A systematic review of mandibular advancement using clear aligners in patients with sleep apnea

INTRODUCTION

Obstructive sleep apnea (OSA) is a prevalent sleep disorder characterized by repeated episodes of partial or complete upper airway obstruction during sleep, resulting in disrupted sleep and oxygen desaturation.^[1] This condition is associated with numerous health consequences, including daytime sleepiness, cognitive dysfunction, and an increased risk of cardiovascular disease.^[1] Sleep apnea is a significant sleep disorder marked by repeated breathing interruptions during sleep, known as “apneas.” These can last anywhere from a few seconds to minutes and may occur over 30 times/h, resulting in poor sleep quality and leading to excessive daytime sleepiness and other health-related issues.^[2] It is a common condition, affecting around 3–7% of men and 2–5% of women in the general population. However, it is believed that many cases go undiagnosed, suggesting that the actual prevalence could be even higher.^[3]

The primary cause of sleep apnea is often the excessive relaxation of the muscles in the back of the throat, which support structures such as the tonsils, the side walls of the throat, and the tongue.^[4] This over-relaxation can impede normal breathing, causing the brain to briefly wake the person to reopen their airway. These awakenings are typically so short that they are not remembered. Symptoms of sleep apnea commonly include loud snoring, episodes of breathing cessation during sleep, abrupt awakenings with shortness of breath, waking up with a dry mouth or a sore throat, morning headaches, difficulty staying asleep, excessive daytime sleepiness, attention problems, and irritability. If not treated, sleep apnea can lead to various health problems, including high blood pressure, stroke, heart failure, irregular heartbeats, heart attacks, diabetes, depression, the worsening of attention deficit hyperactivity disorder (ADHD), and headaches.^[1-3] The treatment for sleep apnea generally involves lifestyle changes, devices to facilitate breathing, mouthpieces, medication, or even surgery.^[4] These lifestyle changes may include weight loss, smoking cessation, avoiding alcohol and sedatives, sleeping on one’s side, and regular physical activity.^[4]

Skeletal Class II malocclusion is a dentofacial anomaly typified by a retrognathic mandible, a prognathic maxilla, or a simultaneous manifestation of both of these conditions.^[1,2] This malformation, essentially a product of irregular maxillary and mandibular growth patterns, is known to catalyze alterations in craniofacial and upper airway morphologies.^[3] Consequently, these alterations can reciprocally affect modifications in craniofacial tissues’ growth and development. Because of this interaction, it is very important to think about the shape of the upper airway when planning early treatment for skeletal Class II malocclusion. It is also noteworthy that the sagittal and vertical dimensions of the mandible and its relative positioning can influence the position of the hyoid bone.^[4] For example, mandibular retrognathism can cause the hyoid bone to move backward, and turning the jaw clockwise can cause the hyoid bone to move inferiorly and posteriorly.^[5]

The pathophysiology of OSA underscores the paramount importance of upper airway patency, with narrow airways being a key contributor to this disorder.^[6] OSA, known to afflict over 2% of the pediatric population, can have long-term detrimental effects on health. Hence, a full check of the upper airway and the position of the hyoid bone is necessary for planning orthodontic treatment and judging how well it worked in cases of malocclusion.^[7]

