Treatment goals are both facial and occlusal: facial harmony and dental aesthetics, and a healthy, stable occlusion in centric relation and in function. Examine the face at rest and in animation, from the front and in profile. Absolute measurements matter less than the proportions of the parts to one another: note any disproportion.
Natural head posture
Natural head posture is the position in which the head is held in normal function. Reproduce it by asking the patient to look straight ahead into the distance, or into a mirror at eye level. It is remarkably reproducible. It lets you judge hard and soft tissues against an extra-cranial true vertical, instead of intra-cranial planes that vary between individuals and can be distorted by the same growth anomaly you are assessing.
Frontal view
- Vertically: the face divides into thirds. The lower third divides again: the upper lip makes up one third and the lower lip and chin two thirds.
- Transversely: the face divides into fifths, each about one eye-width wide. Note any asymmetry.
Lips
Lips are competent if they meet at rest and incompetent if they are apart. Incompetence comes from an anteroposterior skeletal discrepancy or increased vertical proportions. Competence tends to improve in adolescence as the soft tissues mature.
Upper incisor show at rest should be about 3–4 mm in males and 4–5 mm in females in late adolescence and early adulthood. It decreases with age; over 90% of upper lip length is reached by age 7 in girls (Nanda et al., 1990).
The smile
Assess the smile in animation (Sarver, 2001) in three areas:
- Vertical incisor position: most of the upper incisor crown should show, without excessive gingiva. Tooth and gingival display fall with age, so keep this in mind with younger patients. The gingival margins of the central incisors and canines should sit slightly higher than those of the laterals.
- Smile width: a narrow or retrusive arch leaves a wide dark buccal corridor, but some corridor is needed or the smile looks artificial. Expansion, buccal torque and the anteroposterior position of the maxilla relative to the lips all affect it (Isiksal et al., 2006).
- Smile arc: the upper incisal edges should follow the curve of the lower lip. This consonant smile is the most pleasing (Frush and Fisher, 1958); a flat incisal line looks artificial.
Profile view
- Vertically: the face again divides into thirds. With normal vertical proportions, the Frankfort plane and the lower border of the mandible meet near the occiput.
- Anteroposteriorly: describe the dental bases relative to the cranial base and to each other, by palpation or by dropping a vertical line from the forehead through subnasale. The upper lip should lie on or slightly in front of this line and the chin point just behind it. The maxillary dental base should sit about 4 mm in front of the mandibular base.
Soft tissues of the lower face
- Lip protrusion: lips are described as protrusive if they lie in front of the line from nose tip to soft-tissue chin (Ricketts' E-line). They become less protrusive with age.
- Nasolabial angle: between the upper lip and the base of the nose. It should be 90–110°, but it depends on the shape of the nose. In practice, the upper lip drape should be parallel to the true vertical (Arnett and Bergman, 1993), and so should the labial face of the upper incisors.
Temporomandibular joints
Examine both joints for clicking, crepitus, pain, locking or limited opening.
TMD is very common and multifactorial. Some occlusal traits (anterior open bite, deep overbite, large overjet, posterior crossbite with displacement) show only a weak association with TMD (Egermark-Eriksson et al., 1983; Mohlin et al., 2007). There is no evidence that orthodontics treats TMD (Luther et al., 2010), nor that it causes or worsens it, including extraction treatment (Egermark et al., 2005; Hirsch, 2009). Record joint findings before treatment.
Main source: Cobourne MT, Fleming PS, DiBiase AT, Ahmad S. Clinical Cases in Orthodontics. Wiley-Blackwell, 2012, chapter 1. Specific references as cited in the text.