Assessment of Masticatory Muscle Activity and Mandibular Border Movement in Skeletal Class II Malocclusion Adolescents with Mandibular Retrognathia

Assessment of Masticatory Muscle Activity and Mandibular Border Movement in Skeletal Class II Malocclusion Adolescents with Mandibular Retrognathia | 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 Assessment of Masticatory Muscle Activity and Mandibular Border Movement in Skeletal Class II Malocclusion Adolescents with Mandibular Retrognathia Li-Yu Hou, Yu-Yan Zheng, Qing Lin, Wei-Ran Li, Yu Yao This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7489326/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 8 You are reading this latest preprint version Abstract Objective To investigate masticatory muscle activity and mandibular border movement in adolescents with skeletal class II malocclusion and mandibular retrognathia and explore the influence of mandibular retrognathia on masticatory system function. Methods Thirty adolescents aged 10–15 years diagnosed with skeletal class II malocclusion and mandibular retrognathia comprised the skeletal class II malocclusion group, while 30 adolescents with skeletal class I malocclusion constituted the control group. Functional assessments of the masticatory system were performed in both cohorts, encompassing Bio-EMG and JT-3D measurements during rest, clenching, chewing, swallowing, and border movements. Electromyographic (EMG) activity and mandibular kinematics were comprehensively measured and compared between the two groups. Results 1) EMG: During rest, there was no significant difference in the EMG amplitude of the muscles between the skeletal class II malocclusion and control groups. However, during clenching, the EMG amplitude of the anterior temporalis and masseter muscles was lower in the skeletal class II malocclusion group compared to the control group. Similarly, the EMG amplitude of the working-side temporalis and masseter muscles during chewing was lower in the skeletal class II malocclusion group. Furthermore, the mean EMG values of the anterior temporalis and both masseter muscles during swallowing were lower in the skeletal class II malocclusion group, while the mentalis muscle exhibited higher EMG activity. 2) Mandibular movement: The skeletal class II malocclusion group demonstrated increased vertical and coronal displacements in the mandibular resting position compared to the control group. However, during chewing, no significant disparity in mandibular displacement was observed between the skeletal class II malocclusion and control groups. In contrast, during swallowing, the skeletal class II malocclusion group exhibited greater vertical and coronal mandibular displacements, particularly with more pronounced forward sagittal displacement. Notably, there was no significant distinction in the three-dimensional mandibular displacement during maximum mouth opening between the two groups. Conclusion Functional impairments in the masticatory system of adolescents with skeletal class II malocclusion and mandibular retrognathia were evident across multiple activities, encompassing rest position, clenching, chewing, swallowing, and border movements. These results underscore the considerable influence of skeletal class II malocclusion on the functional integrity of the masticatory system. Skeletal class II malocclusion adolescents Electromyography Masticatory Muscle Mandibular movement Introduction Skeletal class II malocclusion affects approximately 27% of adolescents and constitutes around 32% of malocclusion cases during the early permanent dentition stage. This malocclusion type is commonly characterized by sagittal skeletal disharmony, presenting as maxillary protrusion, mandibular retrognathia, or a combination of both. Mandibular retrognathia is reported in 29–65% of skeletal class II malocclusion cases [ 1 ]. Adolescents with mandibular retrognathia often exhibit distal molar relationships, deep overbite, deep overjet, varying degrees of lip incompetence, and a narrower airway compared to those with skeletal class I malocclusion [ 2 ]. They face an elevated risk of developing obstructive sleep apnea in adulthood and demonstrate a higher incidence of lip incompetence compared to individuals with other skeletal malformations [ 3 ]. Mandibular retrognathia not only impacts facial aesthetics but also influences functional aspects. Optimal occlusion is crucial for achieving balance in the stomatognathic system, emphasizing the importance of a harmonious relationship between the dental arches for maintaining functional symmetry [ 4 , 5 ]. In 1980, Pancherz et al. [ 6 ] observed that children with skeletal class II malocclusion exhibited decreased electromyographic (EMG) amplitude in the masseter muscle during chewing compared to those with normal occlusion. Ma et al. [ 7 ] noted that regardless of occlusion type, temporal muscles were more active in the mandibular postural position, whereas the masseter muscle demonstrated higher activity during central occlusion in maximal voluntary contraction of masticatory muscles. Additionally, Lowe et al. [ 8 ] proposed a correlation between skeletal morphology (mandibular angle size and parallelism in jaw bases) and EMG amplitude of the anterior temporal and masseter muscles during maximal voluntary contraction. Moreover, malocclusion can lead to various functional issues, including significant temporomandibular disorders (TMD) [ 9 ]. Factors such as mandibular length, mandibular ramus inclination, and condylar position play pivotal roles in mandibular movement [ 10 , 11 ]. In individuals with skeletal class II malocclusion and mandibular retrognathia, the retrognathic mandibular position and reduced mandibular body length may impact mandibular movement patterns, potentially influencing masticatory system functions such as clenching, chewing, swallowing, and border movements. While several studies have explored the link between craniofacial morphology and the masticatory system [ 12 – 15 ], the existing research predominantly examines muscle activity or mandibular motion in specific functional conditions. However, investigations focusing on masticatory muscle function and mandibular border movement in various functional states in adolescents with skeletal class II malocclusion are lacking. Moreover, conflicting conclusions exist among studies investigating the functional characteristics of the oral system in isolated movement states [ 16 – 18 ]. Consequently, there is a need for research on masticatory muscle function and mandibular border movement in individuals with skeletal class II malocclusion. Electromyography (EMG) serves as the primary method for assessing jaw and facial muscle activity in clinical settings, offering precise and objective evaluations of muscle function. EMG allows for electrophysiological recording and quantitative analysis of muscle activity amplitude and duration [ 19 ]. The variability in EMG impedance and reliability can be addressed through thorough quantitative analysis using normalization procedures. This non-invasive diagnostic tool is known for its simplicity, safety, and reliability, making it a prevalent choice for monitoring muscle function in adolescents [ 20 – 22 ]. Concurrently, incorporating mandibular functional movement assessment during EMG monitoring ensures consistency in quantitative analysis. Utilizing digital jaw position tracking devices enables real-time three-dimensional analysis of mandibular movement, facilitating the quantitative evaluation of various mandibular motion parameters during functional movements. These devices are extensively employed for assessing mandibular motion range [ 23 – 27 ]. Therefore, the objective of this study was to examine potential functional disparities in the masticatory system between adolescents presenting with mandibular retrognathia in conjunction with skeletal class II malocclusion and a control group of individuals with skeletal class I malocclusion. Materials and Methods This study received approval from the Ethics Committee of the Peking University School of Stomatology. (Approval number: PKUSSIRB-201525111), and all patients were duly informed about the study and provided written informed consent. Sample Selection and Grouping From January 2016 to February 2019, a total of 60 patients aged 10–15 years were enrolled from the Department of Orthodontics at Peking University School of Stomatology. The cohort comprised 32 males and 28 females, with a mean age of 13.1 years. Case Group: The case group consisted of 30 patients, comprising 17 males and 13 females, with an average age of 12.3 years. Inclusion criteria: 1. Clinical diagnosis of skeletal class II malocclusion, Division 1 malocclusion, characterized by distal molar relationships ranging from distoclusion to complete distal occlusion; 2. Cephalometric assessment indicating ANB ≥ 5°, with mandibular retrognathia as the primary feature; 3. Overjet exceeding 5 mm. Exclusion criteria: 1. Presence of systemic diseases (particularly in individuals with pacemakers) or mental/intellectual disabilities; 2. History of orthodontic treatment; 3. History of condylar fractures. Control Group: The control group consisted of 30 patients, with 15 males and 15 females, with an average age of 13.9 years. Inclusion criteria: 1. Clinical diagnosis of skeletal class I malocclusion with neutral molar relationships; 2. Cephalometric analysis showing normal position and length of the maxillary and mandibular bones, with ANB between 0° and 4°; 3. Overjet < 4 mm; 4. Presence of mild to moderate crowding or slight dental arch spacing. Exclusion criteria: 1–3 identical to the Skeletal class II malocclusion group; 4. Absence of teeth other than third molars; 5. Supernumerary teeth; 6. Absence of crossbite, reverse bite, or edge-to-edge bite cases; 7. Severe crowding. Experimental Procedures After obtaining informed consent from both the pediatric patients and their guardians, functional assessments were conducted within a designated examination facility. The subjects were seated in an upright position with their heads aligned in the Frankfort horizontal plane, maintaining parallelism with the ground. This standardized postural protocol was consistently applied throughout all evaluations in this research investigation. The evaluation of the masticatory system functionality entailed the utilization of surface EMG and mandibular movement analysis. Surface electromyography data acquisition was performed usingan 8-channel EMG recording system, specifically the BioEMG III device (BioResearch, Inc., Milwaukee, WI, USA). The EMG recorder featured an impedance of 108 Ω, a voltage range of 0–1550mV, and a frequency range of 30–1000 Hz. Bipolar surface electrodes from BioResearch Associates Inc. (Brown Deer, WI, USA) were employed for signal detection. Mandibular movement assessments were executed utilizing the JT-3D apparatus, also from BioResearch in Milwaukee, Wisconsin, ensuring synchronization with the EMG equipment through a dedicated converter. Data acquisition and analysis were carried out using the Bio-Pak 6.0 software package from BioResearch, USA. The detailed methodology for data recording was as follows: EMG The skin surface was meticulously cleansed thrice using 75% ethanol-soaked cotton balls to minimize impedance between the electrodes and the skin. Electrode placements were meticulously executed based on the anatomical locations and fiber orientations of the anterior temporalis (TA), masseter (MM), and mentalis (MT) muscles. Bipolar surface electrodes with longitudinal alignment parallel to the muscle fibers were employed. For the anterior temporalis muscle, the electrode was positioned above the zygomatic arch and along the supraorbital margin at the location of maximal contraction during clenching. The masseter electrode was situated 1 cm anterior to the midpoint of the line connecting the zygomatico-temporal suture and the mandibular angle. In the case of the mentalis muscle, the electrode was situated below the labial mentolabial groove along the muscle fiber direction. Symmetrical placement of electrodes on both sides of all muscles was