Indian Journal of Dental Research

: 2021  |  Volume : 32  |  Issue : 3  |  Page : 280--287

Association of sleep disturbances and craniofacial characteristics in children with class ii malocclusion: An evaluative study

Krishna Balraj, Vabitha Shetty, Amitha Hegde 
 Department of Pedodontics and Preventive Dentistry, A B Shetty Memorial Institute of Dental Sciences, Karnataka, India

Correspondence Address:
Dr. Vabitha Shetty
Department of Pedodontics and Preventive Dentistry, A.B Shetty Memorial Institute of Dental Sciences, Deralakatte, Mangalore - 575 018, Karnataka


Background: Behaviour problems, poor academic performance and failure to thrive are some of the potential sequelae of sleep problems in children. Hence, there is a need to evaluate the prevalence of sleep problems and significant associations in children with skeletal class II malocclusion with mandibular retrognathism. Aims: This study aimed to determine associations if any between sleep practices and problems and craniofacial characteristics in children with skeletal class II malocclusion with mandibular deficiency. Settings and Design: A cross-sectional study was conducted among a group of children with skeletal class II malocclusion with mandibular retrognathism. Materials and Methods: Fifty children aged 8–14 years with skeletal class II with mandibular retrognathism and who required myofunctional therapy were selected. A validated sleep questionnaire assessed the sleep practices and problems. A detailed clinical examination including tonsils and evaluation for mouth breathing was performed. A lateral cephalogram recorded specific linear, angular variables as well as upper and lower pharyngeal airway space. Statistical Analysis: Descriptive statistics, frequency, and percentages were calculated, and the Chi-square test was used. Results: All children reported at least one sleep problem, with snoring reported by 76% of the children. Forty-two percent of the children showed a decreased upper airway, whereas 80% showed a decreased lower airway. Significant associations were seen between SN-MP and noisy breathing, upper airway, and snoring with a P value of 0.017. We also found significant associations between upper and lower airway and sleep positions with a P value of 0.021 and 0.005, respectively. Conclusion: All the children exhibited at least one sleep problem. There was a strong association of certain sleep practices and sleep problems with cephalometric variables.

How to cite this article:
Balraj K, Shetty V, Hegde A. Association of sleep disturbances and craniofacial characteristics in children with class ii malocclusion: An evaluative study.Indian J Dent Res 2021;32:280-287

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Balraj K, Shetty V, Hegde A. Association of sleep disturbances and craniofacial characteristics in children with class ii malocclusion: An evaluative study. Indian J Dent Res [serial online] 2021 [cited 2022 Aug 17 ];32:280-287
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Sleep is a vital indicator of overall health and well-being. We spend up to one-third of our lives asleep, and the overall state of our “sleep health” remains an essential question throughout our lifespan.[1] Babies, children, and teens need significantly more sleep than adults to support their rapid mental and physical development. Most parents know that growing kids need good sleep, but many don't know just how many hours kids require, and what the impact can be of missing as little as 30 to 60 minutes of sleep time.[2]

Slow-wave sleep, the most restorative form of sleep, is largely governed by the frontal cortex, which mediates higher functions, such as decision-making, ambition, and emotional regulation. Disrupting this restorative process via either sleep fragmentation or hypoxemia may affect frontal cortex functioning and lead to aspects of the behavioural phenotype seen with childhood obstructive sleep apnoea (OSA).[3],[4],[5]

Poor sleep affects the mental status of the child leading to problems in attention and behaviour.[6],[7],[8],[9] Even mild sleep disturbances can be associated with several health problems both somatic as well as psychiatric.[6] Behavioural problems, learning problems as well as poor academic performance in school are some of the potential sequelae of sleep problems in children.[10],[11],[12],[13],[14],[15],[16]

Sleep also fuels physical growth. Growth hormone is released from the pituitary gland throughout the day. However, in children, it is released mostly after the beginning of deep sleep. So, disturbances in sleep can also affect the growth of the child.

In a previous study, the sleep practices and sleep problems in a group of 500 school children aged 4–10 years were assessed by a questionnaire survey.[17] We designed and validated a sleep questionnaire that was filled by the parents. We found out that almost half the children exhibited at least one sleep problem and observed a strong association of certain sleep practices with specific sleep problems. During the study, we also noticed a large number of children with dental and skeletal malocclusions. However, the associations between paediatric sleep disorders caused by upper airway obstruction and craniofacial morphology are poorly understood and contradictory.

