Abstract: An orthopedic/orthodontic appliance for treating neuromuscular imbalance which interrupts balanced myofacial growth and development which includes mandible fixation means for maintaining the mandible of the user in an essentially neuromuscularly balanced position when the mouth is closed. The appliance also includes a pressure equalization conduit extending from a position exterior the lip seal of the user to a position in the posterior of the oral cavity which is in fluid communication with the pharyngeal cavity so that the pressure in the user's pharyngeal cavity is equalized to the ambient pressure outside the head while the user's mandible is maintained in the essentially neuromuscularly-balanced position.