1/Mesofacial(標准臉型): A Class I occlusion presents with normal musculature and a pleasant ovoid facial appearance. The face is neither too long nor too wide and is associated with a similar jaw structure and dental arch configuration.
2/Dolichofacial(长脸型): This type of face is long and narrow and is associated with either a Class II division 1 or a Class III malocclusion. The dental arches in these relationships are also narrow and may be associated with a "high" palatal vault. (高拱形的上颚穹隆)
Because of the narrow nasal airway in these patients, they are likely to be "mouth-breathers" (口呼吸)and cause a narrowing of the maxilla due to the abnormal forces placed on the upper jaw structure by the buccinator musculature.
Because these patients keep their mouths open to breathe, there is a tendency for the posterior teeth to supra-erupt causing the mandible to grow in a vertical direction and creating a skeletal open bite.
Also, due to the small mandibular ramus, the masseter muscle on these individuals is also small, and the occlusal forces are weak. This may allow the posterior teeth to erupt more than normal with a concomitant anterior bite opening.
Because of the skeletal and muscular imbalance associated with this facial type, the associated malocclusions are the most difficult to treat orthodontically.
3/Brachyfacial(短脸型): This facial structure is short and wide and is usually seen in a Class II division 2 type of malocclusion. The arch configuration associated with this facial type is also relatively broad and square.
Patients of this facial type are very rarely mouth-breathers because of the relatively wide nasal airway. The mandibles of this facial type are broad and "square" with a large masseter muscle and strong occlusal forces.
Because of the latter, posterior teeth are often infra-erupted causing a skeletal "deep bite." Therefore, the mandible becomes "over- closed," and these patients are often prone to temporomandibular joint problems. Treated early, however, malocclusions associated with this facial type have a good prognosis due to favorable mandibular growth.