Lip Curvature

Lip curvature may be upward, straight, or downward and is assessed by evaluating the position of the midline upper lip compared to the position of the commissure during full smile.^22,27,28 Both straight and upward lip curvatures were assessed by laypersons and dentists as more esthetic than downward lip curvatures.²² Facial musculature is the primary determinant of lip curvature, so interventions that do not address the musculature may be limited in addressing a downward lip curvature (Figure 7).

Figure 7: Comparison of an upward and downward lip curvature.

Figure 7: Comparison of an upward and downward lip curvature.

Upward lip curvature                             Downward lip curvature