INTRODUCTION
Individuals diagnosed with obstructive sleep apnea (OSA) experience recurrent episodes of breathing cessation during sleep. This phenomenon is attributed to the occurrence of obstruction in the upper respiratory tract during periods of sleep, which can be attributed to insufficient motor tone in the tongue or muscles responsible for dilating the airway. Apnea can be classified into three categories: central apnea, which involves a depressed respiratory center with no efferent output; obstructive apnea, characterized by obstructed airflow leading to insufficient ventilation; and mixed apnea, which encompasses both central and obstructive components simultaneously [1]. According to the “International Classification of Sleep Disorders, Third Edition” (ICSD-3), OSA is characterized by an obstructive respiratory disturbance index (RDI) exceeding 5 events per hour, accompanied by the distinctive symptoms of OSA. These symptoms include unrefreshing sleep, daytime sleepiness, fatigue or insomnia, awakening with a gasping or choking sensation, loud snoring, and witnessed apnea. Alternatively, OSA can also be diagnosed if the obstructive RDI surpasses 15 events per hour [2]. Pediatric OSA is a medical disorder that affects children and is distinguished by partial or total blockage of the upper airway during sleep. This obstruction leads to reduced oxygen saturation or disruptions in sleep patterns [3]. OSA is a significant public health concern that is distinguished by recurrent instances of total or partial closure of the upper airway during sleep, leading to sleep fragmentation and reduced oxygen levels [4]. Pediatric OSA is characterized by several factors. Obesity is well recognized as a significant risk factor for OSA in both pediatric and adult populations [5].
In the management of pediatric OSA individuals of Indian descent, a comprehensive strategy is advised, encompassing medical intervention, alterations in lifestyle, and behavioral improvements. Class II malocclusion is strongly associated with pediatric OSA [6]. Class II malocclusion refers to a skeletal and dental anomaly characterized by protrusion of the maxillary teeth and jaw, reduced mandibular length, and constricted maxillary arch. This condition has been associated with elevated susceptibility to OSA. Timely identification of and intervention for malocclusion may have a substantial impact on the management of pediatric OSA. Most of the functional appliances provided for the treatment of OSA primarily focus on advancing the mandible. It has been observed in the literature that maxillary arch constriction has also been associated with OSA in patients with Class II malocclusion [3]. Therefore, this study aimed to evaluate the treatment outcomes of the customized fixed intraoral appliance in treatment of pediatric OSA patients with skeletal Class II malocclusion due to a retrognathic mandible and constricted maxillary arch. The null hypothesis posited was that there was no statistical improvement after treatment.
METHODS
Study Design
This quasi-experimental study was conducted in the Department of Orthodontics after obtaining ethical clearance from the Institutional Review Board (DYPV/EC/109-05/2018), in accordance with the guidelines of the Declaration of Helsinki. Written informed consent from parents and assent from child was obtained following the explanation of the study, while ensuring the utmost confidentiality. The permission was obtained from the patient to use their photos for publication.
Sample Size Calculation
The sample size was calculated using the G*Power software (version 3.2.9; Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany). The power analysis revealed that 22 samples provided a power of 80%, with a type 1 error of 5% and type 2 error of 20%. Therefore, the present study included 22 participants.
Eligibility Criteria
Participants were recruited from the hospital’s outpatient department from January 2019 to July 2021, after they met the following inclusion and exclusion criteria: growing female patients in the age group 9–13 years at cervical vertebral maturation (CVM) of stages 2 and 3, having Skeletal Class II due to retrognathic mandible (ANB of >4°), narrow and constricted maxillary arch, Class II Division 1 malocclusion with full cusp molar relationship, overjet of 5–8 mm, and polysomnography (PSG) with apnea-hypopnea index (AHI) from mild (5–14) to moderate (15–29) events per hour.
Patients with a history of systemic disease, a history of previous orthodontic treatment, severe cases of OSA with events of more than 30 per hour, and those who were not willing to participate in the study were excluded. The current study employed AHI standards that were applicable to adults, rather than children. Previous studies have revealed that there is no discernible difference in the consequences between a child with an AHI less than 1 event per hour and one with an AHI ranging from 1 to 5 events per hour [7]. The study that provided a classification system for pediatric OSA [8], based on the AHI, was restricted by a limited sample size, the absence of electroencephalography validation of sleep, and the disregard of hypopneas or central events.
