Facial Exam

Reference Midline

Midlines

In this section, we will address the positioning of the different facial and dental midlines:

• Are the facial midlines well aligned?
• Is the right and left side of the face well proportioned?
• Is the upper dental midline on?
• Is the lower dental midline on?

If a midline is deviated, make a note of how much (in millimeters) and in which direction. A reference midline is necessary to assess the amount and direction of the discrepancy.

Determination of the reference midline
The best way to assess the symmetry of a face is through the creation of a reference line in the center of the face. This reference line is usually obtained by joining two points of the face: Glabella and Subnasale. The Glabella (Gl) is the midpoint between the eyebrows and the Subnasale (Sn) is the base of the nose.
The line going through Glabella and Subnasale becomes the reference line. In a clinical setting, a piece of dental floss may be used to determine the reference midline. This line will be used to determine the alignment and symmetry of the facial structures in the transverse dimension. From this line, the general symmetry of the face will be assessed. Any noticeable variations should be noted.

Evaluation of the mandibular midline
A point is placed on the center of the chin. This point is called the soft tissue Pogonion. The Pogonion (Pg) is the most anterior part of the chin. If the soft tissue pogonion is aligned with the reference line, the mandible is centered. If this point is not on the reference line, the mandible is deviated in the direction of the point. More investigation is necessary to find out if the deviation is of functional or non-functional origin.

Determination of the upper dental midline
A point is placed between the two central incisors. If the point is on the reference line, the upper dental midline is centered. If the point is located to the left or right of the reference line then the upper midline is deviated and the direction and the amount of deviation should be noted. It is important to differentiate between the facial (Gl-Subnasale) and the upper dental midline.
Remember also that the facial and upper dental midline must be aligned at the end of treatment for an optimal orthodontic treatment.

Determination of the lower dental midline
It is easier to determine the lower midline in relation to the upper dental midline and report the findings to the reference line. Once the upper dental midline has been determined, the lower dental midline is deducted from the preceding measurement. The lower midline is mesured from the upper dental midline and also compared to the reference line. The lower midline may also be directly measured from the reference line with the help of dental floss.