Clinical Assessment of Jaw Symmetry

The plane of symmetry of the face is the median plane. Midline landmarks like glabella, nasion, subnasale, incisal midpoint, and pogonion should lie on the median plane.  Bilateral structures like the eyes, ears, and gonial angles should be aligned on each side of the median plane, as mirror images.

During the physical examination, one infers the symmetry of the jaws by inspecting the face and examining the dentition. To assess facial symmetry, the examiner must first stand in front of the patient, looking at his/her face. While doing this, he should mentally visualize the median plane and appraise two factors. First, it must be determined if the midline structures are on the median plane; second, one must establish whether bilateral structures are positioned as mirror images in relation to this plane. The examiner should also inspect the face from above and below to ascertain if bilateral structures have the same anteroposterior position. All deviations should be measured and recorded (Figure 10).  

Figure 10

Clinicians also determine symmetric jaw alignment by examining the dentition. When the jaws are symmetrically aligned, the upper and lower incisal midpoints lie on the median facial plane. Also, corresponding right and left teeth have the same vertical position and the same horizontal distance to the median and coronal planes.

Transverse deviations of the upper and lower incisal midpoints should be measured and recorded. The roll of the maxilla can be clinically determined by measuring, with a Boley gauge, the vertical distances from each medial canthus to the ipsilateral maxillary teeth (Figure 11). Right-left differences that are consistent through the arch indicate canting (abnormal roll) of the upper jaw. These measurements should be interpreted with caution as they can be affected by local dental irregularities, vertical eye dystopia, and yaw malrotation of the upper jaw. 

Figure 11