Class II malocclusion is more frequently encountered and treated malocclusion in clinical practice. A higher prevalence of narrower upper pharyngeal airways has been observed in cases with class II malocclusion involving vertical growth patterns of the facial structure when compared with controls who have class I and class II with normal growth patterns.[18]

Hence, the present study was undertaken to evaluate the prevalence of sleep practices and problems in a group of children with skeletal class II malocclusion with mandibular retrognathism. We further sought to examine the association of sleep practices and problems in these children with their craniofacial characteristics.

 Materials and Methods

Study design

This cross-sectional study was undertaken from March 2018 to June 2018 among 50 non-syndromic children aged 8–14 years of either gender who reported to the Department of Pedodontics and Preventive Dentistry, for interceptive orthodontic treatment. The study was approved by the institutional ethical committee (Cert. No: ABSM/EC52/2016) and was in accordance with the 1964 Helsinki declaration and its later amendments. The purpose and nature of the study were explained to the parents/care providers, and written informed consent was obtained from them. Verbal assent from children was obtained.

Sampling and sample size

We have included only children who reported to our outpatient department (OPD) requiring myofunctional therapy and who met the inclusion criteria for the study. The sample size was estimated based on a retrospective analysis of the OPD records in the Department from the previous year from March to June (four months). This number was then used in the formula (Yamane method) assuming a 95% confidence interval and error level of 0.05. The sample size calculated was 47, but a total of 50 children reported during this period and gave their assent to be a part of the study.

Inclusion criteria:

Children diagnosed as having:

Skeletal Class II with mandibular retrognathism/deficiency.

Exclusion criteria:

Children with

Underlying systemic diseaseHandicapping conditionChildren on medicationsUncooperative children

Data collection

The following data were collected and recorded by a single well-trained examiner.

A validated sleep study questionnaire[17] was administered to the children regarding their demographic data, medical history, sleep practices and problems.A clinical examination, evaluating the children's oral clinical features with a detailed intraoral assessment[19] including examination of tonsils[20] and mouth breathing tests were done.[21],[22],[23],[24]A lateral cephalogram was used for recording the following:

Specific angular variables were recorded in degrees (+/- standard deviation)[25] [Figure 1]Specific linear variables were recorded in millimetres (+/- standard deviation)[25] [Figure 2]Upper and lower pharyngeal airway space[25] was measured and recorded in millimetres [Figure 3].{Figure 1}{Figure 2}{Figure 3}

Statistical analysis

Descriptive statistics frequency and percentages were calculated. A Chi-square test was used to find an association between clinical findings, medical history, and cephalometric readings with sleep problems and practices. P < 0.05 was considered statistically significant. Microsoft Excel and IBM SPSS Statistics for Windows, version 22.0 Armonk, NY: IBM Corp was used for statistical analysis.



21 girls (42%) and 29 boys (58) with a mean age of 11.4 ± 1.64 (ranging from 8 to 14 years) participated in our study. Using the revised Kuppuswamy scale[26] as a reference for socioeconomic status, we found that 45 (90%) of the children belonged to the upper-middle class and only 5 (10%) belonged to the upper class.

Medical history

Birth history analysis showed that 45 children had full-term birth, whereas 5 of them had a preterm birth. Analysis of the growth of the children showed that 19 children (38%) had a loss of appetite. Using the paediatric growth chart[27] as a reference, it was found that 32 children (64%) had adequate BMI, whereas 10 children (20%) belonged to the thinness category, 1 child (2%) belonged to the severe thinness category, 3 children (6%) were overweight and 4 children (8%) were obese.

Behavioural and academic performance

Analysis of behavioral problems revealed that all the children had at least one behavioural problem out of which, 28 children (56%) had anxiety, 16 children (32%) had attention deficit and 2 children (4%) were shy and timid.

Clinical findings

Assessment of tonsils revealed that more than half of the children (56%) had grade 1 tonsils, 26% had grade 0, and 14% had grade 2. When the presence of mouth breathing was assessed, we found that most children were mouth breathers (92%).

