a body for coupling to an upper dental arch, the body comprising a front stop, a rear stop, and a guide extending between the front stop and rear stop;

a threaded member configured to be coupled between the front stop and rear stop of the body and configured to rotate relative to the body;

a hook configured to be coupled to the guide, comprising a threaded passage configured to engage the threaded member, and comprising an arm configured to engage a lower dental arch, the hook configured to travel in a forward direction along the guide between the front stop and rear stop of the body in response to rotational adjustment of the threaded member to adjust the lower dental arch to an optimum position in the forward direction for a particular user's anatomy and breathing condition;

a receiver configured to be coupled to the lower dental arch, the receiver comprising a shelf extending in a rearward direction opposite the forward direction and configured to engage the arm of the hook; and

an extender configured to be coupled to the receiver and providing a shelf that is more rearward than the shelf of the receiver such that engagement of the shelf of the extender provides additional extension of the lower dental arch in the forward direction relative to engagement of the shelf of the receiver.