Relationships Between the Tonsillar Hypertrophy and Nocturnal Labial Incompetence in Children with Malocclusion

Relationships Between the Tonsillar Hypertrophy and Nocturnal Labial Incompetence in Children with Malocclusion | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Relationships Between the Tonsillar Hypertrophy and Nocturnal Labial Incompetence in Children with Malocclusion Ciao-syuan Cai, Yanmei Huang, Guoping Sheng, Xuepeng Chen, Baozhen Luo This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6501119/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Background : This study aimed to investigate the relationships between the tonsillar hypertrophy and nocturnal labial incompetence (NLI) in children with malocclusion. The findings are intended to inform early orthodontic or medical intervention strategies for children presenting with both tonsil hypertrophy and malocclusion. Methods : A retrospective study was conducted using initial consultation records, lateral cephalograms, online questionnaires, and telephone follow-ups. Tonsil hypertrophy was evaluated in the transverse dimension using Brodsky’s classification and in the anteroposterior dimension using the Baroni method on lateral cephalograms. Children were categorized into a hypertrophic tonsils group (Brodsky grade >2 or sagittal airway obstruction ≥50%) and a non-hypertrophic control group (Brodsky grade ≤2 and obstruction <50%). The prevalence of NLI was assessed with initial consultation records. Intergroup differences were analyzed using the Bonferroni-adjusted χ² test (α = 0.017). Results : A total of 190 children were included, with 68.9% in the hypertrophic group and 31.1% in the non-hypertrophic group. The overall prevalence of NLI was 82.6%, significantly higher in the hypertrophic group (96.2%) compared to the control group (52.6%, χ² = 53.98, P < 0.001). Among children with NLI, the overall improvement rate was 51.6%, with a significantly higher rate observed in those who underwent tonsillectomy (80.7%) than in those who did not (14.5%, χ² = 67.84, P < 0.001). Conclusions : Tonsil hypertrophy is significantly associated with increased prevalence of NLI in children. Tonsillectomy may substantially improve NLI symptoms, suggesting a potential therapeutic benefit in affected patients. Palatine tonsil Nocturnal labial incompetence Malocclusion Tonsil hypertrophy Tonsillectomy Figures Figure 1 1 Introduction Craniofacial development in children is influenced by both genetic and environmental factors. Functional abnormalities in various systems, such as respiratory and swallowing dysfunctions, as well as asymmetrical chewing, can influence craniofacial development, contributing to the occurrence and progression of malocclusion [ 1 ] . Among these, respiration, being a critical function of the craniofacial system, has gained increasing attention from orthodontists and parents due to its impact on craniofacial growth and development [ 2 , 3 ] . Tonsillar hypertrophy may contribute to upper airway compensation in children, leading to anterior displacement of the tongue and mandible, which may subsequently result in the development of skeletal Class III malocclusion. Conversely, adenoid hypertrophy is commonly associated with maxillary protrusion and mandibular retrusion, collectively presenting as the characteristic “Adenoid Facies” [ 4 ] . Nocturnal labial incompetence is a common non-physiological condition in pediatric patients. In comparison to sleep-disordered mouth breathing, it places greater emphasis on the anatomical state. It generally refers to an involuntary, sustained open-mouth posture during sleep, caused by increased resistance in the oropharyngeal airway (e.g., tonsillar hypertrophy) or nasal and nasopharyngeal obstruction (such as chronic rhinitis or adenoid hypertrophy), which induces a posteroinferior rotation of the mandible. Becking et al. categorized this sign of posterior mandibular displacement as one of the clinical manifestations of craniofacial adaptation in patients with obstructive sleep apnea (OSA) [ 5 ] . Nocturnal labial incompetence may exert adverse effects on craniofacial development, temporomandibular joint (TMJ) health, and even overall systemic well-being in children [ 6 – 14 ] . The clinical diagnosis of nocturnal labial incompetence is typically made through history-taking or by having the patient’s guardian complete a questionnaire. This pathological condition must be differentiated from mouth breathing. Not all cases of nocturnal labial incompetence can be diagnosed as sleep-disordered mouth breathing. Based on our clinical observations, many children seeking treatment for malocclusion also present with symptoms of nocturnal labial incompetence (NLI). However, further assessment using the double-mirror method revealed that not all of these patients exhibit mouth breathing [ 15 – 17 ] ; some children are able to maintain nasal respiration despite an open-mouth posture. Studies published in international literature more than a decade ago indicate that the prevalence of nocturnal labial incompetence in children can be as high as 50–56% [ 18 – 20 ] . Currently, no epidemiological studies on the incidence of nocturnal labial incompetence in children have been reported in China. The symptom of nocturnal labial incompetence has received insufficient academic attention from many researchers. This prompted our interest in exploring the NLI among children with malocclusion. Conditions that cause narrowing or obstruction of the upper airway may contribute to nocturnal labial incompetence in children, including chronic rhinitis, nasal polyps, septal deviation, adenoid hypertrophy, tonsil hypertrophy, tongue hypertrophy, laryngeal and tracheal stenosis, malocclusion, and mandibular hypoplasia [ 21 ] . Among these conditions, tonsil and/or adenoid hypertrophy are major commonly contributors to obstructive sleep apnea (OSA) and are significant structural factors in the development of nocturnal labial incompetence. However, most studies have attributed nocturnal labial incompetence to adenoid hypertrophy, and it remains inconclusive whether airway obstruction caused by tonsil hypertrophy is associated with nocturnal labial incompetence. Airway narrowing caused by tonsillar hypertrophy affects not only respiratory in children, but may also trigger compensatory responses, resulting in nocturnal labial incompetence and alterations in craniofacial growth patterns. Hence, investigating the association and underlying mechanisms between tonsillar hypertrophy and nocturnal labial incompetence is crucial for early airway intervention and systemic development in school-aged children with malocclusion. This study contrasts with most previous studies, which have focused on mouth breathing and adenoid hypertrophy. By comparing the prevalence of nocturnal labial incompetence between children with tonsillar hypertrophy and healthy controls, as well as evaluating the improvement of symptoms after tonsillectomy, it proposes a new concept regarding the potential relationship between tonsillar hypertrophy and nocturnal labial incompetence, providing valuable insights for clinical diagnosis and management. 2 Materials and methods This is a retrospective study, and the data required were collected from routine clinical records. Ethical approval for this study was granted by the Institutional Ethics Committee of Shulan (Hangzhou) Hospital (Approval Number: No. KY2025040). Informed consent was waived due to retrospective design of the study and the absence of identifiable patient information. 2.1 Participants Patients who visited the Department of Orthodontics at Stomatology Hospital, Zhejiang University School of Medicine, and the Department of Otolaryngology-Head and Neck Surgery at Shulan Hospital between July 2023 and February 2025 and had lateral cephalograms taken were included in the study. The patients were required to be aged between 3 and 14 years and had a clinical diagnosis of malocclusion. Exclusion criteria were as follows: adenoid A/N ratio ≥ 0.6 [ 22 ] , history of recurrent rhinitis, poor-quality cephalograms, craniofacial syndromes (e.g., cleft lip and palate), incomplete medical history, acute upper respiratory tract infections, maxillofacial trauma, temporomandibular joint osteoarthritis, or a history of previous orthodontic treatment. 2.2 Measurement and analysis 2.2.1 Tonsil size measurement Oral examination (using a tongue depressor) or nasopharynxgolaryngoscopy was used to diagnose tonsil hypertrophy in transverse direction. The Brodsky grading system was used for assessing tonsil size. It classifies tonsil size from 0 to 4 based on the proportion of the oropharyngeal width occupied by the bilateral tonsils, with tonsil hypertrophy diagnosed when the tonsils reach grades 3 or 4 [ 23 ] . Lateral cephalograms was used to diagnose tonsil hypertrophy in sagittal direction with Baroni method. On the lateral cephalograms, the posterior contour of the tonsil was identified, and the point closest to the posterior wall of the oropharyngeal airway was designated as the TP point. A perpendicular line was then drawn from the TP point to the posterior wall of the oropharyngeal airway, intersecting the anterior wall at the OA point and the posterior wall at the OP point. The anteroposterior width of the tonsil was defined as the distance between the OA point and the TP point, while the sagittal width of the oropharyngeal space was measured as the distance between the OA point and the OP point. The tonsillar obstruction rate was defined as the percentage of the anteroposterior width of the tonsil relative to the sagittal width of the oropharyngeal space. A tonsillar obstruction rate < 50% was considered normal, whereas a tonsillar obstruction rate ≥ 50% was classified as tonsil hypertrophy [ 24 ] . L line represents the posterior wall of the oropharyngeal space; red curve marks the posterior contour of the tonsil; blue curve represents the anterior wall of the oropharyngeal space; point TP is the point on the posterior contour of the tonsil that is closest to L line, specifically the most prominent point of the tonsillar contour; point OP is the foot of the perpendicular line from point TP to L line, where the perpendicular intersects the L line; point OA is the intersection of the perpendicular line from point TP to L line with the anterior wall of the oropharyngeal space; the anteroposterior width of the tonsil is the distance between point OA and TP; the sagittal width of the oropharyngeal space is the distance between point OA and OP. Nocturnal labial incompetence (present or absent) was assessed in the hypertrophic tonsils and non- hypertrophic tonsils groups using data from initial consultation records and online questionnaires. The percentage of children who responded “yes” was used to represent the nocturnal mouth opening rate in each group. For children with preexisting nocturnal mouth opening, a follow-up telephone survey was conducted on February 28, 2025, to assess symptom improvement in the tonsillectomy and non-surgical groups. Responses were likewise limited to “yes” or “no,” and the percentage of “yes” responses was calculated as the improvement rate in each group. 2.2.2 Quality control The measurement and diagnosis of tonsil and adenoid hypertrophy were performed by two specially trained physicians. In cases where the diagnosis of tonsil hypertrophy and adenoid hypertrophy was disputed, the final diagnosis was made after consultation with other authors. 