The determination of normative standards for PSG was based on the statistical distribution of data and it has not been established that these standards hold any validity as predictors of long-term outcomes [9]. The patients were then assessed for weight, height, and neck circumference. The height and weight of the patients were entered into the calculator for the computation of the body mass index (BMI). The BMI percentile of the participants was calculated based on the BMI values. The Center for Disease Control and Prevention defined obesity as at or above the 95th percentile of BMI for age and overweight as between the 85th to 95th percentile of BMI for age, and normal weight as between the 5th and 85th percentile of BMI [10].
After establishing a gold standard diagnostic method for OSA, confirmation was made based on the results of the PSG report. Only cases with mild and moderate severity, as indicated by an AHI greater than 5 but less than 29 events/hour, were included in the study. Conversely, severe cases, characterized by more than 30 events per hour, were referred to the pediatric sleep medicine department for further intervention. The study participants were assessed by clinical examination, PSG parameters, cone-beam computed tomography (CBCT), and cephalometric analysis. The cephalometric landmarks used in the present study are listed in Table 1. The clinical examination consisted of measuring the neck circumference, Mallampati scores for tonsillar examinations, and BMI.
Treatment Procedure
Patients were treated with customized fixed intraoral rapid maxillary expansion with a twin-block mandibular advancement appliance (Fig. 1A). A bonded upper component consisted of rapid maxillary expander (RME) screw (Hyrax, Dentaurum, Pforzheim, Germany) (Fig. 1B) fixed in upper component of twin block and bonded lower component for mandibular advancement (Fig. 1C). The fixed twin block was designed in a manner that ensured the cervical margins of the teeth on both buccal and palatal aspects remained devoid of acrylic for oral hygiene maintenance purpose. Patients were advised to refrain from consuming sticky foods, rinse their mouths after each meal, utilize chlorhexidine mouthwash, and brush with a fluoridated toothpaste twice a day using an interdental brush to effectively clean the cervical regions of the teeth with fixed twin block. All patients underwent upper arch expansion using the Timms protocol (two turns per day, one in the morning and one in the evening until the desired expansion was achieved). The bite was registered edge-to-edge for skeletal correction. These cases were observed over a period of 8 months until skeletal correction was achieved. Twelve patients (55%) reported a mild discomfort during activation of RME screw, whereas nine patients (41%) reported mild discomfort during eating in first week of treatment. Eight patients (36%) reported with debonding of appliance, which was rebounded immediately using glass ionomer cement (GIC) type 1 (GC Fuji 1; GC Corp., Tokyo, Japan), which has anticariogenic properties. None of the patient had any incidence of caries during the entire treatment period.
Outcome Assessment
The transverse measurements of the maxillary arch were recorded on dental casts of the patients at pretreatment (T0) and after 8 months of treatment (T1) with digital Vernier calipers to an accuracy of 0.1 mm. The intercanine width (ICW) was measured from cusp tips of right and left maxillary canine (Fig. 2A) and intermolar width (IMW) was measured from mesiobuccal cusps of right and left first maxillary molars (Fig. 2B). The diagnosis of narrow and constricted maxillary arch was made based on clinical features such as deep palatal vault, presence of bilateral posterior crossbite, and later confirmed by Banker’s hypothesis, which states that if the ratio between IMW and ICW is more than 1.15 ± 0.05, and IMW is less than 34.92, it is considered as constricted maxillary arch [11].
The airway analysis was performed using CBCT. The scans were acquired using Planmeca ProMax 3D (Helsinki, Finland). All scans were performed with the following parameters: Voltage at 120 kVp, current at 18.5 mA, field of view of 17 × 23 cm, scan time of 8.9 s, and 0.2–0.4 mm voxel size. The acquired images, next to Digital Imaging and Communications in Medicine (DICOM) files, were processed and analyzed using Romexis Viewer 4.5.0.R software (Planmeca) on a personal computer running Microsoft Windows 10 (Microsoft Corp., Redmond, WA, USA). For standardization, all scans were analyzed after adjusting the slice thickness to 0.4 mm. During CBCT scanning, patients were given specific instructions to uphold an erect seated posture and natural head position, and it was necessary for the tongue to be in a state of rest, in contact with the anterior palate without any contact with the anterior teeth, and to achieve maximum intercuspation. After identification of the posterior nasal spine (PNS), the superior boundary of the epiglottis, and the C3 point (the third cervical vertebra) in the midsagittal plane, the upper airway was partitioned into three segments: the nasopharynx, oropharynx, and hypopharynx through the corresponding cross-sectional slices. The nasopharyngeal airway measurement (NPA) encompasses the area from the apex of the upper airway to the posterior nasal spine (Fig. 3A), the oropharynx airway measurement (OPA) was performed between the posterior nasal spine and the superior boundary of the epiglottis (Fig. 3B), and hypopharyngeal airway measurement (HPA) was taken as the region spanning from the superior boundary of the epiglottis to the level of the C3 point (Fig. 3C). The total airway (TA) volume was also measured (Fig. 3D). MIMICS software (Materialise NV, Leuven, Belgium) automatically calculated the volume (mm3). All scans were performed by a single radiologist with >15 years of experience.
