1. Evaluate the analgesic effect of 30 mg duloxetine twice daily in comparison to matching placebo at baseline (BL) and follow up over a six week period using the primary outcome measure of change in spontaneous pain. 2. Evaluate jaw functioning and evoked pain as measured by range of motion, pain with jaw movement, and pain pressure thresholds. 3. Assess frequency of adverse effects and their impact on patient global satisfaction and study adherence. 4. Examine sleep in relationship to pain. 5. Evaluate genetic susceptibilty to pain and response to duloxetine.