9.1 Oral Appliance Therapy: Indications, Candidacy & Side Effects

9.1 Oral Appliance Therapy: Indications, Candidacy & Side Effects

Quick Answer: Oral Appliance Therapy (OAT) is an established non-PAP treatment for obstructive sleep apnea (OSA). Mandibular Advancement Devices (MAD) mechanically advance the mandible and attached suprahyoid structures anteriorly to enlarge the retroglossal airway and reduce pharyngeal collapsibility (lowering critical closing pressure, Pcrit). Tongue Retaining Devices (TRD) utilize negative suction to secure the tongue forward, serving edentulous patients. Under the 2015 joint AASM/AADSM guideline, sleep physicians should consider a custom, titratable oral appliance, rather than no treatment, for adults with OSA who cannot tolerate CPAP or prefer an alternative. Candidacy requires evaluation by a qualified dentist, enough healthy teeth to anchor the device (often cited as about 8–10 per arch) and adequate jaw protrusion (typically 8–12 mm). Follow-up objective sleep testing (PSG or HSAT) with the appliance in place is mandatory because subjective symptom resolution does not reliably guarantee objective AHI control.

While Continuous Positive Airway Pressure (CPAP) remains the primary treatment for obstructive sleep apnea across all severity categories, real-world effectiveness is frequently hindered by non-adherence. Oral appliances provide a clinically validated alternative that expands upper airway caliber through mechanical repositioning of craniofacial tissues.

Biomechanical Mechanisms of Action

Pharyngeal collapse during sleep occurs when negative intraluminal inspiratory pressure exceeds pharyngeal dilator muscle tone. Oral appliances modify upper airway anatomy through two distinct biomechanical mechanisms:

1. Mandibular Advancement Devices (MAD / MAS)

Mandibular advancement devices (also termed mandibular advancement splints) are custom-fabricated, dual-arch appliances that fit over the maxillary and mandibular dentition:

• Retroglossal Airway Expansion: Forward translation of the mandible exerts anterior traction on the attached genioglossus, geniohyoid, and mylohyoid muscles, pulling the tongue base away from the posterior pharyngeal wall.
• Retropalatal Stabilization: Forward mandibular displacement indirectly tensions the palatoglossus muscle and soft palate, increasing the anteroposterior diameter of the velopharynx.
• Lateral Wall Stiffening: Inferior and anterior displacement stretches the stylopharyngeus and palatopharyngeus muscles, stabilizing the lateral pharyngeal walls against dynamic collapse.
• Pcrit Reduction: By mechanically pre-tensioning pharyngeal tissues, MADs shift the pharyngeal critical closing pressure (Pcrit) toward more negative pressures, preventing inspiratory airway collapse.
• Custom vs. Non-Custom Appliances: AASM/AADSM clinical guidelines specify that patients should receive custom-fabricated, adjustable appliances rather than non-custom, over-the-counter ("boil-and-bite") devices. Over-the-counter appliances demonstrate poor retention, high discontinuation rates, cannot be titrated, and exert erratic orthodontic forces that cause rapid, adverse dental shifts.

2. Tongue Retaining Devices (TRD)

Tongue retaining devices feature a custom or prefabricated silicone bulb that rests between the lips and anterior teeth:

• Mechanism: The patient inserts the tongue into the bulb and creates negative suction. The bulb holds the tongue forward throughout sleep without requiring mandibular advancement.
• Indications: TRDs are indicated primarily for edentulous patients, individuals with severe periodontal disease lacking sufficient anchoring teeth for a MAD, or patients with severe temporomandibular joint (TMJ) arthropathy that prohibits mandibular protrusion.
• Limitations: TRDs are generally less accepted than MADs due to tongue discomfort, mucosal irritation, nocturnal salivary pooling, and frequent dislodgement during sleep.

Clinical Indications & AASM/AADSM Guidelines

Joint clinical practice guidelines from the American Academy of Sleep Medicine (AASM) and American Academy of Dental Sleep Medicine (AADSM) outline clear evidence-based indications for oral appliance therapy:

The current joint guideline (Ramar and colleagues, 2015) makes these main recommendations:

1. Primary snoring: sleep physicians should prescribe oral appliances, rather than no therapy, for adults who request treatment of primary snoring without OSA (standard).
2. Custom, titratable devices: when oral appliance therapy is prescribed, a qualified dentist should use a custom, titratable appliance rather than a non-custom device (guideline).
3. OSA: sleep physicians should consider oral appliances, rather than no treatment, for adults with OSA who are intolerant of CPAP or prefer alternate therapy (standard).
4. Dental oversight: a qualified dentist should provide follow-up to watch for dental side effects and occlusal changes (guideline).
5. Follow-up testing: sleep physicians should arrange follow-up sleep testing to improve or confirm treatment efficacy (guideline), and both the physician and dentist should see the patient periodically.

The older AASM practice parameters (2006) framed oral appliances as appropriate for mild-to-moderate OSA in patients who prefer them or fail CPAP, and advised a CPAP trial first in severe OSA. CPAP remains the most effective therapy for severe OSA, so a patient with severe OSA who chooses an oral appliance needs especially careful objective follow-up.

