Simply a Class III malocclusion is one with a strong, protruding chin, or a deficient, small, upper jaw. Typically, the treatment protocol is the use of a chin cap, or facemask (shown above). Recently, Ngan1 and Ngan et al.2 have described treatment outcomes of Class III patients with maxillary (upper jaw) deficiency with facemask therapy in conjunction with maxillary expansion. The effects are:

1. Positive overjet-forward movement of the maxilla
2. Backward and downward movement of the mandible
3. Proclination of the maxillary incisors
4. Retroclination of the mandibular incisors

Mitani3 responded to two questions in regards to orthopedic changes from chin cap therapy.

1. "Is it possible to inhibit or retard growth of the mandible with chincap force?"
Presumably, chincap force can retard the mandibular form and condylar growth; these changes occur mainly during the first 2 years of chincap use.

2. “Can chincap therapy permanently correct a prognathic skeletal pattern?"Mandibular chin position will be greatly improved anteroposteriorly during the initial stage (approximately 2 years) of chincap therapy, the changes do not take place continuously after that, and the initial changes will not be maintained if chincap use is discontinued before facial growth is complete. Some vertical development of the maxilla might be inhibited.

In conclusion, Turpin4 cautions: Don’t expect total success in a high percentage of patients in the long term. If disharmony is severe, delay treatment until you have proof that growth has ceased and include orthognathic surgery as a treatment option.

REFERENCES:

(1) Ngan P. Biomechanics of maxillary expansion and protraction in Class III patients. Am J Orthod Dentofacial Orthop 2002;121:582-3.

(2) Ngan PW, Haag U, Yiu C, Wei SHY. Treatment response and long-term dentofacial adaptations to maxillary expansion and protraction. Seminar Orthod 1997;3:255-64.

(3) Mitani H. Early application of chincap therapy to skeletal Class III malocclusion. Am J Orthod Dentofacial Orthop 2002;121:584-5.

(4) Turpin Dl. Early treatment conference alters clinical focus. Am J Orthod Dentofacial Orthop 2002;121(4):335-6.