Prevalence of sleep practices in the children

We found a high prevalence of bedroom and bed-sharing amongst the children (96% and 88% respectively). A total of 86% of children watched TV or used the computer after 8 pm or at bedtime. A total of 88% of children showed difficulty in waking up in the morning during weekdays [Table 1].{Table 1}

Prevalence of sleep problems in children

The most commonly reported sleep problem were snoring, sleeping with mouth open and noisy breathing (76%, 100% and 14%, respectively) [Table 2].{Table 2}

Cephalometric values of the children

[Table 3] summarizes the cephalometric variables of the children. Twenty-five (50%) children exhibited decreased sella-nasion/mandibular plane angle (SN-MP) and Basal plane (Pal-MP) angles. Twenty-six (52%) children obtained a higher-than-normal Jarabak's ratio. Forty one (82%) children obtained a larger than average upper incisor-sella/nasion (U-SN) angle, whereas forty-two (84%) children obtained a larger than average lower incisor axis and mandibular plane, posteriorly (L-MP) angle.{Table 3}

Association between SN-MP and noisy breathing

We found significant associations between sella-nasion/ mandibular plane (SN-MP) angle and noisy breathing (P = 0.017, [Table 4]).{Table 4}

Association between upper airway (posterior nasal spine [PNS]-AD1) and snoring

We found a significant association between decreased upper airway and snoring (P = 0.017, [Table 5]).{Table 5}

Association between upper airway (PNS-AD1) and sleep position

We found a significant association between upper airway space and various sleep positions (P = 0.021, [Table 6]). We see from our results that among those children with a normal airway space (56%), the most common sleep position practiced was a side position (32%), whereas among those with decreased upper airway space (42%), the most common sleep position reported was on the stomach position (16%), closely followed by the side position (12%).{Table 6}

Association between lower airway (IAS) and sleep position

Analysis of the findings related to lower airway space showed that a decreased lower airway space (80%) was more commonly associated with reported sleep position on the side (30%), which was closely followed by a combination of side and back positions (26%). The pattern of reported sleep positions is shown to have a statistically significant association with the lower airway space as well (P = 0.005, [Table 7]).{Table 7}


Sleep-disordered breathing symptoms and the associated craniofacial features are often reported in the orthodontic clinical setting. Although a large orthodontic population is an ideal setting for screening morphologic features associated with paediatric sleep-disordered breathing, few studies have screened such populations or attempted to correlate sleep-disordered breathing symptoms with craniofacial characteristics.[19]

Behavioural symptoms are very often the primary complaints reported by parents of children with sleep-disordered breathing. The data from our study revealed that all children had at least one behavioural problem of which the majority reported attention deficit (32%) and anxiety (56%). This is in contrast with a study conducted by Venkata et al.[28] who found a prevalence of attention deficit hyperactivity (11.32%).

In our study, children were observed to have an adequate duration of sleep as per recommended guidelines.[2] Interestingly, we found that almost all children shared a bedroom as well as shared a bed with either a parent or sibling. This could reflect the cultural, social and familial norms in our country which emphasize the development of interdependence and family closeness and are socially well accepted. Bed-sharing is prevalent in other Asian countries as well.[29],[30] However, our study showed a higher prevalence of bed-sharing than reported by Yang and Hahn[31] (45.0%). It is uncertain, however, what impact bedroom/bed-sharing could have had on the sleep patterns of the children. The data from our study showed that most of the children (86%) used TV or computer after 8 pm or at bedtime. The practice could be a reflection of the changing lifestyle and modernization taking place in all sections of the society in our country today.

Analysis of sleep problems revealed that all children reported at least one sleep problem with snoring and sleeping with mouth open, the most commonly reported sleep problems (76% and 100% respectively), followed by noisy breathing (14%). Chronic snoring although common in adulthood is considered abnormal in the paediatric population.[32] According to the American Academy of Paediatrics clinical practice guidelines for sleep-disordered breathing, children should be routinely screened for snoring.[33]

We had found a prevalence of 4.2% for snoring in a previous study[17] which had assessed sleep problems in a group of school-going children. Therefore, the high percentage of children with snoring (76%) found in the present study is significant and could be considered as a potential predictor for sleep problems in this group of children.

