Authors: Magdalena Piełunowicz, Jacek Kotuła, Krzysztof Kotuła, Mieszko Więckiewicz, Joanna Lis, Beata Kawala, Anna Ewa Kuc, Michał Sarul
Categories: Research, Functional appliance, Malocclusion, Quality of life, Sleep apnea in children, Sleep quality
Source: BMC Oral Health
Authors: Magdalena Piełunowicz, Jacek Kotuła, Krzysztof Kotuła, Mieszko Więckiewicz, Joanna Lis, Beata Kawala, Anna Ewa Kuc, Michał Sarul
Sleep disordered breathing (SDB) in children, characterized by sleep apnea episodes or other episodic or persistent breathing disorders, can be associated with the occurrence of some malocclusions. However, there are few clinical studies on the correlation of the occurrence of malocclusions and the effects of their treatment with reduction of SDB symptoms. Therefore, we conducted a systematic review of this topic, focusing on the population of children during the age of tooth replacement demanding orthopedic treatment for maxillary transverse growth deficiency and anterior mandibular growth modification. This systematic review seeks to assess effect on quality of sleep resulting from Rapid Maxillary Expansion and functional orthodontic treatment in patients with SDB and morphological changes occurring in the oral cavity and upper respiratory tract contributing to the reduction of SDB symptoms.
The review was conducted in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses 2020 (PRISMA 2020). The study design was defined in the PICO format—Population (P): non-syndromic prepubertal and adolescent patients requiring orthodontic treatment, who additionally have coexisting sleep disorders; Intervention (I): Orthodontic treatment of malocclusion with differentiated appliances; Comparison (C): evaluation of Apnea Hypopnea Index (AHI) and sleep questionnaires pre and post treatment; Outcome (O): effect of orthodontic treatment on sleep quality. Search filters included the time of the publication—articles of 11 last years and publications that was published in English. The following variables were established for the selected sample size, demographic characteristics, orthodontic treatment methods, type of study, AHI (Apnea–Hypopnea Index) parameter. The following scientific databases were PubMed, Embase, Cochrane Central. The articles were analyzed for risk of bias and quality using the Risk Of Bias In Non-randomized Studies—of Interventions (ROBINS-I) protocol.
After entering the keywords, 3,252 articles were retrieved. Of these, 16 articles were deemed eligible for systematic review and were thoroughly analyzed, of which 11 articles did not meet the inclusion criteria. Five articles (n = 248 individuals, 163 girls and 124 boys) aged 8–12.5 years, mean age 10.6, were included in the review. In 124 patients with class II malocclusions or mandibular retrognathia, a modification of the anterior growth of the mandible was used using Twin-Block appliances with the possible use of class II traction, and in 124 patients with bilateral crossbite, the Rapid Maxillary Expansion (RME) method was used. The quality of upper airway patency and sleep quality related to SDB was examined using polysomnographic analysis, polygraphy analysis, cephalometric studies and questionnaires.
The literature review suggests that orthodontic treatment may improve sleep quality, alleviate symptoms of SDB, and enhance sleep parameters however one article does not support this thesis. A close correlation between these phenomena has not yet been fully established. The current review is a good starting point for introducing simpler methods of examining the quality of sleep, in children, which requires further research on this topic. Registration CRD42024565669.
Sleep plays a key role in proper physical and intellectual development and in shaping well-being [1]. Sleep-disordered breathing (SDB) refers to a broad spectrum of common sleep-related conditions. The characteristic symptoms of SDB are repetitive respiratory episodes associated with intermittent hypoxia [2–4]. The primary signs and symptoms of SDB in pediatric population include snoring, drowsiness, increased apathy, and sometimes hyperactivity during the day. Among the daytime symptoms patients experience low mood, irritability and cognitive dysfunctions [1, 4–7]. They pose a significant threat to health and life as well as to the proper development and quality of life of children and adolescents [7–10].