Among the various treatment modalities, continuous positive airway pressure (CPAP) remains the gold standard for OSA.^[2] However, patient compliance with CPAP is often suboptimal due to discomfort, noise, and inconvenience. Consequently, there is a growing interest in alternative treatment strategies, among which mandibular advancement devices (MADs) have emerged as a promising option.^[9] By moving the lower jaw forward, MADs make the upper airway bigger and less likely to collapse, which helps people with OSA.^[10] In addition to these, surgical treatment options for OSA are typically considered when non-surgical options such as lifestyle modifications, CPAP therapy, or oral appliances do not work well enough or the patient does not tolerate them. The goal of surgical treatment is to remove the obstruction in the airway that leads to sleep interruptions. There are several types of surgical procedures, each targeting different areas of the airway. One of the most common is uvulopalatopharyngoplasty,^[5] which involves the removal of excess tissue from the throat, including the uvula, part of the soft palate, and, in some cases, the tonsils and adenoids. This surgery widens the airway and facilitates unobstructed breathing. In cases where large tonsils are the primary cause of OSA, particularly in children, a tonsillectomy can significantly improve or even cure the condition.^[11] Various nasal surgeries can also rectify obstructions in the nasal passage, such as a deviated septum or turbinate hypertrophy. For severe cases of OSA, maxillomandibular advancement (MMA) might be considered.^[1,7] This procedure, which involves moving the upper and lower parts of the jaw forward to increase the size of the airway, is invasive but is among the most effective surgical treatments for OSA. Another option is genioglossus advancement, a surgery that moves the base of the tongue forward. This enlargement of the airway reduces the chances of airway obstruction.^[12] A relatively new treatment, hypoglossal nerve stimulation, involves the implantation of a device that stimulates the hypoglossal nerve, which controls the movement of the tongue. The stimulation keeps the tongue in a position that prevents it from blocking the airway.^[8]

The twin-block (TB) functional appliance, traditionally employed in managing Class II skeletal patterns due to retrognathic mandible, has demonstrated efficacy in enhancing upper airway morphology and optimally repositioning the hyoid bone in pediatric and adolescent patients with retrognathic mandibular.^[11] Furthermore, Invisalign mandibular advancement (MA), a new, clear functional appliance, is mostly used for people who have skeletal Class II malocclusion and mandibular retrusion.^[12] Although the operational principle of the MA appliance bears resemblance to that of the TB appliance, their mechanisms of action are not identical.

In recent years, aligners, clear removable appliances, have been increasingly used for MA in OSA patients.^[10,12] Aligners offer several advantages over traditional appliances, including better comfort, less oral dryness, and improved esthetics.^[9,10] However, the clinical effectiveness and safety of aligners for MA in OSA patients remain uncertain, with very few studies that exist reporting mixed results. This systematic review aims to consolidate the existing literature on the use of aligners for MA in patients with OSA. Specifically, we aimed to evaluate the effectiveness of aligners in reducing OSA symptoms.

MATERIAL AND METHODS

Review protocol

The preferred reporting items for systematic reviews and meta-analysis guidelines^[13] were followed in the process of making this systematic review, with the search strategy, selection criteria, bias assessment, and variable extraction all done in accordance with the stated guidelines. The study selection process for this review is represented in [Figure 1] is a representation of the study selection process for this review.

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Figure 1:

Preferred reporting items for systematic reviews and meta-analysis protocol utilized for this review. PECO; P: patient E: exposure C: comparison O: outcome

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The PECO protocol for the review “MA using aligners in patients with sleep apnea” was as follows:

Patient

Individuals diagnosed with sleep apnea of varying demographics and health backgrounds.

Exposure

The use of aligners for MA as a non-surgical orthodontic intervention to alleviate symptoms of sleep apnea.

Comparison

Although not the primary focus, a comparison was made with patients receiving alternative treatments or no treatment when such data were available.

Outcome

Effectiveness and safety of the aligner-based treatment, focusing on reduction of sleep apnea symptoms, improvement in sleep quality, and any associated adverse events.

Bias assessment

The bias assessment protocol for this review included the use of two different tools. The quality and completeness of reporting in case reports and case series were assessed using the CARE (case report) guidelines^[14] for this review [Figure 2]. For observational studies, including cohort and case-control studies included in the review, the Newcastle– Ottawa scale was used^[15] [Figure 3].

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Figure 2:

Bias assessment protocol utilized for the case reports included in this review.

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Figure 3:

Bias assessment protocol utilized for the retrospective studies included in this review.

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RESULTS

DISCUSSION

Ash^[16] demonstrated the successful use of the Somnowell^® chrome cobalt MAD in conjunction with orthodontic aligners. This was contrasted by Pan,^[17] who observed that clear aligners for upper arch expansion led to a significant increase in nasal airway volume and intermolar distance, mainly in pediatric patients, suggesting that the type of appliance and the age group significantly influence the treatment outcomes. For young adults in their early twenties, non-surgical rapid maxillary expansion (RME) has been demonstrated to be a viable procedure.

