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Obstructive sleep apnea (OSA) is a mild form of sleep disorder in which the airway passage is blocked by the patient's neck, throat, oral anatomy, a medical condition, and/or overall health status. It is characterized by periodic stops in breathing, known as apnea, and restarting periods, including hypopnea, during sleep. Hypopnea includes shallow breathing episodes which result in lower levels of oxygen saturation due to the blockage of the airflow.1 To diagnose the severity of this condition, the apnea-hypopnea index (AHI) measures the average frequency of apnea and hypopnea episodes per hour.2
OSA is more prevalent in the elderly population, predominantly for edentulous patients, due to the changes in anatomy and physiology of the patient's bone and soft tissue structure. This article investigates the available options for developing innovative solutions such as oral appliances to enhance the current therapies for edentulous patients wearing removable partial or complete dentures, as well as analyzing different sleep apnea devices for ventilation, intubation, and opening of the airway passage given the anatomical and cognitive changes due to aging.
Demographics and Diagnosis
The American Sleep Apnea Association reports that one in five adults, or at least 25 million Americans, suffer from OSA-with many more undiagnosed. Additionally, this disorder is linked to other medical conditions such as heart disease, stroke, cognitive disability, etc.3-5
Studies show that age has a significant impact on exacerbating and elevating the acuteness of OSA. Young adults are more willing to be tested and diagnosed compared to the elderly population. Currently, 26% of people between the ages of 30 and 70 years old are being diagnosed,3 but only 8% of people 65 and older are tested.6,7Additionally, statistics appear to indicate a difference between genders, with 17% of men and 9% of women diagnosed between the ages of 50 and 70 years old in the US.6 Further, 40.99 million Americans are edentulous patients,8 thus increasing the probability that they are suffering from OSA and in need of treatment.
As expected, from the clinical perspective, OSA therapies are different for younger adult patients with natural dentition as opposed to older edentulous patients, who often present with other medical factors affecting their health.
Options for OSA Treatment
Currently, there are several OSA therapies for edentulous patients, involving either the use of continuous positive airway pressure (CPAP) therapy or oral appliances such as mandibular advancement devices (MADs). For more severe cases, surgical therapy may be advised, including soft tissue surgery or maxillomandibular advancement (MMA). Each type of therapy presents its own unique challenges based on the patients' age and medical and cognitive conditions. As patients age, anatomical and physiological changes are accentuated and amplified by other medical conditions, such as diabetes, heart conditions, pulmonary issues, obesity, etc, and medications used to treat these conditions.9 Additionally, elderly patients might present diminished cognitive functions, making their cooperation with the treatment plan more difficult, as noted by Johnson, et al: "Finally, cognitive changes (eg, dementia) not often seen as related to airway management may affect patient cooperation, especially if an awake intubation is required. Overall, degradation of the airway along with other physiopathologic and cognitive changes makes the elderly population more prone to complications related to airway management."10
Though some studies suggest that OSA conditions are improved by wearing dentures during sleep, others argue that some patients might sleep with their mouths open, thus worsening the apnea. Additional detrimental factors include the slight movement of dentures during sleep, which can generate soft-tissue lesions and inflammations, as well as denture stomatitis, which can lead to alveolar bone resorption. Therefore, further long-term observations and studies are needed to accurately evaluate the efficacy of these therapies.11-16
The development of different treatment options for these patients is critical for improving their medical conditions and increasing their life expectancy. In addition, to generate a successful treatment plan, a strong collaboration between different medical specialists is necessary in order to evaluate and select the best approach.
The following therapies are currently used for treating OSA for edentulous patients.
