Cephalometrics and the Restorative Connection Part One: Soft Tissue Profile

As dentists we are trained to look at teeth and evaluate how they fit and function together. We are comfortable with casts in our hands, putting them together, turning them over, rotating them right and left, mimicking the patient's movements. We carefully check the dental relationships, the overbite and the overjet, looking for wear patterns, cracks, fissures and poor margins. Quickly our thoughts slip to what could be done to improve health and function.

Photography portrays another entire dimension to evaluating our patients' issues and concerns. Photos allow us to see the teeth in the face to understand the framework in which the dentition functions. Facial photos of the smile and lip at rest, we have learned, are essential to visualize how the teeth live in the facial framework. The dentition and occlusion details become remarkably focused when we review the photos of the teeth together and apart.

Finally, when you routinely include the facial profile photo in your treatment planning evaluation, it provides an important but often overlooked third dimension to the framework within which the teeth must function. The profile is commonly used to judge esthetic outcomes in dentistry, particularly in orthodontic and combined orthodontic and surgical treatments. A restorative dentist should be equally diligent to evaluate the results of restorative treatment on the profile esthetics. Being confident that the treatment plan will be favorable to the profile is a strong component in planning the treatment options.

The natural head position

Let’s look at what information can be found within the profile photo. When we take our profile photos, the patient's head position is an important consideration. Just as we consider the horizon in the frontal photos, using the pupils as a guide to a level head position, the profile photo has it own orientation. Looking straight ahead – far out at the horizon or as if looking into your eyes in a mirror – produces the natural head position (NHP). This will orient the profile for gathering some helpful information for treatment planning.

The natural head position has proved to be more reliable and repeatable, which is an important factor when you want to compare serial photographs during treatment. In Figure 1, this profile photo was taken in repose, with the patient looking out at the horizon. We can begin to evaluate for esthetic concerns that could affect our treatment plan. The facial profile angle uses the upper facial height measured from glabella, the most prominent point on the forehead to subnasale, at the base of the nose; and the lower facial height measured from subnasale to chin point.

The inner angle that is formed should be in the range of 165 to 175 degrees. The greater the angle beyond 175 degrees, the more prominent the chin position. This can also be an indication of Class III growth. In our Figure 1 example, the angle is 178 degrees. The higher angle measurement indicates a straight profile; the chin is in a more forward position than average and there is the potential for a Class III skeletal pattern. In Figure 2, the angle decreases to 160 degrees. This is an indication of a more retrognathic skeletal pattern.

The esthetic plane

Another measurement that can assist you in your esthetic treatment planning is evaluating the relative protrusion or retrusion of the lips. As our esthetic treatment planning always begins with the position of the upper central incisor, its horizontal position in profile is going to directly affect the upper and lower lip position.

The esthetic plane (“E Plane”) is based on Ricketts’ (1968) analysis and is shown in Figure 3. It is an indication of the relaxed lip position relative to the nose and chin. Ricketts states that the lower lip should be 2 mm behind the E plane for an adolescent and 4 mm for an adult. The upper lip in both adults and adolescents should be just slightly posterior to the lower lip – as seen in Figure 3. Deviation from that standard can give you direction for your restorative plan. In Figure 4, the lower lip is posterior to the upper lip, and your plan options should include considerations to move closer to the standard.

The subnasale-pogonion plane

Burstone (1967) has also described the importance of lip posture when treatment planning, specifically noting that the relaxed lip posture is important to accurate evaluation. The lip-at-rest photo position should be duplicated in the profile-rest photo as well. This means the lips have no contraction of lip musculature and lips are lightly separated. Burstone recommends using the subnasale-pogonion plane as the more stable reference plane as compared to Ricketts’ esthetic plane. If you are treating a growing patient, the nose will change significantly over the planned treatment time. An adult patient, however, has much slower changes to the nose position during the restorative treatment time.

The lips should fall forward of the subnasale-pogonion line; the upper lip 3.5 mm ahead and the lower lip 2.2 mm ahead, according to Burstone's study. (Figure 5)

When the lips fall behind the subnasale-pogonion line, methods of advancing the upper incisor position could be considered in your treatment plan. (Figure 6)

Let’s use Figure 7 as a treatment planning example. Evaluating the lip position indicates the treatment plan can afford to have some retraction of the lips when the excess protrusion to the subnasale-pogonion line is noted. The finished treatment shows a lip position more within the standard range. (Figure 8)

Applying cephalometrics

You are no doubt recognizing that the upper incisor has a strong affect on the lip posture, and so its horizontal position becomes as equally an important factor in your restorative plan as the vertical position of the central incisor. As with all measurements, care must be taken to recognize that these are guidelines for treatment planning, not absolute markers or goals. The goal should be to enhance the esthetic position of the lips with the restorative treatment as much as possible. Your dentistry alone may not be a significant influence to the lip position in the E Plane or subnasale-pogonion line. However, when you visualize the lip position in profile, it can guide you in the correct direction that will maximize the best lip support rather than compromise the esthetic results in the treatment options.

With the addition of the facial profile and applying the “soft tissue cephalometrics” in your treatment planning, you can find useful guidelines from this valuable third dimension in treatment planning esthetics.

(Click this link to read more dentistry articles by Dr. Donna Stenberg.)

Donna J. Stenberg D.D.S., M.S., P.A., Spear Visiting Faculty and Contributing Author - djstenbergdds@gmail.com

References

Arnett G. W., Jelic J. S., Kim J., et al. Soft tissue cephalometric analysis: diagnosis and treatment planning of dentofacial deformity. American Journal of Orthodontics and Dentofacial Orthopedics. 1999;116(3):239-253.

Arnett G. W., Bergman R. T. Facial keys to orthodontic diagnosis and treatment planning. Part I. American Journal of Orthodontics and Dentofacial Orthopedics. 1993;103(4):299-312.

Legan H. L., Burstone C. J. Soft tissue cephalometric analysis for orthognathic surgery. Journal of Oral Surgery. 1980;38(10):744-751.

Arnett G.W. Facial keys to orthodontic diagnosis and treatment planning, Parts I and II. American Journal of Orthodontics and Dentofacial Orthopedics. 1993; 103(4):299-312 and 395-411.

Ricketts R.M. Esthetics, environment and the law of lip relationship. American Journal of Orthodontics and Dentofacial Orthopedics. 1968; 54(4):272-289.

Burstone, C. J. Lip posture and its significance in treatment planning. American Journal of Orthodontics and Dentofacial Orthopedics. 1967; 53(4):262-284.