Obstructions of the upper airways due to adenotonsillar hypertrophy can induce prolonged oral respiration during critical growth periods in children and consequently initiate a sequence of events that commonly result in dental and skeletal alterations which could predispose the child to sleep-disordered breathing.[34],[35] However, in our study, assessment of tonsils revealed that only one-fifth of the children had significant enlargement of the tonsils. This finding demonstrates that in the present study, sleep problems observed in the children cannot be attributed to enlarged tonsils alone. We also found that most of the children had mouth breathing (92%). Mouth breathing, in turn, could cause abnormal craniofacial development.[36]

A total of twelve cephalometric measurements were measured for each child, seven angular and five linear measurements. About half of the children had sella-nasion-A point (SNA) within the normal range, whereas 32% had decreased SNA, and very few children had increased SNA. Hence, we infer that half of the children had a normal maxilla, whereas all children had a retrognathic mandible as part of the fulfilment of the inclusion criteria. We found an increased A point-nasion-B point (ANB) angle in all children. In the present study, most children had larger than average Upper Incisor-Sella/Nasion (U-SN) and L-MP angles which indicated that most children had maxillary and mandibular incisor protrusion. However, the increased ANB angle, overjet, and overbite were not highly associated with the sleep practices and problems found in the children.

In our study, we found that half of the children had a decreased SN-MP as well as a decreased Pal-MP angles. From this, we infer that about half the children exhibited a horizontal type of growth pattern. Increased lower anterior face height and mandibular plane hyper divergence are common in adults diagnosed with OSA.[37] A meta-analysis in adults has shown the strongest correlation between mandibular plane divergence with the severity of OSA.[38] However, in our study, we found decreased SN-MP and Pal-MP values in half the children. This indicated that most children had a horizontal growth pattern. This finding was supported by the values obtained from Jaraback's ratio which also indicated a predominantly horizontal growth pattern in the children.

When airway assessment was done, we found almost half the children had a decreased upper airway, whereas the majority of the children showed a decreased lower airway. This could be probably because pharyngeal airway dimensions become narrower due to posterior positioning of the tongue and soft palate in subjects with retrognathic mandibles.[39],[40]

In children diagnosed with OSA, the upper airway shows narrowing. Upper airway narrowing in children with primary snoring has also been reported in the literature but to a lesser extent in comparison with children with OSA.[41],[42] The size of the upper airway and factors contributing to its narrowing can lead to an increased risk of collapse and subsequent abnormal breathing during sleeping.

We found significant associations between SN-MP and noisy breathing as well as between decreased upper airway and snoring in the present study. The most common sleep position among the children with decreased upper airway space was observed to be on the stomach position. The possible reason for this could be that these children found breathing easier in this position. The most common sleep position among the children with decreased lower airway space was on the side as well as a combination of side and back positions.

At the end of the present study, all children were treated with myofunctional appliances (twin block with and without headgear) for the correction of the skeletal disharmony, for a minimum period of 10 months. They were recalled for regular (monthly) follow-ups and evaluations. Twenty children were followed up with a re-evaluation of their sleep problems, as well as skeletal and airway assessment at the end of the myofunctional treatment. We also assessed lung function using spirometry tests before and after the myofunctional treatment to determine changes in lung volume.

One limitation of our study was the reliance on the two-dimensional lateral cephalogram to assess three-dimensional structures. Nevertheless, it is a valid screening tool with greater accessibility, lower costs and lower radiation doses than 3-dimensional volumetric cone-beam computed tomography (CBCT) in our orthodontic setting.

There is a growing need to make medical and dental practitioners aware of sleep disturbances in young children and associated craniofacial disharmony. As the otolaryngologist and the paediatrician are the first to have contact with children with these problems, these professionals must be alert for the presence of sleep disorders thus intervening early. A detailed recording of sleep history, clinical examination and cephalometric analysis can provide the paediatric dentist easy accessible early warning signs of the possible presence or future development of sleep problems, paving the way for further investigation and specialist referrals. The importance of identifying risk factors or predictors at an early stage so that early intervention with a multidisciplinary approach could be adopted is crucial so that children at high risk for sleep-disordered breathing could be identified. Appropriate therapeutic intervention by a paediatric dentist using functional appliance therapy to improve the skeletal relationship and increasing pharyngeal airway dimensions could improve facial aesthetics, dentoalveolar relationship as well as improve airflow, thereby having a long-term impact on the child's overall quality of life.


