Smile design not only alters the shape of the teeth but also regulates the macro-aesthetic relationship of the face as a whole. One of the most frequently used parameters in this process is the E-line (Aesthetic Line), an imaginary line connecting the tip of the nose and the tip of the chin, and the distance of the lips from this line determines the balance of the profile view. The interpupillary line (the horizontal line passing through the pupils) is used as a reference to check the parallelism of the chewing plane of the teeth to the horizon line. If there is asymmetry between the patient’s pupils, dynamic symmetry is created by selecting alternative anatomical reference points such as inner ear balance or the midline of the face. Using computer-aided software, these lines are superimposed, optimizing the lip-tooth relationship millimeter by millimeter while the patient is speaking, smiling, and at rest.