2.3 Categorize All lateral cephalograms of the patients were obtained under standardized conditions by the lead radiologic technologist using the same device, Digital Diagnost, Philips Medical Systems, Eindhoven, Netherlands, with a tube voltage of 73.0 kV, tube current of 10.0 mA, and an exposure time of 1.1 seconds. All lateral cephalograms were obtained with the patient in the natural head position and the Intercuspal Position (ICP). Combined with intraoral examination findings, classification was carried out according to the Brodsky grading system and the Baroni method: the hypertrophic tonsils group (oral Brodsky grade > 2 or sagittal obstruction rate ≥ 50%) and non-hypertrophic tonsil group (oral Brodsky grade ≤ 2 and sagittal obstruction rate < 50%). Based on initial consultation records and online questionnaires, all patients were categorized into the tonsillectomy group and the non-surgical group according to their surgical history. Children who had undergone either intracapsular or extracapsular tonsillectomy were included in the tonsillectomy group. 2.4 Statistical methods Statistical analysis was conducted using SPSS version 27.0. A chi-square test (χ²) was used to compare the prevalence of nocturnal labial incompetence between the hypertrophic tonsils group and the non- hypertrophic tonsils group. A two-tailed P-value of < 0.05 was considered statistically significant. For those presenting with nocturnal labial incompetence, the χ² test was similarly employed to compare improvement rates between the tonsillectomy and non-surgical groups, considering P < 0.05 (two-tailed) as statistically significant. 3 Results Initially, a total of 203 patients meeting the inclusion criteria were enrolled, thirteen cases were excluded due to loss to follow-up or invalid responses, and 190 participants were finally included. Among these, 131 were from the hypertrophic tonsils group (68.9%) and 59 from the non-hypertrophic tonsils group (31.1%). The basic characteristics are presented in Table 1 . Eighty-eight patients (46.3%) underwent tonsillectomy, while 102 patients (53.7%) did not receive surgery. Table 1 Baseline characteristics of the participants Group N Underwent tonsillectomy Non-surgical Number of cases (%) Male/female (n) Age (years old) Number of cases (%) Gender (n) Age (years old) Hypertrophic tonsils 131 76 (58.0) 43/33 8.7 ± 2.4 55 (42.0) 35/20 7.5 ± 2.4 Non-hypertrophic tonsils 59 12 (20.3) 8/4 9.0 ± 2.0 47 (79.7) 23/24 8.6 ± 2.5 3.1 General condition The overall nocturnal labial incompetence rate in all patients was 82.6% (157/190), with rates of 85.3% (93/109) in males and 79.0% (64/81) in females. According to the χ² test, there was no statistically significant difference in nocturnal labial incompetence between sexes (χ² = 1.29, P = 0.256). 3.2 Hypertrophic tonsils group In this cohort of patients, the preoperative in the hypertrophic tonsils group and the non-hypertrophic tonsils group were 96.2% (126/131) and 52.6% (31/59), respectively (Table 2 ). The χ² test revealed that the nocturnal labial incompetence rate in the experimental group was significantly higher than in the non-hypertrophic tonsils group (χ² = 53.98, P < 0.001). Table 2 Comparison of preoperative nocturnal labial incompetence the frequency and rate between the hypertrophic tonsils group and the non-hypertrophic tonsils group Group Male Female x 2 (2) P N Preoperative nocturnal labial incompetence [n(%)] N Preoperative nocturnal labial incompetence [n(%)] Hypertrophic tonsils 78 73 (93.6) 53 53 (100.0) 3.53 0.081 Non-hypertrophic tonsils 31 20 (64.5) 28 11 (39.3) 3.76 0.053 x 2 (2) 14.97 40.73 - - P < 0.001 < 0.001 - - The prevalence of nocturnal labial incompetence in the hypertrophic tonsils group was significantly higher than that in the non-hypertrophic tonsils group (P < 0.001). A total of 126 tonsil hypertrophy patients with preoperative nocturnal labial incompetence were included in the study. The preoperative nocturnal labial incompetence proportions in children with both anteroposterior and lateral hypertrophy, pure anteroposterior hypertrophy, and pure lateral hypertrophy were 96.2% (51/53), 95.9% (70/73), and 100.0% (5/5), respectively. No statistically significant differences were found in the preoperative nocturnal labial incompetence proportions among the different tonsil hypertrophy dimensions (χ² = 0.22, P = 0.898). 3.3 Underwent tonsillectomy group Preoperative nocturnal labial incompetence rates of 100.0% (88/88) in the tonsillectomy group and 67.6% (69/102) in the non-surgical group. The χ² test revealed that the proportion of preoperative nocturnal labial incompetence in the tonsillectomy group was significantly higher than in the non-surgical group (χ² = 34.46, P < 0.001). A total of 157 patients with preoperative nocturnal labial incompetence were included (Table 3 ). The overall improvement rate of nocturnal labial incompetence was 51.6% (81/157). The improvement rates in the underwent tonsillectomy group and the non-surgical group were 80.7% (71/88) and 14.5% (10/69), respectively, indicating that the improvement rate in the underwent tonsillectomy group was significantly higher than that in the non-surgical group (χ² = 67.84, P < 0.001). Additionally, the improvement rates for male and female patients were 52.7% (49/93) and 51.6% (33/64), respectively. The χ² test showed no statistically significant difference between the two groups (P > 0.05). Table 3 Comparison of the frequency and rate of improvement in nocturnal labial incompetence between the underwent tonsillectomy and non-surgical groups Group Male Female x 2 (2) P N Improvement of nocturnal labial incompetence [n(%)] N Improvement of nocturnal labial incompetence [n(%)] Underwent tonsillectomy 51 42 (82.4) 37 30 (81.1) 0.02 0.879 Non-surgical 42 7 (16.7) 27 3 (11.1) 0.41 0.729 x 2 (2) 39.87 30.60 - - P < 0.001 < 0.001 - - 4 Discussion 4.1 Participant characteristics Based on our clinical observations, it was noted that a significant proportion of children with malocclusion exhibit nocturnal labial incompetence (NLI), despite not meeting the diagnostic criteria for mouth breathing (i.e., oral airflow exceeding 25–30%) [ 15 – 17 ] . Nasopharynxgolaryngoscopy examinations further revealed that although these children were nasal breathers, their upper airways appeared more patent during open-mouth breathing compared to closed-mouth breathing. Moreover, most children presenting with NLI were found to have visibly tonsillar hypertrophy. Motivated by these findings, this study was designed to investigate the relationships between tonsillar hypertrophy and nocturnal labial incompetence in children with malocclusion through an analysis of initial clinical records, questionnaires, and lateral cephalograms. 4.1.1 Hypertrophic tonsils group The preoperative nocturnal labial incompetence rate in the hypertrophic tonsils group (93.6% in males, 100.0% in females) was significantly higher than in the non- hypertrophic tonsils group (64.5% in males, 39.3% in females) (P < 0.001), suggesting that tonsillar hypertrophy may be an important clinical indicator for the development of nocturnal labial incompetence. The proposed mechanism is that tonsillar hypertrophy causes airway obstruction, forcing children to maintain an open-mouth posture to alleviate ventilation difficulties, leading to the abnormal behavior of nocturnal labial incompetence. Although this study controlled for various confounding variables known to affect nocturnal labial incompetence—such as adenoid hypertrophy, recurrent rhinitis, and prior orthodontic treatment—31 children in the non-hypertrophy group still exhibited nocturnal labial incompetence. This may be attributed to three factors: (1) Dentofacial characteristics—older children, particularly those in later stages of development, may already exhibit compensatory features related to airway compromise, such as maxillary protrusion or excessive lip strain, leading to difficulty in lip closure [ 5 ] ; (2) Adenoid contribution—some children may have A/N ratios approaching the diagnostic threshold (0.6), which could still influence oral breathing [ 25 ] ; (3) Clinical observations suggest that many Brodsky grade 2 children demonstrate typical symptoms of tonsillar hypertrophy, including snoring and nocturnal labial incompetence, possibly inflating the control group’s prevalence. These findings raise questions regarding the accuracy of classifying Brodsky grade 2 patients as “non-hypertrophic” in clinical settings. Lastly, no statistically significant differences were observed in the rates of nocturnal labial incompetence among children when stratified by sex or by different dimensions of tonsillar hypertrophy (anteroposterior and lateral diameters, isolated anteroposterior or lateral hypertrophy) (P > 0.05), suggesting that these factors are not decisive in determining the occurrence of nocturnal labial incompetence in children. 4.1.2 Underwent tonsillectomy group Among children with nocturnal labial incompetence, the overall improvement rate was 51.6% (81/157). Notably, the improvement rate in those who underwent tonsillectomy (80.7%) was significantly higher than that in the non-surgical group (14.5%), indicating that tonsillectomy is an effective intervention for alleviating nocturnal labial incompetence in children. This may be attributed to the surgical removal of the underlying cause of upper airway obstruction, which relieves ventilatory insufficiency and subsequently leads to the gradual disappearance of the non-physiological labial incompetence behavior. Notably, in the non-surgical group, 10 children demonstrated improvement in nocturnal labial incompetence. Several possible explanations are proposed: (1) Rhinitis-related factors—some children may have experienced nocturnal labial incompetence due to previously undiagnosed rhinitis, which had resolved by the time of follow-up, leading to spontaneous lip closure; (2) Adenoid-related factors—children with borderline adenoid hypertrophy (A/N ratio near 0.6) may have shown improvement in nocturnal labial incompetence due to medication or natural involution of adenoid tissue with age; (3) Age-related factors—older children may have developed craniofacial characteristics associated with airway obstruction, such as anterior crossbite or Class III malocclusion. According to previous studies and the authors’ clinical observations, children with Class III facial profiles rarely exhibit nocturnal labial incompetence, possibly due to forward mandibular compensation that facilitates airway patency and alleviates the need for mouth opening [ 26 – 28 ] . Furthermore, 11 participants in this study, despite being diagnosed without tonsillar hypertrophy, underwent tonsillectomy attributable to a history of chronic tonsillitis, which conforms to the surgical indications specified in the 2025 clinical guidelines promulgated by the China Maternal and Child Health Association Minimally Invasive Chapter Pediatric ORL Group [ 29 ] . 