Sun^[18] had taken the research a step further by integrating surgery with orthodontics. Their study showed that MMA surgery followed by post-operative treatment with SCAs not only successfully managed OSA but also led to an impressive resolution rate, with an apnea-hypopnea index (AHI) of just 2.9 events/hour. This finding was significant when compared to the non-surgical interventions used in the other studies and demonstrated the potential of this integrated approach for severe OSA cases. SCAs entail careful patient selection and are less effective in addressing significant intra- and inter-dental arch discrepancies.^[19] With these removable appliances, regular usage for 20–22 hours/day is required; hence, strong patient compliance is essential. Sun report outlines a typical treatment protocol for patients who meet certain criterias: (1) have OSA that is not responsive to conservative treatment or is untreatable; (2) are able to tolerate significant advancements in their maxillomandibular jaws; (3) have a stable pre-operative occlusion; (4) have mild-to-moderate dental arch malocclusion; (5) have a surgically experienced SCA team; and (6) have a high level of health awareness and good adherence to treatment.

In a different vein, Yue et al.^[19] compared the effectiveness of two specific appliances: Invisalign MA and TB appliances. They found that both appliances improved upper airway morphology and reduced respiratory resistance. Interestingly, when compared to the MAD used in the Ash study, the MA and TB appliances also promoted the anterior downward movement of the hyoid bone, thus further improving airway openness.

Our review’s findings resonate with those of Conley^[20] and Palomo et al.,^[21] while also offering additional insights and expanding the scope of orthodontic treatments considered for OSA management. Like Conley,^[20] our study found that oral appliance therapy, specifically with a cast chrome cobalt MAD and orthodontic aligners, proved successful in managing snoring and mild OSA. Our findings also align with the notion that while CPAP remains the most effective therapy, patient preference and compliance are vital in the treatment choice. We further demonstrated the effectiveness of other orthodontic appliances, such as Invisalign MA and TB appliances, in improving upper airway morphology and hyoid bone position, which were not explicitly discussed in the review by Conley.

Comparing our findings with Palomo et al.,^[21] both studies underscore the crucial role of orthodontic approaches in OSA management. However, our study extends the conversation to include clear aligners for upper arch expansion and a postoperative SCA treatment protocol following MMA surgery. Palomo et al. talked about the benefits of other devices and procedures, such as headgear, functional appliances, RME, micro-implant-assisted rapid palatal expansion, and orthognathic surgery.^[21] However, our study did not specifically look into these areas.

OSA susceptibility can often be traced to certain anatomical deviations, such as a diminished mandibular length and jaw retrognathia, both of which can precipitate airway obstruction due to tongue displacement.^[23] Among the therapeutic strategies are (1) CPAP, a relatively intrusive device that necessitates nightly utilization for efficacy yet often faces patient non-compliance owing to its noise and bulk;^[23] (2) mandibular repositioning appliances that advance the jaw, thereby precluding airway obstruction;^[24] and (3) surgical interventions.^[25] Typically, non-surgical modalities are explored before resorting to surgical measures, yet CPAP therapy is often declined or poorly tolerated by many patients, making mandibular repositioning appliances a preferred alternative.^[22]

Patients with sleep-related respiratory disorders may already be undergoing or require orthodontic intervention to rectify malocclusions.^[26] It was observed that patients with severe OSA have significantly narrower upper and lower arches and shorter and more tapered maxillary arch with reduced palatal height and area.^[27,28] Orthodontic correction of these conditions may create additional space for the tongue, thereby mitigating or even eliminating OSA symptoms.^[22,29] However, the extended duration of orthodontic treatment can pose an obstacle to the concurrent utilization of sleep appliances. This has historically been a conundrum, necessitating the completion of orthodontic therapy before the initiation of sleep oral appliance treatment.^[30] This delay can be a concern given the serious, potentially life-threatening implications of OSA and other sleep-related respiratory disorders.