The most common, although still underdiagnosed type of SDB is Obstructive Sleep Apnea (OSA) [1–11].
The etiology of SDB in children is multifactorial. The primary causes in pediatric population include hypertrophy of the palatine, tonsils and adenoids. The prevalence of SDB is associated with malocclusion in children [11–18]. On the other hand, there are studies that do not confirm this dependence [19]. The most common coexisting defects with SDB include crossbites associated with a transverse deficiency in the growth of the palate and its high arch reducing the lumen of the nasal cavity, as well as a deficiency in the anterior growth of the mandible [13].
In order to make a correct diagnosis of SDB, especially in connection with malocclusion, multidisciplinary diagnostics should be implemented, starting with an ENT and orthodontic examination supported by cephalometric analysis [20, 21] assessing the size of the upper respiratory tract and diagnostics of nocturnal polysomnography to determine the severity of breathing disorders during sleep [22–26].
Orthodontic treatment is one of the directions of comprehensive treatment of SDB [12–18, 27–32]. The basic directions of orthodontic treatment in the light of available research should be considered to be transverse orthopedic modification of maxillary growth using RME and modification of anterior growth of the mandible using activators and bite splints set in a construction bite [25, 26, 33]. Promising results of studies available in the literature indicate a positive effect on improving the size of the upper airways, significantly increasing the nasopharyngeal and oropharyngeal airway volume based on the expansion of the palate [34]. Recent study reported improvement in pharyngeal airway passage due to adaptive increase in the distance of the tongue from the uvula as a result of mandibular protraction with the Twin Block appliance [35]. The changes that occurred increase the anatomical size of the airways, which in turn reduces the symptoms of SDB [22–26].
The primary objective of this review is to assess effectiveness of orthodontic therapy related to Rapid Maxillary Expansion, also known as Rapid Palatal Expansion (RME/RPE) and modification of the anterior growth of the mandible using functional orthodontic appliances on the quality of sleep and improvement of the quality of life in children with sleep disordered breathing.
The secondary objective is to assess the impact of these appliances on improving the patency of the upper airways and reducing the symptoms of SDB in children.
The systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 (PRISMA 2020) [36] and was registered in the international prospective registry of the systematic reviews database PROSPERO under the number CRD42024565669. The PRISMA 2020 flow diagram is presented in Fig. 1.Fig. 1The PRISMA 2020 flow diagram
The research questions were defined in PICO Population (P): non-syndromic children and adolescent patients requiring orthodontic treatment, who additionally have coexisting sleep disorders;Intervention (I): Orthodontic treatment of malocclusion with differentiated appliances;Comparison (C): evaluation of AHI (Apnea–Hypopnea Index) and sleep questionnaires pre and post treatment;Outcome (O): the effect of orthodontic treatment on sleep quality.Search filters included the time of the publication—articles of 11 last years and publications that was published in English.
The following online databases were searched by two researchers independently (MP, JK): PubMed, Embase, Cochrane Centrale Register of Controlled Trials, Google Scolar, ResearchGate. A search of the American Journal of Orthodontics and Dentofacial Orthopedics and The Angle Orthodontist was also conducted. Database were searched using the following Orthodontic treatment and SDBOrthodontic treatment and OSAOrthodontic treatment and OSA and life qualityPediatric orthodontic treatment and OSA and life qualityRME and OSA and life qualityTwin block and OSA and life qualityRME and snoring and childrenRME and apnea and childrenRME and hypopnea and childrenFunctional appliance and apnea and childrenFunctional appliance and hypopnea and childrenFunction appliance and snoring and children
The literature review was performed in May and June 2024. The database review was performed independently by the authors (M.P., J.K. and M.S.). After eliminating duplicates, the titles were assessed for their relevance to the topic of this systematic review. Titles that cleared the initial screening were subsequently subjected to a thorough evaluation. Throughout this process, the authors were blind to each other's choices. Any disagreements were resolved through discussion, with a third author (M.S.) stepping in when necessary to help reach a consensus.
