TMJ has returned 3 months after 25 units of Botox to masseter muscle. How long until the masseter muscles begin to reappear?

Botox results resolve in 3-4 months. Botox combined with radiofrequency can reduce the masseter. See an expert. Best, Dr. Emer

Botox typically takes 3-4 months to return,  With such a high but appropriate dose for masseter reduction I expect you to start seeing the return month 4 or 5.

Botox weakens the masseter and does not make it disappear so the return of the TMJ means it has worn off and can be repeated and if you want  filler it can also be done

Neuromodulator treatments like Botox and Dysport are temporary lasting 3-4 months on the upper face and 4-6 months for the masseters. The treatments need to be repeated to maintain results. Since your results lasted 3 months, you need to get your masseters injected with Botox every 3 months or 4 times a year. 

The fact that your TMJ has returned 3 months following the treatment using Botox, indicates that your body breaks down Botox within the masseter muscle in approximately 3 months. The masseter muscle does not disappear and return, it's simply retains its strength after the botox wears off. You should put yourself in a regular schedule of Botox injections every 3 months and I'm sure this will help you a great deal. Good luck from New York City