Inclusion Criteria:  AHI > 5 on polygraphy sufficient set of teeth to hold a splint written informed consent  Exclusion Criteria:  use of medication that could affect breathing or sleep oxygen-dependent or decompensated lung disease decompensated congestive heart failure evidence of other sleep disorders (narcolepsy, restless legs syndrome, insomnia) abnormalities of the upper airway periodontal problems and untreated caries mental disorders