Effects of orthognathic surgery for class III malocclusion on signs and symptoms of temporomandibular disorders and on pressure pain thresholds of the jaw muscles.

The aim of this longitudinal study was to determine the effects of orthognathic surgery on signs and symptoms of temporomandibular disorders (TMD) and on pressure pain thresholds (PPTs) of the jaw muscles. Fourteen consecutive class III patients undergoing pre-surgical orthodontic treatment were treated by combined Le Fort I osteotomy and bilateral sagittal ramus osteotomy. The clinical examination included the assessment of signs and symptoms of TMD and the assessment of PPTs of the masseter and temporalis muscles. Anamnestic, clinical and algometric data were collected during five sessions over a 1-year period. Seven out of 14 patients presented with disc displacement with reduction at baseline, whereas four patients (two of them were new cases) did so at the end of follow up (p>0.05). None of the patients were diagnosed with myofascial pain of the jaw muscles at the beginning or end of follow up. PPTs of the masseter and temporalis muscles did not change significantly from baseline values throughout the whole study period. The occurrence of signs and symptoms of TMD fluctuates with an unpredictable pattern after orthognathic surgery for class III malocclusions.