4.2 Impact of nocturnal labial incompetence on malocclusion The most readily observable adverse effect of nocturnal labial incompetence in children is altered dentofacial development. Changes in breathing patterns during critical growth periods can result in adaptations of the oral and maxillofacial structures. It affects the development and morphology of the tongue, dental arches, alveolar bone, and jaws [ 6 – 8 , 30 ] , resulting in maxillary arch constriction, a high-arched palate, underdevelopment of the midface and nasal cavity, excessive labial inclination of the upper incisors, mandibular retrusion accompanied by clockwise rotation, posterior tongue positioning, low positioning of the hyoid bone, elongated facial height, and an altered craniofacial musculature balance [ 25 ] . Linder-Aronson’s study indicated that nocturnal labial incompetence leads to a lowered tongue position and mandibular retrusion, which subsequently contribute to a hyperdivergent growth pattern, anterior open bite, and a high-arched palate [ 31 , 32 ] . Experimental studies in animals have further confirmed that prolonged nocturnal labial incompetence in primates results in skeletal abnormalities, including clockwise mandibular rotation and maxillary constriction [ 33 ] . Prolonged nocturnal labial incompetence may also inhibit functional mandibular protrusion through the trigeminal nerve-brainstem-masticatory muscle feedback loop, exacerbating mandibular retrusion. This process can result in irreversible skeletal malocclusion, further contributing to the onset and progression of obstructive sleep apnea (OSA) [ 26 , 34 ] . The findings of our study indicate that the overall rate of nocturnal labial incompetence among participants (82.6%) was markedly higher than that reported in previous studies (50–56%) [ 18 – 20 ] . One possible explanation is a selection bias related to healthcare utilization, as most participants sought medical attention due to notable clinical symptoms, which may have inflated the positivity rate. Another contributing factor may be the current clinical emphasis on mouth breathing, with insufficient recognition of the high prevalence of nocturnal labial incompetence. 4.3 Impact of tonsillar hypertrophy on nocturnal labial incompetence and malocclusion Nasal breathing is the normal physiological mode of respiration, maintaining a balance between intraoral and extraoral muscular forces, including those of the cheeks and tongue, which helps preserve normal oral cavity volume and dental arch width. However, upper airway obstruction caused by conditions such as adenotonsillar hypertrophy can lead to respiratory dysfunction, resulting in nocturnal labial incompetence. This disrupts the balance of orofacial muscle forces, triggering adaptive changes in the oral and maxillofacial system. Prolonged alterations in facial muscle activity and head posture can significantly impact the morphology, position, and growth direction of the jawbones [ 17 , 35 ] . In our study, the rate of tonsillar hypertrophy in all participants (68.9%) was notably higher than that reported in previous studies (11%) [ 36 ] . In addition to differences in patient presentation and referral patterns, the disparity may reflect a shift in diagnostic perspectives over time. Earlier evaluations primarily focused on lateral tonsillar hypertrophy based on Brodsky classification [ 23 , 37 ] , potentially underestimating the clinical significance of anteroposterior hypertrophy and its contribution to airway obstruction. Previous studies have demonstrated that adenotonsillar hypertrophy in children may result in sagittal, transverse, and vertical three-dimensional alterations of craniofacial morphology [ 31 ] . It is generally believed that the mechanism by which tonsillar hypertrophy contributes to Class III malocclusion may involve a reduction in upper airway volume, forcing affected children to maintain airway patency by adopting a mandibular open-mouth posture and elevating the hyoid bone. Such postural adjustments may result in a backward and downward rotation of the mandible, further contributing to a hyperdivergent growth pattern, anterior open bite, and narrowing of the maxillary dental arch [ 26 ] . Iwasaki found that, in children with Class III malocclusion, tonsil size was associated with the anterior positioning of both the tongue and the mandibular incisors. Tonsillar hypertrophy may push the tongue forward, consequently promoting mandibular protrusion and exacerbating anterior crossbite [ 26 ] . Additionally, Nunes et al. observed that children with tonsillar hypertrophy often presented with pseudo-Class III malocclusion, likely due to compensatory forward tongue positioning caused by airway obstruction. Habitual mouth breathing and forward tongue posture in these children may result in progressive mandibular protrusion, further contributing to the development of Class III malocclusion [ 27 , 28 ] . Tonsillectomy is one of the most commonly performed routine procedures in pediatric otolaryngology and head and neck surgery. Several studies have shown that tonsillectomy can have a positive impact on dentofacial development in children with tonsillar hypertrophy, with postoperative findings indicating a mandibular advancement of 0.8–1.5 mm and a 34% reduction in the incidence of posterior crossbite [ 5 ] .Based on the findings of this study, among patients with preexisting nocturnal labial incompetence, the proportion of improvement in nocturnal labial incompetence was significantly higher in the tonsillectomy group (82.4% in males, 81.1% in females) compared to the non-surgical group (16.7% in males, 11.1% in females). These results suggest that tonsillectomy effectively alleviates upper airway obstruction and plays a crucial role in improving nocturnal labial incompetence in school-aged children. These positive findings are consistent with the study by Linder-Aronson et al., which demonstrated that children who underwent tonsillectomy exhibited a gradual shift in mandibular growth direction toward counterclockwise rotation. This evidence supports the notion that tonsillectomy can effectively alleviate airway obstruction and contribute to the correction of jaw development in children [ 32 ] .However, it is important to note that tonsillectomy alone does not guarantee the complete correction of nocturnal labial incompetence in children. Postoperatively, a combined approach with orthodontic intervention is recommended to actively address nocturnal labial incompetence and prevent its persistent adverse effects on craniofacial development. 4.4 Multidisciplinary treatment In summary, nocturnal labial incompetence, tonsillar hypertrophy and malocclusion interact in a mutually reinforcing manner, collectively contributing to disturbances in craniofacial growth and systemic health in school-aged children. Tonsillar hypertrophy induces upper airway obstruction, which promotes nocturnal labial incompetence and alters orofacial muscle dynamics. This disruption leads to adaptive changes in maxillofacial morphology, further exacerbating malocclusion. In turn, malocclusion can perpetuate nocturnal breathing dysfunction, reinforcing airway obstruction and maintaining the cycle of impairment. The interdependence of these three factors highlights their compounded impact on both facial development and overall health. School-aged children are in a critical period of rapid craniofacial growth and development, during which nocturnal labial incompetence and other detrimental oral habits can exert adverse and potentially irreversible effects on the dentition and maxillofacial structures. These negative impacts may progressively worsen with growth, amplifying their influence over time. If not addressed through timely and effective intervention, these habits may lead to severe dentofacial deformities, significantly increasing the complexity of subsequent orthodontic and other corrective treatments. As a result, it is recommended that orthodontists routinely assess the degree of upper airway obstruction caused by tonsillar hypertrophy in children with nocturnal labial incompetence using intraoral examination and lateral cephalograms during clinical evaluations. Patients diagnosed with tonsil hypertrophy should be promptly referred to the otolaryngology department for further assessment and management. A multidisciplinary approach integrating orthodontic and otolaryngologic expertise can enhance treatment efficiency and ensure the long-term stability of subsequent orthodontic interventions. 4.5 Limitations Several limitations of the present study should be acknowledged. Firstly, the assessment of nocturnal labial incompetence was primarily based on parental reports and retrospective consultation records, which may introduce recall bias and lack objective clinical verification. Secondly, the participants were recruited from children seeking treatment at an orthodontic clinic, there is a possibility of selection bias, which may limit the generalizability of the findings to the broader pediatric population. Lastly, the cross-sectional nature of this study precludes the establishment of causal relationships between tonsillar hypertrophy and nocturnal labial incompetence. 5 Conclusions In contrast to the traditional emphasis on mouth breathing, nocturnal labial incompetence (NLI) is highly prevalent in children with malocclusion. Without timely intervention, it can adversely affect craniofacial growth and compromise orthodontic treatment results. Increased attention from both clinicians and caregivers is therefore essential. After excluding other potential causes of upper airway obstruction, the prevalence of nocturnal labial incompetence was found to be significantly higher in children with tonsillar hypertrophy compared to the control group, suggesting that tonsillar hypertrophy may be one of the contributing factors to nocturnal labial incompetence. The rate of improvement in nocturnal labial incompetence was significantly higher among children who underwent tonsillectomy than those who did not, indicating that tonsillectomy may serve as an effective therapeutic approach for managing nocturnal labial incompetence. Declarations Clinical trial number Not applicable. Ethics approval and consent to participate This retrospective study was approved by the Institutional Ethics Committee of Shulan (Hangzhou) Hospital (Approval Number: No. KY2025040). The requirement for informed consent was waived due to the retrospective nature of the study and the use of anonymized data. No identifiable personal information of individual patients was collected or disclosed. Consent to participate Not applicable. Informed consent was waived due to retrospective design of the study and the absence of identifiable patient information. Consent for publication Not applicable. This manuscript does not contain any individual person’s data in any form (including images, videos, or other identifying information), thus consent for publication was not required. Availability of data and materials All data generated or analysed during this study are included in this published article. Competing interests The authors declare that they have no competing interests. Funding This research was supported by the National Key Research and Development Program of China (Grant No. 2024YFA1307100). Author Guoping Sheng received funding. Authors' contributions CC: Methodology, Investigation, Visualization, Writing – original draft. YH: Data collection, Formal analysis, Writing – review & editing. GS: Funding acquisition, Writing – review & editing. XC: Supervision, Writing – review & editing. BL: Conceptualization, Resources, Writing – review & editing. All authors have read and approved the final manuscript. CC and YH contributed equally to this work and share first authorship. Acknowledgements The authors would like to thank Stomatology Hospital, School of Stomatology, Zhejiang University School of Medicine and Department of Otolaryngology-Head and Neck Surgery, Shulan (Hangzhou) Hospital for providing support for this study. References Moss M L, Salentijn L. The primary role of functional matrices in facial growth[J]. Am J Orthod, 1969, 55(6): 566-77. Behrents R G, Shelgikar A V, Conley R S, et al. Obstructive sleep apnea and orthodontics: An American Association of Orthodontists White Paper[J]. Am J Orthod Dentofacial Orthop, 2019, 156(1): 13-28.e1. He H. [Interpretation of "Obstructive sleep apnea and orthodontics: an American Association of Orthodontists White Paper"][J]. Zhonghua Kou Qiang Yi Xue Za Zhi, 2020, 55(9): 667-672. Zhao T, Yang Z, Ngan P, et