Articles were included by following Randomized clinical trials (RCTs)Controlled prospective clinical trials (CCTs)Polysomnography or portable respiratory polygraphy as sleep assessment toolsSleep questionnaireChildren with skeletal Class II malocclusion with mandibular retrognathia and normal maxillary position exhibiting symptoms of OSAChildren with narrow maxilla and bilateral crossbiteNo previous orthodontic treatment or adenotonsillectomyPrepubertal and/or adolescent patientsPre- and post-intervention assessment.
The articles were excluded by following Retrospective studies, case reports, literature reviewStudies with limited dataStudies in patients with completed skeletal growthSurgically assisted treatmentStudies on a non-representative group of patients (group of less than 10 patients)Studies in patients with syndromesPatients with respiratory diseasesAnimal experimentsArticles that did not provide information on patient treatment completionArticles that did not provide information on how malocclusion affects sleep quality.The following variables were established for the selected sample size, demographic characteristics, orthodontic treatment methods, type of study, and AHI value.
The analysis of the risk of bias was performed using the Robins-I tool [37]. The following domains were included in the random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective reporting and other biases. Two independent reviewers evaluated the risk of bias and any discrepancies was resolved by a third reviewer. The results is presented in Table 1. Table 1Risk of Bias Assessment of Studies Investigating the Association Between Symptoms of Sleep-Disordered Breathing (SDB) and Orthodontic Appliances Used in the Treatment of Malocclusions in Pediatric Patients [22, 38, 39]
High
Moderate
Low
Risk of bias was assessed using the Robins-I tool [37]. The following areas were random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective reporting, and other biases. Two independent reviewers independently assessed the risk of bias, and any discrepancies between them were resolved by a third reviewer. The results of the risk of bias significance level are presented in Table 1. Green indicates low risk of bias. In the case of random sequence generation, the selection of patients to the study and/or control group was maintained. In the case of allocation concealment, it indicates that patients were randomly assigned to the study or control group. In the case of blinding of participants and personnel, low risk of bias corresponds to the fact that both the patient and the physician were blinded to the proposed treatment. Low level of bias was considered when the outcome assessments were blinded. Also, when complete outcome data were reported, the risk level was low. Selective reporting and other biases were considered low if reporting was complete. No reporting was considered moderate risk of bias or high risk of bias. Yellow indicates moderate level of bias and refers to moderate level of disagreement with respect to low risk of bias. Red indicates high level of bias with significant deviation from the low level values described above. The following criterion was included in the summary assessment of risk of bias. When a low level was achieved in all categories, the summary level of risk of bias was assessed as low. Moderate level was assessed if moderate level of risk of bias applied to at least 1 criterion. High level was assessed for articles in which at least one level of risk of bias was high.
The overall risk of bias was assessed as moderate if any individual risk was classified as high and/or if two risks were classified as moderate. Otherwise, the risk of bias was considered high. The quality assessment of a study was considered low if the risk of bias was assessed as high, and moderate if the risk of bias was assessed as moderate.The overall risk of bias was assessed as moderate if any individual risk was classified as high and/or if two risks were classified as moderate. Otherwise, the risk of bias was considered high. The quality assessment of a study was considered low if the risk of bias was assessed as high, and moderate if the risk of bias was assessed as moderate.
The review of articles was hampered by the inability to perform a reliable statistical assessment due to the heterogeneity of the study results. Although all the articles refer to studies on sleep disorders in adolescents and the impact of malocclusion on the quality of life, the study methods differed in the orthodontic appliances used and the treatment used in the control groups. The appliances included three different expander modifications and differed in the construction of the functional appliances. The individual studies differed in their inclusion criteria, measurement methodology and classification of the results such as using polysomnography, CBCT or sleep questionnaires to investigate how the treatment affected the quality of sleep. This limitation arose from inconsistency in the findings across individual studies. These criteria prevented the preparation of a uniform summary and may have contributed to bias in the analysis, thereby affecting the reliability of the estimates. Due to the lack of comparable data, there is a high risk that the review may lack credibility, and its results may be subject to bias and error. For these reasons, it was decided to base the conclusions on a qualitative analysis of the available data, which will be used in the future to standardize the criteria necessary to conduct research that will allow for obtaining precise and comparable results using statistical analyses.
