CPAP vs Oral Appliance Therapy:

Obstructive sleep apnea (OSA) occurs when the upper airway collapses or becomes unstable during sleep. The body continues to make an effort to breathe, but airflow is partially or completely blocked.

This collapse typically involves soft tissues of the throat, including the tongue and surrounding pharyngeal structures. During inspiration, negative pressure within the airway can further narrow an already unstable airway, contributing to repetitive obstruction.

When airflow is reduced (hypopnea) or stopped (apnea), oxygen levels may decline, carbon dioxide levels may rise, the brain briefly arouses the body from deeper sleep, and the sympathetic nervous system (“fight-or-flight”) activation increases.

These repetitive arousals result in a fragmented sleep architecture and may contribute to daytime fatigue, cognitive changes, cardiovascular strain, and metabolic stress. People sometimes refer to these symptoms with different terms like low-energy, daytime sleepiness, morning headaches, unrested, brain fog, memory issues, heart issues, high blood pressure, and diabetic issues.

OSA is fundamentally a mechanical and structural airway problem, even though its effects are systemic.

Central sleep apnea differs significantly from obstructive sleep apnea.

In central apnea, there is a temporary pause in breathing because the brain does not send the appropriate signal to the respiratory muscles. In other words, there is no respiratory effort during the event.

This is not caused by airway collapse, as in OSA.

Central sleep apnea may be associated with:

Heart failure

Neurologic conditions

Certain medications (including opioids)

High altitude exposure

Complex sleep apnea syndromes

Because the mechanism is neurologic rather than structural, oral appliance therapy does not treat central sleep apnea.

Identifying whether events are obstructive, central, or mixed is one reason proper sleep study interpretation by a physician is essential before selecting treatment.

The Apnea-Hypopnea Index (AHI) is the number of apneas (stopped airflow) and hypopneas (reduced airflow) that occur per hour of sleep. AHI is commonly used to classify severity:

Mild: 5–14 events per hour

Moderate: 15–29 events per hour

Severe: 30 or more events per hour

Because it is one of the metrics people most often ask about, AHI is being highlighted here. And it is a very important metric. But it is not the whole story. Some things AHI does not fully describe. We’ll use the examples of Paul and Tim to help you understand the significance.

Depth of oxygen desaturation. Paul and Tim both had AHIs of 8, meaning they had 8 apnea/hypopnea events per hour, which categorizes both of them as “mild.”

Paul had 8 apneas/hypopneas that dropped him from 96% to 90% oxygen desaturation. Tim had 8 events that dropped him from 98% to 82%. While these men both had the same number of events, these events were very different for Paul and Tim. The effects on Tim will be significantly different—the event will put a greater strain on his cardiovascular system, increase his sympathetic activation, and will be associated with higher long-term health risk, even though his AHI is technically “mild,” just like Paul’s.

Duration of individual events. In order to qualify as an AHI event, an event has to last at least 10 seconds. Paul had events that lasted between 11-15 seconds each. Tim had events that lasted 45-55 seconds each. You can imagine that longer events mean prolonged oxygen deprivation and stronger stress responses for Tim. The physiologic burden of one longer AHI can even be more significant than a number of multiple, shorter AHIs.

On another note, it’s also a possible scenario that Megan had 50 events that lasted between 5-8 seconds. But because none of her events lasted the minimum threshold of 10 seconds, she recorded 0 (ZERO!!!) AHI events. This poses a different complication that I’ll write more about in a different post. But while her AHI score might be excellent, she may be waking up each morning feeling like she isn’t rested—because she’s NOT. More on this later.

Sleep fragmentation patterns. Many respiratory events cause micro-arousals without dramatic oxygen drops. These repeated arousals fragment sleep architecture, which will result in reductions in restorative slow-wave and REM sleep. AHI doesn’t quantify how disrupted the sleep cycle becomes. So patients may have “mild” AHI but SEVERE sleep fragmentation—again leading to feeling profoundly unrefreshed when waking up in the morning.

Even when AHI appears modest or low, poor sleep quality can still exist, especially in upper airway resistance patterns. More on this on another post as well.