In response to this challenge, many clinicians are now employing clear aligner treatments to address orthodontic malocclusions.^[31] When used in conjunction with ancillary accelerators such as micro-osteoperforation and/or high-frequency vibration, these treatments offer more predictable outcomes and can expedite the orthodontic treatment process by approximately 60%, thereby addressing both the orthodontic and sleep disorder treatment needs in a more efficient and patient-friendly manner.^[32]

Several similarities and differences emerge when comparing our results to those of other recent investigations^[32-38] in terms of maxillary and mandibular repositioning. We found that clear aligners showed promise in improving upper airway dimensions and reducing the severity of sleep apnea symptoms. These findings were consistent with the reviews by Wu et al.,^[32] and Liu et al.,^[33] which also investigated the use of clear aligners for MA, although their primary focus was on the treatment of Class II malocclusions in children and adolescents.

Interestingly, the reviews by Rocha et al.^[34] and Gonçalves et al.^[35] provided additional insights into the potential of clear aligners to achieve dentoalveolar expansion, which can indirectly contribute to the improvement of upper airway dimensions. While these studies did not directly address sleep apnea, their findings support the notion that clear aligners can effectively modify the dental arch form, potentially leading to favorable changes in the upper airway.

However, it is important to note that the other reviews included in this comparison had different primary objectives and patient populations compared to our systematic review. For instance, the reviews by Maino et al.,^[36] Manni et al.,^[37] and Akbulut et al.^[38] focused on the treatment of various malocclusions, such as Class II and Class III, in growing patients. These studies also investigated the use of clear aligners in combination with other orthodontic appliances and treatment modalities, such as RME and facemask therapy. In contrast, our systematic review specifically targeted adult patients with sleep apnea and evaluated the effects of MA using clear aligners as a standalone treatment.

Furthermore, the outcome measures differed between our systematic review and the other reviews. While we primarily focused on the impact of MA on sleep apnea parameters and upper airway dimensions, the other reviews assessed various dentoskeletal effects, such as changes in sagittal and vertical skeletal relationships, dental alignment, and soft tissue profile.

Certain key recommendations can be hypothesized in light of the findings obtained through this review with regard to aligner therapy in cases of OSA, a domain with very little research, as evidenced by the literature on this. For patients undergoing orthodontic treatment who also suffer from snoring or mild OSA, the use of a cast chrome cobalt MAD in tandem with orthodontic aligners can be an effective management strategy. This approach not only addresses the symptoms of snoring and OSA but also allows the continuation of necessary orthodontic treatment without interruption. Clear aligners, particularly when used for upper arch expansion, can have a positive impact on nasal airway volume and morphology. This is especially significant in pediatric patients, where the effect was found to be more pronounced. However, a similar trend was observed in adult patients, albeit to a lesser degree, suggesting that this strategy may also be beneficial for them.

In cases where MMA surgery is performed to treat OSA, post-operative treatment with SCAs may be a viable protocol for maintaining the success of the surgical outcome. This approach has been demonstrated to effectively resolve OSA symptoms while ensuring successful post-operative orthodontic treatment. Both Invisalign MA and TB appliances were also found effective in improving the upper airway morphology and the position of the hyoid bone in children. These appliances can alleviate structural narrowness in the upper airway and reduce respiratory resistance, thereby enhancing breath quality. Furthermore, the MA appliance specifically showed superior efficacy in improving the narrowest part of the hypopharynx compared to the TB appliance. The hyoid bone could move forward and downward with the help of both appliances. This opened the upper airways in the oropharynx and hypopharynx and helped return the shape of the upper airways to normal.

CONCLUSION

According to our findings, clear aligners have shown potential in managing OSA through MA. A cast chrome cobalt MAD and orthodontic aligners effectively treated snoring and mild OSA while permitting orthodontic treatment. Both Invisalign MA and TB appliances improved upper airway morphology and hyoid bone location, although MA more effectively improved the narrowest hypopharynx. These data imply that clear aligners, especially MA ones, may help manage OSA.