Is it bad to jut the mandible foward?

Can be: Best to let it relax in the natural position. Jutting it forward puts strain on the muscles and ligaments and can cause muscle hypertrophy which may alter your facial appearance. If your lower jaw is set back, see the Orthodontist and Oral Surgeon to learn your options. Good Question. Good Luck.

Undesirable habit: Thrusting the jaw forward forces the TMJs out of their sockets. When the jaw is placed in a forward position, undesirable tension in the submandibular region (lateral pterigoid muscle ) See an Orofacial Pain practitioner for habit evaluation and any underlying psychological or emotional cause for this excessive tension.

Could be: Could cause problems with your jaw joint or jaw muscles. If you do this because of your bite, see orthodontist for evaluation.