ensured, with the ground electrode positioned at the posterior neck. A photographic record was captured following the initial electrode placement for subsequent reference. Muscle activity was captured utilizing the BioEMG III system, while patients maintained a relaxed posture in the resting position. Subsequent analysis of the electromyographic data allowed for the documentation of EMG amplitudes associated with the TA, MM, and MT muscles. Mandibular Movement Tracing Synchronized measurements were facilitated through the utilization of a common converter interfaced with the EMG apparatus. A magnetic marker measuring 14×6.3×4.3 mm³ was affixed to the labial gingival third of the lower anterior teeth using glass ionomer cement (Shanghai Medical Equipment Co., Ltd., China). Subsequently, a cap-style measuring device was positioned, ensuring alignment of the magnetic marker with the positioning rod to maintain the accurate relative orientation between the tracing instrument and the marker. The placement of the EMG electrodes remained consistent throughout the procedure. Comprehensive recordings of mandibular position and displacement in the vertical, sagittal, and coronal planes were meticulously documented. In accordance with previous research [ 28 ], the subsequent functional movements were meticulously documented and analyzed. Rest Position: Patients were directed to achieve a state of relaxation without occlusal contact, with the upper and lower lips resting naturally, and the mandible held in a condition of perceived muscle relaxation for 10 s. During this period, the EMG data captured the average EMG amplitudes of the TA, MM, and MT muscles, alongside the mandibular position at rest. Clenching: Patients were directed to relax and sustain the resting position before being prompted to exert maximal force by clenching their teeth in the intercuspal position for 3 s, with a 30-s interval between each measurement, totaling three measurements. The EMG data recorded the average amplitudes of the TA, MM, and MT during the clenching tasks. Chewing: EMG and mandibular movement tracing were employed in this study. Patients were directed to chew a single piece of gum (Extra, Wrigley Company Ltd., China) until it reached a uniform texture. The gum was positioned in the posterior region of the left or right side, and participants were instructed to assume a relaxed resting position. Subsequently, patient were guided to engage in chewing movements on the left or right side for 10 cycles per sequence, separated by a 30-s rest period between each set, with a total of three measurement sessions. EMG data acquisition documented variations in EMG amplitude of the TA, MM, and MT during left and right chewing episodes, while mandibular movement tracing captured positional changes and alterations in mandibular dynamics. Swallowing: EMG and mandibular movement tracing were used. Patients were directed to execute their habitual saliva-swallowing pattern. Once they had acclimated to the task, they were instructed to maintain the resting position and subsequently perform a swallow, with a 1-min interval between each measurement, across three measurement instances. The EMG data documented alterations in the electromyographic amplitude of the TA, MM, and MT muscles, while mandibular movement tracing captured changes in mandibular position dynamics during the swallowing process. Border Movements: Mandibular movement tracing was employed in this investigation. Patients were instructed to execute maximum opening and closing movements, as well as maximal left/right lateral and protrusive movements. Following sufficient practice sessions to ensure proficiency in the movements, measurements were conducted. Mandibular movement tracing documented the range of mandibular displacement during maximum opening, left/right lateral, and protrusive movements. Statistical Methods: Synchronized recording and analysis of EMG and mandibular movement data were performed utilizing Bio-Pak 6.0. The EMG measurements exhibited a precision of 0.1µV, while the mandibular movement measurements had a precision of 0.1 mm. Data analysis was carried out SPSS 20.0, with the normality of data assessed using Shapiro-Wilk tests. Depending on data distribution normality, either independent sample t-tests or Mann-Whitney tests were applied. A two-tailed test with a significance level of α = 0.05 was employed to evaluate the statistical significance between the two groups. Results EMG The EMG data for the TA, MM, and MT muscles during various mandibular functional movements are presented in Table 1 . At rest, there were no statistically significant differences in EMG amplitudes among the TA, MM, and MT muscles. During clenching, individuals with skeletal class II malocclusion exhibited significantly lower EMG amplitudes in the bilateral anterior temporalis and masseter muscles than control group. However, no significant differences were observed in the mentalis muscles. Participants with skeletal class II malocclusion showed lower EMG activity in the anterior temporalis and masseter muscles compared to the control group during chewing. Notably, the right mentalis muscle exhibited higher EMG amplitudes than the control group, while the left mentalis muscle did not demonstrate a significant difference. During swallowing, individuals with skeletal class II malocclusion demonstrated significantly lower average EMG amplitudes in the right anterior temporalis and bilateral masseter muscles compared to the control group. Conversely, the EMG amplitudes of the bilateral mentalis muscles were notably higher in the skeletal class II malocclusion group compared to the control group. Table 1 The results of the masticatory muscle EMG recordings during different mandibular functional movement in the adolescents studied Control (µv) Skeletal II (µv) P value Mean SD Mean SD Rest TA-R 1.3 0.7 1.4 0.8 0.21 TA-L 1.3 0.8 1.4 1.0 0.773 MM-R 1.1 0.2 1.1 0.3 0.475 MM-L 1.0 0.4 0.9 0.5 0.988 MT-R 1.6 1.6 2.3 1.3 0.154 MT-L 1.7 2.0 2.2 1.9 0.409 Clench TA-R 124.1 48.1 68.9 37.7 0.001** TA-L 115.3 24.1 62.8 46.8 0.001** MM-R 123.8 74.1 68.0 56.7 0.031* MM-L 88.1 58.9 66.2 45.1 0.026* MT-R 6.2 3.5 5.3 6.4 0.797 MT-L 6.0 3.6 5.6 8.0 0.907 Chew TA-R 65.1 24.8 43.1 25.5 0.001** TA-L 70.9 43.9 45.7 28.5 0.015* MM-R 84.8 39.7 58.5 33.1 0.019* MM-L 73.4 45.7 42.8 37.0 0.009** MT-R 20.8 9.2 32.6 17.2 0.039* MT-L 23.9 11.0 25.5 18.8 0.762 Swallow TA-R 5.0 7.6 3.2 2.0 0.014* TA-L 3.5 3.7 3.5 3.9 0.848 MM-R 5.6 4.9 3.2 2.6 0.009** MM-L 4.7 5.3 3.1 2.1 0.012* MT-R 13.7 9.9 22.1 18.5 0.010* MT-L 10.8 11.7 21.9 17.6 0.010* ∗ Statistically significant difference. P < 0.05 ∗∗ Statistically significant difference. p < 0.01 TA-R: Right anterior temporalis; TA-L: Left anterior temporalis; MM-R: Right masseter muscles; MM-L: Left masseter muscles; MT-R: Right mentalis muscles; MT-L: Left mentalis muscles; Control: skeletal I malocclusion adolescents; Skeletal II: skeletal II malocclusion adolescents with mandibular retrognathia Mandibular Movement Tracing The mandibular movement tracing data during different functional motions are presented in Tables 2 – 3 . At rest, the mandibular position is defined in relation to the intercuspal position. The total displacement from the intercuspal position was notably greater in the skeletal class II malocclusion group compared to the control group. Specifically, vertical and coronal displacements in the skeletal class II malocclusion group exceeded those in the control group with statistical significance, while no significant disparity was observed in sagittal displacement. During chewing, no significant differences in mandibular movement displacement were noted between the two groups across all three directional axes. In the context of swallowing, the skeletal class II malocclusion group displayed significantly greater mandibular displacement than the control group in all three directions. For maximum opening movements, there were no significant differences between the skeletal class II malocclusion and control groups in the three directions. However, during lateral and protrusive movements, mandibular displacement in the skeletal class II malocclusion group surpassed that of the control group with statistical significance. Table 2 The results of the mandibular movement tracing recordings during different mandibular functional movement in the adolescents studied Control (mm) Skeletal II (mm) P value Mean SD Mean SD Rest Total Displacement 1.9 1.0 2.6 1.3 0.010* Vertical Displacement 1.7 0.9 2.3 1.3 0.046* Sagittal Displacement −0.1 1.0 −0.4 1.8 0.609 Coronal Displacement 0.3 0.3 0.5 0.4 0.009** Chew Total Displacement 12.0 3.3 11.7 4.2 0.822 Vertical Displacement 11.1 3.3 10.3 4.0 0.452 Sagittal Displacement 1.3 4.7 1.4 5.5 0.929 Coronal Displacement 2.6 1.4 2.3 2.1 0.655 Swallow Total Displacement 1.1 0.7 1.7 1.5 0.001** Vertical Displacement 1.0 0.8 1.6 1.4 0.002** Sagittal Displacement 0.0 0.5 −0.4 1.7 0.034* Coronal Displacement 0.1 0.1 0.3 0.5 0.004** Maximum Opening Movements Total Displacement 43.0 7.1 41.4 9.2 0.488 Vertical Displacement 33.5 5.1 32.1 6.0 0.369 Sagittal Displacement 25.4 9.9 23.4 13.6 0.536 Coronal Displacement 4.4 2.4 5.5 3.7 0.193 ∗ Statistically significant difference. p < 0.05 ∗∗ Statistically significant difference. p < 0.01 Control: skeletal I malocclusion adolescents; Skeletal II: skeletal II malocclusion adolescents with mandibular retrognathia Table 3 The results of the mandibular movement tracing recordings during lateral and protrusive movements in the adolescents studied Control (mm) Skeletal II (mm) P value Mean SD Mean SD Mandibular Border Movement Left Lateral Movement 3.8 1.6 5.5 2.6 0.007** Right Lateral Movement 4.1 1.8 5.8 3.0 0.037* Protrusive Movement 3.3 1.7 6.2 3.0 0.001** ∗ Statistically significant difference. p < 0.05 ∗∗ Statistically significant difference. p < 0.01 Control: skeletal I malocclusion adolescents; Skeletal II: skeletal II malocclusion adolescents with mandibular retrognathia Discussion The masticatory muscles within the facial region and their functionally modulated motor activities play a pivotal role in the developmental trajectory of the craniofacial system in adolescents. Comprehensive insights into the EMG patterns of these muscles and the kinematics associated with mandibular functional movements contribute significantly to elucidating the inherent mechanisms governing compensatory developments within the dentofacial hard tissue structures, particularly within the realm of facial soft tissues. This study focused on adolescent participants and investigated their muscle activity and mandibular dynamics across various functional states (e.g., resting, clenching, chewing, swallowing, and border movement) utilizing electromyography and a mandibular motion analysis system. During the early permanent dentition stage in adolescents, the prevalence of class I malocclusion is approximately 38.5%, representing about half of all malocclusion cases and surpassing the occurrence of skeletal class II malocclusion [ 1 ]. Class I malocclusion is characterized by sagittal skeletal harmony between the maxilla and the mandible. However, the presence of malocclusion can impact certain muscle functions. Previous investigations have revealed that individuals with class I malocclusion exhibit diminished electromyographic (EMG) amplitudes in the masticatory muscles during clenching compared to those with normal occlusion [ 29 ]. Moreover, studies have demonstrated that individuals with class I malocclusion exhibit reduced occlusal contact and bite force relative to individuals with normal occlusion [ 30 ]. To minimize the impact of dental discrepancy on the analysis, the control group in this study consisted of individuals with class I malocclusion rather than normal occlusion. Prolonged unilateral chewing habits have the potential to induce asymmetry in the size of bilateral muscles and the amplitude of EMG activity. To ensure sample integrity, individuals with unilateral chewing habits were excluded during participant recruitment. During the rest position, patients with skeletal class I and skeletal class II malocclusion demonstrate increased activation of the temporal muscles for postural functions, while the masseter muscles exhibit relatively lower responsiveness. Within this study, patients with skeletal class II malocclusion did not show a significant impact on the average EMG amplitude of the anterior temporalis and masseter muscles during the resting phase. These observations are consistent with the findings of Ali A. Saker et al. [ 31 , 32 ], but contradict the results of Ardani et al.