Anteriorposterior AP

Although precise skeletal relationships can be determined using a lateral cephalostat radiograph, many practices do not have this facility and it is important to be able to assess the skeletal relationships clinically.

To assess the AP skeletal pattern the patient has to be postured carefully with the head in a neutral horizontal position (Frankfort Plane horizontal to the floor). Different head postures can mask the true relationship. If the head is tipped back the chin tends to come further forward and makes the patient appear to be more Class III.

A tracing of a lateral cephalostat radiograph identifying soft tissue points A and B

A tracing of a lateral cephalostat radiograph identifying soft tissue points A and B

Conversely, if the head is tipped down the chin moves back and the patient appears to be more Class II. Sit the patient upright in the dental chair and ask them to occlude gently on their posterior teeth. Ask them to gaze at a distant point; this will usually bring them into a fairly neutral horizontal head position. Look at the patient in profile and identify the most concave points on the soft tissue profile of the upper and lower lips (Fig. 1).

The point on the upper lip is called soft tissue A point and on the lower lip soft tissue B point. In a patient with a class I skeletal pattern B point is situated approximately 1 mm behind A point. The further back B point is, the more the pattern is skeletal II and the more anterior, the more skeletal III it becomes. Figure 2 shows a patient with a skeletal III pattern where the outline of the hard tissues has been superimposed on the photograph. This demonstrates that although we are examining the soft tissue outline this also gives an indication of the

Fig. 2 Shows a patient with a skeletal III pattern where a tracing of the lateral cephalostat radiograph has been superimposed on the photograph. The soft tissue masks to some extent a significant skeletal III pattern

underlying skeletal pattern. Obviously the soft tissue thickness may vary and mask the A-P skeletal pattern to some degree but generally the thickness of the upper and lower lips is similar. The underlying skeletal pattern is therefore often reflected in the soft tissue pattern. The more severe the skeletal pattern is the more difficult treatment of the resulting malocclusion becomes. Figure 3 a and b, shows an adult with an obvious skeletal III pattern and a malocclu-

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