Botox or Dysport both work equally well in decreasing the muscle mass of the jaw muscle called the masseter. This procedure is very safe. I have never had any serious issues with this use. The amount of botox or dysport to use is dependent on the person because everybody has different responses and different volume of muscle. I usually tell this to people and then explain that I recommend starting at a lower dose like 15-25 units of botox for each side. Dysport requires 2.5 to 3.0 times the units of botox for equivalent dosing. Then I tell them that they can see if this adequate muscle relaxation in 2 weeks for botox and 1 week for dysport. If there is still significant muscle movement of the masseter you can elect to do more. One important point is that the muscle mass reduction lags behind the muscle movement. It takes from 3-5 months to see the maximum volume changes in the masseter muscle and then it slowly increases the mass to normal by one year. So, in short, there are some doctors that are seeing results from botox to the jaws for one year. In my experience, the mass usually comes back earlier than this but the results are more longer lasting than what can be expected with other facial muscles.
Thanks for reading, Dr Young
Dr Young specializes in Facial Plastic and Reconstructive Surgery and is located in Bellevue near Seattle, Washington