Computational analysis of airflow dynamics for predicting collapsible sites in the upper airways: a preliminary study.

The present study aimed to detail the relationship between the flow and structure characteristics of the upper airways and airway collapsibility in obstructive sleep apnea. Using a computational approach, we performed simulations of the flow and structure of the upper airways in two patients having different facial morphologies: retruding and protruding jaws, respectively. First, transient flow simulation was performed using a prescribed volume flow rate to observe flow characteristics within upper airways with an unsteady effect. In the retruding jaw, the maximum magnitude of velocity and pressure drop with velocity shear and vortical motion was observed at the oropharyngeal level. In contrast, in the protruding jaw, the overall magnitude of velocity and pressure was relatively small. To identify the cause of the pressure drop in the retruding jaw, pressure gradient components induced by flow were examined. Of note, vortical motion was highly associated with pressure drop. Structure simulation was performed to observe the deformation and collapsibility of soft tissue around the upper airways using the surface pressure obtained from the flow simulation. At peak flow rate, the soft tissue of the retruding jaw was highly expanded, and a collapse was observed at the oropharyngeal and epiglottis levels. NEW & NOTEWORTHY Aerodynamic characteristics have been reported to correlate with airway occlusion. However, a detailed mechanism of the phenomenon within the upper airways and its impact on airway collapsibility remain poorly understood. This study provides in silico results for aerodynamic characteristics, such as vortical structure, pressure drop, and exact location of the obstruction using a computational approach. Large deformation of soft tissue was observed in the retruding jaw, suggesting that it is responsible for obstructive sleep apnea.

Impact of orthognathic surgery on velopharyngeal function by evaluating speech and cephalometric radiographs.

BACKGROUND: Maxillary retrognathia is a well-known consequence of abnormal facial growth in patients with cleft lip and palate. Orthognathic surgery improves facial appearance and occlusion but may induce velopharyngeal insufficiency. The aim of this study was to evaluate the effect of orthognathic surgery on velopharyngeal function by using speech analysis and lateral cephalometric radiographs. PATIENTS AND METHODS: We conducted a retrospective study of 47 patients who underwent maxillary advancement ±â€¯mandibular setback between 2006 and 2016. Preoperative and 1 year postoperative audio recordings were blinded for scoring by three trained speech therapists. Preoperative and 1 year postoperative lateral cephalometric radiographs were used to obtain information about skeletal movement and its relationship with the velopharyngeal area. Correlations between speech outcomes and cephalometric radiographs were determined. RESULTS: Hyponasality improved significantly after surgery (p < 0.05), whereas hypernasality deteriorated significantly only in patients who underwent maxillary advancement alone (p < 0.05). No difference in speech parameters was found between patients with hypernasality or patients who had a pharyngoplasty preoperatively and the rest of the group. No correlation was found between the amount of maxillary advancement and hypernasality. A significant correlation (r < -0.49, p < 0.05) was found between the preoperative velar length and hypernasality postoperatively. CONCLUSIONS: Maxillary advancement has a negative impact on velopharyngeal function, whereas bimaxillary surgery seems to protect from deterioration. No difference was found in the amount of maxillary advancement or in velopharyngeal measurements between the Le Fort I group and the bimaxillary group. A short soft palate is a predictor of hypernasality after orthognathic surgery.

3D Comparison of Mandibular Response to Functional Appliances: Balters Bionator versus Sander Bite Jumping.

AIM: To assess the three-dimensional (3D) maxillomandibular and dental response to Balters Bionator (BB) and the Sander Bite Jumping Appliance (SBJA) in growing patients. MATERIALS AND METHODS: Twenty-seven Class II division 1 patients (13 males, 14 females), consecutively treated with either the BB (9 females, 7 males; 10.1 ± 1.6 years) or SBJA (5 females, 6 males; 11 ± 1.9 years), were collected from a single orthodontic practice. All patients presented overjet ≥5 mm, full Class II or end-to-end molar relationship, mandibular retrusion. CBCT scans were available at T1 and after removal of the functional appliances (T2) with a mean interval of 18 months. The 3D location and direction of skeletal and dental changes with growth and treatment were quantitatively assessed. Statistical analysis was performed by means of Mann-Whitney U test (p < 0.05). RESULTS: Patients treated with the SBJA and BB orthopedic appliances presented, respectively, 4.7 mm and 4.5 mm of 3D displacement of the chin, with marked ramus growth of, respectively, 3.7 mm and 2.3 mm. While the mandible and maxilla grew downward and forward, no opening of the mandible plane was observed. Both appliances adequately controlled labial inclination of lower incisors (1.3° and 0.3°, for the SBJA and BB groups, resp.). No significant between-group differences were found for the T2-T1 changes for any of the variables, with the exception of molar displacements (significantly greater in the SBJA group than in the BB group, 1.2 mm and 0.9 mm, resp.). CONCLUSIONS: The maxillomandibular and dental growth responses to BB and SBJA therapies are characterized by vertical ramus growth and elongation of mandible that improve the maxillomandibular relationship with adequate control of lower incisor position.