[ 33 ]. Discrepancies in these outcomes may stem from variations in the age compositions of the study populations. Given that the resting position entails facial muscle relaxation without the necessity for firm closure, no significant differences were noted in the mentalis muscle activity. During tooth clenching, individuals with skeletal class II malocclusion exhibited reduced activity in both the bilateral temporalis and masseter muscles, while no notable differences were observed in the mentalis muscles. During chewing movements, individuals with skeletal class II malocclusion consistently demonstrated diminished activity in the working side TA and MM muscles compared to the control group. This observation aligns with the reduced EMG amplitudes recorded bilaterally during maximum tooth clenching and supports the conclusions of Moreno et al.[ 34 ]. In the context of swallowing, a process requiring effective lip sealing, individuals with skeletal class II malocclusion exhibited significantly heightened activity in the mentalis muscle, nearly doubling in intensity. This pronounced activation of the mentalis muscle was essential for achieving lip closure, suggesting a compensatory mechanism employed by individuals with skeletal class II malocclusion during this functional motion [ 35 , 36 ]. The mandibular movement range encompasses the extent of mandibular motion during functional activities, delineating the limits of maximal jaw opening, protrusion, and lateral movements. In this study, we evaluated the mandibular movement range during simulated rest, clenching, chewing, swallowing, and maximal border positions to investigate the impact of skeletal discrepancies, particularly mandibular retrusion, on functional mandibular movements. Understanding the influence of skeletal discrepancies on the mandibular movement range can provide insights into the compensatory mechanisms of dental and orofacial soft and hard tissues, offering objective metrics for assessing functional enhancements in the stomatognathic system following orthodontic and orthognathic interventions [ 37 – 39 ]. At the rest position, individuals with skeletal class II malocclusion displayed increased vertical and coronal mandibular displacement. Conversely, no significant differences in mandibular movement range were observed in the three-dimensional directions during chewing. The observed range aligned with the average maximal mandibular displacement during left/right chewing motions, indicating that mild impairment of chewing muscle function on the working side did not lead to aberrant mandibular movements during chewing, reflecting the compensatory capacity of the stomatognathic system. Furthermore, in the context of swallowing, subjects with skeletal class II malocclusion exhibited heightened vertical, coronal, and sagittal mandibular displacement from the intercuspal position, including instantaneous mandibular protrusion during swallowing. These findings are indicative of atypical swallowing patterns, affirming the presence of more pronounced abnormal swallowing behaviors in patients with skeletal class II malocclusion. During maximum jaw opening, craniofacial morphology exhibited minimal impact on mandibular movement, consistent with prior research findings [14,40–42]. However, in lateral and protrusive movements, individuals with skeletal class II malocclusion displayed increased mandibular displacement on the working side. Specifically, during protrusive movements, subjects with skeletal class II malocclusion demonstrated an expanded protrusive range, indicative of a greater overjet. In the realm of craniofacial skeletal pattern influence on mandibular movement, scholarly investigations date back to 1971[14]. While some studies have revealed a notable association between vertical mandibular displacement and the ANB angle, the correlation between lateral mandibular displacement and craniofacial morphological parameters appears relatively modest [ 42 ]. This discrepancy from our findings may stem from the fact that the referenced study focused on condylar movement range, whereas our research specifically targeted mandibular movement range. The comprehensive scope of the mandibular movement range is influenced by various factors, encompassing condylar movement, the configuration of the mandibular ramus and body, and occlusal anatomy [ 43 ]. It is essential to recognize that condylar movement alone cannot comprehensively depict the entirety of mandibular motion. In a previous study, no significant distinctions were detected in the mandibular movement range between individuals with skeletal class II malocclusion and class I malocclusion, whether chewing or border movements [ 41 ]. Nonetheless, this conclusion contrasts with our results. These discrepancies could be linked to population demographics, as their study predominantly centered on adult subjects, while our research encompassed adolescent participants. Prolonged engagement in functional movements may have prompted adults to develop effective compensatory mechanisms for mandibular motion. This study compared the electromyographic activity differences in bilateral masticatory muscles and mandibular movement range between adolescents presenting with skeletal class II malocclusion and skeletal class I patterns under functional movements. While our findings offer insights into the interplay between craniofacial morphology and oral function, this study is not without limitations. Primarily, the research was confined to adolescents with skeletal class II malocclusion patterns, excluding participants with other craniofacial skeletal patterns. Future investigations should broaden the sample scope to encompass adolescents with diverse skeletal facial configurations for comprehensive exploration. Moreover, the study solely focused on adolescents with mandibular retrusion who had not undergone orthodontic interventions, omitting discussions on the influence of orthodontic treatment on muscle activity or mandibular movements. Subsequent research endeavors aim to delve into the impact of orthodontic interventions on the functional activity of masticatory muscles in adolescent populations. Conclusion Based on the methodology employed in this study, the following conclusions can be drawn: Adolescents with skeletal class II malocclusion demonstrated reduced activity in the anterior temporalis and masseter muscles during clenching and chewing. During swallowing, adolescents with skeletal class II malocclusion exhibited decreased activity in the anterior temporalis and both masseter muscles, while displaying heightened activity in the mentalis muscle. Mandibular motion exhibited increased displacements in the resting and swallowing positions among adolescents with skeletal class II malocclusion. Functional disruptions in the masticatory system of adolescents with skeletal class II malocclusion and mandibular retrognathia were apparent across various activities, including rest position, clenching, chewing, swallowing, and border movements. These observations underscore the notable impact of skeletal class II malocclusion on the functional dynamics of the masticatory system. Declarations Ethics approval and consent to participate This study received approval from the Ethics Committee of the Peking University School of Stomatology. (Approval number: PKUSSIRB-201525111), and all patients were duly informed about the study and provided written informed consent. All records were de-identified before being enrolled in the study. All methods were carried out in accordance with the Declaration of Helsinki. Informed consent was obtained from all subjects/or their legal guardian(s) for the use of their records. Neither minors nor illiterates were included in this study. Consent for publication Not applicable. Availability of data and materials The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Competing interests No potential conflicts of interest relevant to this article were reported. Funding This study was funded by the Sanming Project of Medicine in Shenzhen (No. SZSM202311009) . Authors' contributions L-Y H, Y Y and W-R L conceived and designed this project. L-Y H and Y-Y Z conducted experiments and interpreted the results of experiments. 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Masticatory muscle activity in children and adults with different facial types. AM J Orthod Dentofacial Orthop. 2000;118:63–68. doi:10.1067/mod.2000.99142 Ingervall B. Variation of the range of movement of the mandible in relation to facial morphology in young adults. European J Oral Sciences. 1971;79:133–140. doi:10.1111/j.1600-0722.1971.tb02003.x Ramsundar K, Rengalakshmi S, Venugopalan S, Jain RK, Nagesh S. Electromyographic assessment of the masseter and temporalis muscles in skeletal II malocclusion subjects with varying overjets: a pilot study. Cureus. 2023;15(9):e44645. doi:10.7759/cureus.44645 Cha BK, Kim CH, Baek SH. Skeletal sagittal and vertical facial types and electromyographic activity of the masticatory muscle. Angle Orthod. 2007;77:463–470. doi:10.2319/0003-3219(2007)077%5B0463:SSAVFT%5D2.0.CO;2 Miralles R, Hevia R, Contreras L, Carvajal R, Bull R, Manns A. Patterns of electromyographic activity in subjects with different skeletal facial types. Angle Orthod. 1991;61:277–284. doi:10.1043/0003-3219(1991)061%3C0277:POEAIS%3E2.0.CO;2 Antonini G, Colantonio L, Macretti N, Lenzi GL. Electromyographic findings in class II division 2 and class III malocclusions. Electromyogr Clin Neurophysiol. 1990;30:27–30. Woźniak K, Piątkowska D, Lipski M, Mehr K. Surface electromyography in orthodontics - a literature review. Med Sci Monit: Int Med J Exp Clin Res. 2013;19:416–423. doi:10.12659/MSM.883927 Bykova KM. Measurement of surface electromyography activity during swallowing in paediatrics: a scoping literature review. Eur J Pediatr. 2024;183:4145–4157. doi:10.1007/s00431-024-05685-2 Ko K, Jones A, Francis D, Robidoux S, McArthur G. Physiological correlates of anxiety in childhood and adolescence: a systematic review and meta-analysis. Stress Health: J Int Soc Investig Stress. 2024;40:e3388. doi:10.1002/smi.3388 Ierardo G, Mazur M, Luzzi V, Calcagnile F, Ottolenghi L, Polimeni A. Treatments of sleep bruxism in children: a systematic review and meta-analysis. Cranio: J Craniomandib Pract. 2021;39:58–64. doi:10.1080/08869634.2019.1581470 Farook TH, Haq TM, Ramees L, Dudley J. Predictive modelling of freeway space utilising clinical history, normalised muscle activity, dental occlusion, and mandibular movement analysis. Sci Rep. 2024;14:16423. doi:10.1038/s41598-024-67640-3 Fuentes R, Arias A, Lezcano MF, Saravia D, Kuramochi G, Dias FJ. Systematic standardized and individualized assessment of masticatory cycles using electromagnetic 3D articulography and computer scripts. Biomed Res Int‌. 2017;2017:1–9. doi:10.1155/2017/7134389 Saad FH, Farook TH, Ahmed S, Zhao Y, Liao Z, Verjans JW, et al. Facial and mandibular landmark tracking with habitual head posture estimation using linear and fiducial markers. Healthcare Tech Letters. 2024;11:21–30. doi:10.1049/htl2.12076 Kim KA, Park HS, Lee SY, Kim SJ, Baek SH, Ahn HW. Short-term changes in muscle activity and jaw movement patterns after orthognathic surgery in skeletal Class III patients with facial asymmetry. Korean J Orthod. 2019;49:254. doi:10.4041/kjod.2019.49.4.254 Junior PFP, Albuquerque LCA, Silva CLDL, Da Silva NF, Da Cunha DA, Da Silva HJ. Amplitude speed of masticatory movements in total laryngectomy patients. Braz J Otorhinolar. 