Evaluating Facial Esthetics: Lip Symmetry
Among the aspects of the face often overlooked during esthetic procedures are the lips of a patient. In reality the lips create the frame for the teeth just like a picture frame does for a piece of art. I’m sure many of you have taken a photograph to a frame shop and have evaluated multiple frames to see what looks best. You’re able to note that as certain parameters of the frame are changed, so does the appearance of the artwork. This is also true for smiles.
As a general rule I evaluate two primary areas concerning the lips, the way they move, what I will call symmetry, and their thickness or fullness. It is of course in this day and age necessary to determine if the patient has any plans to alter their lips for the following evaluation to have value in planning treatment. If they do have plans to use fillers, or any other procedure that alters the lips, I would prefer they be done prior to the dental procedures.
My first evaluation begins with viewing the upper lip as it moves from rest to a full smile, is it symmetrical in its movement, or does one side rise further up then the other. Research has shown that around 30 percent of adults have some form of lip asymmetry, so it is very common. The challenge is that if one side rises further up, it means that side will show more tooth and potentially more gingival display in a full smile.
It is possible to improve this asymmetry with Botox unilaterally, ensuring the higher side doesn’t move as much, but most patients don’t choose the Botox correction. In reality what this means is that we need to simply counsel the patient about how common this finding is and that it simply means they will always have a slight asymmetry to their smile. In other words, I don’t let the upper lip asymmetry alter my tooth position choices or gingival levels.
The concept of Facially Generated Treatment Planning can greatly simplify treatment planning for wear patients. You can find more information about treatment planning, esthetics and occlusion within the Spear Digital Suite. Download the free resource:
The 8 Steps Checklist-Facially Generated Treatment Planning.
My next evaluation is to watch the lower lip move from rest to a full smile, again looking for symmetry. If the lower lip is asymmetric in its movement, it can be problematic for the tooth position ultimately chosen. As dentists we often talk about using the interpupillary line as a reference for leveling the incisal plane-occlusal plane, but the eyes are quite a distance from the edges of the teeth; it is actually quite difficult to look at the eyes and teeth at the same time. In addition it is not uncommon for a patient to have significant asymmetry in the levels of one eye relative to the other. I find the most important thing determining the incisal plane is not the interpupillary line, but the relationship of the teeth to the lower lip—a pleasing smile line if you will. The patient in Figure 1 (left) has symmetric upper and lower lips and a pleasing level smile line.
This becomes challenging if the lower lip is asymmetric, as creating what you perceive as a level occlusal plane relative to the eyes can create an unattractive smile line relative to the lower lip. In these instances the lip does alter how I position the teeth.
The patient in the Figure 2 (right) has a maxillary reconstruction with anterior veneers and posterior crowns, her lower lip has a significant asymmetry during a full smile, going up much more on the left and down on the right. My original diagnostic wax-up and provisional restorations were done parallel to her interpupillary line, but it became clear almost immediately after the provisional restorations were placed that it wasn’t a pleasing incisal plane in relation to her lower lip.
I modified the provisional, shortening the left lateral, canine and premolars until in a full smile the relationship was more pleasant. A model of the corrected provisional was then sent to the laboratory to communicate the correct tooth position. Obviously in shortening the teeth visually it is still necessary to maintain an acceptable functional relationship. The teeth don’t follow her lip exactly because the amount of lip asymmetry is too great for that, but they do have a pleasant relationship to the lip.
Learn more about lip symmetry and other related topics to help strengthen your treatment planning skills and educate your team, by using Case Assistant, as part of the Spear Digital Suite. Schedule a free one-on-one demo with a Digital Suite Advisor today.