Abstract
The occlusal plane often passes through the dens in persons with normal maxillofacial morphology. However, In patients with severe jaw deformity, the occlusal plane may widely deviate from this level, upward or downward. In such cases, abnormalities are often observed in the inclination of the occlusal plane. But the posterior point of the occlusal plane has been unknown in surgical correction of the occlusal plane.
We analyzed individual normal occlusion, mandibular protrusion without maxillary hypogrowth, mandibular retrusion, and mandibular protrusion with maxillary hypogrowth, with regard to the position where the posterior extension of the occlusal plane crossed the cervical vertebrae, on cephalometric radiograms of the facial profile.
As a result, in individual normal occlusion, the occlusal plane crossed around the upper 1/4 of the length of the dens from the midpoint of the basement of the dens. In mandibular protrusion without maxillary hypogrowth, the occlusal plane in males crossed around the lower 1/2 of the length of the dens from the midpoint of the basement of the dens, and the occlusal plane in females crossed around the upper 1/10 of the length of the dens from the basement of the dens. In mandibular retrusion, the occlusal plane in females crossed around the upper 2/3 of the length of the dens from the midpoint of the basement of the dens. In mandibular protrusion with maxillary hypogrowth, the occlusal plane in males crossed around the lower 3/4 of the length of the dens from the midpoint of the basement of the dens, and the occlusal plane in females crossed around the lower 1/2 of the length of the dens from the midpoint of the basement of the dens.
In orthognathic surgery, we considered that the posterior reference point of the anterio-posterior inclination of the occlusal plane is determined using the DENS Index in individual normal occlusion, and is useful in planning treatment for severe jaw deformity.