Bedroom/bed sharing was seen in almost all children. All children had at least one behaviour problem with anxiety and attention deficit found to be most common. All children reported at least one sleep problem, with sleeping with mouth open seen in all children and snoring seen in most of the children. The majority of the children showed a decreased lower airway, whereas almost half the children had a decreased upper airway. A significant association was seen between SN-MP and noisy breathing and upper airway and snoring. We also found significant associations between upper and lower airway and sleep positions.


All children should be evaluated for the presence of snoringCBCT evaluation of airway should be planned for a more detailed examination of the pharyngeal airway.The importance of identifying risk factors and predictors at an early stage is of vital importance in these children so that early intervention could be instituted.Polysomnographic examination of the children at risk is recommended for a definitive diagnosis.We should consider functional appliance therapy in growing children with the anatomic predisposition to narrowing of the pharyngeal airways as part of their clinical management.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


1How much sleep do we really need?. 2017. Available from: [Last accessed on 2017 Oct 10].
2How much sleep do babies and kids need?. 2017. Available from: and-kids-need. [Last accessed on 2017 Oct 10].
3Jan JE, Reiter RJ, Bax MC, Ribary U, Freeman RD, Wasdell MB. Long-term sleep disturbances in children: A cause of neuronal loss. Eur J Paediatr Neurol 2010;14:380-90.
4Beebe DW. Cognitive, behavioural, and functional consequences of inadequate sleep in children and adolescents. Pediatr Clin North Am 2011;58:649-65.
5Gozal D, Kheirandish-Gozal L. Neurocognitive and behavioural morbidity in children with sleep disorders. Curr Opin Pulm Med 2007;13:505-9.
6Paavonen E, Aronen E, Moilanen I, Piha J, Räsänen E, Tamminen T, et al. Sleep problems of school-aged children: A complementary view. Acta Paediatrica 2000;89:223-8.
7Chervin R, Dillon J, Bassetti C, Ganoczy DA, Pituch KJ. Symptoms of sleep disorders, inattention, and hyperactivity in children. Sleep 1997;20:1185-92.
8Wiggs L, Stores G. Severe sleep disturbance and daytime challenging behaviour in children with severe learning disabilities. J Intellect Disabil Res 1996;40:518-28.
9Kahn A, Van de Merckt C, Rebuffat E, Mozin MJ, Sottiaux M, Blum D, et al. Sleep problems in healthy preadolescents. Pediatrics 1989;84:542-6.
10Ipsiroglu O, Fatemi A, Werner I, Paditz E, Schwarz B. Self-reported organic and nonorganic sleep problems in schoolchildren aged 11 to 15 years in Vienna. J Adolesc Health 2002;31:436-42.
11Anders TF, Eiben LA. Pediatric sleep disorders: A review of the past 10 years. J Am Acad Child Adolesc Psychiatry 1997;36:9-20.
12Dahl R. The impact of inadequate sleep on children's daytime cognitive function. Semin Pediatr Neurol 1996;3:44-50.
13Gozal D. Sleep-disordered breathing and school performance in children. Pediatrics 1998;102:616-20.
14Webb WB. Sleep, The Gentle Tyrant. 2nd ed. Boston: Anker Pub Co; 1992.
15Wiggs L, Stores G. Behavioural treatment for sleep problems in children with severe learning disabilities and challenging daytime behaviour: Effect on daytime behaviour. J Child Psychol Psychiatry 1999;40:627-35.
16Wolfson AR, Carskadon MA. Sleep schedules and daytime functioning in adolescents. Child Dev 1998;69:875-87.
17Yerra A, Shetty V, Hegde MA. Correlation of nutritional status to sleep problems in school children: A preliminary study. Indian J Sleep Med 2018;13:1-4.
18Carroll JL. Obstructive sleep-disordered breathing in children: New controversies, new directions. Clin Chest Med 2003;24:261-82.
19Huynh NT, Morton PD, Rompré PH, Papadakis A, Remise C. Associations between sleep-disordered breathing symptoms and facial and dental morphometry, assessed with screening examinations. Am J Orthod Dentofacial Orthop 2011;140:762-70.