Candidacy Assessment & Dental Evaluation

Successful oral appliance therapy requires close multidisciplinary collaboration between the sleep physician, the clinical sleep health specialist (CCSH), and a qualified sleep dentist (a dentist who is a Diplomate of the American Board of Dental Sleep Medicine [ABDSM] or holds accredited training). Pre-treatment dental evaluation assesses several anatomical and functional parameters:

Dentition & Periodontal Requirements

To withstand reciprocal anchoring forces without tooth loosening or periodontal breakdown, patients must meet strict dental criteria:

• Sound Tooth Count: A commonly cited rule of thumb is about 8 to 10 healthy teeth per arch; the dentist judges whether the remaining teeth can anchor the device.
• Periodontal Health: Active, untreated periodontitis, alveolar bone loss exceeding 50%, or Grade II/III tooth mobility represent strict contraindications to MAD therapy until periodontally stabilized.
• Crown Morphology: Retentive anatomical crowns or stable restorations are required to keep the appliance seated securely during sleep.

Temporomandibular Joint (TMJ) & Protrusion Screening

The qualified sleep dentist examines masticatory muscles, TMJ range of motion, and maximum voluntary protrusion using a precision gauge:

• Maximum Voluntary Protrusion: Baseline physiological mandibular protrusion typically ranges from 8 to 12 mm.
• Titration Starting Point: The initial construction bite is typically set at 50% to 70% of maximum voluntary protrusion (e.g., 5 to 7 mm forward in a patient with 10 mm maximum protrusion) with 2 to 5 mm of interincisal vertical opening.
• Incremental Advancement: The appliance is advanced incrementally (typically 0.25 to 0.5 mm every 1 to 2 weeks) based on clinical symptom improvement, snoring reduction, and jaw comfort.
• Contraindications: Severe active TMJ arthralgia, painful internal disc derangement without reduction, advanced fibrous or bony ankylosis, or severe limitation of opening (less than 25 mm) contraindicate MAD placement.

Side Effects & Clinical Management

Adverse effects of oral appliance therapy are classified as short-term transient symptoms or long-term irreversible structural changes:

Short-Term Side Effects

Short-term side effects typically arise during the initial acclimation and titration phases and resolve with consistent use or minor adjustments:

• Excessive Salivation (Hypersalivation): Foreign body stimulation in the oral cavity stimulates salivary flow; typically resolves within 2 to 4 weeks.
• Morning Xerostomia (Dry Mouth): Lip incompetence or mouth breathing around the device causes oral mucosal dehydration.
• Transient Tooth Tenderness: Localized pressure on anchoring teeth upon morning removal, generally lasting 15 to 60 minutes.
• Masticatory Muscle Fatigue & Jaw Stiffness: Transient soreness in the masseter, temporalis, and lateral pterygoid muscles upon waking.
• Management: Instruct patients in morning repositioning exercises and provide a morning alignment jig (bite wafer). Chewing a morning wafer for 5 to 10 minutes helps re-engage centric occlusion and repositions the condyles within the glenoid fossae.

Long-Term Irreversible Sequelae

Persistent nocturnal forward traction over months and years creates reciprocal orthodontic forces that alter tooth positions and occlusal contact:

• Dental Occlusal Changes: Mesial movement of mandibular molars and distal tipping of maxillary molars.
• Incisor Tipping: Lingual tipping (retroclination) of maxillary incisors and labial tipping (proclination) of mandibular incisors.
• Decreased Overjet and Overbite: Progressive reduction in horizontal overlap (overjet) and vertical overlap (overbite), occasionally resulting in an anterior edge-to-edge relationship or anterior crossbite.
• Posterior Open Bite: Loss of bilateral occlusal contact in the molar and premolar regions.
• Management: Dental follow-up is commonly scheduled every 6 months during the first year and at least yearly thereafter, as the 2015 guideline advises ongoing dental oversight. Sleep dentists take baseline study models or digital 3D intraoral scans to track subclinical dental movements.

Verification of Efficacy & Follow-Up Protocols

A critical responsibility of the Clinical Sleep Health Specialist (CCSH) is educating patients that subjective symptom relief does not equal objective physiological control:

• The Clinical Trap of Subjective Improvement: Patients often report complete elimination of snoring and marked improvement in daytime alertness despite having a persistently elevated residual AHI.
• Mandatory Objective Sleep Testing: Once the qualified sleep dentist achieves optimal clinical titration, a follow-up objective sleep study (in-laboratory polysomnography or home sleep apnea testing) must be conducted with the oral appliance titrated and worn in place to objectively quantify residual AHI, respiratory disturbance index (RDI), and oxygen desaturation.
• Treatment Success Criteria: Complete response is defined as a reduction in AHI to less than 5 events/hour. A partial response is defined as an AHI reduction $\ge 50\%$ from baseline with residual AHI less than 10 events/hour. If residual AHI remains elevated, further dental advancement or transition/combination with PAP therapy is warranted.

Comparison: MAD vs. TRD vs. CPAP