Unexpected TMJ responses to functional jaw orthopedic therapy

Area of Science:

• Orthodontics
• Temporomandibular Joint (TMJ) Disorders
• Craniofacial Orthopedics

Background:

• Functional jaw orthopedic (FJO) appliances like the Herbst, Bionator, and Fränkel are increasingly popular for treating mandibular growth and TMJ issues.
• A key goal of FJO appliances is to prevent posterior condylar displacement and anterior disk displacement, by repositioning the condyle anteriorly.
• Radiographic monitoring is used to assess changes in condylar position during FJO treatment.

Observation:

• Despite the intended anterior repositioning of the condyle by FJO appliances, TMJ responses are not always predictable.
• Three case histories revealed unexpected TMJ responses where condyles remained posteriorly displaced post-treatment.
• This unexpected outcome occurred in only 2% to 3% of the author's patient cases.

Findings:

• TMJ responses during FJO treatment can be complex and unpredictable.
• Even with appliances designed to reposition the condyle, posterior displacement can persist.
• No specific physiologic mechanism explains these unexpected TMJ responses.

Implications:

• The complexity of the TMJ necessitates careful consideration during orthopedic treatment.
• No single FJO appliance guarantees efficacy for all TMJ treatment goals.
• Clinicians should be aware of potential unpredictable TMJ responses despite appliance use.