After entering the keywords, 3,252 articles were displayed. A total of 16 articles were classified as eligible for systematic review and carefully analyzed. After eliminating 12 articles that did not meet the inclusion criteria, 5 studies remained and were selected for review. The selection process is shown in Fig. 1. The study groups included a total of 248 participants, including 125 boys and 123 girls. The largest group of study participants was presented by Zreaqat in his article, 94 participants [38]. The group in the article by Machado-Junior et al. had the smallest size, 14 participants [40].
The study groups consisted of prepubertal children. The mean age of the youngest participants was 8.13 years in the studies by Machado-Junior et al. [40] while the oldest participants had a mean age of 12.5 years in the work of Gokce et al. [41].The Zreaqat [38] study was assessed as high-risk of bias due to high risks in random sequence generation, allocation concealment, blinding of participants and per-sonnel and moderate risk of selective reporting and other risks. In summary, the study was considered to have low value.Similarly, in the Katyal [22] study, high risk of bias was assessed based on high risk Random sequence generation, Allocation concealment and moderate risk of Blinding of participants and personnel and selective reporting. In summary, the study was considered to have low value.The Machado–Junior [40] study was assessed at moderate risk of bias due to high risk of Blinding of participants and personnel. In summary, the study was considered of moderate value.Similarly, in the Golce [41] study, moderate risk of bias was assessed due to high risk of Blinding of participants and personal. In summary, the study was considered of moderate value.The Idris [39] study was assessed as having a moderate risk of bias due to the mod-erate risk of blinding of participants and personnel. Overall, the study was as-sessed as having moderate value.
Based on the risk of bias assessment, the evidential value of individual studies was assessed. The results of this assessment are the values recorded in the last column of Table 1. The presented values indicate that the collected studies are characterized by low evidential value (Zreagal, Katyal) or moderate quality of evidence (Machado Junior, Gokce, Idris).
Rapid Maxillary Expansion:Katyal et al. [22] showed that rapid maxillary expansion improves sleep quality based on a Pediatric Sleep Questionnaire and OSA-18 Quality of Life questionnaire.Gokce et al. [41] reported that the use of RME did not provide statistically significant improvements in sleep quality based on polygraphy results.
Mandibular growth The study by Idris et al. [39] confirms the effectiveness of the Twin-Block device in treating patients with SDB, resulting in a reduction of the Apnea–Hypopnea Index (AHI).Machado-Junior et al. [40] showed that the use of a mandibular growth device has a positive effect on improving sleep quality based on pre and post PSG resulting in AHI reduction in experimental group.Zreaqad et al. [38] observed a significant improvement in sleep quality after the use of the Twin-Block appliance by improving AHI and increase of the volume in upper airways based on result from PSG.
