Cl II surgeryRetrognathismGenioplastyASOCondylar resorptionSleep apneaOSAGummy smileOpen bite
5.1 Orthognathic Surgery for Patients with Class II Malocclusions
In Korea, the frequencies of Class II and Class III malocclusions are similar. However, significantly fewer patients with Class II malocclusions seek orthognathic surgery, compared with those with Class III malocclusions (Fig. 5.1).
Why do so few patients with skeletal Class II malocclusions elect to undergo surgery? The possible reasons for the lower surgical rate for Class II deformities, compared with Class III deformities, are listed as below:
Orthodontists and patients recognize the esthetic differences between Class II and III malocclusions
Preferable profile for females (small size of face)
Alternative orthodontic camouflage treatments are available for Class II patients
Alternative surgical options are available for Class II patients
In general, a larger mandible can have a positive esthetic effect in men, reflecting a stronger, more masculine image; a smaller mandible can give a more positive, feminine image to women who prefer smaller faces. In fact, many patients with skeletal Class II malocclusions and retrognathic mandibles visit orthodontic offices complaining of lip protrusion. Despite the lip protrusion being due to a small mandible, orthodontic camouflage treatments that involve tooth extractions produce relatively satisfactory results (Fig. 5.2).
Additional surgical procedures, such as advancement genioplasty, can be performed after camouflage orthodonvtic treatment of skeletal Class II malocclusions (Fig. 5.3). From the patient’s point of view, these treatment options have the advantage of minimizing the burden of additional surgical operations.
5.2 Surgical Treatment Objective for Class II Orthognathic Surgery
Although skeletal Class II malocclusion results from mandibular undergrowth, the location of the maxilla is especially important when planning the surgical procedure. This is because the postoperative position of the maxilla also determines the postoperative location of the mandible. In planning Class II surgery, not only the mandibular position, but also combined maxillomandibular position needs to be evaluated carefully prior to surgical planning. This evaluation contains anteroposterior and vertical position of the maxilla (Fig. 5.4).
If a skeletal Class II malocclusion exists due to anteroposterior overgrowth of the maxilla, there are anatomical limitations for the surgical retraction of maxilla. Therefore, surgical planning that includes an anterior segmental osteotomy of the maxilla is necessary (Fig. 5.5).