2014;80:138–145. doi:10.5935/1808-8694.20140029 Brown T. Mandibular movements. Monogr Oral Sci. 1975;4:126–150. doi:10.1159/000397870 Sales RD, Vitti M. [Electromyographic analysis of orbicularis oris muscles in individual with class I malocclusion before and after being subjected to orthodontic therapy]. Rev Assoc Paul Cir Dent. 1979;33:399–341. Rodrigues KA, Ferreira LP. Masseter muscles electromyography study of individuals with and without malocclusion during dental clenching. Electromyogr Clin Neurophysiol. 2004;44:271–275. Saker AA, Hajeer MY, Youssef M. A comparative electromyographic analysis of masticatory muscles between skeletal class II and skeletal class I malocclusion: a cross-sectional study on a syrian population. Cureus. 2024;16(2):e53960. doi:10.7759/cureus.53960 Saker AA, Mousa MM, Hajeer MY, Haddad I, Alhaffar JB, Youssef M. A comparison between skeletal class II and Class III malocclusion patients in terms of the masticatory muscles’ activity: a cross-sectional study. Cureus. 2024;16(5):e59861. doi:10.7759/cureus.59861 Ardani IGAW, Dinata FC, Triwardhani A. The importance of the occlusal plane in predicting better facial soft tissue in class II malocclusion in ethnic javanese. Eur J Dent. 2020;14:429–434. doi:10.1055/s-0040-1713331 Moreno I, Sanchez T, Ardizone I, Aneiros F, Celemin A. Electromyographic comparisons between clenching, swallowing and chewing in jaw muscles with varying occlusal parameters. Med Oral Patol Oral Cir Bucal. 2008;13(3):E207–213. Dutra EH, Maruo H, Vianna-Lara MS. Electromyographic activity evaluation and comparison of the orbicularis oris (lower fascicle) and mentalis muscles in predominantly nose- or mouth-breathing subjects. AM J Orthod Dentofacial Orthop‌. 2006; 129:722.e1–722.e9. doi:10.1016/j.ajodo.2006.02.027 Stavridi R, Ahlgren J. Muscle response to the oral-screen activator. An EMG study of the masseter, buccinator, and mentalis muscles. Eur J Orthodont. 1992;14:339–349. doi:10.1093/ejo/14.5.339 Nomura T, Sasaki A, Fujimoto M, Mano M, Suda N, Kondo K. Effects of jaw movement in bimaxillary orthognathic surgery on the upper airway: computational fluid dynamics analysis. Orthod Craniofac Res. 2023;26:311–319. doi:10.1111/ocr.12627 Thomas GP, Throckmorton GS, Ellis E, Sinn DP. The effects of orthodontic treatment on isometric bite forces and mandibular motion in patients before orthognathic surgery. J Oral Maxillofac Surg. 1995;53:673–678; discussion 678–679. doi:10.1016/0278-2391(95)90168-x Phan XL, Schneider BJ, Sadowsky C, BeGole EA. Effects of orthodontic treatment on mandibular rotation and displacement in angle class II division 1 malocclusions. Angle Orthod. 2004;74:174–183. doi:10.1043/0003-3219(2004)074%3C0174:EOOTOM%3E2.0.CO;2 Lundeen HC, Shryock EF, Gibbs CH. An evaluation of mandibular border movements: Their character and significance. J Prosthet Dent. 1978;40:442–452. doi:10.1016/0022-3913(78)90130-0 Farfán NC, Lezcano MF, Navarro-Cáceres PE, Sandoval-Vidal HP, Martinez-Gomis J, Muñoz L, et al. Characterization of mandibular border movements and mastication in each skeletal class using 3D electromagnetic articulography: a preliminary study. Diagnostics. 2023;13:2405. doi:10.3390/diagnostics13142405 Kataoka T, Kawanabe N, Shiraga N, Hashimoto T, Deguchi T, Miyawaki S, et al. The influence of craniofacial morphology on mandibular border movements. Cranio. 2013; 31:14–22. doi:10.1179/crn.2013.003 Muto T, Kanazawa M. Linear and angular measurements of the mandible during maximal mouth opening. J Oral Maxillofac Surg. 1996; 54:970–974. doi:10.1016/s0278-2391(96)90394-8 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 21 Oct, 2025 Reviewers agreed at journal 12 Oct, 2025 Reviewers agreed at journal 06 Oct, 2025 Reviewers invited by journal 03 Oct, 2025 Editor invited by journal 04 Sep, 2025 Editor assigned by journal 30 Aug, 2025 Submission checks completed at journal 30 Aug, 2025 First submitted to journal 29 Aug, 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-7489326","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":528880690,"identity":"66512de2-0746-4a4d-aa16-da994a0dbdc4","order_by":0,"name":"Li-Yu Hou","email":"","orcid":"","institution":"Shenzhen People’s Hospital, Southern University of Science and Technology)","correspondingAuthor":false,"prefix":"","firstName":"Li-Yu","middleName":"","lastName":"Hou","suffix":""},{"id":528880691,"identity":"51ec33b2-b06e-46d9-b209-7c45ecb1e08e","order_by":1,"name":"Yu-Yan Zheng","email":"","orcid":"","institution":"Shenzhen People’s 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This malocclusion type is commonly characterized by sagittal skeletal disharmony, presenting as maxillary protrusion, mandibular retrognathia, or a combination of both. Mandibular retrognathia is reported in 29\u0026ndash;65% of skeletal class II malocclusion cases [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Adolescents with mandibular retrognathia often exhibit distal molar relationships, deep overbite, deep overjet, varying degrees of lip incompetence, and a narrower airway compared to those with skeletal class I malocclusion [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. They face an elevated risk of developing obstructive sleep apnea in adulthood and demonstrate a higher incidence of lip incompetence compared to individuals with other skeletal malformations [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Mandibular retrognathia not only impacts facial aesthetics but also influences functional aspects. Optimal occlusion is crucial for achieving balance in the stomatognathic system, emphasizing the importance of a harmonious relationship between the dental arches for maintaining functional symmetry [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In 1980, Pancherz et al. [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] observed that children with skeletal class II malocclusion exhibited decreased electromyographic (EMG) amplitude in the masseter muscle during chewing compared to those with normal occlusion. Ma et al. [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] noted that regardless of occlusion type, temporal muscles were more active in the mandibular postural position, whereas the masseter muscle demonstrated higher activity during central occlusion in maximal voluntary contraction of masticatory muscles. Additionally, Lowe et al. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] proposed a correlation between skeletal morphology (mandibular angle size and parallelism in jaw bases) and EMG amplitude of the anterior temporal and masseter muscles during maximal voluntary contraction.\u003c/p\u003e\u003cp\u003eMoreover, malocclusion can lead to various functional issues, including significant temporomandibular disorders (TMD) [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Factors such as mandibular length, mandibular ramus inclination, and condylar position play pivotal roles in mandibular movement [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. In individuals with skeletal class II malocclusion and mandibular retrognathia, the retrognathic mandibular position and reduced mandibular body length may impact mandibular movement patterns, potentially influencing masticatory system functions such as clenching, chewing, swallowing, and border movements.\u003c/p\u003e\u003cp\u003eWhile several studies have explored the link between craniofacial morphology and the masticatory system [\u003cspan additionalcitationids=\"CR13 CR14\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], the existing research predominantly examines muscle activity or mandibular motion in specific functional conditions. However, investigations focusing on masticatory muscle function and mandibular border movement in various functional states in adolescents with skeletal class II malocclusion are lacking. Moreover, conflicting conclusions exist among studies investigating the functional characteristics of the oral system in isolated movement states [\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Consequently, there is a need for research on masticatory muscle function and mandibular border movement in individuals with skeletal class II malocclusion.\u003c/p\u003e\u003cp\u003eElectromyography (EMG) serves as the primary method for assessing jaw and facial muscle activity in clinical settings, offering precise and objective evaluations of muscle function. EMG allows for electrophysiological recording and quantitative analysis of muscle activity amplitude and duration [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The variability in EMG impedance and reliability can be addressed through thorough quantitative analysis using normalization procedures. This non-invasive diagnostic tool is known for its simplicity, safety, and reliability, making it a prevalent choice for monitoring muscle function in adolescents [\u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Concurrently, incorporating mandibular functional movement assessment during EMG monitoring ensures consistency in quantitative analysis. Utilizing digital jaw position tracking devices enables real-time three-dimensional analysis of mandibular movement, facilitating the quantitative evaluation of various mandibular motion parameters during functional movements. These devices are extensively employed for assessing mandibular motion range [\u003cspan additionalcitationids=\"CR24 CR25 CR26\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eTherefore, the objective of this study was to examine potential functional disparities in the masticatory system between adolescents presenting with mandibular retrognathia in conjunction with skeletal class II malocclusion and a control group of individuals with skeletal class I malocclusion.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003e This study received approval from the Ethics Committee of the Peking University School of Stomatology. (Approval number: PKUSSIRB-201525111), and all patients were duly informed about the study and provided written informed consent.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eSample Selection and Grouping\u003c/h2\u003e\u003cp\u003eFrom January 2016 to February 2019, a total of 60 patients aged 10\u0026ndash;15 years were enrolled from the Department of Orthodontics at Peking University School of Stomatology. The cohort comprised 32 males and 28 females, with a mean age of 13.1 years.\u003c/p\u003e\u003cp\u003eCase Group: The case group consisted of 30 patients, comprising 17 males and 13 females, with an average age of 12.3 years. Inclusion criteria: 1. Clinical diagnosis of skeletal class II malocclusion, Division 1 malocclusion, characterized by distal molar relationships ranging from distoclusion to complete distal occlusion; 2. Cephalometric assessment indicating ANB\u0026thinsp;\u0026ge;\u0026thinsp;5\u0026deg;, with mandibular retrognathia as the primary feature; 3. Overjet exceeding 5 mm. Exclusion criteria: 1. Presence of systemic diseases (particularly in individuals with pacemakers) or mental/intellectual disabilities; 2. History of orthodontic treatment; 3. History of condylar fractures.\u003c/p\u003e\u003cp\u003eControl Group: The control group consisted of 30 patients, with 15 males and 15 females, with an average age of 13.9 years. Inclusion criteria: 1. Clinical diagnosis of skeletal class I malocclusion with neutral molar relationships; 2. Cephalometric analysis showing normal position and length of the maxillary and mandibular bones, with ANB between 0\u0026deg; and 4\u0026deg;; 3. Overjet\u0026thinsp;\u0026lt;\u0026thinsp;4 mm; 4. Presence of mild to moderate crowding or slight dental arch spacing. Exclusion criteria: 1\u0026ndash;3 identical to the Skeletal class II malocclusion group; 4. Absence of teeth other than third molars; 5. Supernumerary teeth; 6. Absence of crossbite, reverse bite, or edge-to-edge bite cases; 7. Severe crowding.