Symptom burden. AHI is a numerical index. It does not measure how the patient actually feels. Some individuals with low AHI experience significant daytime fatigue, cognitive fog (“brain fog”), headaches, bruxism (teeth grinding), mood changes, or TMJ strain. Others with higher AHI may report fewer subjective complaints. Clinical impact is not always proportional to event frequency. This is why treatment decisions should consider functional symptoms and not just the index score number.

Cardiovascular impact. AHI does not directly measure blood pressure spikes, heart rate variability changes, arrhythmogenic stress (stress from irregular heart rhythms), or endothelial (inner lining of blood vessel) dysfunction triggered during events. Repeated surges in sympathetic nervous (“fight-or-flight”) system activity can occur even in cases categorized as “mild.” Oxygen variability and arousal patterns contribute to cardiovascular strain beyond what AHI alone reflects. This is complex because cardiometabolic risk is influenced by the physiologic stress response to events, not just the pure number of events.

AHI severity classification helps guide treatment discussions, but individualized assessment remains very important. This highlights the importance of sleep studies. PSGs (polysomnographs, or “in-lab” studies) are capable of capturing some of these other factors; HSTs (“home sleep test” studies) will capture less than PSGs but are also able to capture some of those factors. Other factors, like symptom burdens, are noted through interviews, questionnaires, and discussions between patients and professionals.

Continuous Positive Airway Pressure (CPAP) therapy uses air pressure to act as a pneumatic “splint,” preventing airway collapse during sleep.

By maintaining positive pressure, the airway remains open, obstructive events are reduced, and oxygen stability improves, which hopefully results in decreased sleep fragmentation.

CPAP is often considered first-line therapy, particularly in moderate to severe OSA and in patients with significant oxygen desaturation.

It can also be appropriate in cases involving central apnea or mixed apnea patterns, depending on physician evaluation.

When tolerated and used consistently, CPAP is highly effective.

Oral appliance therapy uses a custom-fabricated, adjustable device that gently advances the lower jaw (mandible) during sleep.

By repositioning the mandible forward, airway diameter may increase by relieving the compression from the base of the tongue (by shifting the tongue forward with the jaw), pharyngeal collapse may decrease, and airway stability may improve.

Oral appliances are most effective in appropriately selected patients with obstructive sleep apnea.

They do not treat central sleep apnea.

Effectiveness should be confirmed with follow-up sleep testing after titration to ensure that AHI and oxygen parameters have improved to acceptable levels.

Treatment selection is a very individualized process and depends on multiple factors.

CPAP may be preferred when:

• OSA is moderate to severe

• Oxygen desaturation is significant

• Central apnea components are present

• Structural advancement is unlikely to sufficiently reduce obstruction

Oral appliance therapy may be appropriate when:

• OSA is mild to moderate

• The patient cannot tolerate CPAP

• The patient declines CPAP after informed discussion

• Airway anatomy suggests favorable response

• Positional or supine-dependent OSA is present

In some cases, combination therapy or alternative approaches may be discussed under physician guidance.

Sleep apnea management is not about choosing sides between devices.

It is about understanding: the type of apnea present, severity metrics (including AHI), oxygen stability, patient tolerance, and long-term monitoring.

Oral appliance therapy can be an excellent option for properly selected patients with obstructive sleep apnea. CPAP remains an important (and often first-line) therapy in many moderate to severe cases.

At REST Dentistry, our approach to oral appliance therapy is to provide medically appropriate care—not a one-size-fits-all solution.

If you are in the Vancouver, WA or Portland, OR area and would like to better understand your diagnosis or treatment options, learn more about our process or call our team and we’ll help guide the next steps within a medically supervised framework.

Professional Guidance:

Clinical guidelines from sleep medicine and dental sleep medicine organizations recognize oral appliance therapy as an appropriate treatment for selected patients with obstructive sleep apnea, particularly in mild to moderate cases or when CPAP is not tolerated. CPAP remains first-line therapy in many moderate to severe cases. Proper diagnosis, physician interpretation of sleep studies, and follow-up testing are essential components of responsible care.