Background and rationale {6a}
Obstructive sleep apnea/hypopnea syndrome (OSAHS) is a sleep disorder characterized by recurrent narrowing or collapse of the upper airway (UA), resulting in sleep fragmentation and multiple episodes of apnea and/or hypopnea [
1]. Pediatric and adult OSAHS share a similar pathophysiology, i.e., a recurrent reduction or cessation of airflow caused by the narrow anatomic structure and defective function of the UA. However, they are actually different disease categories due to their different pathogeneses [
2]. Adenotonsillar hypertrophy is currently the major cause of pediatric OSAHS, while in adults, the major risk factor may be obesity [
3,
4].
The prevalence of pediatric OSAHS is reported to be between 2 and 10% in different countries [
5]. Children with OSAHS may have a variety of problems, such as cardiovascular disorders, metabolic interferences, cognitive dysfunction, and attention problems [
6‐
9].
Conventional treatments for OSAHS include adenotonsillectomy (AT), orthodontic treatment, continuous positive airway pressure (CPAP), medication, and weight loss [
10]. At present, drug therapy is mainly applied in mild OSAHS or as a complementary method for other treatments [
11,
12]. For severe OSAHS or obesity, medical management has clear limitations. CPAP, which expands the UA but does not regulate the underlying mechanisms of disease, was suggested as an effective treatment [
13,
14]. CPAP has been used in OSAHS treatments for many years, but its clinical application is greatly limited by poor compliance [
15]. It has been reported that 46–83% of adult patients cannot adhere to treatment when 4 h of nightly use is required [
16]. For children, CPAP adherence varies between studies, but the application of CPAP at night is not optimistic due to their longer sleep hours. [
17,
18]. Besides, additional data show that CPAP masks can have an adverse impact on the craniofacial development of a child, which means aggravating maxillofacial deformities and leading to increased collapsibility of the UA [
19].
As the main reason for pediatric OSAHS is adenotonsillar hypertrophy, the primary treatment in children has always been AT, even though many studies have suggested that the efficacy of this treatment method may not be as favorable as expected [
20]. Recent reports have confirmed that the efficacy of AT varies from 27.2 to 82.9% [
21‐
23]. Recent evidence suggested that AT could ameliorate OASHS, but that the residual apnea/hypopnea index (AHI) may persist in some cases, especially in obese children [
24,
25]. Orthodontic treatment has been widely used in recent years as an alternative or combination therapy with AT.
Craniofacial deformity has an obvious influence on the collapsibility of the UA [
26,
27]. It can be a primary pathogenesis of OSAHS as well as a complication caused by long-term abnormal mouth breathing [
28]. Mouth breathing is one of the main clinical symptoms of OSAHS in children, and it is common to find OSAHS among mouth breathers [
29]. Mouth breathing during growth may alter the muscle tone of the oropharynx, which affects the development of maxillofacial structures and presents long faces, maxillary constriction, high arched palates, and mandibular retrognathia [
28,
30]. The elimination of obstructive factors is the basis for nasal respiration and normal growth of maxillofacial bone and dentition [
31]. Some cohort studies have observed that AT has the potential to block the progression of craniofacial malformation [
32]. However, the roles of AT in dentofacial growth were found to be limited [
15,
16,
33,
34] and could be achieved only if an AT was performed before 6 years of age [
34,
35]. Dentofacial deformity was more unlikely to reverse spontaneously after AT surgery for children in the mixed dentition stage [
36].
Therefore, clinical workers wondered whether it was necessary for all children with OSAHS to go to an orthodontist. Rapid maxillary expansion (RME) and mandibular advancement devices (MADs) are the most commonly used appliances for children with OSAHS [
37‐
41]. RME benefits children with OSAHS through the following mechanisms: (1) it enlarges the dimension of the nasal cavity and increases nasal respiration; (2) it increases the maxillary width so that a better tongue position can be induced; (3) the normal width of the dental arch stimulates the development of the lower jaw. Camacho et al. stated in a systematic review that RME has stable long-term efficacy for pediatric OSAHS patients with transverse maxillary deficiency or narrow hard palates [
39]. Villa et al. assessed the outcome of AT and RME in a non-randomized controlled trial and found that both of these treatment methods were effective, but further studies were needed to evaluate their long-term efficacy [
42].
MADs, in the form of oral appliances, can promote the anterior displacement of the mandible and hyoid bone, leading to anterior traction of the tongue and thus an enlarged UA dimension. Pavoni et al. found that after MAD treatment, significant improvements in sagittal airway dimensions, hyoid position, and tongue position were induced, and obvious relief in subjective symptoms was observed in children with sleep-disordered breathing [
43]. Many studies have reported that the clinical use of functional therapy for mandibular advancement such as twin-block and Frankel appliances significantly reduced AHI in patients with OSAHS [
10,
40,
41]. In recent years, the combination of RME and MADs was illustrated by some clinicians.
For OSAHS children with adenotonsillar hypertrophy and dentoskeletal Class II malocclusions, who represent a large proportion of pediatric OSAHS patients, both orthodontic treatment and AT may be effective, but little evidence-based medical research has been found to our knowledge. There have been longstanding debates among clinicians about the indications for AT, especially for children with mild OSAHS. More convincing evidence is needed to prove that AT/orthodontic treatment has a therapeutic effect for children with OSAHS and that it improves the craniomaxillofacial deformity caused by mouth breathing.