Growth and Development of Craniofacial Structures in Patients at Different Ages With Unrepaired Submucous Cleft Palate.

PURPOSE: Submucous cleft palate (SMCP) is a particular subtype of cleft palate deformity; research related to the craniofacial features of patients with SMCP is comparatively rare. The study objective was to perform a cephalometric comparison of the craniofacial features of patients with SMCP and non-cleft controls at different ages. MATERIALS AND METHODS: The sample in this cross-sectional study was composed of 2 groups: SMCP patients and non-cleft controls. The primary predictor variables were study group (cleft and non-cleft) and age. Age was divided into 3 groups. The outcome variables of interest were craniofacial measurements. The measurements used reflect cranial length, cranial angle, maxillary sagittal length and protrusion, maxillary vertical height, pharyngeal depth, facial height, mandibular length and protrusion, mandibular plane angle, and intermaxillary relation. Adjusted cephalometric craniofacial measurements between the groups were compared in 3 age groups using generalized linear models after being adjusted for age and gender. RESULTS: The study included 60 SMCP patients and 60 non-cleft controls. SMCP patients and non-cleft controls were divided into 3 subgroups: those aged 5 to 7 years, those aged 9 to 11 years, and those aged 18 to 30 years. Patients with SMCP at age 5 to 7 years showed a shortened cranial base length, maxillary sagittal length and height, and bony pharynx depth. Patients with SMCP at age 9 to 11 years showed a smaller maxillary sagittal length and bony pharynx depth and an inharmonious jaw relationship. Patients with SMCP at age 18 to 30 years showed a smaller maxillary sagittal length and height and an inharmonious jaw relationship. CONCLUSIONS: SMCP is associated with progressive maxillary retrognathism and reduced profile convexity from childhood to adulthood.

Determining the Patient-Specific Optimum Osteotomy Line for Severe Mandibular Retrognathia Patients.

PURPOSE: The purpose of this study is to suggest a patient-specific osteotomy line to optimize the distractor position and thus to minimize the disadvantages of conventional mandibular distraction osteogenesis (MDO) protocols. In addition, this study also aims to compare the conventional MDO protocols with the new MDO protocol proposed in this study in terms of both orthodontic outcomes and mechanical effects of osteotomy level on callus stabilization by means of the finite element method. METHODS: A preoperative patient-specific 3-dimensional bone model was created and segmented by using computed tomography images of an individual patient. Virtual orthodontic set-up was applied to the segmented model prior to the virtual surgery. In order to compare the proposed osteotomy line with the conventional lines used in clinical applications, virtual surgery simulations were performed and callus tissues were modelled for each scenario. The comparison of the success of each osteotomy line was carried out based on the occlusion of the teeth. RESULTS: The osteotomy line determined using the method proposed in this study has resulted in far less malocclusion than the conventional method. Namely, any angular deviation from the optimum osteotomy line determined in this study might result in deep-bite or open-bite. On the other hand, the finite element analysis results have indicated that this deviation also negatively affects the callus stability. CONCLUSION: In order to achieve a better MDO treatment in terms of occlusion of the teeth and the callus stability, the location of the osteotomy line and the distractor position can be computationally determined. The results suggest that MDO protocol developed in this study might be used in clinic to achieve a better outcome from the MDO treatment.

A Triad of Temporomandibular Joint Ankylosis, Mandibular Retrognathia and Severe Obstructive Sleep Apnoea: Case report.

The surgical management of paediatric patients with temporomandibular joint (TMJ) ankylosis, mandibular retrognathia and obstructive sleep apnoea (OSA) is challenging. We report a nine-year-old boy who presented to the Department of Oral Health, Sultan Qaboos University Hospital, Muscat, Oman, in 2016 with complaints of limited mouth opening, loud snoring and excessive daytime sleepiness. He was diagnosed with TMJ ankylosis, mandibular retrognathia and severe OSA. The patient initially underwent mandibular distraction and, subsequently, release of the TMJ ankylosis and rib graft reconstruction. The overall patient outcome was successful, with improvement in OSA-related symptoms, good facial symmetry and adequate mouth opening.

Growth-related changes of skeletal and upper-airway features in bilateral cleft lip and palate patients.

