with rapid maxillary expansion and facemask