al. Association between adenotonsillar hypertrophy and dentofacial characteristics of children seeking for orthodontic treatment: A cross-sectional study[J]. J Stomatol Oral Maxillofac Surg, 2024, 125(4): 101751. Becking B E, Verweij J P, Kalf-Scholte S M, et al. Impact of adenotonsillectomy on the dentofacial development of obstructed children: a systematic review and meta-analysis[J]. Eur J Orthod, 2017, 39(5): 509-518. Al Ali A, Richmond S, Popat H, et al. The influence of snoring, mouth breathing and apnoea on facial morphology in late childhood: a three-dimensional study[J]. BMJ Open, 2015, 5(9): e009027. Fraga W S, Seixas V M, Santos J C, et al. Mouth breathing in children and its impact in dental malocclusion: a systematic review of observational studies[J]. Minerva Stomatol, 2018, 67(3): 129-138. Grippaudo C, Paolantonio E G, Antonini G, et al. Association between oral habits, mouth breathing and malocclusion[J]. Acta Otorhinolaryngol Ital, 2016, 36(5): 386-394. Cheynet F. [TMJ, eating and breathing][J]. Rev Stomatol Chir Maxillofac Chir Orale, 2016, 117(4): 199-206. Ueki K, Moroi A, Sotobori M, et al. A hypothesis on the desired postoperative position of the condyle in orthognathic surgery: a review[J]. Oral Surg Oral Med Oral Pathol Oral Radiol, 2012, 114(5): 567-76. Alzarea B K. Temporomandibular Disorders (TMD) in Edentulous Patients: A Review and Proposed Classification (Dr. Bader's Classification)[J]. J Clin Diagn Res, 2015, 9(4): Ze06-9. Olczak-Kowalczyk D, Korporowicz E, Gozdowski D, et al. Oral findings in children and adolescents with Prader-Willi syndrome[J]. Clin Oral Investig, 2019, 23(3): 1331-1339. Lee S Y, Guilleminault C, Chiu H Y, Sullivan S S. Mouth breathing, "nasal disuse," and pediatric sleep-disordered breathing[J]. Sleep Breath, 2015, 19(4): 1257-64. Basheer B, Hegde K S, Bhat S S, et al. Influence of mouth breathing on the dentofacial growth of children: a cephalometric study[J]. J Int Oral Health, 2014, 6(6): 50-5. Vig P S, Spalding P M, Lints R R. Sensitivity and specificity of diagnostic tests for impaired nasal respiration[J]. Am J Orthod Dentofacial Orthop, 1991, 99(4): 354-60. Xianglong Z, Xuemei G. Diagnosis and treatment of mouth breathing in children[J]. Chinese Journal of Stomatology, 2020, 55(01): 3-8. Tingting Z, Hong H. Pediatric mouth breathing and malocclusion[J]. Chinese Journal of Stomatology, 2019, 26(04): 195-198. Gill A I, Schaughency E, Galland B C. Prevalence and factors associated with snoring in 3-year olds: early links with behavioral adjustment[J]. Sleep Med, 2012, 13(9): 1191-7. Garde J B, Suryavanshi R K, Jawale B A, et al. An epidemiological study to know the prevalence of deleterious oral habits among 6 to 12 year old children[J]. J Int Oral Health, 2014, 6(1): 39-43. Kharbanda O P, Sidhu S S, Sundaram K, Shukla D K. Oral habits in school going children of Delhi: a prevalence study[J]. J Indian Soc Pedod Prev Dent, 2003, 21(3): 120-4. Pacheco M C, Casagrande C F, Teixeira L P, et al. Guidelines proposal for clinical recognition of mouth breathing children[J]. Dental Press J Orthod, 2015, 20(4): 39-44. Shun Z M. The adenoid nasopharynx ratio: its clinical value in children[J]. Chinese Journal of Radiology, 1997(03): 43-45. Brodsky L. Modern assessment of tonsils and adenoids[J]. Pediatr Clin North Am, 1989, 36(6): 1551-69. Baroni M, Ballanti F, Franchi L, Cozza P. Craniofacial features of subjects with adenoid, tonsillar, or adenotonsillar hypertrophy[J]. Prog Orthod, 2011, 12(1): 38-44. Zhao Z, Zheng L, Huang X, et al. Effects of mouth breathing on facial skeletal development in children: a systematic review and meta-analysis[J]. BMC Oral Health, 2021, 21(1): 108. Iwasaki T, Sato H, Suga H, et al. Relationships among nasal resistance, adenoids, tonsils, and tongue posture and maxillofacial form in Class II and Class III children[J]. Am J Orthod Dentofacial Orthop, 2017, 151(5): 929-940. Diouf J S, Ngom P I, Sonko O, et al. Influence of tonsillar grade on the dental arch measurements[J]. Am J Orthod Dentofacial Orthop, 2015, 147(2): 214-20. Nunes W R, Jr., Di Francesco R C. Variation of patterns of malocclusion by site of pharyngeal obstruction in children[J]. Arch Otolaryngol Head Neck Surg, 2010, 136(11): 1116-20. Maternal C, Group C H a M I C P O. Standardized treatment technology for pediatric tonsillectomy and adenoidectomy with low-temperature coblation[J]. Journal of Clinical Otorhinolaryngology Head and Neck Surgery, 2025, 39(02): 97-109. Petraccone Caixeta A C, Andrade I, Jr., Bahia Junqueira Pereira T, et al. Dental arch dimensional changes after adenotonsillectomy in prepubertal children[J]. Am J Orthod Dentofacial Orthop, 2014, 145(4): 461-8. Linder-Aronson S. Adenoids. Their effect on mode of breathing and nasal airflow and their relationship to characteristics of the facial skeleton and the denition. A biometric, rhino-manometric and cephalometro-radiographic study on children with and without adenoids[J]. Acta Otolaryngol Suppl, 1970, 265: 1-132. Linder-Aronson S, Woodside D G, Lundström A. Mandibular growth direction following adenoidectomy[J]. Am J Orthod, 1986, 89(4): 273-84. Harvold E P, Tomer B S, Vargervik K, Chierici G. Primate experiments on oral respiration[J]. Am J Orthod, 1981, 79(4): 359-72. Yuanyuan L, Yuehua L. Multidisciplinary sequential diagnosis and treatment for mouth breathing in children[J]. Stomatology, 2024, 44(08): 565-569. Zheng W, Zhang X, Dong J, He J. Facial morphological characteristics of mouth breathers vs. nasal breathers: A systematic review and meta-analysis of lateral cephalometric data[J]. Exp Ther Med, 2020, 19(6): 3738-3750. Kara C O, Ergin H, Koçak G, et al. Prevalence of tonsillar hypertrophy and associated oropharyngeal symptoms in primary school children in Denizli, Turkey[J]. Int J Pediatr Otorhinolaryngol, 2002, 66(2): 175-9. Kumar D S, Valenzuela D, Kozak F K, et al. The reliability of clinical tonsil size grading in children[J]. JAMA Otolaryngol Head Neck Surg, 2014, 140(11): 1034-7. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 22 Oct, 2025 Reviews received at journal 19 Jun, 2025 Reviewers agreed at journal 14 Jun, 2025 Reviews received at journal 13 Jun, 2025 Reviewers agreed at journal 05 Jun, 2025 Reviewers invited by journal 04 Jun, 2025 Editor invited by journal 07 May, 2025 Editor assigned by journal 06 May, 2025 Submission checks completed at journal 06 May, 2025 First submitted to journal 22 Apr, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6501119","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":466985818,"identity":"c86e080a-2dd3-4b8e-9557-5dc7a0588b29","order_by":0,"name":"Ciao-syuan Cai","email":"","orcid":"","institution":"Stomatology Hospital, School of Stomatology, Zhejiang University School of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Ciao-syuan","middleName":"","lastName":"Cai","suffix":""},{"id":466985819,"identity":"5ac9afe8-206a-41cc-bb1d-9feccf1159d1","order_by":1,"name":"Yanmei Huang","email":"","orcid":"","institution":"Stomatology Hospital, School of Stomatology, Zhejiang University School of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Yanmei","middleName":"","lastName":"Huang","suffix":""},{"id":466985820,"identity":"c9db619d-a976-4fa7-a3bc-d25cb584886b","order_by":2,"name":"Guoping Sheng","email":"","orcid":"","institution":"Department of Otolaryngology-Head and Neck Surgery, Shulan (Hangzhou) Hospital, Shulan International Medical College, Zhejiang Shuren University","correspondingAuthor":false,"prefix":"","firstName":"Guoping","middleName":"","lastName":"Sheng","suffix":""},{"id":466985821,"identity":"30564fce-c89e-46d1-8336-97ab4176d2e5","order_by":3,"name":"Xuepeng Chen","email":"","orcid":"","institution":"Stomatology Hospital, School of Stomatology, Zhejiang University School of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Xuepeng","middleName":"","lastName":"Chen","suffix":""},{"id":466985822,"identity":"4f64c5a7-e9e6-4e4b-97d7-194a224830c8","order_by":4,"name":"Baozhen Luo","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4klEQVRIiWNgGAWjYBACAyBmBjH4GBgYHzA2MMgQr4UNSBsAtfCQpIVNgigt5uyHD38uqLgDVJ98rPLnjsM8/LMbGD98zMGtxbInLcF4xplnQC1pabd5zxzmkbhzgFly5jY8DjuQY5DM23YYqCXH7DZj22EehhsJbMy8+LScf2NwmPcfREvhT6AWeYJabuQYNvM2QLQwAK3jMSCkxXLGs2RmnmOHedh4niVL87al8xjeSGzG6xdz/uTDn3lqDsvxsycf/PizzVpO7kbywQ8f8WiBAeToAMbOKBgFo2AUjALKAADAEUtSIDZCcwAAAABJRU5ErkJggg==","orcid":"","institution":"Department of Otolaryngology-Head and Neck Surgery, Shulan (Hangzhou) Hospital, Shulan International Medical College, Zhejiang Shuren University","correspondingAuthor":true,"prefix":"","firstName":"Baozhen","middleName":"","lastName":"Luo","suffix":""}],"badges":[],"createdAt":"2025-04-22 06:53:27","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6501119/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6501119/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":84326385,"identity":"2f43b246-73cb-42c4-9c63-01ef7f4ba31d","added_by":"auto","created_at":"2025-06-10 15:09:26","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":914388,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic representation of tonsil and oropharyngeal airway measurements on a lateral cephalogram.\u003c/p\u003e\n\u003cp\u003eL line represents the posterior wall of the oropharyngeal space; red curve marks the posterior contour of the tonsil; blue curve represents the anterior wall of the oropharyngeal space; point TP is the point on the posterior contour of the tonsil that is closest to L line, specifically the most prominent point of the tonsillar contour; point OP is the foot of the perpendicular line from point TP to L line, where the perpendicular intersects the L line; point OA is the intersection of the perpendicular line from point TP to L line with the anterior wall of the oropharyngeal space; the anteroposterior width of the tonsil is the distance between point OA and TP; the sagittal width of the oropharyngeal space is the distance between point OA and OP.\u003c/p\u003e\n\u003cp\u003eNocturnal labial incompetence (present or absent) was assessed in the hypertrophic tonsils and non- hypertrophic tonsils groups using data from initial consultation records and online questionnaires. The percentage of children who responded “yes” was used to represent the nocturnal mouth opening rate in each group. For children with preexisting nocturnal mouth opening, a follow-up telephone survey was conducted on February 28, 2025, to assess symptom improvement in the tonsillectomy and non-surgical groups. Responses were likewise limited to “yes” or “no,” and the percentage of “yes” responses was calculated as the improvement rate in each group.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6501119/v1/0797c21637ee58b94f3dad2f.png"},{"id":84326888,"identity":"fb6123dc-4dc2-4619-9a31-ef6f7628c161","added_by":"auto","created_at":"2025-06-10 15:17:27","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1783502,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6501119/v1/0170074d-0d12-4c90-9be1-be48e8d80559.