16.1 Concept of Occlusal Plane-Altering Orthognathic Surgery
Dentofacial deformities impact not only occlusion but also the facial profile. Facial profiles can be categorized based on the patient’s occlusal status. Class II dentofacial deformities tend to result in convex profiles while Class III deformities result in concave facial profiles (Fig. 16.1).
The standard approach for the management of Class III dentofacial deformities is simultaneous maxillary advancement and mandibular setback. These have become standard protocols because of the maxillary hypoplasia related to the mandibular prognathism in patients with Class III dentofacial deformities (Fig. 16.2).
However, there is another way to correct the dentofacial deformity. This alternative method involves occlusal plane-altering orthognathic surgery, which is a powerful tool for changing the facial profile. An alteration of the occlusal plane directly influences the facial profile. In my personal clinical practice, I have been actively using occlusal plane-altering orthognathic surgery since 2005. I am now confident that this method is one of the best tools for not only changing facial profiles but also for simultaneously correcting malocclusion (Fig. 16.3).
Most Asian patients have varying degrees of dentoalveolar protrusion, making the Asian face look different from the Caucasian face. In these patients, maxillary advancement procedures may aggravate the dentoalveolar protrusion or widen the alar base, both of which are critically harmful for the aesthetics of the Asian face. Moreover, most Asian females have flat occlusal planes and prominent mandibular angles that cause the square appearance of the Asian face.
The surgery-first approach (SFA), accompanied by occlusal plane alteration, has been very effective in my practice. If using SFA, the surgeon needs to very effectively adopt occlusal plane-altering orthognathic surgery. Because the effective range of orthognathic movement surpasses that of orthodontic treatment, many tooth relocations can be achieved through occlusal plane alteration. Figure 16.1 shows a Proffit and White’s discrepancy diagram of the maxillary (a) and mandibular dentition (b) with envelopes that represent the amount of dental repositioning possible using orthodontic movement, alone (yellow), orthodontic movement with growth modification (green), and orthodontic movement with orthognathic surgery (blue). The effective range of the orthognathic tooth movement is much broader than that of orthodontic movement. Thus, occlusal plane alteration can be a very powerful tool in conjunction with SFA (Fig. 16.4).
There are three maxillomandibular complex (MMC) movements: pitch, roll, and yaw. The roll movement is mostly used to correct vertical facial asymmetry while the yaw movement is used to correct horizontal facial asymmetry. If we consider MMC movements, regardless of facial asymmetry correction, the pitch movement is the one most closely related to my occlusal plane-altering orthognathic surgery concept (Figs. 16.5 and 16.6).
16.2 Classification Of Occlusal Plane Altering Orthognathic Surgery
There are four ways to change the occlusal plane during orthognathic surgery:
Clockwise rotation based on posterior nasal spine (PNS) impaction.
Clockwise rotation based on anterior nasal spine (ANS) lengthening.
Counterclockwise rotation based on PNS lengthening.
Counterclockwise rotation based on ANS impaction.
I will address and explain my concept of occlusal plane-altering orthognathic surgery.