An intra-oral device used for people that snore or have sleep apnea is designed to move a user's lower jaw forward relative to the user's immovable upper jaw and to prevent the user's mouth from inadvertently opening while sleeping. The device includes upper and lower appliances fitted to the user's respective upper and lower dental arches. The lower appliance possesses a partially embedded bracket. An adjustment element is integrated into the upper portion of the bracket. With the user's mouth closed and the upper and lower appliances positioned over the user's respective dental arches, the adjustment element is moved rearward by worm action into load bearing contact against the forward facing immovable vertical contact wall of the upper appliance. This action moves the lower appliance forward, and thus, the user's lower jaw with its anatomically attached tongue are also moved forward relative to the mouth which in turn opens the user's airway. Also, a forward facing horizontal shoulder positioned at the lowest portion of the vertical contact wall acts against the adjustment element to prevent the user's mouth from opening while sleeping.