What you are describing is not typical from a masseter Botox treatment. I encourage you to return to your injector to discuss your concerns. The effects of Botox are temporary and typically last three to four months, so the unwanted effects should gradually improve with time.
Botox is commonly used to help with TMJ discomfort. It helps by relaxing the affected muscles resulting in less clenching and pain. An expert injector can help treat you in the office. It takes two weeks for final results and the effects will last typically three to four months.
Botox and other neuromodulator resistance is rare but real. PDO threads for wrinkle control/reduction is a great option is this case whether you have natural or induced resistance.
