Will my jaw return to normal after Botox?

The full effects of Botox will resolve in 3 to 4 months. In some cases it could last up to 6 months. But expect resolution somewhere between the 3rd and 4th month. 

Botox to the masseter muscles can help to narrow the face and help with grinding of the teeth.  Any side effects, such as changes to the smile, should resolve completely over time.  It could take a few months for this to occur however.