Continuous Positive
Airway Pressure (CPAP)
CPAP therapy is considered the most effective method for treating older edentulous patients suffering from OSA because it does not involve surgical solutions and provides better control of the oxygen intake during sleep, therefore decreasing the AHI. One of the greatest challenges with CPAP is that patients often find it uncomfortable and therefore stop using it. A recent study shows that despite the effectiveness of this therapy, many patients reject it after a few months, citing problems with the CPAP unit's mask, including discomfort resulting from nasal dryness or congestion, and trouble adjusting to the pressure generated by the unit's ventilation.17-19 Other challenges are created by the patients' reduced capabilities for intubation, ventilation, and oxygenation, as well as risk of aspiration.10 In addition, there are other factors to consider for elderly patients when evaluating their ability to comply with this therapy, including whether they are living alone and if they have diminished cognitive capacity, neurological disorders, reduced dexterity, etc.20-24
Oral Appliance Therapy
Oral appliance therapy is one of the latest available treatment options for OSA, and it presents some advantages over CPAP therapy, such as its ease of use, which can improve compliance. This treatment option also allows for customization to the patient's needs based on their oral, neck, and throat anatomy and physiology. Studies suggest that there is little difference when comparing CPAP versus oral appliance therapy results.25, 26
This therapy involves the fabrication of a mandibular advancement device (MAD), an oral appliance that moves the mandibula into a forward position, thus freeing the airway passage. Because edentulous patients have a resorbed alveolar process, an enlarged tongue, and well-developed masseter muscles, the MAD's designs must take these conditions into consideration to achieve retention and stability in a patient's mouth when sleeping. Moreover, the mandibular element of the appliance must be placed in the correct protrusive position where it is comfortable for the patient and does not induce temporomandibular joint (TMJ) pain, soft-tissue lesions, or other oral discomfort. The position of the mandibular element of the appliance can be set from 25% to 100% advancement, but studies indicate that most patients are comfortable at 50% protrusive advancement. The protrusive movement varies from patient to patient but can be increased as needed. Studies show that "the mean protrusive capability has been reported as approximately 11 mm with a range of 6 mm to 14 mm," and according to the Journal of Dental Sleep Medicine, "the mandibular protrusion mechanism should allow for advancement in increments of 1 mm or less over a minimum of 5 mm. Smaller increments of advancement can allow for evaluation of subjective parameters, while minimizing potential temporomandibular discomfort."27
There are different types of MADs which can be customized to the patients' needs. One successful treatment option for OSA oral appliances in edentulous patients wearing dentures is the use of dental implants for retention and stability. This is beneficial only for patients who are good candidates for dental implants and in relatively good health. For these patients, the treatment plan includes the fabrication of overdentures and is therefore a more expensive treatment option.
There are different designs for the oral appliances based on the type of retention elements used in the overdentures. For overdentures supported by abutment locators with retentive position locators and O rings, an oral appliance for OSA can be designed as a one-piece MAD that can be inserted over the dentures. The design of the appliances can vary depending on the patient's bite force, among other factors. The appliance is made to engage the posterior areas of both arches in the protrusive movement. Additionally, distal stops can be added to the last denture teeth to increase appliance stability.
Another option when dealing with overdentures supported by abutment locators with retentive position locators and O rings is to design and fabricate a separate MAD that will allow patients to remove their overdentures and insert the appliance before sleeping. In these cases, retention will be achieved by processing the position locators into the appliance and selecting the O rings necessary to achieve the highest appliance retention. There are some appliance modifications available, such as a device, either one piece or two pieces, that is connected and stabilized in the mandibular advanced position by attaching lateral retention rods. This gives the dentist the flexibility to increase or decrease the length of the rods as needed, as well as to increase or decrease the rigidity of the appliance by selecting the strength of the rods.28
For overdentures supported by a bar substructure, the design of the appliance can be a one-piece MAD inserted over the denture. However, in these cases, due to the minimum height requirements of the bar and overdenture size of about 15 mm, special attention must be given to the thickness of the appliance in order to avoid over-increasing the patient's vertical dimension, which can generate temporomandibular joint and muscle pain. Other concerns include increased force applied on the implants, leading to loosened screws or even implant failures. Similar to the Hader bar with clip retention elements, the MAD will have clips processed inside that will be locked into the bar substructure, providing stability and retention. Hoekema, et al, suggest based on their case study that the mandibular advancement should be at 50% for these types of patients.29
For patients with one edentulous arch, the appliance can be anchored on the opposing arch, which may have natural dentition or fixed prostheses.30 The MAD would be one piece and can have different modifications, including:
• Increased palatal coverage for appliance retention and stability
• Use of the teeth undercut area for retention
• A limited increased vertical dimension
• Reduced appliance thickness on the mandibular aspect for patients with mandibular edentulous arch and enlarged tongue
• Anterior opening in the appliance (between the upper and the lower elements) to provide increased breathing space
For edentulous patients wearing maxillary and mandibular dentures, there are several types of designs for the MAD. These cases are the most complex and challenging due to retention and stability requirements. The following modifications can be added to the oral appliance:
• If the dentures have good retention, then the appliance can cover the posterior teeth.
• Dentists can bring the mandibular jaw forward and lock it in position.
• If the denture retention is not particularly good, then it is recommended to fabricate the appliance as a separate one-piece MAD that requires the patient to remove the dentures and insert the appliance before sleeping. To make the appliance more efficient, it is recommended that an opening or a gap on the anterior portion of the appliance should be made to provide increased breathing space.