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Relationships Between the Tonsillar Hypertrophy and Nocturnal Labial Incompetence in Children with Malocclusion","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eCraniofacial development in children is influenced by both genetic and environmental factors. Functional abnormalities in various systems, such as respiratory and swallowing dysfunctions, as well as asymmetrical chewing, can influence craniofacial development, contributing to the occurrence and progression of malocclusion\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. Among these, respiration, being a critical function of the craniofacial system, has gained increasing attention from orthodontists and parents due to its impact on craniofacial growth and development\u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e. Tonsillar hypertrophy may contribute to upper airway compensation in children, leading to anterior displacement of the tongue and mandible, which may subsequently result in the development of skeletal Class III malocclusion. Conversely, adenoid hypertrophy is commonly associated with maxillary protrusion and mandibular retrusion, collectively presenting as the characteristic \u0026ldquo;Adenoid Facies\u0026rdquo;\u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eNocturnal labial incompetence is a common non-physiological condition in pediatric patients. In comparison to sleep-disordered mouth breathing, it places greater emphasis on the anatomical state. It generally refers to an involuntary, sustained open-mouth posture during sleep, caused by increased resistance in the oropharyngeal airway (e.g., tonsillar hypertrophy) or nasal and nasopharyngeal obstruction (such as chronic rhinitis or adenoid hypertrophy), which induces a posteroinferior rotation of the mandible. Becking et al. categorized this sign of posterior mandibular displacement as one of the clinical manifestations of craniofacial adaptation in patients with obstructive sleep apnea (OSA)\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. Nocturnal labial incompetence may exert adverse effects on craniofacial development, temporomandibular joint (TMJ) health, and even overall systemic well-being in children\u003csup\u003e[\u003cspan additionalcitationids=\"CR7 CR8 CR9 CR10 CR11 CR12 CR13\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e. The clinical diagnosis of nocturnal labial incompetence is typically made through history-taking or by having the patient\u0026rsquo;s guardian complete a questionnaire. This pathological condition must be differentiated from mouth breathing. Not all cases of nocturnal labial incompetence can be diagnosed as sleep-disordered mouth breathing. Based on our clinical observations, many children seeking treatment for malocclusion also present with symptoms of nocturnal labial incompetence (NLI). However, further assessment using the double-mirror method revealed that not all of these patients exhibit mouth breathing\u003csup\u003e[\u003cspan additionalcitationids=\"CR16\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e; some children are able to maintain nasal respiration despite an open-mouth posture. Studies published in international literature more than a decade ago indicate that the prevalence of nocturnal labial incompetence in children can be as high as 50\u0026ndash;56%\u003csup\u003e[\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e. Currently, no epidemiological studies on the incidence of nocturnal labial incompetence in children have been reported in China. The symptom of nocturnal labial incompetence has received insufficient academic attention from many researchers. This prompted our interest in exploring the NLI among children with malocclusion.\u003c/p\u003e \u003cp\u003eConditions that cause narrowing or obstruction of the upper airway may contribute to nocturnal labial incompetence in children, including chronic rhinitis, nasal polyps, septal deviation, adenoid hypertrophy, tonsil hypertrophy, tongue hypertrophy, laryngeal and tracheal stenosis, malocclusion, and mandibular hypoplasia\u003csup\u003e[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e. Among these conditions, tonsil and/or adenoid hypertrophy are major commonly contributors to obstructive sleep apnea (OSA) and are significant structural factors in the development of nocturnal labial incompetence. However, most studies have attributed nocturnal labial incompetence to adenoid hypertrophy, and it remains inconclusive whether airway obstruction caused by tonsil hypertrophy is associated with nocturnal labial incompetence.\u003c/p\u003e \u003cp\u003eAirway narrowing caused by tonsillar hypertrophy affects not only respiratory in children, but may also trigger compensatory responses, resulting in nocturnal labial incompetence and alterations in craniofacial growth patterns. Hence, investigating the association and underlying mechanisms between tonsillar hypertrophy and nocturnal labial incompetence is crucial for early airway intervention and systemic development in school-aged children with malocclusion. This study contrasts with most previous studies, which have focused on mouth breathing and adenoid hypertrophy. By comparing the prevalence of nocturnal labial incompetence between children with tonsillar hypertrophy and healthy controls, as well as evaluating the improvement of symptoms after tonsillectomy, it proposes a new concept regarding the potential relationship between tonsillar hypertrophy and nocturnal labial incompetence, providing valuable insights for clinical diagnosis and management.\u003c/p\u003e"},{"header":"2 Materials and methods","content":"\u003cp\u003eThis is a retrospective study, and the data required were collected from routine clinical records. Ethical approval for this study was granted by the Institutional Ethics Committee of Shulan (Hangzhou) Hospital (Approval Number: No. KY2025040). Informed consent was waived due to retrospective design of the study and the absence of identifiable patient information.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Participants\u003c/h2\u003e \u003cp\u003ePatients who visited the Department of Orthodontics at Stomatology Hospital, Zhejiang University School of Medicine, and the Department of Otolaryngology-Head and Neck Surgery at Shulan Hospital between July 2023 and February 2025 and had lateral cephalograms taken were included in the study. The patients were required to be aged between 3 and 14 years and had a clinical diagnosis of malocclusion. Exclusion criteria were as follows: adenoid A/N ratio\u0026thinsp;\u0026ge;\u0026thinsp;0.6\u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e, history of recurrent rhinitis, poor-quality cephalograms, craniofacial syndromes (e.g., cleft lip and palate), incomplete medical history, acute upper respiratory tract infections, maxillofacial trauma, temporomandibular joint osteoarthritis, or a history of previous orthodontic treatment.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Measurement and analysis\u003c/h2\u003e \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e \u003ch2\u003e2.2.1 Tonsil size measurement\u003c/h2\u003e \u003cp\u003e Oral examination (using a tongue depressor) or nasopharynxgolaryngoscopy was used to diagnose tonsil hypertrophy in transverse direction. The Brodsky grading system was used for assessing tonsil size. It classifies tonsil size from 0 to 4 based on the proportion of the oropharyngeal width occupied by the bilateral tonsils, with tonsil hypertrophy diagnosed when the tonsils reach grades 3 or 4\u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eLateral cephalograms was used to diagnose tonsil hypertrophy in sagittal direction with Baroni method. On the lateral cephalograms, the posterior contour of the tonsil was identified, and the point closest to the posterior wall of the oropharyngeal airway was designated as the TP point. A perpendicular line was then drawn from the TP point to the posterior wall of the oropharyngeal airway, intersecting the anterior wall at the OA point and the posterior wall at the OP point. The anteroposterior width of the tonsil was defined as the distance between the OA point and the TP point, while the sagittal width of the oropharyngeal space was measured as the distance between the OA point and the OP point. The tonsillar obstruction rate was defined as the percentage of the anteroposterior width of the tonsil relative to the sagittal width of the oropharyngeal space. A tonsillar obstruction rate\u0026thinsp;\u0026lt;\u0026thinsp;50% was considered normal, whereas a tonsillar obstruction rate\u0026thinsp;\u0026ge;\u0026thinsp;50% was classified as tonsil hypertrophy\u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eL line represents the posterior wall of the oropharyngeal space; red curve marks the posterior contour of the tonsil; blue curve represents the anterior wall of the oropharyngeal space; point TP is the point on the posterior contour of the tonsil that is closest to L line, specifically the most prominent point of the tonsillar contour; point OP is the foot of the perpendicular line from point TP to L line, where the perpendicular intersects the L line; point OA is the intersection of the perpendicular line from point TP to L line with the anterior wall of the oropharyngeal space; the anteroposterior width of the tonsil is the distance between point OA and TP; the sagittal width of the oropharyngeal space is the distance between point OA and OP.\u003c/p\u003e \u003cp\u003eNocturnal labial incompetence (present or absent) was assessed in the hypertrophic tonsils and non- hypertrophic tonsils groups using data from initial consultation records and online questionnaires. The percentage of children who responded \u0026ldquo;yes\u0026rdquo; was used to represent the nocturnal mouth opening rate in each group. For children with preexisting nocturnal mouth opening, a follow-up telephone survey was conducted on February 28, 2025, to assess symptom improvement in the tonsillectomy and non-surgical groups. Responses were likewise limited to \u0026ldquo;yes\u0026rdquo; or \u0026ldquo;no,\u0026rdquo; and the percentage of \u0026ldquo;yes\u0026rdquo; responses was calculated as the improvement rate in each group.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e2.2.2 Quality control\u003c/h2\u003e \u003cp\u003eThe measurement and diagnosis of tonsil and adenoid hypertrophy were performed by two specially trained physicians. In cases where the diagnosis of tonsil hypertrophy and adenoid hypertrophy was disputed, the final diagnosis was made after consultation with other authors.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Categorize\u003c/h2\u003e \u003cp\u003eAll lateral cephalograms of the patients were obtained under standardized conditions by the lead radiologic technologist using the same device, Digital Diagnost, Philips Medical Systems, Eindhoven, Netherlands, with a tube voltage of 73.0 kV, tube current of 10.0 mA, and an exposure time of 1.1 seconds. All lateral cephalograms were obtained with the patient in the natural head position and the Intercuspal Position (ICP). Combined with intraoral examination findings, classification was carried out according to the Brodsky grading system and the Baroni method: the hypertrophic tonsils group (oral Brodsky grade\u0026thinsp;\u0026gt;\u0026thinsp;2 or sagittal obstruction rate\u0026thinsp;\u0026ge;\u0026thinsp;50%) and non-hypertrophic tonsil group (oral Brodsky grade\u0026thinsp;\u0026le;\u0026thinsp;2 and sagittal obstruction rate\u0026thinsp;\u0026lt;\u0026thinsp;50%).\u003c/p\u003e \u003cp\u003eBased on initial consultation records and online questionnaires, all patients were categorized into the tonsillectomy group and the non-surgical group according to their surgical history. Children who had undergone either intracapsular or extracapsular tonsillectomy were included in the tonsillectomy group.