have been handled in one fell swoop, but without the surgical option, I had to rely on an ever- changing combination of bite blocks for intru- sion on the Brodie side and up-and-down elastics on the contralateral side. Today, with the avail- ability of miniscrews that are relatively comfort- able and cannot be seen in conversation, I proba- bly could have convinced the patient to give them a try. But this case occurred before the era of skeletal anchorage.
Management of the occlusal plane is part and parcel of any orthodontic graduate training program, and the ability to control this plane is one of the hallmarks of the conscientious spe- cialist. According to Vaden, Dale, and Klontz, “The occlusal plane angle expresses a dento- skeletal relationship of the occlusal plane to the Frankfort horizontal plane. . . . In most ortho- dontic corrections the original value should be maintained or decreased. An increase in the occlusal plane angle during treatment indicates a loss of control.”1 Actually, I never lost control of the case mentioned above; it just took me an inordinately long time to gain control in the first place. In this patient, as in many others, the occlusal plane was clearly the factor that would determine my success or failure. That conclusion is substantiated by an extensive analysis of suc- cessful and unsuccessful cases conducted by the late Jim Gramling of Jonesboro, Arkansas.2 The “probability index” devised by Gramling to pre- dict treatment success included elements such as FMA, ANB, FMIA, SNB, and, of course, the occlusal plane.
In our treatment planning, we generally visualize the occlusal plane from the side, as in a lateral cephalogram. While the sagittal occlusal plane angle is undoubtedly an essential measure- ment of treatment progress, it is just as important to control the occlusal plane in the transverse dimension. Causes of a canted occlusal plane can range from major developmental or growth dis- turbances, such as those seen in hemifacial microsomia, to lesser problems, such as anky- losed deciduous teeth. In my patient, some devel- opmental disruption had resulted in buccal tip- ping of the upper left posterior teeth and lingual
tipping of the opposing lower teeth. Inevitably, the premolars and molars on that side supraerupt- ed in both arches, producing the Brodie bite and subsequent cant of the occlusal plane.
It can be even more difficult to control a canted occlusal plane in the anterior segments than to control it posteriorly. A cant of the ante- rior dentition, or the “incisal plane” as described by Drs. DeLuke, Uribe, and Nanda in this issue of JCO, is every bit as detrimental to the overall occlusion as a posterior cant is—and far more obvious to the patient looking in the mirror. In such a case, orthognathic surgery may have a dubious prognosis, and it will be more difficult to employ the combinations of bite blocks and up- and-down elastics that finally allowed me to achieve success with my patient. Although skele- tal anchorage can be an effective option, there are other ways of achieving appropriate control of the incisal plane.
Drs. DeLuke, Uribe, and Nanda present a unique approach, utilizing segmental mechanics and an off-center, cantilevered force system to establish a rotational moment around a center of rotation in the frontal plane, between the roots of the central incisors. These vectors produce a dif- ferential intrusion and extrusion of the incisor segment, which is shown to correct a canted incisal plane in two similar cases. Given the incredible array of techniques available to us nowadays, I am always impressed when a new variation on an old theme produces such remark- able results. In a time when surgery or mini- screws can make virtually any malocclusion cor- rectable, it is refreshing to see that an under- standing and application of the fundamental principles of orthodontic biomechanics can still
make a tremendous difference.
Vaden, J.L.; Dale, J.G.; and Klontz, H.A.: The Tweed-Merrifield edgewise appliance: Philosophy, diagnosis, and treatment, in Orthodontics: Current Principles and Techniques, ed. T.M. Graber, R.L. Vanarsdall, and K.W.L. Vig, 4th ed., Elsevier Mosby, St. Louis, 2005, p. 683.
Gramling, J.F.: The probability index, Am. J. Orthod. 107:165- 171, 1995.