Sleep Apnea is a condition in which the airway closes repeatedly during sleep, interfering with breathing. Snoring is often associated with sleep apnea because it results from a partial closure or blockage of the airway. The sound of snoring is actually the vibration of air traveling through a partially obstructed airway. In sleep apnea, the airway is not just partially obstructed but it is completely closed for ten seconds or longer. Pauses in breathing are normal throughout the night, but the condition of sleep apnea is characterized by these events occurring much more frequently, sometimes 20, 30, or 50 times per hour or more.

The result is that someone suffering with sleep apnea may "sleep" for 8 or 10 hours per night, but in reality, they are holding their breath for much of the time. With sleep apnea it is common to awaken feeling unrefreshed, and often to experience headaches or excessive sleepiness during the day. Over time people become accustomed to these patterns. Most people who have sleep apnea are not even aware they have it, because it only occurs during sleep.

Dentists can identify patients that may be at risk for sleep apnea. However, dentists cannot make a diagnosis; sleep apnea is a medical condition that can only be diagnosed by a physician, usually a specialist board certified in sleep medicine. A diagnosis of sleep apnea traditionally has been made based on an overnight polysomnogram. This test is conducted in a sleep laboratory and provides the data that physicians use to diagnose not only sleep apnea but a range of other sleep disorders. Snoring is often indicative of sleep apnea; almost everyone who has sleep apnea snores, but many people snore and do not have sleep apnea. Sleep study data help physicians determine the presence and severity of sleep apnea.

The Apnea Hypopnea Index (AHI) is the number of times per hour that the airway collapses, in duration of at least 10 seconds each, during sleep. Snoring, even severe loud snoring events do not count towards this number, because during a snore the air is still moving through the airway, even though it is partially obstructed. Up to 5 events per hour is considered in the normal range and does not require treatment. Between 5 -14 events per hour is considered mild obstructive sleep apnea; 15 - 29 events is moderate; and 30 events or more per hour is considered severe.