Orthodontists commonly specify the alignment of the teeth and jaws by means of a set of k angles and their relationship with each other. Each individual can thus be visualized as a point in k-dimensional space. Individuals regarded as having an ideal occlusion and well-balanced face, form a cloud of points that is termed the 'norm' population. Individuals far from the cloud require orthodontic intervention.In this study, a method is presented - the multiharmony method (MHM), which assists in treatment planning. With multiple regression analysis, the expected value that each angle should take in a norm individual when the remaining angles are given is estimated. The residual difference between the measured angle and its expected value then indicates the deviation from a harmonic appearance in the respective angle.The MHM was applied to a data set of 134 Korean individuals identified as the norm population (Class I, mean age: 19.6 years) and to 87 patients (Class III, mean age: 21.2 years). From the number and size of the residuals, the two populations could be separated almost completely. Almost all patients showed residuals larger than any residual in the norm population (sensitivity: 99 per cent), whereas 90 per cent of all norm individuals showed no extreme residuals. The MHM can also be used to assist in visualizing different treatment effects, thereby assisting the orthodontist in choosing the best course of treatment for each patient.
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