is it normal to not see improvement 5 days after botox injections in the masseter muscles?

Most patients will have see full effect ~7 days, but some patients will not observe full results for ~2 weeks.  Especially for a bulky muscle as the masseter, the full effect of Botox will have "kicked" in by 2 weeks, but the visible reduction in size may take up to a month.  

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.

Yes, you may see the paralysis as early as 3 to 10 days but it may take 6-8 weeks for the muscle bulk to reduce substantially.

Botox is very effective for treatment of TMJ, masseter hypertrophy, or tension in the temporalis and masseter muscles causing symptoms and headaches.  The effective dose varies quite a bit between individuals.  I usually start with 6 to 8 units in each muscle and gradually increase the dose based on patient feedback.  It takes up to 2 or occasionally 3 weeks to feel the full effect of Botox. 

Some patients begin to see results just a few days after the injections, however it is normal to not see big results after 5 days. Everything typically appears around the 2 week mark from the injections.