Various soft tissue and skeletal parameters were assessed using the lateral cephalograms. Lateral cephalograms were obtained using a KODAC 8000 C Digital Panoramic and Cephalometric system (Carestream Dental, Atlanta, GA, USA) at a voltage range of 70 kVp and a current range of 10 mA. To ensure proper head positioning, a cephalostat was employed and the central beam was directed towards the left side of the face with a standardized magnification of 10%. All patients were instructed to bite in a centric occlusion and were advised to swallow. All caphalograms were obtained by an oral and maxillofacial radiologist with 10 years of experience at T0 and T1 (Fig. 4).
A level 1 testing protocol was employed for PSG examination (Alice 5 Philips Respironics PSG; Murrysville, PA, USA), necessitating overnight sleep in a sleep laboratory under the supervision of a trained technician. This procedure entailed recording a minimum of 7 data channels (although typically ≥16), encompassing respiratory, cardiovascular, and neurologic parameters, to generate an all-encompassing representation of sleep architecture. All parameters were assessed at T0 (pretreatment) and after 8 months of treatment with an intraoral appliance denoted as T1 (posttreatment).
Assessment of Reliability
Twenty lateral cephalograms and CBCT scans were evaluated after 2 weeks by the same investigators, who were blinded to the previous scores and measurements. The intraclass correlation coefficient (ICC) of reliability and Dahlberg’s method were used to assess intra-examiner reliability, and a paired sample t-test was applied to detect any systematic errors in the measurements. The ICCs demonstrated strong intra-examiner reliability, ranging from 0.823–0.947. The method error, according to Dahlberg’s formula, ranged between 0.3% and 1.8%, and paired sample t-tests indicated no significant differences between the first and second measures (p > 0.05), reflecting non-significant systematic errors.
Statistical Analysis
Statistical analysis was performed at a 95% confidence level with a statistical significance of p-value less than 0.05. Statistical analyses were performed using IBM SPSS version 23 (IBM Corp., Armonk, NY, USA). The Shapiro-Wilk test was used to check the normality of the data. As data were normally distributed for all variables, parametric tests, such as the paired t-test, were used for intragroup comparisons. Continuous variables were summarized as mean and standard deviation, and categorical variables were summarized using percentage.
RESULTS
The mean age of the participants was 11.7 ± 1.5 years. Fourteen patients were in CVM stage 2 and 8 patients were in CVM stage 3, which shows that all patients were in the active growth phase. The baseline characteristics of the study participants are presented in Table 2. The mean BMI of the participants was 34.12 ± 5.89 kg/m2 which showed that 54% patients were obese and 32% were overweight [12]. The mean neck circumference was 28.62 ± 3.81 cm. This showed that the patients were obese according to a study that established the thresholds for neck circumference in girls, which was found to be 26.9 cm, and can be utilized as indicative measures of excess body weight and obesity within the 6–10-year age group of children [13]. The pretreatment mean IMW and ICW indicated a narrow maxillary arch. The overjet was increased with the presence of normal overbite. Eight patients had Mallampati Class 1 score, 12 patients had Mallampati Class 2 score, and 2 patients had Mallampati Class 3 score. Based on a research analysis, it had been determined that for each incremental unit of the Mallampati score, the likelihood of experiencing OSA was doubled [14].
The null hypothesis was rejected as statistically significant improvements in airway and skeletal parameters were observed after treatment. Customized fixed intraoral appliance was very effective in bringing about skeletal and soft tissue changes. Statistically significant changes were observed in all cephalometric variables (p < 0.05), except for tongue length (p > 0.05). There was restriction in maxillary growth (0.55° decrease in SNA angle), increase in mandibular growth (1.98° increase in SNB angle), maxilla-mandibular relationship improved by 1.01° (as observed by decrease in ANB angle), hyoid bone moved anteriorly and cranially (increase in anterior displacement of hyoid bone by 0.29 mm and cranial movement by 0.79 mm). This led to an increase in the posterior pharyngeal space, improving the airway in patients with OSA. An increase in the length and thickness of the soft palate was observed (Table 3).