• To compensate for enlarged tongue, the lingual aspect of the appliance should be kept to minimum thickness and for patients who present laterally developed masseter muscles, the appliance should be thicker on both the left and right side.
• For patients who present with lateral deviation, the appliance should have lateral wings or stops that prevent the lateral deviation movement.
• Dentists may also add a tongue-retaining device to the MAD that will position the tongue in a protrusive position, therefore creating more breathing space.
For partially edentulous patients using partial dentures, there are several therapy options for MADs. The following modifications can be added to the oral appliance in this case:
• For patients wearing partial dentures on one arch and having natural dentition on the opposing arch, the MAD can be one piece, which will engage the posterior teeth in a protrusive position. This type of appliance is recommended in cases where the partial denture is retentive and stable in the patient's mouth.
• For patients wearing partial dentures for both maxillary and mandibular arches, the MAD can be made as:
• A one-piece, non-adjustable appliance to keep the mandibula in a protrusive position
• A one-piece, non-adjustable appliance with a tongue retainer
• A two-piece, adjustable appliance where the interlocking mechanism is maintaining the mandibula in protrusive movement. The interlocking mechanism can be a male and female type, processed into the appliance on the anterior area.
When a two-piece adjustable appliance is used, it is important that the mandibular element is able to be moved and locked in different positions. It may start at 25%, and then when the patient becomes comfortable with the appliance, the protrusive advancement can be increased.
Special attention must be given to the retention and stability of the partial dentures. If they are loose, that can create movement in the appliance, which can lead to damage of the anchor teeth engaged by the partial dentures' major and minor connectors; TMJ issues; and discomfort that may result in the patient no longer wearing the device.
According to a study conducted by Eskafi, et al, "Dental complications were observed in two patients who had at least 10 teeth in each jaw. In one of the patients, an FPD in the upper jaw, almost 10 years old, loosened 6 months after the use of the MAD. This patient withdrew from the study but asked for a new MAD after prosthodontic treatment. In the other patient, a maxillary premolar with extensive restorations in amalgam was used for clasp retention and fractured after the device had been in use for 6 months. After the tooth was restored, the patient was no longer interested in using the device."31
Hybrid Therapies
Another option involves a hybrid therapy which makes use of a combination of CPAP and oral appliance in which the tube of the CPAP unit is connected into the MAD. As presented by de Vries, et al, based on a pilot study, the advantage of using this therapy is that the patient's mandibula is set in a protrusive position, freeing the air passage near the MAD. Thus, the pressure generated by the CPAP unit can be lowered. This also eliminates the use of the CPAP mask, which makes it more comfortable for the patient.37 However, because this option is more complex, it requires dexterity and willingness to continue the treatment.
Important Considerations
As mentioned before, the retention and stability of the oral appliance is vital; therefore it is recommended that one-piece or monoblock MADs be used for edentulous patients. There is less chance of additional movement of the appliance during sleep when patients do not have as much control over their jaw movements.
Some of the issues with OSA appliances for edentulous patients are related to retention. Similar to dentures, both the monoblock and two-piece MADs need to be periodically relined due to the patient's alveolar ridge resorption, and other anatomical and physiological changes must also be taken into account.32-38
For the two-piece MAD, adding locking mechanisms can increase the appliance's stability and give the dentist easy access to increase or decrease the mandibular advancement. These locking mechanisms are used only for two-piece adjustable MADs and have two elements, called hardware, processed into both the upper and lower portions of the appliance. It can be as simple as orthodontic wire processed into the lower element that is attached to a loop wire, and then attached to the upper element of the appliance.38 Other locking mechanisms are more complex and designed specially to allow for the increase or decrease of protrusive mandibular movement by the insertion of an adjustable screw into the locking mechanism. This can then be adjusted by the dentist.39,40
Conclusion
Using CPAP therapy or/and MADs as treatment options for patients wearing removable partial or complete dentures and suffering from OSA can become challenging because of anatomical changes due to the aging process. These challenges can be exacerbated in elderly patients who present additional medical and cognitive conditions. Studies have demonstrated that patients who were able to follow the treatment improved their sleep conditions and therefore their overall health. However, to achieve and maintain successful OSA therapies, the healthcare team must perform extensive physical and mental evaluations for each patient. Additionally, the patient's collaboration is important in customizing these treatment options for their individual needs. More research and long-term studies are necessary to develop more accurate diagnosis methods and to evaluate the effectiveness of these therapies for edentulous and older patients.
About the Author
Laura Andreescu, MBA, CDT
Assistant Professor of Restorative Dentistry
New York City College of Technology, CUNY
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