Malocclusion represents a public health problem in Chile. Government policies create preventive and interceptive programs for these conditions. Nevertheless, there are no uniform criteria for the selection of patients who need early treatment; the decision is made by a specialist during orthodontic treatment. Here, we propose the Index for Early Intervention (IEI) for early detection of malocclusions. We treat malocclusions with a simple interceptive treatment to minimize or eliminate the need for orthodontic treatment in a child population. Furthermore, the IEI can be used in general dentistry as a screening method. The purpose of this study was to compare the reliability and validity of an index used to assess the need for orthodontic treatment, as compared to the view of a panel of experts formed by three orthodontists. We used a set of 55 study casts representing all types of malocclusion. The accuracy of the diagnostic or the validity of each index was calculated using the opinions of three orthodontic raters as a “gold standard;” these measures obtained an agreement of 0.82. Receiver Operating Characteristic curves was plotted for the index. Results: Diagnostic accuracy was determined by the area under the curve, the cut point was 20, sensitivity was 0.977 and specificity was 0.167. Conclusions: This occlusal index provided valuable information for selecting children in need of early and simple orthodontic treatment.