The results of the systematic review are presented in Table 2 and Table 2AHI apnea/hypopnea index; B/L baseline; F/U follow up; HR high risk of OSA; LR low risk of OSA, PSQ Pediatric Sleep Questionnaire, OSA-18 QoL Quality of life questionnaireReferencePatientsGroupsAgePatients MalocclusionTreatment MethodsAssessment MethodsResultsKatyal V. et al., 2013 [22]N = 78 (M = 33,F = 45)G1 = 56G2 = 22MEAN ± SD12,3 ± 2,5 years oldPalatal crossbite, narrow maxillaRME appliancePre- and post treatment PSQ Pediatric Sleep Questionnaire,OSA-18 Quality of Life Questionnaire, Cephalograms, cast analysesChanges in clinical variables in high-risk and low-risk SDB children after 9 months of treatmentPSQ scores T1:HR 9.73 ± 3.43LR 2.88 ± 2.01OSA-18 QoL score T1:HR 39.91 ± 15.64LR 22.63 ± 6.91OSA-18 QoL score T2:HR 28.40 ± 13.35LR 22.0 ± 2.45OSA-18 QoL parental score T1:HR 7.30 ± 1.65LR 8.72 ± 1.28OSA-18 QoL parental score T2:HR 9.00 ± 1.00LR 8.80 ± 1.10Gokce G. et al., 2021N = 46(M = 16, F = 30)G1 = 15G2 = 15G3 = 16MEAN12,5 years oldBilateral crossbiteRME -tooth-tissue borne (TTB)-tooth borne (TB)- bone borne (BB)Pre- and post treatment Polygraphy,Posterior-anterior radiographyChanges in the polygraphyAHI (events/h) after 3 months of treatmentTTB—tooth tissue borneB/L: 9,2F/U: 8.0TB—tooth borneB/L: 5.4F/U: 5.5BB—bone borneB/L: 5.8F/U: 5.1Supin AHITTBB/L: 8F/U: 7TBB/L: 7F/U: 3BBB/L: 4,5F/U: 5Machado-Junior A-J. et al., 2016N = 14(M = 5,F = 9)G1 = 6G2 = 8MEANExperimental group = 8,13 years oldControl group = 8,39 years oldMandibularretrusionMandibular advancement devicesPre- and post treatment PSGChanges in the polysomnography after 12 months of treatmentAHIExperimental groupT0 = 1.66 ± 0.28T1 = 0.30 ± 0.23Control groupT0 = 1.58 ± 0.42T1 = 1.97 ± 0.30Idris G. et al., 2018 [39]N = 16(M = 13, F = 3)G1 = 7G2 = 9MEAN ± SD9,8 ± 1.4 years oldSkeletal Class I n = 12Skeletal Class II n = 4Mandible Advancement Splint: Twin-Block appliance with elastics, SHAM MASPre- and post treatment Home-based PSGChanges in the polysomnography after 3 weeks of treatmentAHI (events/h)Twin-BlockT0 = 2.8 ± 3,0T1 = 1.9 ± 2.1Sham MAST0 = 2.4 ± 3.0T1 = 3.7 ± 4.7AHI supine (events/h)Twin-BlockT0 = 4.7 ± 6.7T1 = 2.2 ± 3.2Sham MAST0 = 3.8 ± 7.4T1 = 5.7 ± 7.3Snoring time per night (min)Twin blockT0 = 52.9 ± 61,8T1 = 39.0 ± 51.5Sham MAST0 = 46.0 ± 61.8T1 = 73.7 ± 108.4Zreaqat M. et al., 2023 [38]N = 94(M = 58, F = 36)G1 = 47G2 = 47MEAN ± SDG1 = 10,29 ± 1,21 years oldG2 = 10,42 ± 1,35 years oldSkeletal class II, associated with normal maxilla and mandibular retrusionTwin-Block myofunctional appliance; sectional, fixed orthodontic appliancePre- and post treatment PSG, CBCT, cephalogramsChanges in upper airwaysAHI (events/our) 30 days after the end of treatmentTreatment groupT0 = 14.9 ± 5.5T1 = 11.2 ± 4.6Control groupT0 = 0.4 ± 0.3
Previous studies suggest a likelihood of association between malocclusions and SDB in children [42, 43]. This study presents an analysis of the literature, which indicates increase airway patency in upper respiratory tract and improvement of sleep quality and consequently improvement of quality of life. Patients in whom SDB or OSA were confirmed through polysomnographic examination show discrepancies in dental arche size, maxillary narrowing and increased horizontal overjet [44]. Patients with a convex profile and mandibular retrognathia show a higher incidence of SBD [45] than those in the control group. Orthodontic treatment should focus on correcting malocclusions, which can lead to proper occlusion, increased airflow in the upper respiratory tract, and improved sleep quality, ultimately enhancing the patient’s quality of life. To achieve these outcomes, treatment methods such as maxillary expansion and/or mandibular growth modification should be employed in patients with SBD.