There was statistically significant increase in the mean intermolar width by 9.39 ± 4.26 mm and 5.55 ± 8.91 mm in mean intercanine width after 8 months of treatment due to maxillary arch expansion by hyrax screw incorporated in the customized fixed intraoral appliance. There was no statistically significant difference in the mean BMI and neck circumference of the patients during the treatment period, as shown in Table 4.
PSG examination revealed statistically significant improvements in all parameters after placement of fixed intraoral mandibular advancement with maxillary expansion (p < 0.05). There was a significant improvement in AHI, events/hour, SpO2%, and sleep efficiency. The duration of longest OSA episode was reduced by 6.9 ± 4.5 seconds, and duration of desaturation in total sleep time of 7–8 hours was reduced by 13.1 ± 1.6 seconds (Table 5).
CBCT measurements revealed that there was statistically significant increase in NPA (10.9 ± 2.2 mm3), OPA (10.5 ± 1.34 mm3), HPA (3.3 ± 1.17 mm3), and TA (19.0 ± 4.77 mm3) after placement of appliance in OSA patients. The maximum increase was noticed in upper airway as compared to lower airway (Table 6).
DISCUSSION
OSA is characterized by distinct characteristics, such as repetitive narrowing or blockage of the upper airway during sleep, resulting in frequent drops in oxygen levels that lead to awakening [1]. Failure to address OSA can adversely affect neurocognitive abilities. Study by Triplett et al. [15] has shown a relatively higher prevalence of OSA in individuals with skeletal Class II than in those with skeletal Class I OSA. The present study was undertaken to assess the dentofacial parameters, airway, and PSG in skeletal Class II children with a constricted maxillary arch and retrognathic mandible suffering from OSA. According to clinical practice guidelines established by the American Academy of Sleep Medicine (AASM) and the American Academy of Dental Sleep Medicine (AADSM), the diagnosis and ongoing management of OSA are typically within the purview of sleep physicians [16]. However, according to Behrents et al. [17], dentists and orthodontists have a unique opportunity to screen and identify potential OSA patients given the frequency of recommended dental visits and the inclusion of upper airway assessment as part of routine dental examinations.
The proper utilization of screening tools can play a crucial role in reducing the risk of OSA. Nevertheless, it is concerning that fewer than 50% of dentists can recognize the common signs and symptoms of OSA according to previous studies [18,19]. This highlights the need for closer examination of the content covered in dental education programs and ongoing professional development courses. As part of the irregular dental checkups, which are typically recommended every 4–6 months, dentists have the opportunity to identify a narrow upper airway and various anatomical factors and signs indicative of OSA.
This research constituted the screening of patients with skeletal Class II malocclusion, after which a thorough intraoral examination was performed with respect to grading of tonsils according to the Mallampati scoring [14], measurement of intercanine distance, and inter-molar width. Cephalometric analysis using a cephalogram was used to assess skeletal Class II malocclusion, the position of the hyoid, and the length and thickness of the soft palate and tongue. PSG was used to confirm the diagnosis of OSA and to assess improvement after treatment with a fixed intraoral appliance. CBCT scans were used for the airway analysis. Class II patients with OSA were provided an RME device incorporated with a modified twin-block appliance. The RME technique was used to expand the maxillary arch using a Timms protocol, and a fixed twin-block appliance was employed to advance the mandibular arch. This was a modification of the original twin block appliance [20]. The fixed design of the twin block increased the wearing time of the appliance to 24 hours and was not dependent on patient compliance, leading to more improvement, compared to removable twin block [19]. The independence of the two components of twin-block appliances allows for the mandible to be elongated and the maxilla to be expanded concurrently. The primary benefits associated with this device include the patient’s ability to utilize it during meals and its capacity to advance the mandible in individuals experiencing transverse issues simultaneously. RME exerts a positive influence on the nasal airway, leading to a notable augmentation in the nasopharyngeal area. The previous studies have used removable twin block with jack screw for slow maxillary expansion (SME). It has been well documented that RME produce more skeletal effects, compared to SME [21], and therefore, the present study used RME screw for skeletal effects which required bonded (fixed) twin block. Moreover, in a recent study conducted by Wei and Xue [22] in 2023, it was concluded that fixed twin block led to more skeletal effects than removable twin block in growing patients at CVM stage of 2 and 3.
