Sagittal schematics of jaw position and craniofacial structures. (A) Schematic of Class I anatomy. (B) Schematic of Class III anatomy with mandibular prognathism and maxillary retrognathism. A Class III skeletal relationship may result from maxillary deficiency, mandibular excess, or a combination of both. One type of Class III jaw relationship is shown here (maxillary deficiency and mandibular excess), though variations exist within Class III malocclusions with differing degrees of upper and lower jaw involvement. Anterior space is commonly reduced in Class III patients, with decreased or negative overjet (OJ) as the maxillary incisors are retruded relative to the mandibular incisors. Class III patients can also present with proclined maxillary incisors, retroclined mandibular incisors, condylar hyperplasia, anterior positioning of the condyle, a short anterior cranial base length, acute cranial base angle, an obtuse gonial angle, and an excessive lower anterior face height (if high angle) (32,33). Class III patients present with a range of severity and combinations of these features. Our large DFD database encompasses a spectrum of Class III presentations, quantified by occlusal and cephalometric measurements (Figure 2B). Labels: U1 = upper 1, L1 = lower 1, UL = upper lip, LL = lower lip, SP = soft palate (or velum), HP = hard palate, TT = tongue tip, Mx = maxilla, and Md = mandible. OJ is the extent of horizontal (anterior–posterior) overlap of the maxillary central incisors over the mandibular central incisors.