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eExperimental Procedures\u003c/h3\u003e\n\u003cp\u003eAfter obtaining informed consent from both the pediatric patients and their guardians, functional assessments were conducted within a designated examination facility. The subjects were seated in an upright position with their heads aligned in the Frankfort horizontal plane, maintaining parallelism with the ground. This standardized postural protocol was consistently applied throughout all evaluations in this research investigation. The evaluation of the masticatory system functionality entailed the utilization of surface EMG and mandibular movement analysis. Surface electromyography data acquisition was performed usingan 8-channel EMG recording system, specifically the BioEMG III device (BioResearch, Inc., Milwaukee, WI, USA). The EMG recorder featured an impedance of 108 Ω, a voltage range of 0\u0026ndash;1550mV, and a frequency range of 30\u0026ndash;1000 Hz. Bipolar surface electrodes from BioResearch Associates Inc. (Brown Deer, WI, USA) were employed for signal detection. Mandibular movement assessments were executed utilizing the JT-3D apparatus, also from BioResearch in Milwaukee, Wisconsin, ensuring synchronization with the EMG equipment through a dedicated converter. Data acquisition and analysis were carried out using the Bio-Pak 6.0 software package from BioResearch, USA. The detailed methodology for data recording was as follows:\u003c/p\u003e\n\u003ch3\u003eEMG\u003c/h3\u003e\n\u003cp\u003eThe skin surface was meticulously cleansed thrice using 75% ethanol-soaked cotton balls to minimize impedance between the electrodes and the skin. Electrode placements were meticulously executed based on the anatomical locations and fiber orientations of the anterior temporalis (TA), masseter (MM), and mentalis (MT) muscles. Bipolar surface electrodes with longitudinal alignment parallel to the muscle fibers were employed. For the anterior temporalis muscle, the electrode was positioned above the zygomatic arch and along the supraorbital margin at the location of maximal contraction during clenching. The masseter electrode was situated 1 cm anterior to the midpoint of the line connecting the zygomatico-temporal suture and the mandibular angle. In the case of the mentalis muscle, the electrode was situated below the labial mentolabial groove along the muscle fiber direction. Symmetrical placement of electrodes on both sides of all muscles was ensured, with the ground electrode positioned at the posterior neck. A photographic record was captured following the initial electrode placement for subsequent reference. Muscle activity was captured utilizing the BioEMG III system, while patients maintained a relaxed posture in the resting position. Subsequent analysis of the electromyographic data allowed for the documentation of EMG amplitudes associated with the TA, MM, and MT muscles.\u003c/p\u003e\n\u003ch3\u003eMandibular Movement Tracing\u003c/h3\u003e\n\u003cp\u003eSynchronized measurements were facilitated through the utilization of a common converter interfaced with the EMG apparatus. A magnetic marker measuring 14\u0026times;6.3\u0026times;4.3 mm\u0026sup3; was affixed to the labial gingival third of the lower anterior teeth using glass ionomer cement (Shanghai Medical Equipment Co., Ltd., China). Subsequently, a cap-style measuring device was positioned, ensuring alignment of the magnetic marker with the positioning rod to maintain the accurate relative orientation between the tracing instrument and the marker. The placement of the EMG electrodes remained consistent throughout the procedure. Comprehensive recordings of mandibular position and displacement in the vertical, sagittal, and coronal planes were meticulously documented.\u003c/p\u003e\u003cp\u003eIn accordance with previous research [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e], the subsequent functional movements were meticulously documented and analyzed.\u003c/p\u003e\u003cp\u003eRest Position: Patients were directed to achieve a state of relaxation without occlusal contact, with the upper and lower lips resting naturally, and the mandible held in a condition of perceived muscle relaxation for 10 s. During this period, the EMG data captured the average EMG amplitudes of the TA, MM, and MT muscles, alongside the mandibular position at rest.\u003c/p\u003e\u003cp\u003eClenching: Patients were directed to relax and sustain the resting position before being prompted to exert maximal force by clenching their teeth in the intercuspal position for 3 s, with a 30-s interval between each measurement, totaling three measurements. The EMG data recorded the average amplitudes of the TA, MM, and MT during the clenching tasks.\u003c/p\u003e\u003cp\u003eChewing: EMG and mandibular movement tracing were employed in this study. Patients were directed to chew a single piece of gum (Extra, Wrigley Company Ltd., China) until it reached a uniform texture. The gum was positioned in the posterior region of the left or right side, and participants were instructed to assume a relaxed resting position. Subsequently, patient were guided to engage in chewing movements on the left or right side for 10 cycles per sequence, separated by a 30-s rest period between each set, with a total of three measurement sessions. EMG data acquisition documented variations in EMG amplitude of the TA, MM, and MT during left and right chewing episodes, while mandibular movement tracing captured positional changes and alterations in mandibular dynamics.\u003c/p\u003e\u003cp\u003eSwallowing: EMG and mandibular movement tracing were used. Patients were directed to execute their habitual saliva-swallowing pattern. Once they had acclimated to the task, they were instructed to maintain the resting position and subsequently perform a swallow, with a 1-min interval between each measurement, across three measurement instances. The EMG data documented alterations in the electromyographic amplitude of the TA, MM, and MT muscles, while mandibular movement tracing captured changes in mandibular position dynamics during the swallowing process.\u003c/p\u003e\u003cp\u003eBorder Movements: Mandibular movement tracing was employed in this investigation. Patients were instructed to execute maximum opening and closing movements, as well as maximal left/right lateral and protrusive movements. Following sufficient practice sessions to ensure proficiency in the movements, measurements were conducted. Mandibular movement tracing documented the range of mandibular displacement during maximum opening, left/right lateral, and protrusive movements.\u003c/p\u003e\u003cp\u003eStatistical Methods: Synchronized recording and analysis of EMG and mandibular movement data were performed utilizing Bio-Pak 6.0. The EMG measurements exhibited a precision of 0.1\u0026micro;V, while the mandibular movement measurements had a precision of 0.1 mm. Data analysis was carried out SPSS 20.0, with the normality of data assessed using Shapiro-Wilk tests. Depending on data distribution normality, either independent sample t-tests or Mann-Whitney tests were applied. A two-tailed test with a significance level of α\u0026thinsp;=\u0026thinsp;0.05 was employed to evaluate the statistical significance between the two groups.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eEMG\u003c/h2\u003e\u003cp\u003eThe EMG data for the TA, MM, and MT muscles during various mandibular functional movements are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. At rest, there were no statistically significant differences in EMG amplitudes among the TA, MM, and MT muscles. During clenching, individuals with skeletal class II malocclusion exhibited significantly lower EMG amplitudes in the bilateral anterior temporalis and masseter muscles than control group. However, no significant differences were observed in the mentalis muscles. Participants with skeletal class II malocclusion showed lower EMG activity in the anterior temporalis and masseter muscles compared to the control group during chewing. Notably, the right mentalis muscle exhibited higher EMG amplitudes than the control group, while the left mentalis muscle did not demonstrate a significant difference. During swallowing, individuals with skeletal class II malocclusion demonstrated significantly lower average EMG amplitudes in the right anterior temporalis and bilateral masseter muscles compared to the control group. Conversely, the EMG amplitudes of the bilateral mentalis muscles were notably higher in the skeletal class II malocclusion group compared to the control group.\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\u003eThe results of the masticatory muscle EMG recordings during different mandibular functional movement in the adolescents studied\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=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" morerows=\"1\" nameend=\"c2\" namest=\"c1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eControl (\u0026micro;v)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003eSkeletal II (\u0026micro;v)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" 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align=\"left\" colname=\"c3\"\u003e\u003cp\u003e65.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e24.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e43.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e25.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.001**\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTA-L\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e70.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e43.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e45.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e28.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.015*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMM-R\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e84.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e39.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e58.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e33.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.019*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMM-L\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e73.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e45.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e42.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e37.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.009**\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMT-R\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e9.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e32.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e17.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.039*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMT-L\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e23.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e11.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e25.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e18.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.762\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"5\" rowspan=\"6\"\u003e\u003cp\u003eSwallow\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTA-R\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.014*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTA-L\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.848\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMM-R\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.009**\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMM-L\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.012*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMT-R\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e13.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e22.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e18.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.010*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMT-L\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e11.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e21.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e17.