However, in the context of OSA, which primarily involves upper respiratory issues, the focus is on expanding the constricted maxilla and correcting retrognathic mandible. The present study revealed that the modified twin block effectively increased mandibular growth and led to significant improvement in the posterior airway, decreased AHI, and increased SpO2 levels, which aligns with the findings of a systematic review [23]. Maxilla expansion was performed using an RME screw. Eight months of treatment, with simultaneous advancement of the mandibular jaw, led to condylar growth. This change in mandibular repositioning resulted in improved facial profile and airway function in patients with OSA, eventually improving their quality of life. A study by Alansari and Kaki [20] demonstrated an improved effect of oval palatal expansion in diminishing the size of upper airway lymphoid tissues in the pediatric OSA population characterized by an arrow high-arched palate and adenotonsillar hypertrophy. The results of our study showed statistically significant improvements in airway function. This exemplifies the significance of utilizing a combination of two efficacious techniques (RME and mandibular advancement by twin block) in order to optimize their respective effects. The outcomes of the intervention in our research were achieved within a span of 8 months, and the brevity of this duration could possibly be attributed to the prompt initiation of treatment during a stage where bone plasticity is high and growth potential is at its peak. A recent meta-analysis showed that RME led to 70% AHI reduction and improvement in the lowest oxygen saturation up to 5.7% in children with OSA [23].
The observed enhancement in the upper airway, namely the NPA, following RME and mandibular advancement therapy can be related to the augmentation of nasal volume, particularly the internal nasal valve level, which showed significant changes with a mean difference of 10.58 mm3 in the present study. The process of nasal volume expression results in a reduction in air velocity and resistance within the nasal cavity [24], consequently alleviating recurrent inflammation in the lymphoid tissue, which enhances the flow of air through the nasal passages, leading to the generation of reduced inspiratory pressure below atmospheric levels, which reduces the susceptibility of the pharyngeal airway to collapse [25]. The appliance also led to the correction of tongue position, which showed a significant change in tongue height, resulting in an improvement in the retroglossal and retropharyngeal dimensions [26,27], thus increasing the OPA by 8.2 mm3. Finally, enlargement of the posterior portion of the maxilla might have a direct impact on the tension and functioning of the soft palate, leading to an increase in the length and thickness of the soft palate.
The present study also revealed significant changes in the position of the hyoid bone, which showed anterior and cranial movements after treatment with mandibular advancement. This further improved the posterior airway. This finding was in agreement with that of a previous study [28]. Ozdemir et al. [29] did not observe any alteration in the positioning of the hyoid bone subsequent to the implementation of fixed functional therapy for Class II malocclusion. It is possible that the patients in the post-peak growth period could have played a role in the lack of modification in the placement of the hyoid bone, as seen in the study [29].
The present study revealed a significant improvement in cervical flexion angle. It has been observed that children belonging to skeletal Class II exhibited a markedly greater inclination of the cranium in relation to the vertebral column compared to children classified as Class I and Class III [30]. This could be due to hyperextension of the head due to breathing difficulties associated with the retrognathic mandible in class II patients. Such alterations in the posture of the craniocervical region may represent a compensatory response aimed at facilitating the opening of the airways that become obstructed as a result of allergies or adenoid hypertrophy. Conversely, this misalignment of the cervical spine may not be a reaction but rather a factor contributing to impaired respiratory function. Broadly speaking, inadequate muscle tone in any area of the body can give rise to changes in the posture of the craniocervical region and position of the mandible, both of which serve as attachment sites for myofascial chains [31,32]. Our findings were in agreement with those of a systematic review by Zokaitė et al. [33]. Therefore, the customized fixed intra-oral appliance used in our study proved to be beneficial in cases of pediatric OSA where both maxilla and mandible are affected.
One of the limitations of the present study was that it was a single-center study. A multicenter, randomized controlled trial will provide concrete evidence. Further studies can also include the use of magnetic resonance imaging to enhance the resolution of the soft tissue in order to evaluate alterations in the adenoid volume subsequent to RME and to explore the potential changes in the cephalometric parameters and the specific anatomical region affected by these alterations. The present study was conducted on female patients only, to avoid any bias due to gender differences. Moreover, the limited sample size in this study restricts the application of multivariate analysis. Consequently, forthcoming randomized controlled trials involving a larger sample size encompassing both genders is recommended to evaluate the effectiveness of the customized appliance employed in the current study.
The customized fixed intraoral appliance employed in this study proved to be efficacious in rectifying skeletal Class II caused by a retrognathic mandible and a constricted maxillary arch. This ultimately results in the improvement of the soft tissue profile, dental relation, skeletal jaw bases, and overall enhancement of the airway in individuals with OSA, thereby augmenting the patient’s quality of life from a young age.
Significant improvements in airway, PSG assessment, and skeletal parameters were observed in skeletal Class II patients with retrognathic mandible and narrow maxillary arch in OSA. Significant anterior and caudal movements were observed for the hyoid bone, with improvement in the craniocervical flexure. Early diagnosis and treatment of OSA are essential for its effective management.
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