Idris et al. [39] noted that the use of the Twin-Block device as an active device for mandibular protraction improves sleep quality by reducing the AHI and shortening snoring duration. The subjects showed a wide spectrum of SDB symptoms from mild snoring to severe OSA. The use of the Twin-Block device reduced the AHI, in contrast to the use of acrylic plate therapy. Additionally, it was noted that treatment with the Twin-Block device improves oxygen saturation. Symptoms related to sleep breathing disorders, i.e. quality of life and behavior, confirmed by the results of the Pediatric Sleep Questionnaire, improved as a result of wearing the Twin-Block functional appliance. The authors observed a tendency for the AHI to also increase after the use of acrylic plates in the control group. The studies emphasized that the position adopted by the child during sleep affects the value of the AHI. The supine position during sleep caused an increase in AHI. Overall, both positions adopted during sleep affected the value of the AHI which decreased after the use of the Twin-Block device and showed average decreases of 37% and 53%, respectively. Effective treatment of OSA is defined as a ≥ 50% reduction in AHI. As a result of the use of the functional appliance, 44% of participants (7 children) showed a ≥ 50% reduction in the total AHI, while 50% of the sample (8 children) showed a ≥ 50% reduction in AHI during supine sleep. In 5 participants, OSA was completely eliminated by reducing the AHI value in any body position during sleep to less than one apnea/hypopnea episode per hour. The authors also found that the AHI level increased in the control group, in which acrylic plates were used. This allowed them to conclude that the reason for this is the opening of the bite by about 0.5–1 mm, caused by the presence of clasps providing retention of the appliance on the lateral teeth. The authors identify a second reason in the presence of the acrylic plate of the appliance, which occupies space for the tongue and contributes to its lowered position in the oral cavity. In both groups, the duration of snoring during the night, assessed on the basis of audio recordings, was significantly reduced. The assessment observed significant positive changes in the results obtained using the BESS questionnaire (Behavioral and Emotional Screening System), designed for the rapid analysis of emotional changes and behavioral disorders in children. Further studies are needed to confirm the validity of this treatment method.
Machado-Junior et al. [40] used an appliance consisting of two acrylic plates connected by tracks in the study group, aimed at protruding the mandible. The control group did not receive any orthodontic treatment or other therapy for SDB, during the study period. After 12 months of therapy with a mandibular protraction device, a statistically significant reduction in AHI was demonstrated in the study group and an increase in AHI in the control group. Improvement of airway patency with the use of a functional device was achieved by moving the mandible forward, modifying the position of the tongue and improving lip seal. The authors emphasize that one of the factors determining the success of the study was the age of the patients. The factor influencing the outcome of the treatment is also the length of time the appliance is worn during the day. The patients were advised to wear the appliance 24 h a day. It was recommended to remove the appliance during oral hygiene and during meals. Although the treatment was planned for a year, it was observed that the goal of orthodontic treatment was achieved before the intended time was reached.
A limitation in the Zreaqad et al. [38] study was the standing position in which Cone-Beam Computed Tomography (CBCT) examinations were performed to assess the volumetric changes in the upper respiratory tract. While breathing disorders that occur during sleep happen in the supine position, the position of the tongue and the soft tissues surrounding the upper airways, among other things, are altered. The study confirmed a significant decrease in AHI by 11.2 events/hour, and additionally, CBCT revealed an increase in the volume of the airways at the level of the nasal, oral and laryngeal parts of the pharynx.