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.010*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003e\u0026lowast;\u003c/sup\u003eStatistically significant difference. \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003e\u0026lowast;\u0026lowast;\u003c/sup\u003eStatistically significant difference. \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003eTA-R: Right anterior temporalis; TA-L: Left anterior temporalis; MM-R: Right masseter muscles; MM-L: Left masseter muscles; MT-R: Right mentalis muscles; MT-L: Left mentalis muscles; Control: skeletal I malocclusion adolescents; Skeletal II: skeletal II malocclusion adolescents with mandibular retrognathia\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eMandibular Movement Tracing\u003c/h3\u003e\n\u003cp\u003eThe mandibular movement tracing data during different functional motions are presented in Tables\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. At rest, the mandibular position is defined in relation to the intercuspal position. The total displacement from the intercuspal position was notably greater in the skeletal class II malocclusion group compared to the control group. Specifically, vertical and coronal displacements in the skeletal class II malocclusion group exceeded those in the control group with statistical significance, while no significant disparity was observed in sagittal displacement. During chewing, no significant differences in mandibular movement displacement were noted between the two groups across all three directional axes. In the context of swallowing, the skeletal class II malocclusion group displayed significantly greater mandibular displacement than the control group in all three directions. For maximum opening movements, there were no significant differences between the skeletal class II malocclusion and control groups in the three directions. However, during lateral and protrusive movements, mandibular displacement in the skeletal class II malocclusion group surpassed that of the control group with statistical significance.\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\u003eThe results of the mandibular movement tracing recordings during different mandibular functional movement in the adolescents studied\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"9\"\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\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" morerows=\"1\" nameend=\"c2\" namest=\"c1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c5\" namest=\"c3\"\u003e\u003cp\u003eControl (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"3\" nameend=\"c8\" namest=\"c6\"\u003e\u003cp\u003eSkeletal II (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003eSD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e\u003cp\u003eSD\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eRest\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e1.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e2.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.010*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eVertical Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e1.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e2.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.046*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSagittal Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e\u0026minus;0.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e\u0026minus;0.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.609\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCoronal Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e0.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.009**\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eChew\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e12.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e11.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e4.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.822\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eVertical Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e11.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e10.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e4.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.452\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSagittal Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e1.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e1.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e5.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.929\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCoronal Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e2.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e2.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e2.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.655\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eSwallow\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e1.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e1.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.001**\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eVertical Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e1.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.002**\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSagittal Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e0.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e\u0026minus;0.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e1.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.034*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCoronal Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e0.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e0.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.004**\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003eMaximum Opening Movements\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTotal Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e43.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e7.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e41.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e9.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.488\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eVertical Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e33.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e5.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e32.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e6.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.369\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSagittal Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e25.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e23.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e13.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.536\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCoronal Displacement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003e4.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003e5.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003e3.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e0.193\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"9\"\u003e\u003csup\u003e\u0026lowast;\u003c/sup\u003eStatistically significant difference. \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"9\"\u003e\u003csup\u003e\u0026lowast;\u0026lowast;\u003c/sup\u003eStatistically significant difference. \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"9\"\u003eControl: skeletal I malocclusion adolescents; Skeletal II: skeletal II malocclusion adolescents with mandibular retrognathia\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\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\u003eThe results of the mandibular movement tracing recordings during lateral and protrusive movements in the adolescents studied\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\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eControl (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003eSkeletal II (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eSD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMean\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eSD\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eMandibular\u003c/p\u003e\u003cp\u003eBorder Movement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLeft Lateral Movement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e5.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.007**\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eRight Lateral Movement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e5.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.037*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eProtrusive Movement\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e3.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.001**\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003e\u0026lowast;\u003c/sup\u003eStatistically significant difference. \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003e\u0026lowast;\u0026lowast;\u003c/sup\u003eStatistically significant difference. \u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"7\"\u003eControl: skeletal I malocclusion adolescents; Skeletal II: skeletal II malocclusion adolescents with mandibular retrognathia\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe masticatory muscles within the facial region and their functionally modulated motor activities play a pivotal role in the developmental trajectory of the craniofacial system in adolescents. Comprehensive insights into the EMG patterns of these muscles and the kinematics associated with mandibular functional movements contribute significantly to elucidating the inherent mechanisms governing compensatory developments within the dentofacial hard tissue structures, particularly within the realm of facial soft tissues. This study focused on adolescent participants and investigated their muscle activity and mandibular dynamics across various functional states (e.g., resting, clenching, chewing, swallowing, and border movement) utilizing electromyography and a mandibular motion analysis system.\u003c/p\u003e\u003cp\u003eDuring the early permanent dentition stage in adolescents, the prevalence of class I malocclusion is approximately 38.5%, representing about half of all malocclusion cases and surpassing the occurrence of skeletal class II malocclusion [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Class I malocclusion is characterized by sagittal skeletal harmony between the maxilla and the mandible. However, the presence of malocclusion can impact certain muscle functions. Previous investigations have revealed that individuals with class I malocclusion exhibit diminished electromyographic (EMG) amplitudes in the masticatory muscles during clenching compared to those with normal occlusion [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Moreover, studies have demonstrated that individuals with class I malocclusion exhibit reduced occlusal contact and bite force relative to individuals with normal occlusion [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. To minimize the impact of dental discrepancy on the analysis, the control group in this study consisted of individuals with class I malocclusion rather than normal occlusion. Prolonged unilateral chewing habits have the potential to induce asymmetry in the size of bilateral muscles and the amplitude of EMG activity. To ensure sample integrity, individuals with unilateral chewing habits were excluded during participant recruitment.\u003c/p\u003e\u003cp\u003eDuring the rest position, patients with skeletal class I and skeletal class II malocclusion demonstrate increased activation of the temporal muscles for postural functions, while the masseter muscles exhibit relatively lower responsiveness. Within this study, patients with skeletal class II malocclusion did not show a significant impact on the average EMG amplitude of the anterior temporalis and masseter muscles during the resting phase. These observations are consistent with the findings of Ali A. Saker et al. [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], but contradict the results of Ardani et al.