20Brodsky L. Modern assessment of tonsils and adenoids. Pediatr Clin North Am 1989;36:1551-69.
21Massler M, Zwemer JD. Mouth breathing. II. Diagnosis and treatment. J Am Dent Assoc 1953;46:658-71.
22Lusvarghi L, Paiva JB de, Arrais A, Bianchini EMG, Rino ML de M. Identifying the mouth breather. [Interview]. Journal of the São Paulo Association of Dental Surgeons. 1999;53:265-74.
23De Menezes VA, Leal RB, Pessoa RS, Pontes RM. Prevalence and factors related to mouth breathing in school children at the Santo Amaro project-Recife, 2005. Brazilian Journal of otorhinolaryngology. 2006;72:394-8.
24Bae P. Deglutição atípica. Separata Reeducação mioterápica nas pressões atípicas da língua. Ortodontia 1976;9:5-9.
25Katyal V, Pamula Y, Daynes CN, Martin J, Dreyer CW, Kennedy D, et al. Craniofacial and upper airway morphology in pediatric sleep-disordered breathing and changes in quality of life with rapid maxillary expansion. Am J Orthod Dentofacial Orthop 2013;144:860-71.
26Kumar BR, Dudala SR, Rao AR. Kuppuswamy's socio-economic status scale–A revision of economic parameter for 2012. Int J Res Dev Health 2013;1:2-4.
27Onis MD, Onyango AW, Borghi E, Siyam A, Nishida C, Siekmann J. Development of a WHO growth reference for school-aged children and adolescents. Bull World Health Organ 2007;85:660-7.
28Venkata JA, Panicker AS. Prevalence of attention deficit hyperactivity disorder in primary school children. Indian J Psychiatry 2013;55:338-42.
29Liu X, Liu L, Wang R. Bed sharing, sleep habits, and sleep problems among Chinese school-aged children. Sleep 2003;26:839-44.
30Latz S, Wolf AW, Lozoff B. Cosleeping in context: Sleep practices and problems in young children in Japan and the United States. Arch Pediatr Adolesc Med 1999;153:339-46.
31Yang CK, Hahn HM. Cosleeping in young Korean children. J Dev Behav Pediatr 2002;23:151-7.
32O'Brien LM, Mervis CB, Holbrook CR, Bruner JL, Klaus CJ, Rutherford J, et al. Neurobehavioral implications of habitual snoring in children. Pediatrics 2004;114:44-9.
33Gislason T, Benediktsdottir B. Snoring, apneic episodes, and nocturnal hypoxemia among children 6 months to 6 years old. An epidemiologic study of lower limit of prevalence. Chest 1995;107:963-6.
34Luzzi V, Di Carlo G, Saccucci M, Ierardo G, Guglielmo E, Fabbrizi M, et al. Craniofacial morphology and airflow in children with primary snoring. Eur Rev Med Pharmacol Sci 2016;20:3965-71.
35Guilleminault C, Akhtar F. Pediatric sleep-disordered breathing: New evidence on its development. Sleep Med Rev 2015;24:46-56.
36Sousa JB, Anselmo-Lima WT, Valera FC, Gallego AJ, Matsumoto MA. Cephalometric assessment of the mandibular growth pattern in mouth-breathing children. Int J Pediatr Otorhinolaryngol 2005;69:311-7.
37Tangugsorn V, Skatvedt O, Krogstad O, Lyberg T. Obstructive sleep apnoea: A cephalometric study. Part II. Uvulo-glossopharyngeal morphology. Eur J Orthod 1995;17:57-67.
38Miles PG, Vig PS, Weyant RJ, Forrest TD, Rockette HE Jr. Craniofacial structure and obstructive sleep apnea syndrome—A qualitative analysis and meta-analysis of the literature. Am J Orthod Dentofacial Orthop 1996;109:163-72.
39Abu Allhaija ES, Al-Khateeb SN. Uvulo-glosso-pharyngeal dimensions in different anteroposterior skeletal patterns. Angle Orthod 2005;75:1012-8.
40Ceylan I, Oktay H. A study on the pharyngeal size in different skeletal patterns. Am J Orthod Dentofacial Orthop 1995;108:69-75.
41Liukkonen K, Virkkula P, Haavisto A, Suomalainen A, Aronen ET, Pitkäranta A, et al. Symptoms at presentation in children with sleep-related disorders. Int J Pediatr Otorhinolaryngol 2012;76:327-33.
42Pirilä-Parkkinen K, Löppönen H, Nieminen P, Tolonen U, Pirttiniemi P. Cephalometric evaluation of children with nocturnal sleep-disordered breathing. Eur J Orthod 2010;32:662-71.