The study performed by Gokce et al. [41] was the first to measure the effects of different rapid maxillary expansion appliances on the treatment of patients with OSA. Maxillary expansion was performed in three groups using three successive subtypes of the Hyrax one supported on posterior teeth with acrylic onlays, another on soldered bands, and a third supported on skeletal anchorage. None of the above groups showed statistically significant changes in sleep parameters as assessed by polysomnographic examination. The authors suggest that this result may be due to the low AHI index at the study’s outset. The analysis of the number of apneas and hypopneas did not reveal significant changes compared to baseline values. All three appliances had a similar effect on crossbite correction and no significant differences were found in maxillary expansion between the appliances. The Oxygen Desaturation Index (ODI) showed similar values at the initial and post-study stage. The application of RME treatment did not yield effective improvements in OSA, unlike the effective treatment for skeletal and dental reduction of maxillary transverse dimension and crossbite.
Katyal et al. [22] studies have shown a high correlation between children at increased risk of sleep-disordered breathing and poor quality of life. Studies have shown that the use of RME, improved the quality of life measures by 14% in children at high risk of SDB compared to children at low risk. Based on measurements from the analysis of diagnostic models, it was observed that there is an association between reduced intercanine, premolar and intermolar width and an increased risk of SDB in young children and children of pubertal age. The dimensions of the airways at the oropharyngeal, nasopharyngeal level and the patency of the nasopharyngeal airways in the high-risk group, were smaller than in the low-risk group. An average intercanine width of less than 27 mm in the maxilla indicated the possibility of SDB in older children and adolescents. In the mandible, an intercanine width of 24 mm was associated with the risk of SDB only in younger children. The studies indicated positive changes in the OSA-18 Quality of Life score following orthodontic treatment. Improvement was observed in the high-risk group of SDB.
The use of RME as an orthopedic method of maxillary expansion to eliminate crossbite, as well as to correct the incorrect position of the mandible in patients with class II malocclusions can be a very effective method of supporting the treatment of children at high risk of SDB [46]. Orthopedic maxillary expansion helps to open the airways, increase their volume, improve nasal airflow, and causes an enlargement of the dental arch envelope, which affects the proper position of the tongue and lip seal [16]. This was confirmed by the studies of Katyal [22] and Golce[41]. Unfortunately, the evidential value of these studies was low or moderate. Despite many studies published in the literature, not all of them could be included in this review because they did not meet the inclusion criteria. In the interest of scientific transparency, it is important to mention several studies that, although related, did not directly meet the inclusion criteria for this review). The articles described, among others, the effect of using functional appliances on the patency of the upper airways, nasal airflow and air resistance, but did not refer to the effect of changes on the quality of sleep, in children. Although focused on Class III malocclusion, one study examined the effect of RME with maxillary protraction, which may have implications for understanding its effects on airway dimensions.
The studies of Villa et al. [47] presented research results confirming a decrease in all respiratory parameters after using a device to modify the growth of the mandible. As a result of the action of the device changing the position of the mandible, the size of the tonsils decreased. The authors attribute the cause of the changes to the change in the respiratory path from oral to nasal.
Shirke et al. [44] showed that there is a greater likelihood of SDB in children with malocclusion than in those with normal occlusion. The Pediatric Sleep Questionnaire (PSQ) as well as the Index of Orthodontic Treatment Need (IOTN) were used in the study. The results from the children's sleep questionnaire showed that 69% of the children included in the study had features of SDB. Studies show that the occurrence of SDB in children can be correlated with gender. Girls are at higher risk of SDB, who constituted 57.27% of children with SDB. In addition, 43% of children showed IOTN grade IV, which means a high need for orthodontic treatment, and 6% of children showed grade 5, which means a very high need for treatment. Although SDB can occur in patients with any type of occlusion, it is noted to be more common in patients with Angle's class II and III.
Entrenas et al. [48] observed that patients with grade II malocclusions, deficiency of mandibular advancement and mandibular retrognathia, accompanied by snoring and mouth breathing, showed a significant increase in the size of the upper airways at the level of the nasopharynx and oropharynx after undergoing therapy with the Twin-Block functional device. Similar conclusions were drawn from the study Tahmasbi et al. [49]. In patients who did not undergo therapy, snoring symptoms worsened, potentially leading to future development of OSA.