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Statistical methods\u003c/h2\u003e \u003cp\u003eStatistical analysis was conducted using SPSS version 27.0. A chi-square test (χ\u0026sup2;) was used to compare the prevalence of nocturnal labial incompetence between the hypertrophic tonsils group and the non- hypertrophic tonsils group. A two-tailed P-value of \u0026lt;\u0026thinsp;0.05 was considered statistically significant. For those presenting with nocturnal labial incompetence, the χ\u0026sup2; test was similarly employed to compare improvement rates between the tonsillectomy and non-surgical groups, considering P\u0026thinsp;\u0026lt;\u0026thinsp;0.05 (two-tailed) as statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results","content":"\u003cp\u003eInitially, a total of 203 patients meeting the inclusion criteria were enrolled, thirteen cases were excluded due to loss to follow-up or invalid responses, and 190 participants were finally included. Among these, 131 were from the hypertrophic tonsils group (68.9%) and 59 from the non-hypertrophic tonsils group (31.1%). The basic characteristics are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Eighty-eight patients (46.3%) underwent tonsillectomy, while 102 patients (53.7%) did not receive surgery.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003cem\u003eBaseline characteristics of the participants\u003c/em\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c5\" namest=\"c3\"\u003e \u003cp\u003eUnderwent tonsillectomy\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c8\" namest=\"c6\"\u003e \u003cp\u003eNon-surgical\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNumber of cases (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMale/female\u003c/p\u003e \u003cp\u003e(n)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAge (years old)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eNumber of cases (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eGender (n)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eAge (years old)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHypertrophic tonsils\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e131\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e76 (58.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e43/33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e8.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e55 (42.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e35/20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e7.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNon-hypertrophic tonsils\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e12 (20.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8/4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e9.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e47 (79.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e23/24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e8.6\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.1 General condition\u003c/h2\u003e \u003cp\u003eThe overall nocturnal labial incompetence rate in all patients was 82.6% (157/190), with rates of 85.3% (93/109) in males and 79.0% (64/81) in females. According to the χ\u0026sup2; test, there was no statistically significant difference in nocturnal labial incompetence between sexes (χ\u0026sup2; = 1.29, P\u0026thinsp;=\u0026thinsp;0.256).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Hypertrophic tonsils group\u003c/h2\u003e \u003cp\u003eIn this cohort of patients, the preoperative in the hypertrophic tonsils group and the non-hypertrophic tonsils group were 96.2% (126/131) and 52.6% (31/59), respectively (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The χ\u0026sup2; test revealed that the nocturnal labial incompetence rate in the experimental group was significantly higher than in the non-hypertrophic tonsils group (χ\u0026sup2; = 53.98, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003cem\u003eComparison of preoperative nocturnal labial incompetence the frequency and rate between the hypertrophic tonsils group and the non-hypertrophic tonsils group\u003c/em\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ex\u003csup\u003e2\u003c/sup\u003e(2)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePreoperative nocturnal labial incompetence [n(%)]\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePreoperative nocturnal labial incompetence [n(%)]\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHypertrophic tonsils\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e73 (93.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e53 (100.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.081\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNon-hypertrophic tonsils\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20 (64.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e11 (39.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.053\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ex\u003csup\u003e2\u003c/sup\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e14.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e40.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe prevalence of nocturnal labial incompetence in the hypertrophic tonsils group was significantly higher than that in the non-hypertrophic tonsils group (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). A total of 126 tonsil hypertrophy patients with preoperative nocturnal labial incompetence were included in the study. The preoperative nocturnal labial incompetence proportions in children with both anteroposterior and lateral hypertrophy, pure anteroposterior hypertrophy, and pure lateral hypertrophy were 96.2% (51/53), 95.9% (70/73), and 100.0% (5/5), respectively. No statistically significant differences were found in the preoperative nocturnal labial incompetence proportions among the different tonsil hypertrophy dimensions (χ\u0026sup2; = 0.22, P\u0026thinsp;=\u0026thinsp;0.898).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Underwent tonsillectomy group\u003c/h2\u003e \u003cp\u003ePreoperative nocturnal labial incompetence rates of 100.0% (88/88) in the tonsillectomy group and 67.6% (69/102) in the non-surgical group. The χ\u0026sup2; test revealed that the proportion of preoperative nocturnal labial incompetence in the tonsillectomy group was significantly higher than in the non-surgical group (χ\u0026sup2; = 34.46, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e \u003cp\u003eA total of 157 patients with preoperative nocturnal labial incompetence were included (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The overall improvement rate of nocturnal labial incompetence was 51.6% (81/157). The improvement rates in the underwent tonsillectomy group and the non-surgical group were 80.7% (71/88) and 14.5% (10/69), respectively, indicating that the improvement rate in the underwent tonsillectomy group was significantly higher than that in the non-surgical group (χ\u0026sup2; = 67.84, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Additionally, the improvement rates for male and female patients were 52.7% (49/93) and 51.6% (33/64), respectively. The χ\u0026sup2; test showed no statistically significant difference between the two groups (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003cem\u003eComparison of the frequency and rate of improvement in nocturnal labial incompetence between the underwent tonsillectomy and non-surgical groups\u003c/em\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ex\u003csup\u003e2\u003c/sup\u003e(2)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eImprovement of nocturnal labial incompetence [n(%)]\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eImprovement of nocturnal labial incompetence [n(%)]\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnderwent tonsillectomy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e42 (82.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e30 (81.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.879\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNon-surgical\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7 (16.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3 (11.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.729\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ex\u003csup\u003e2\u003c/sup\u003e(2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e39.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e30.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4 Discussion","content":"\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Participant characteristics\u003c/h2\u003e \u003cp\u003eBased on our clinical observations, it was noted that a significant proportion of children with malocclusion exhibit nocturnal labial incompetence (NLI), despite not meeting the diagnostic criteria for mouth breathing (i.e., oral airflow exceeding 25\u0026ndash;30%)\u003csup\u003e[\u003cspan additionalcitationids=\"CR16\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e. Nasopharynxgolaryngoscopy examinations further revealed that although these children were nasal breathers, their upper airways appeared more patent during open-mouth breathing compared to closed-mouth breathing. Moreover, most children presenting with NLI were found to have visibly tonsillar hypertrophy. Motivated by these findings, this study was designed to investigate the relationships between tonsillar hypertrophy and nocturnal labial incompetence in children with malocclusion through an analysis of initial clinical records, questionnaires, and lateral cephalograms.\u003c/p\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003e4.1.1 Hypertrophic tonsils group\u003c/h2\u003e \u003cp\u003eThe preoperative nocturnal labial incompetence rate in the hypertrophic tonsils group (93.6% in males, 100.0% in females) was significantly higher than in the non- hypertrophic tonsils group (64.5% in males, 39.3% in females) (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), suggesting that tonsillar hypertrophy may be an important clinical indicator for the development of nocturnal labial incompetence. The proposed mechanism is that tonsillar hypertrophy causes airway obstruction, forcing children to maintain an open-mouth posture to alleviate ventilation difficulties, leading to the abnormal behavior of nocturnal labial incompetence.\u003c/p\u003e \u003cp\u003eAlthough this study controlled for various confounding variables known to affect nocturnal labial incompetence\u0026mdash;such as adenoid hypertrophy, recurrent rhinitis, and prior orthodontic treatment\u0026mdash;31 children in the non-hypertrophy group still exhibited nocturnal labial incompetence. This may be attributed to three factors: (1) Dentofacial characteristics\u0026mdash;older children, particularly those in later stages of development, may already exhibit compensatory features related to airway compromise, such as maxillary protrusion or excessive lip strain, leading to difficulty in lip closure\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e; (2) Adenoid contribution\u0026mdash;some children may have A/N ratios approaching the diagnostic threshold (0.6), which could still influence oral breathing\u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e; (3) Clinical observations suggest that many Brodsky grade 2 children demonstrate typical symptoms of tonsillar hypertrophy, including snoring and nocturnal labial incompetence, possibly inflating the control group\u0026rsquo;s prevalence. These findings raise questions regarding the accuracy of classifying Brodsky grade 2 patients as \u0026ldquo;non-hypertrophic\u0026rdquo; in clinical settings.\u003c/p\u003e \u003cp\u003eLastly, no statistically significant differences were observed in the rates of nocturnal labial incompetence among children when stratified by sex or by different dimensions of tonsillar hypertrophy (anteroposterior and lateral diameters, isolated anteroposterior or lateral hypertrophy) (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05), suggesting that these factors are not decisive in determining the occurrence of nocturnal labial incompetence in children.