[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Discrepancies in these outcomes may stem from variations in the age compositions of the study populations. Given that the resting position entails facial muscle relaxation without the necessity for firm closure, no significant differences were noted in the mentalis muscle activity. During tooth clenching, individuals with skeletal class II malocclusion exhibited reduced activity in both the bilateral temporalis and masseter muscles, while no notable differences were observed in the mentalis muscles. During chewing movements, individuals with skeletal class II malocclusion consistently demonstrated diminished activity in the working side TA and MM muscles compared to the control group. This observation aligns with the reduced EMG amplitudes recorded bilaterally during maximum tooth clenching and supports the conclusions of Moreno et al.[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. In the context of swallowing, a process requiring effective lip sealing, individuals with skeletal class II malocclusion exhibited significantly heightened activity in the mentalis muscle, nearly doubling in intensity. This pronounced activation of the mentalis muscle was essential for achieving lip closure, suggesting a compensatory mechanism employed by individuals with skeletal class II malocclusion during this functional motion [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe mandibular movement range encompasses the extent of mandibular motion during functional activities, delineating the limits of maximal jaw opening, protrusion, and lateral movements. In this study, we evaluated the mandibular movement range during simulated rest, clenching, chewing, swallowing, and maximal border positions to investigate the impact of skeletal discrepancies, particularly mandibular retrusion, on functional mandibular movements. Understanding the influence of skeletal discrepancies on the mandibular movement range can provide insights into the compensatory mechanisms of dental and orofacial soft and hard tissues, offering objective metrics for assessing functional enhancements in the stomatognathic system following orthodontic and orthognathic interventions [\u003cspan additionalcitationids=\"CR38\" citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAt the rest position, individuals with skeletal class II malocclusion displayed increased vertical and coronal mandibular displacement. Conversely, no significant differences in mandibular movement range were observed in the three-dimensional directions during chewing. The observed range aligned with the average maximal mandibular displacement during left/right chewing motions, indicating that mild impairment of chewing muscle function on the working side did not lead to aberrant mandibular movements during chewing, reflecting the compensatory capacity of the stomatognathic system. Furthermore, in the context of swallowing, subjects with skeletal class II malocclusion exhibited heightened vertical, coronal, and sagittal mandibular displacement from the intercuspal position, including instantaneous mandibular protrusion during swallowing. These findings are indicative of atypical swallowing patterns, affirming the presence of more pronounced abnormal swallowing behaviors in patients with skeletal class II malocclusion.\u003c/p\u003e\u003cp\u003eDuring maximum jaw opening, craniofacial morphology exhibited minimal impact on mandibular movement, consistent with prior research findings [14,40\u0026ndash;42]. However, in lateral and protrusive movements, individuals with skeletal class II malocclusion displayed increased mandibular displacement on the working side. Specifically, during protrusive movements, subjects with skeletal class II malocclusion demonstrated an expanded protrusive range, indicative of a greater overjet.\u003c/p\u003e\u003cp\u003eIn the realm of craniofacial skeletal pattern influence on mandibular movement, scholarly investigations date back to 1971[14]. While some studies have revealed a notable association between vertical mandibular displacement and the ANB angle, the correlation between lateral mandibular displacement and craniofacial morphological parameters appears relatively modest [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. This discrepancy from our findings may stem from the fact that the referenced study focused on condylar movement range, whereas our research specifically targeted mandibular movement range. The comprehensive scope of the mandibular movement range is influenced by various factors, encompassing condylar movement, the configuration of the mandibular ramus and body, and occlusal anatomy [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. It is essential to recognize that condylar movement alone cannot comprehensively depict the entirety of mandibular motion.\u003c/p\u003e\u003cp\u003eIn a previous study, no significant distinctions were detected in the mandibular movement range between individuals with skeletal class II malocclusion and class I malocclusion, whether chewing or border movements [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Nonetheless, this conclusion contrasts with our results. These discrepancies could be linked to population demographics, as their study predominantly centered on adult subjects, while our research encompassed adolescent participants. Prolonged engagement in functional movements may have prompted adults to develop effective compensatory mechanisms for mandibular motion.\u003c/p\u003e\u003cp\u003eThis study compared the electromyographic activity differences in bilateral masticatory muscles and mandibular movement range between adolescents presenting with skeletal class II malocclusion and skeletal class I patterns under functional movements. While our findings offer insights into the interplay between craniofacial morphology and oral function, this study is not without limitations. Primarily, the research was confined to adolescents with skeletal class II malocclusion patterns, excluding participants with other craniofacial skeletal patterns. Future investigations should broaden the sample scope to encompass adolescents with diverse skeletal facial configurations for comprehensive exploration. Moreover, the study solely focused on adolescents with mandibular retrusion who had not undergone orthodontic interventions, omitting discussions on the influence of orthodontic treatment on muscle activity or mandibular movements. Subsequent research endeavors aim to delve into the impact of orthodontic interventions on the functional activity of masticatory muscles in adolescent populations.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eBased on the methodology employed in this study, the following conclusions can be drawn:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eAdolescents with skeletal class II malocclusion demonstrated reduced activity in the anterior temporalis and masseter muscles during clenching and chewing.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eDuring swallowing, adolescents with skeletal class II malocclusion exhibited decreased activity in the anterior temporalis and both masseter muscles, while displaying heightened activity in the mentalis muscle.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eMandibular motion exhibited increased displacements in the resting and swallowing positions among adolescents with skeletal class II malocclusion.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eFunctional disruptions in the masticatory system of adolescents with skeletal class II malocclusion and mandibular retrognathia were apparent across various activities, including rest position, clenching, chewing, swallowing, and border movements. These observations underscore the notable impact of skeletal class II malocclusion on the functional dynamics of the masticatory system.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study received approval from the Ethics Committee of the Peking University School of Stomatology. (Approval number: PKUSSIRB-201525111), and all patients were duly informed about the study and provided written informed consent. All records were de-identified before being enrolled in the study. All methods were carried out in accordance with the Declaration of Helsinki. Informed consent was obtained from all subjects/or their legal guardian(s) for the use of their records. Neither minors nor illiterates were included in this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo potential conflicts of interest relevant to this article were reported.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was funded by the Sanming Project of Medicine in Shenzhen (No. SZSM202311009) .\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eL-Y H, Y Y and W-R L conceived and designed this project. L-Y H and Y-Y Z conducted experiments and interpreted the results of experiments. L-Y H and Y Y drafted the paper, edited, and revised the manuscript. Y-Y Z and Q L perform data analysis and figures. All the authors have read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eLombardo G, Vena F, Negri P, Pagano S, Barilotti C, Paglia L, et al. Worldwide prevalence of malocclusion in the different stages of dentition: a systematic review and meta-analysis. Eur J Paediatr Dent. 2020; 21:115\u0026ndash;22. doi:10.23804/ejpd.2020.21.02.05\u003c/li\u003e\n\u003cli\u003eThomas J, Kannan A, Kailasam V. Morphological dimension of the permanent dentition in various malocclusion: a systematic review and meta-analysis. BMC Oral Health. 2025; 25:857. doi:10.1186/s12903-025-06203-y\u003c/li\u003e\n\u003cli\u003eKoaban A, Al-Harbi SK, Al-Shehri AZ, Al-Shamri BS, Aburazizah MF, Al-Qahtani GH, et al. Current trends in pediatric orthodontics: a comprehensive review. Cureus. 2024; 16:e68537. doi:10.7759/cureus.68537\u003c/li\u003e\n\u003cli\u003eParadowska-Stolarz A, Kawala B. Occlusal disorders among patients with total clefts of lip, alveolar bone, and palate. Biomed Res Int. 2014; 2014:583416. doi:10.1155/2014/583416\u003c/li\u003e\n\u003cli\u003eWoźniak K, Szyszka-Sommerfeld L, Lichota D. The electrical activity of the temporal and masseter muscles in patients with TMD and unilateral posterior crossbite. Biomed Res Int. 2015; 2015:259372. doi:10.1155/2015/259372\u003c/li\u003e\n\u003cli\u003ePancherz H. Activity of the temporal and masseter muscles in class II, division 1 malocclusions. An electromyographic investigation. Am J Orthod. 1980;77:679\u0026ndash;688. doi:10.1016/0002-9416(80)90159-1\u003c/li\u003e\n\u003cli\u003eMa SYL, Whittle T, Descallar J, Murray GM, Darendeliler MA, Cistulli P, et al. Association between resting jaw muscle electromyographic activity and mandibular advancement splint outcome in patients with obstructive sleep apnea. Am J Orthod Dentofacial Orthop. 2013;144:357\u0026ndash;367. doi: 10.1016/j.ajodo.2013.04.015\u003c/li\u003e\n\u003cli\u003eLowe AA, Takada K, Taylor LM. Muscle activity during function and its correlation with craniofacial morphology in a sample of subjects with class II, division 1 malocclusions. Am J Orthod. 1983;84:204\u0026ndash;211. doi:10.1016/0002-9416(83)90127-6\u003c/li\u003e\n\u003cli\u003eThomas DC, Singer SR, Markman S. Temporomandibular disorders and dental occlusion: what do we know so far? Dent Clin North Am. 2023;67:299\u0026ndash;308. doi:10.1016/j.cden.2022.11.002\u003c/li\u003e\n\u003cli\u003eAnanthan S, Pertes RA, Bender SD: Biomechanics and derangements of the temporomandibular joint. Dent Clin North Am. 2023;67:243\u0026ndash;257. doi:10.1016/j.cden.2022.11.004\u003c/li\u003e\n\u003cli\u003eZheng H, Shi L, Lu H, Liu Z, Yu M, Wang Y, et al. Influence of edentulism on the structure and function of temporomandibular joint. Heliyon. 2023; 9:e20307. doi:10.1016/j.heliyon.2023.e20307\u003c/li\u003e\n\u003cli\u003eToro A, Buschang PH, Throckmorton G, Rold\u0026aacute;n S. Masticatory performance in children and adolescents with Class I and II malocclusions. Eur J Orthodont. 2006; 28:112\u0026ndash;119. doi:10.1093/ejo/cji080\u003c/li\u003e\n\u003cli\u003eUeda HM, Miyamoto K, Saifuddin M, Ishizuka Y, Tanne K. Masticatory muscle activity in children and adults with different facial types. AM J Orthod Dentofacial Orthop. 2000;118:63\u0026ndash;68. doi:10.1067/mod.2000.99142\u003c/li\u003e\n\u003cli\u003eIngervall B. Variation of the range of movement of the mandible in relation to facial morphology in young adults. European J Oral Sciences. 