Zreagat et al. [38] performed measurements of the size of the airways using CBCT. The authors demonstrated changes in the size of the airways at the level of the nasopharynx and oropharynx after the use of the Twin Block device. The increase in the length of the upper airways is caused by the vertical displacement of the mandible during the functional treatment, and the hyoid bone is positioned forward and downward. Interesting results were obtained in the assessment of the MCA (Minimum Cross-sectional Area), which is a critical place where the greatest airflow resistance occurs. Positive changes at the level of the oropharynx and laryngeal part of the pharynx after the mandible is pushed forward with the functional device indicate a large clinical increase in airflow in the upper airways. The researchers considered the MCA to be potentially the most important parameter explaining how the anatomy of the upper airways affects the development of OSA. An important factor in the treatment was the patient's cooperation in wearing the Twin-Block device for an appropriate length of time. In younger patients, compliance with the recommendations is problematic. The authors concluded that functional devices used to treat class II defects improve the profile and may also be a tool to prevent the development of OSA in the future.
Cephalometric X-rays are useful for assessing respiratory tract size. Despite the inconvenience of the two-dimensional nature of the X-ray examination, which limits the possibility of assessing the three-dimensional space of the respiratory tract, it is one of the basic, commonly used examinations in orthodontic practice [20, 21]. Cephalometric X-ray is a cheap, widely available examination, giving a relatively low dose of radiation, and at the same time allowing for a preliminary assessment of the width of the upper respiratory tract [48].
It has been observed that the time of active wearing of the functional appliance by the patient has an impact on the treatment outcome also related to the improvement of sleep quality, reduction of SBD and prevention of OSA [50].
In the future, it will be necessary to conduct well standardized Randomized Controlled Trial (RCT) studies to minimize the discrepancies in the results of studies, with particular attention to the sample size, long-term monitoring and precise evaluation of the effect of the applied orthodontic treatment on improving the quality of sleep and quality of life in children and the evaluation of the impact of malocclusion on the occurrence of SDB and OSA.
Given the small sample size and relatively short duration of observation, it is necessary to conduct standardized RCT studies in the future with large groups of patients to investigate the effect of orthodontic treatment on improving the quality of sleep, in children using different orthodontic appliances.
The unreliability of the results is often related to the small number of study and control groups, whether depending on the specific malocclusion or the severity of SDB and OSA symptoms. In future studies, the possibility of systematizing research criteria should be taken into account and the sample size should be increased in order to determine the effectiveness of treatment with given methods depending on the severity of symptoms. The questionnaire assessment of SDB symptoms in available tests, e.g. Pittsburgh, should also be taken into account. It is necessary to conduct high-quality randomized clinical trials and prospective studies to assess the effects of multi-directional orthodontic treatment on sleep quality across different age groups and on quality of life after orthodontic treatment.
The studies presented in this publication indicate effectiveness of orthodontic therapy in patients with mandibular retrognathia associated with Class II malocclusions on the quality of sleep and improvement of the quality of life in children with sleep disordered breathing.
Studies confirms that functional appliances have impact on improving the patency of upper airways and reducing the symptoms of SDB in children. Orthodontic treatment with modification of mandibular growth forward affects decrease in the AHI index, which is the result of increasing the volume of the upper respiratory tract, unblocking the airflow through the nasal cavity, improving the position of the tongue, proper lip sealing and proper muscle tension of the facial part of the skull.
However, studies in patients with deficient transverse maxillary growth and crossbite using maxillary palatal expansion contradict each other and results are inconclusive.
Further studies are therefore needed to assess the long-term effects of RME and jaw growth modification on improving sleep quality. Further high-quality studies—primarily RCTs with clearly defined methodology—are needed for better quality analyses and more reliable conclusions.