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e \u003ch2\u003e\u003cb\u003e4.1.2 Underwent tonsillectomy group\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eAmong children with nocturnal labial incompetence, the overall improvement rate was 51.6% (81/157). Notably, the improvement rate in those who underwent tonsillectomy (80.7%) was significantly higher than that in the non-surgical group (14.5%), indicating that tonsillectomy is an effective intervention for alleviating nocturnal labial incompetence in children. This may be attributed to the surgical removal of the underlying cause of upper airway obstruction, which relieves ventilatory insufficiency and subsequently leads to the gradual disappearance of the non-physiological labial incompetence behavior.\u003c/p\u003e \u003cp\u003eNotably, in the non-surgical group, 10 children demonstrated improvement in nocturnal labial incompetence. Several possible explanations are proposed: (1) Rhinitis-related factors\u0026mdash;some children may have experienced nocturnal labial incompetence due to previously undiagnosed rhinitis, which had resolved by the time of follow-up, leading to spontaneous lip closure; (2) Adenoid-related factors\u0026mdash;children with borderline adenoid hypertrophy (A/N ratio near 0.6) may have shown improvement in nocturnal labial incompetence due to medication or natural involution of adenoid tissue with age; (3) Age-related factors\u0026mdash;older children may have developed craniofacial characteristics associated with airway obstruction, such as anterior crossbite or Class III malocclusion. According to previous studies and the authors\u0026rsquo; clinical observations, children with Class III facial profiles rarely exhibit nocturnal labial incompetence, possibly due to forward mandibular compensation that facilitates airway patency and alleviates the need for mouth opening\u003csup\u003e[\u003cspan additionalcitationids=\"CR27\" citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eFurthermore, 11 participants in this study, despite being diagnosed without tonsillar hypertrophy, underwent tonsillectomy attributable to a history of chronic tonsillitis, which conforms to the surgical indications specified in the 2025 clinical guidelines promulgated by the China Maternal and Child Health Association Minimally Invasive Chapter Pediatric ORL Group\u003csup\u003e[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Impact of nocturnal labial incompetence on malocclusion\u003c/h2\u003e \u003cp\u003eThe most readily observable adverse effect of nocturnal labial incompetence in children is altered dentofacial development. Changes in breathing patterns during critical growth periods can result in adaptations of the oral and maxillofacial structures. It affects the development and morphology of the tongue, dental arches, alveolar bone, and jaws\u003csup\u003e[\u003cspan additionalcitationids=\"CR7\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e, resulting in maxillary arch constriction, a high-arched palate, underdevelopment of the midface and nasal cavity, excessive labial inclination of the upper incisors, mandibular retrusion accompanied by clockwise rotation, posterior tongue positioning, low positioning of the hyoid bone, elongated facial height, and an altered craniofacial musculature balance\u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e. Linder-Aronson\u0026rsquo;s study indicated that nocturnal labial incompetence leads to a lowered tongue position and mandibular retrusion, which subsequently contribute to a hyperdivergent growth pattern, anterior open bite, and a high-arched palate\u003csup\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/sup\u003e. Experimental studies in animals have further confirmed that prolonged nocturnal labial incompetence in primates results in skeletal abnormalities, including clockwise mandibular rotation and maxillary constriction\u003csup\u003e[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]\u003c/sup\u003e. Prolonged nocturnal labial incompetence may also inhibit functional mandibular protrusion through the trigeminal nerve-brainstem-masticatory muscle feedback loop, exacerbating mandibular retrusion. This process can result in irreversible skeletal malocclusion, further contributing to the onset and progression of obstructive sleep apnea (OSA) \u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe findings of our study indicate that the overall rate of nocturnal labial incompetence among participants (82.6%) was markedly higher than that reported in previous studies (50\u0026ndash;56%)\u003csup\u003e[\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e. One possible explanation is a selection bias related to healthcare utilization, as most participants sought medical attention due to notable clinical symptoms, which may have inflated the positivity rate. Another contributing factor may be the current clinical emphasis on mouth breathing, with insufficient recognition of the high prevalence of nocturnal labial incompetence.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Impact of tonsillar hypertrophy on nocturnal labial incompetence and malocclusion\u003c/h2\u003e \u003cp\u003e Nasal breathing is the normal physiological mode of respiration, maintaining a balance between intraoral and extraoral muscular forces, including those of the cheeks and tongue, which helps preserve normal oral cavity volume and dental arch width. However, upper airway obstruction caused by conditions such as adenotonsillar hypertrophy can lead to respiratory dysfunction, resulting in nocturnal labial incompetence. This disrupts the balance of orofacial muscle forces, triggering adaptive changes in the oral and maxillofacial system. Prolonged alterations in facial muscle activity and head posture can significantly impact the morphology, position, and growth direction of the jawbones\u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]\u003c/sup\u003e. In our study, the rate of tonsillar hypertrophy in all participants (68.9%) was notably higher than that reported in previous studies (11%)\u003csup\u003e[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/sup\u003e. In addition to differences in patient presentation and referral patterns, the disparity may reflect a shift in diagnostic perspectives over time. Earlier evaluations primarily focused on lateral tonsillar hypertrophy based on Brodsky classification\u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/sup\u003e, potentially underestimating the clinical significance of anteroposterior hypertrophy and its contribution to airway obstruction.\u003c/p\u003e \u003cp\u003ePrevious studies have demonstrated that adenotonsillar hypertrophy in children may result in sagittal, transverse, and vertical three-dimensional alterations of craniofacial morphology\u003csup\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e. It is generally believed that the mechanism by which tonsillar hypertrophy contributes to Class III malocclusion may involve a reduction in upper airway volume, forcing affected children to maintain airway patency by adopting a mandibular open-mouth posture and elevating the hyoid bone. Such postural adjustments may result in a backward and downward rotation of the mandible, further contributing to a hyperdivergent growth pattern, anterior open bite, and narrowing of the maxillary dental arch\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. Iwasaki found that, in children with Class III malocclusion, tonsil size was associated with the anterior positioning of both the tongue and the mandibular incisors. Tonsillar hypertrophy may push the tongue forward, consequently promoting mandibular protrusion and exacerbating anterior crossbite\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. Additionally, Nunes et al. observed that children with tonsillar hypertrophy often presented with pseudo-Class III malocclusion, likely due to compensatory forward tongue positioning caused by airway obstruction. Habitual mouth breathing and forward tongue posture in these children may result in progressive mandibular protrusion, further contributing to the development of Class III malocclusion\u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eTonsillectomy is one of the most commonly performed routine procedures in pediatric otolaryngology and head and neck surgery. Several studies have shown that tonsillectomy can have a positive impact on dentofacial development in children with tonsillar hypertrophy, with postoperative findings indicating a mandibular advancement of 0.8\u0026ndash;1.5 mm and a 34% reduction in the incidence of posterior crossbite\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e.Based on the findings of this study, among patients with preexisting nocturnal labial incompetence, the proportion of improvement in nocturnal labial incompetence was significantly higher in the tonsillectomy group (82.4% in males, 81.1% in females) compared to the non-surgical group (16.7% in males, 11.1% in females). These results suggest that tonsillectomy effectively alleviates upper airway obstruction and plays a crucial role in improving nocturnal labial incompetence in school-aged children. These positive findings are consistent with the study by Linder-Aronson et al., which demonstrated that children who underwent tonsillectomy exhibited a gradual shift in mandibular growth direction toward counterclockwise rotation. This evidence supports the notion that tonsillectomy can effectively alleviate airway obstruction and contribute to the correction of jaw development in children\u003csup\u003e[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/sup\u003e.However, it is important to note that tonsillectomy alone does not guarantee the complete correction of nocturnal labial incompetence in children. Postoperatively, a combined approach with orthodontic intervention is recommended to actively address nocturnal labial incompetence and prevent its persistent adverse effects on craniofacial development.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e4.4 Multidisciplinary treatment\u003c/h2\u003e \u003cp\u003eIn summary, nocturnal labial incompetence, tonsillar hypertrophy and malocclusion interact in a mutually reinforcing manner, collectively contributing to disturbances in craniofacial growth and systemic health in school-aged children. Tonsillar hypertrophy induces upper airway obstruction, which promotes nocturnal labial incompetence and alters orofacial muscle dynamics. This disruption leads to adaptive changes in maxillofacial morphology, further exacerbating malocclusion. In turn, malocclusion can perpetuate nocturnal breathing dysfunction, reinforcing airway obstruction and maintaining the cycle of impairment. The interdependence of these three factors highlights their compounded impact on both facial development and overall health. School-aged children are in a critical period of rapid craniofacial growth and development, during which nocturnal labial incompetence and other detrimental oral habits can exert adverse and potentially irreversible effects on the dentition and maxillofacial structures. These negative impacts may progressively worsen with growth, amplifying their influence over time. If not addressed through timely and effective intervention, these habits may lead to severe dentofacial deformities, significantly increasing the complexity of subsequent orthodontic and other corrective treatments. As a result, it is recommended that orthodontists routinely assess the degree of upper airway obstruction caused by tonsillar hypertrophy in children with nocturnal labial incompetence using intraoral examination and lateral cephalograms during clinical evaluations. Patients diagnosed with tonsil hypertrophy should be promptly referred to the otolaryngology department for further assessment and management. A multidisciplinary approach integrating orthodontic and otolaryngologic expertise can enhance treatment efficiency and ensure the long-term stability of subsequent orthodontic interventions.