Does the Masseter Return to Its Full Former Size Once Botox Wears off in That Area, or Does It Take Time to "Build Up" Again?

I am not aware of any study investigating the time in which it takes for the volume of the masseter muscle to regain its orginal size after Botox wears off, and determining whether this would take more time if someone has maintained treatment for a long while vs. just having one treatment. An expert in this treatment, such as an ENT physician, Dr. Andrew Blitzer, NYC, who deals with TMJ syndrome (jaw clenching) has a great deal of clinical experience about this treatment and has communicated with me that the masseter muscle returns to full volume in 4 to 6 months, the time depending on the dose used and the extent of atrophy the muscle developed initially after treatment.

Botox weakens the masseter, which results in a slow atrophy of the muscle.  Once the botox wears off and the masseter regains its strength, it will bulk up again.  This takes time.  How much time depends on how atrophic the muscle is, as well as whether the patient clenches or grinds the teeth or chews gum.  These habits make the muscle bulk up more quickly.

Thank you for your question. Botox in the masseter region usually takes longer than in the standard areas to take effect. I tend to use anywhere from 15 units (conservative treatment) to 50 units (for someone with really strong masseters) on each side to get the desired result. It may start within the first week but I tell my patients to wait three weeks before doing a more thorough evaluation. The treatment typically lasts longer than the forehead/crows feet/frown regions. It is also a gradual onset of the return of masseter function. I have tried the masseter injections myself and space the treatments around 4 months apart, but use smaller doses to maintain the effect. I normally know the effects are wearing down when I start to clench my teeth more heavily at night when asleep.  Once you stop using Botox, the masseter muscles will return to their original baseline when the effects of Botox  wears off completely.