Diagnostic classification for malocclusions with facial prognathism and its incorporation into mandibular morphological analysis

Abstract

: Since its introduction, the diagnostic classification for malocclusions with facial prognathism has been well recognized and practically applied in orthodontic specialty. According to this classification, the malocclusions with a prognathic facial profile can be categorized into 4 classes: dento-alveolar originated, skeletally originated, mandibular positioning and combined skeletal and mandibular positioning, i.e, combined subtype I and subtype II. Among the new developments of this innovative malocclusion classification, the morphological assessment of mandibular body highlights a new impetus. Other than measuring the angular and linear perimeters only, this new dogma focuses on evaluating the physical contours of the mandible through cephalometric images. It includes the determination of geometric morphology of the mandible and the depth of symphysis curvature. Two types of mandibular morphology are common in patients with facial prognathism: a favorable flat and horizontally rectangular body with a prominent chin; and a unfavorable thick and vertically triangular body with a retrusive chin. The depth of the symphysis, on the other hand, is shown to be shallow or deep. It is noted that the prognathism with mandibular retruded positioning has a flat mandible and unfavorable triangle-shaped mandible exists only in skeletal prognathism. This new classification restricts the extraction indications for malocclusions with a prognathic facial profile: extraction should be refrained in cases with increased overjet, overbite and deep curve of Spee, and SGTB orthopedic therapy, instead, is recommended.