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e4.5 Limitations\u003c/h2\u003e \u003cp\u003eSeveral limitations of the present study should be acknowledged. Firstly, the assessment of nocturnal labial incompetence was primarily based on parental reports and retrospective consultation records, which may introduce recall bias and lack objective clinical verification. Secondly, the participants were recruited from children seeking treatment at an orthodontic clinic, there is a possibility of selection bias, which may limit the generalizability of the findings to the broader pediatric population. Lastly, the cross-sectional nature of this study precludes the establishment of causal relationships between tonsillar hypertrophy and nocturnal labial incompetence.\u003c/p\u003e \u003c/div\u003e"},{"header":"5 Conclusions","content":"\u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eIn contrast to the traditional emphasis on mouth breathing, nocturnal labial incompetence (NLI) is highly prevalent in children with malocclusion. Without timely intervention, it can adversely affect craniofacial growth and compromise orthodontic treatment results. Increased attention from both clinicians and caregivers is therefore essential.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eAfter excluding other potential causes of upper airway obstruction, the prevalence of nocturnal labial incompetence was found to be significantly higher in children with tonsillar hypertrophy compared to the control group, suggesting that tonsillar hypertrophy may be one of the contributing factors to nocturnal labial incompetence.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe rate of improvement in nocturnal labial incompetence was significantly higher among children who underwent tonsillectomy than those who did not, indicating that tonsillectomy may serve as an effective therapeutic approach for managing nocturnal labial incompetence.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eClinical trial number\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEthics approval and consent to participate\u003c/p\u003e\n\u003cp\u003eThis retrospective study was approved by the Institutional Ethics Committee of Shulan (Hangzhou) Hospital (Approval Number: No. KY2025040). The requirement for informed consent was waived due to the retrospective nature of the study and the use of anonymized data. No identifiable personal information of individual patients was collected or disclosed.\u003c/p\u003e\n\u003cp\u003eConsent to participate\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;Informed consent was waived due to retrospective design of the study and the absence of identifiable patient information.\u003c/p\u003e\n\u003cp\u003eConsent for publication\u003c/p\u003e\n\u003cp\u003eNot applicable. This manuscript does not contain any individual person\u0026rsquo;s data in any form (including images, videos, or other identifying information), thus consent for publication was not required.\u003c/p\u003e\n\u003cp\u003eAvailability of data and materials\u003c/p\u003e\n\u003cp\u003eAll data generated or analysed during this study are included in this published article.\u003c/p\u003e\n\u003cp\u003eCompeting interests\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThis research was supported by the National Key Research and Development Program of China (Grant No. 2024YFA1307100). Author Guoping Sheng received funding.\u003c/p\u003e\n\u003cp\u003eAuthors\u0026apos; contributions\u003c/p\u003e\n\u003cp\u003eCC: \u0026nbsp;Methodology, Investigation, Visualization, Writing \u0026ndash; original draft.\u003c/p\u003e\n\u003cp\u003eYH: Data collection, Formal analysis, Writing \u0026ndash; review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003eGS: Funding acquisition, Writing \u0026ndash; review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003eXC: Supervision, Writing \u0026ndash; review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003eBL: Conceptualization, Resources, Writing \u0026ndash; review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003eAll authors have read and approved the final manuscript. CC and YH contributed equally to this work and share first authorship.\u003c/p\u003e\n\u003cp\u003eAcknowledgements\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank Stomatology Hospital, School of Stomatology, Zhejiang University School of Medicine and Department of Otolaryngology-Head and Neck Surgery, Shulan (Hangzhou) Hospital for providing support for this study.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMoss M L, Salentijn L. The primary role of functional matrices in facial growth[J]. Am J Orthod, 1969, 55(6): 566-77.\u003c/li\u003e\n\u003cli\u003eBehrents R G, Shelgikar A V, Conley R S, et al. Obstructive sleep apnea and orthodontics: An American Association of Orthodontists White Paper[J]. Am J Orthod Dentofacial Orthop, 2019, 156(1): 13-28.e1.\u003c/li\u003e\n\u003cli\u003eHe H. [Interpretation of \u0026quot;Obstructive sleep apnea and orthodontics: an American Association of Orthodontists White Paper\u0026quot;][J]. 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Chinese Journal of Stomatology, 2019, 26(04): 195-198.\u003c/li\u003e\n\u003cli\u003eGill A I, Schaughency E, Galland B C. Prevalence and factors associated with snoring in 3-year olds: early links with behavioral adjustment[J]. Sleep Med, 2012, 13(9): 1191-7.\u003c/li\u003e\n\u003cli\u003eGarde J B, Suryavanshi R K, Jawale B A, et al. An epidemiological study to know the prevalence of deleterious oral habits among 6 to 12 year old children[J]. J Int Oral Health, 2014, 6(1): 39-43.\u003c/li\u003e\n\u003cli\u003eKharbanda O P, Sidhu S S, Sundaram K, Shukla D K. Oral habits in school going children of Delhi: a prevalence study[J]. J Indian Soc Pedod Prev Dent, 2003, 21(3): 120-4.\u003c/li\u003e\n\u003cli\u003ePacheco M C, Casagrande C F, Teixeira L P, et al. Guidelines proposal for clinical recognition of mouth breathing children[J]. Dental Press J Orthod, 2015, 20(4): 39-44.\u003c/li\u003e\n\u003cli\u003eShun Z M. The adenoid nasopharynx ratio: its clinical value in children[J]. 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Am J Orthod Dentofacial Orthop, 2015, 147(2): 214-20.\u003c/li\u003e\n\u003cli\u003eNunes W R, Jr., Di Francesco R C. Variation of patterns of malocclusion by site of pharyngeal obstruction in children[J]. Arch Otolaryngol Head Neck Surg, 2010, 136(11): 1116-20.\u003c/li\u003e\n\u003cli\u003eMaternal C, Group C H a M I C P O. Standardized treatment technology for pediatric tonsillectomy and adenoidectomy with low-temperature coblation[J]. Journal of Clinical Otorhinolaryngology Head and Neck Surgery, 2025, 39(02): 97-109.\u003c/li\u003e\n\u003cli\u003ePetraccone Caixeta A C, Andrade I, Jr., Bahia Junqueira Pereira T, et al. Dental arch dimensional changes after adenotonsillectomy in prepubertal children[J]. Am J Orthod Dentofacial Orthop, 2014, 145(4): 461-8.\u003c/li\u003e\n\u003cli\u003eLinder-Aronson S. Adenoids. Their effect on mode of breathing and nasal airflow and their relationship to characteristics of the facial skeleton and the denition. 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Prevalence of tonsillar hypertrophy and associated oropharyngeal symptoms in primary school children in Denizli, Turkey[J]. Int J Pediatr Otorhinolaryngol, 2002, 66(2): 175-9.\u003c/li\u003e\n\u003cli\u003eKumar D S, Valenzuela D, Kozak F K, et al. The reliability of clinical tonsil size grading in children[J]. JAMA Otolaryngol Head Neck Surg, 2014, 140(11): 1034-7.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Palatine tonsil, Nocturnal labial incompetence, Malocclusion, Tonsil hypertrophy, Tonsillectomy","lastPublishedDoi":"10.21203/rs.3.rs-6501119/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6501119/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e: This study aimed to investigate the relationships between the tonsillar hypertrophy and nocturnal labial incompetence (NLI) in children with malocclusion. The findings are intended to inform early orthodontic or medical intervention strategies for children presenting with both tonsil hypertrophy and malocclusion.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e: A retrospective study was conducted using initial consultation records, lateral cephalograms, online questionnaires, and telephone follow-ups. Tonsil hypertrophy was evaluated in the transverse dimension using Brodsky’s classification and in the anteroposterior dimension using the Baroni method on lateral cephalograms. Children were categorized into a hypertrophic tonsils group (Brodsky grade \u0026gt;2 or sagittal airway obstruction ≥50%) and a non-hypertrophic control group (Brodsky grade ≤2 and obstruction \u0026lt;50%). The prevalence of NLI was assessed with initial consultation records. Intergroup differences were analyzed using the Bonferroni-adjusted χ² test (α = 0.017).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e: A total of 190 children were included, with 68.9% in the hypertrophic group and 31.1% in the non-hypertrophic group. The overall prevalence of NLI was 82.6%, significantly higher in the hypertrophic group (96.2%) compared to the control group (52.6%, χ² = 53.98, P \u0026lt; 0.001). Among children with NLI, the overall improvement rate was 51.6%, with a significantly higher rate observed in those who underwent tonsillectomy (80.7%) than in those who did not (14.5%, χ² = 67.84, P \u0026lt; 0.001).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e: Tonsil hypertrophy is significantly associated with increased prevalence of NLI in children. Tonsillectomy may substantially improve NLI symptoms, suggesting a potential therapeutic benefit in affected patients.\u003c/p\u003e","manuscriptTitle":"Relationships Between the Tonsillar Hypertrophy and Nocturnal Labial Incompetence in Children with Malocclusion","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-10 15:01:21","doi":"10.21203/rs.3.rs-6501119/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-22T09:39:15+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-19T07:18:39+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"264086364871910506166548113208218919066","date":"2025-06-14T09:08:42+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-13T13:26:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"287347601120027028392932853118394891274","date":"2025-06-05T06:59:28+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-05T03:23:26+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-05-07T11:23:20+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-05-06T07:11:21+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-05-06T07:02:00+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Oral Health","date":"2025-04-22T06:48:35+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7b914147-f594-4369-ac1e-0893d58bb91f","owner":[],"postedDate":"June 10th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-03-23T16:40:06+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-10 15:01:21","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6501119","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6501119","identity":"rs-6501119","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}