The upper jaw. The maxilla is an irregularly shaped bone of the mid-face that is a major component of the skull. Its bony structure includes the hard palate that contains the upper teeth, part of the eye sockets, and the nasal cavity including the maxillary sinus. The maxilla may be less developed or recessed. As a result, the upper teeth may be set back (underbite) and the bone structure of the nose may be less prominent. This anatomical variation may contribute to sleep-disordered breathing, including snoring and sleep apnea. Surgical correction may be accomplished with jaw surgery called maxillomandibular advancement. In children, these conditions may be treated with an orthodontic treatment called rapid maxillary expansion. This involves a butterfly brace placed on the roof the mouth with gradual adjustment to spread the hard palate, resulting in a wider smile and improved airflow through the nose.