• Sleep apnea and sleep measured by polysomnography [ Time Frame: Baseline and after 4 months ] [ Designated as safety issue: No ]
  
• Daytime sleepiness and sleep apnea symptoms assessed in questionnaires and objective testing [ Time Frame: Baseline and after 4 months ] [ Designated as safety issue: No ]
  
• Quality of life [ Time Frame: Baseline and after 4 months ] [ Designated as safety issue: No ]
  

• Headaches [ Time Frame: Baseline and after 4 months ] [ Designated as safety issue: No ]
  
• Blood pressure [ Time Frame: Baseline and after 4 months ] [ Designated as safety issue: Yes ]
  
• Vigilance [ Time Frame: Baseline and after 4 months ] [ Designated as safety issue: No ]
  
• Markers of stress [ Time Frame: Baseline and after 4 months ] [ Designated as safety issue: No ]
  
• Markers of inflammation [ Time Frame: Baseline and after 4 months ] [ Designated as safety issue: No ]
  
• Markers of cardiovascular health and oxidative stress [ Time Frame: Baseline and after 4 months ] [ Designated as safety issue: No ]
  
• Side-effects from the treatment [ Time Frame: After 4 months treatment ] [ Designated as safety issue: No ]
  
• Predictors of effects on symptoms and sleep apneas [ Time Frame: After 4 months treatment ] [ Designated as safety issue: No ]
  

Mandibular repositioning appliances for the treatment of snoring and sleep apneas are increasingly used over the world, although the number of prescriptions of this therapy varies between countries. The appliance widens the upper airways during sleep in order to reduce sleep-disordered breathing. The device is easy to use and has become popular among patients. Despite this, the evidence for effects of this treatment is not very strong and based on only a few studies. The aim of this study is therefore to test the hypothesis that a mandibular repositioning appliance reduces sleep apneas, daytime sleepiness and other sleep apnea symptoms and increases the quality of life in sleepy patients with mild to moderate obstructive sleep apnea and in patients with symptomatic snoring. Secondary outcomes include effects on headaches, blood pressure and markers of stress, inflammation, cardiovascular health and oxidative stress. At baseline and after 4 month's treatment, the patients will respond to questionnaires about symptoms and quality of life. They will undergo measurements of sleepiness, sleep apneas and blood pressure as well as sampling of saliva, urine and blood. Factors that predict a successful treatment outcome will be analyzed in order to more exactly clarify the indications for this treatment modality in a group of patients who have been suggested to benefit from mandibular repositioning appliances according to previous studies and reviews.

Inclusion Criteria:

• Obstructive sleep apnea, apnea-hypopnea index of <30 with excessive daytime sleepiness
• Snoring with excessive daytime sleepiness, apnea-hypopnea index of <5
• Body mass index of <35

Exclusion Criteria:

• Unable to give informed consent
• Psychiatric disorders including dementia that may interfere with the study protocol
• Other concomitant diseases that demand acute, effective treatment of sleep apnea
• Pharyngeal soft tissue abnormalities
• Living to far away from the University Hospital
• Professional drivers
• Pregnancy
• Included in other studies
• Other sleep apnea treatments
• Severe craniomandibular disorders
• Acute or advanced periodontal disease
• Insufficient number of teeth