1971;79:133\u0026ndash;140. doi:10.1111/j.1600-0722.1971.tb02003.x\u003c/li\u003e\n\u003cli\u003eRamsundar K, Rengalakshmi S, Venugopalan S, Jain RK, Nagesh S. Electromyographic assessment of the masseter and temporalis muscles in skeletal II malocclusion subjects with varying overjets: a pilot study. Cureus. 2023;15(9):e44645. doi:10.7759/cureus.44645\u003c/li\u003e\n\u003cli\u003eCha BK, Kim CH, Baek SH. Skeletal sagittal and vertical facial types and electromyographic activity of the masticatory muscle. Angle Orthod. 2007;77:463\u0026ndash;470. doi:10.2319/0003-3219(2007)077%5B0463:SSAVFT%5D2.0.CO;2\u003c/li\u003e\n\u003cli\u003eMiralles R, Hevia R, Contreras L, Carvajal R, Bull R, Manns A. Patterns of electromyographic activity in subjects with different skeletal facial types. Angle Orthod. 1991;61:277\u0026ndash;284. doi:10.1043/0003-3219(1991)061%3C0277:POEAIS%3E2.0.CO;2\u003c/li\u003e\n\u003cli\u003eAntonini G, Colantonio L, Macretti N, Lenzi GL. Electromyographic findings in class II division 2 and class III malocclusions. Electromyogr Clin Neurophysiol. 1990;30:27\u0026ndash;30. \u003c/li\u003e\n\u003cli\u003eWoźniak K, Piątkowska D, Lipski M, Mehr K. Surface electromyography in orthodontics - a literature review. Med Sci Monit: Int Med J Exp Clin Res. 2013;19:416\u0026ndash;423. doi:10.12659/MSM.883927\u003c/li\u003e\n\u003cli\u003eBykova KM. Measurement of surface electromyography activity during swallowing in paediatrics: a scoping literature review. Eur J Pediatr. 2024;183:4145\u0026ndash;4157. doi:10.1007/s00431-024-05685-2\u003c/li\u003e\n\u003cli\u003eKo K, Jones A, Francis D, Robidoux S, McArthur G. Physiological correlates of anxiety in childhood and adolescence: a systematic review and meta-analysis. Stress Health: J Int Soc Investig Stress. 2024;40:e3388. doi:10.1002/smi.3388\u003c/li\u003e\n\u003cli\u003eIerardo G, Mazur M, Luzzi V, Calcagnile F, Ottolenghi L, Polimeni A. Treatments of sleep bruxism in children: a systematic review and meta-analysis. Cranio: J Craniomandib Pract. 2021;39:58\u0026ndash;64. doi:10.1080/08869634.2019.1581470\u003c/li\u003e\n\u003cli\u003eFarook TH, Haq TM, Ramees L, Dudley J. Predictive modelling of freeway space utilising clinical history, normalised muscle activity, dental occlusion, and mandibular movement analysis. Sci Rep. 2024;14:16423. doi:10.1038/s41598-024-67640-3\u003c/li\u003e\n\u003cli\u003eFuentes R, Arias A, Lezcano MF, Saravia D, Kuramochi G, Dias FJ. Systematic standardized and individualized assessment of masticatory cycles using electromagnetic 3D articulography and computer scripts. Biomed Res Int\u0026zwnj;. 2017;2017:1\u0026ndash;9. doi:10.1155/2017/7134389\u003c/li\u003e\n\u003cli\u003eSaad FH, Farook TH, Ahmed S, Zhao Y, Liao Z, Verjans JW, et al. Facial and mandibular landmark tracking with habitual head posture estimation using linear and fiducial markers. Healthcare Tech Letters. 2024;11:21\u0026ndash;30. doi:10.1049/htl2.12076\u003c/li\u003e\n\u003cli\u003eKim KA, Park HS, Lee SY, Kim SJ, Baek SH, Ahn HW. Short-term changes in muscle activity and jaw movement patterns after orthognathic surgery in skeletal Class III patients with facial asymmetry. Korean J Orthod. 2019;49:254. doi:10.4041/kjod.2019.49.4.254\u003c/li\u003e\n\u003cli\u003eJunior PFP, Albuquerque LCA, Silva CLDL, Da Silva NF, Da Cunha DA, Da Silva HJ. Amplitude speed of masticatory movements in total laryngectomy patients. Braz J Otorhinolar. 2014;80:138\u0026ndash;145. doi:10.5935/1808-8694.20140029\u003c/li\u003e\n\u003cli\u003eBrown T. Mandibular movements. Monogr Oral Sci. 1975;4:126\u0026ndash;150. doi:10.1159/000397870\u003c/li\u003e\n\u003cli\u003eSales RD, Vitti M. [Electromyographic analysis of orbicularis oris muscles in individual with class I malocclusion before and after being subjected to orthodontic therapy]. Rev Assoc Paul Cir Dent. 1979;33:399\u0026ndash;341. \u003c/li\u003e\n\u003cli\u003eRodrigues KA, Ferreira LP. Masseter muscles electromyography study of individuals with and without malocclusion during dental clenching. Electromyogr Clin Neurophysiol. 2004;44:271\u0026ndash;275. \u003c/li\u003e\n\u003cli\u003eSaker AA, Hajeer MY, Youssef M. A comparative electromyographic analysis of masticatory muscles between skeletal class II and skeletal class I malocclusion: a cross-sectional study on a syrian population. Cureus. 2024;16(2):e53960. doi:10.7759/cureus.53960\u003c/li\u003e\n\u003cli\u003eSaker AA, Mousa MM, Hajeer MY, Haddad I, Alhaffar JB, Youssef M. A comparison between skeletal class II and Class III malocclusion patients in terms of the masticatory muscles\u0026rsquo; activity: a cross-sectional study. Cureus. 2024;16(5):e59861. doi:10.7759/cureus.59861\u003c/li\u003e\n\u003cli\u003eArdani IGAW, Dinata FC, Triwardhani A. The importance of the occlusal plane in predicting better facial soft tissue in class II malocclusion in ethnic javanese. Eur J Dent. 2020;14:429\u0026ndash;434. doi:10.1055/s-0040-1713331\u003c/li\u003e\n\u003cli\u003eMoreno I, Sanchez T, Ardizone I, Aneiros F, Celemin A. Electromyographic comparisons between clenching, swallowing and chewing in jaw muscles with varying occlusal parameters. Med Oral Patol Oral Cir Bucal. 2008;13(3):E207\u0026ndash;213.\u003c/li\u003e\n\u003cli\u003eDutra EH, Maruo H, Vianna-Lara MS. Electromyographic activity evaluation and comparison of the orbicularis oris (lower fascicle) and mentalis muscles in predominantly nose- or mouth-breathing subjects. AM J Orthod Dentofacial Orthop\u0026zwnj;. 2006; 129:722.e1\u0026ndash;722.e9. doi:10.1016/j.ajodo.2006.02.027\u003c/li\u003e\n\u003cli\u003eStavridi R, Ahlgren J. Muscle response to the oral-screen activator. An EMG study of the masseter, buccinator, and mentalis muscles. Eur J Orthodont. 1992;14:339\u0026ndash;349. doi:10.1093/ejo/14.5.339\u003c/li\u003e\n\u003cli\u003eNomura T, Sasaki A, Fujimoto M, Mano M, Suda N, Kondo K. Effects of jaw movement in bimaxillary orthognathic surgery on the upper airway: computational fluid dynamics analysis. Orthod Craniofac Res. 2023;26:311\u0026ndash;319. doi:10.1111/ocr.12627\u003c/li\u003e\n\u003cli\u003eThomas GP, Throckmorton GS, Ellis E, Sinn DP. The effects of orthodontic treatment on isometric bite forces and mandibular motion in patients before orthognathic surgery. J Oral Maxillofac Surg. 1995;53:673\u0026ndash;678; discussion 678\u0026ndash;679. doi:10.1016/0278-2391(95)90168-x\u003c/li\u003e\n\u003cli\u003ePhan XL, Schneider BJ, Sadowsky C, BeGole EA. Effects of orthodontic treatment on mandibular rotation and displacement in angle class II division 1 malocclusions. Angle Orthod. 2004;74:174\u0026ndash;183. doi:10.1043/0003-3219(2004)074%3C0174:EOOTOM%3E2.0.CO;2\u003c/li\u003e\n\u003cli\u003eLundeen HC, Shryock EF, Gibbs CH. An evaluation of mandibular border movements: Their character and significance. J Prosthet Dent. 1978;40:442\u0026ndash;452. doi:10.1016/0022-3913(78)90130-0\u003c/li\u003e\n\u003cli\u003eFarf\u0026aacute;n NC, Lezcano MF, Navarro-C\u0026aacute;ceres PE, Sandoval-Vidal HP, Martinez-Gomis J, Mu\u0026ntilde;oz L, et al. Characterization of mandibular border movements and mastication in each skeletal class using 3D electromagnetic articulography: a preliminary study. Diagnostics. 2023;13:2405. doi:10.3390/diagnostics13142405\u003c/li\u003e\n\u003cli\u003eKataoka T, Kawanabe N, Shiraga N, Hashimoto T, Deguchi T, Miyawaki S, et al. The influence of craniofacial morphology on mandibular border movements. Cranio. 2013; 31:14\u0026ndash;22. doi:10.1179/crn.2013.003\u003c/li\u003e\n\u003cli\u003eMuto T, Kanazawa M. Linear and angular measurements of the mandible during maximal mouth opening. J Oral Maxillofac Surg. 1996; 54:970\u0026ndash;974. doi:10.1016/s0278-2391(96)90394-8\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":"Skeletal class II malocclusion adolescents, Electromyography, Masticatory Muscle, Mandibular movement","lastPublishedDoi":"10.21203/rs.3.rs-7489326/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7489326/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective\u003c/h2\u003e\u003cp\u003eTo investigate masticatory muscle activity and mandibular border movement in adolescents with skeletal class II malocclusion and mandibular retrognathia and explore the influence of mandibular retrognathia on masticatory system function.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eThirty adolescents aged 10\u0026ndash;15 years diagnosed with skeletal class II malocclusion and mandibular retrognathia comprised the skeletal class II malocclusion group, while 30 adolescents with skeletal class I malocclusion constituted the control group. Functional assessments of the masticatory system were performed in both cohorts, encompassing Bio-EMG and JT-3D measurements during rest, clenching, chewing, swallowing, and border movements. Electromyographic (EMG) activity and mandibular kinematics were comprehensively measured and compared between the two groups.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003e1) EMG: During rest, there was no significant difference in the EMG amplitude of the muscles between the skeletal class II malocclusion and control groups. However, during clenching, the EMG amplitude of the anterior temporalis and masseter muscles was lower in the skeletal class II malocclusion group compared to the control group. Similarly, the EMG amplitude of the working-side temporalis and masseter muscles during chewing was lower in the skeletal class II malocclusion group. Furthermore, the mean EMG values of the anterior temporalis and both masseter muscles during swallowing were lower in the skeletal class II malocclusion group, while the mentalis muscle exhibited higher EMG activity. 2) Mandibular movement: The skeletal class II malocclusion group demonstrated increased vertical and coronal displacements in the mandibular resting position compared to the control group. However, during chewing, no significant disparity in mandibular displacement was observed between the skeletal class II malocclusion and control groups. In contrast, during swallowing, the skeletal class II malocclusion group exhibited greater vertical and coronal mandibular displacements, particularly with more pronounced forward sagittal displacement. Notably, there was no significant distinction in the three-dimensional mandibular displacement during maximum mouth opening between the two groups.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eFunctional impairments in the masticatory system of adolescents with skeletal class II malocclusion and mandibular retrognathia were evident across multiple activities, encompassing rest position, clenching, chewing, swallowing, and border movements. These results underscore the considerable influence of skeletal class II malocclusion on the functional integrity of the masticatory system.\u003c/p\u003e","manuscriptTitle":"Assessment of Masticatory Muscle Activity and Mandibular Border Movement in Skeletal Class II Malocclusion Adolescents with Mandibular Retrognathia","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-16 09:38:11","doi":"10.21203/rs.3.rs-7489326/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2025-10-21T12:20:02+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"195101400366310978704936883473625753847","date":"2025-10-12T17:35:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"58323105415919485471595533340650580874","date":"2025-10-06T11:54:12+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-10-03T13:38:41+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-09-04T04:32:13+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-30T10:18:39+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-08-30T10:18:15+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Oral Health","date":"2025-08-29T14:02:46+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":"ebe0eb93-8cfe-4984-ac7e-16b3f8af4889","owner":[],"postedDate":"October 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-10-16T09:38:11+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-16 09:38:11","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7489326","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7489326","identity":"rs-7489326","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}