When do you usually start to feel the effects of square jaw Botox?

Lately, when I take photos, the lower part of my face feels wider than before, so I am looking into Botox or fillers. In particular, my jaw muscles tend to protrude quite a bit when I clench my teeth, so I am considering getting square jaw Botox.

I looked it up and heard that square jaw Botox doesn't make your face slimmer immediately after injection, but rather the effects appear over time. I am curious how many weeks it actually takes to notice changes after the procedure. I would also like to know if I can see some degree of line shaping effect even if I have a bit of facial fat.

I am also curious about the dosage when getting square jaw Botox for the first time. I have read that getting too much can cause the cheeks to sink in or make chewing uncomfortable, so I am a bit worried about getting a high dose right from the start. I am also wondering if the dosage is adjusted during the consultation based on my face shape and muscle size.

I would like to know how long the effects of square jaw Botox usually last and how long to wait before getting the next injection. My chin is on the shorter side, so I understand that some people get fillers along with it if needed, but I am wondering if it would be okay to try just the Botox first before deciding. For those who have received this treatment, please share your experiences and tell me when you noticed a change in your facial contours.