INTRODUCTION: The craniofacial morphology of subjects with cleft lip and palate differs from that of subjects without clefts. Subjects with bilateral cleft lip and palate tend to have maxillary retrognathism, a smaller mandible with an obtuse gonial angle, greater anterior upper and lower facial heights, and retroclined maxillary incisors. The purposes of this research were to compare the skeletal and upper-airway features of subjects with bilateral cleft lip and palate with the same features in control subjects without clefts and to determine the growth-related changes at different growth stages. METHODS: The sample comprised 212 subjects divided into 2 groups: 68 with bilateral cleft lip and palate, and 144 controls without clefts; each group was further divided into 4 subgroups according to growth stage using the cervical vertebral maturation stage method. The subgroups were defined as early childhood (stage 1), prepubertal (stage 2), pubertal (stage 3), and postpubertal (stage 4). The cephalometric variables were evaluated with 2-way analysis of variance and the Bonferroni test. RESULTS: Maxillary position showed no significant differences between the male groups. The maxilla was more prognathic at stage 2 and became more retrognathic at stages 3 and 4 in the females. The mandible was more retrusive in the bilateral cleft lip and palate subjects at stage 1 in males and at stages 3 and 4 in females. ANB was larger at stages 1 and 2, and it became similar to the controls at stages 3 and 4 in male and female bilateral cleft lip and palate subjects. Vertical growth was seen in the bilateral cleft lip and palate subjects regardless of sex, and no change was observed with age. Posterior airway space was narrower in all stages (except for stage 1 in females). Middle airway space was wider after stage 1 in the male and female bilateral cleft lip and palate subjects. Inferior airway space was narrower in the male bilateral cleft lip and palate patients at the early childhood and pubertal stages. CONCLUSIONS: Age- and sex-dependent differences in skeletal morphology and upper-airway widths of the bilateral cleft lip and palate subjects were identified when compared with the control subjects without clefts.

Effects of mandibular retrusive deviation on prefrontal cortex activation: a functional near-infrared spectroscopy study.

The objective of this study was to evaluate occlusal condition by assessing brain activity in the prefrontal cortex, which is associated with emotion. Functional near-infrared spectroscopy (fNIRS) was used to detect changes in cerebral blood flow in the prefrontal cortex of 12 healthy volunteers. The malocclusion model was a custom-made splint that forced the mandible into retrusion. A splint with no modification was used as a control. The cortical activation during clenching was compared between the retrusive position condition and the control condition. A visual analog scale score for discomfort was also obtained during clenching and used to evaluate the interaction between fNIRS data and psychiatric changes. Activation of the prefrontal cortex was significantly greater during clenching in the mandibular retrusive condition than during clenching in the control condition. Furthermore, Spearman rank-correlation coefficient revealed a parallel relation between prefrontal cortex activation and visual analog scale score for discomfort. These results indicate that fNIRS can be used to objectively evaluate the occlusal condition by evaluating activity in the prefrontal cortex.

Mandibular growth comparisons of Class I and Class II division 1 skeletofacial patterns.

OBJECTIVE: To determine class and sex differences in mandibular growth and modeling. MATERIALS AND METHODS: A mixed-longitudinal sample of 130 untreated French-Canadian adolescents, 77 (45 boys and 32 girls) with Class I (normal or abnormal) occlusion and 53 (26 boys and 27 girls) with Class II division 1 malocclusion, was used. Based on eight landmarks, eight traditional measurements were used to compare the anteroposterior position of the maxilla and mandible, relationship between the jaws, and mandibular size. Mandibular superimpositions were used to compare the horizontal and vertical changes of condylion, gonion, and menton. RESULTS: While there were no differences in maxillary position based on the SNA angle, Class IIs had more retrognathic mandibles than did Class Is. Total mandibular length was greater in Class Is than in Class IIs at 15 years of age. Superior and total growth and modeling changes at condylion and gonion, respectively, were greater for Class Is than Class IIs. Boys were more prognathic than girls; they had larger mandibles and exhibited greater size increases and growth changes than girls did. CONCLUSIONS: There are both class and sex differences in mandibular growth and modeling.

Electromyographic muscular activity improvement in Class II patients treated with the pre-orthodontic trainer.

OBJECTIVE: A study was designed to determine changes in the amplitude of the EMG muscular activity of the Masseter and Temporalis muscles at clench in children with a Class II, division 1 malocclusion treated with the pre-orthodontic Trainer functional appliance, for 12 months. STUDY DESIGN: 36 Class II, division 1 malocclusion patients (mean age 7.6 ± 1.3 years) composed the treated group and wore the functional appliance; 22 children with a similar age and malocclusion composed the untreated controls; and, 20 children with no dental malocclusion participated as normal controls. Electromyographic (EMG) muscular activity of the Temporalis and Masseter muscles were recorded before and after treatment. RESULTS: Subjects in the treated group reported a bilateral significant increase in the muscular electrical activity in the both tested muscles (p < 0.001). After treatment, they recorded values similar to those measured in normal controls, whereas the untreated controls remained on lower values. CONCLUSION: These results confirm that treatment with the pre-orthodontic Trainer functional appliance significantly increases the EMG muscular activity in the Temporalis and Masseter muscles at clench in patients with Class II, division 1 malocclusion.

Morphometric evaluation of condylar cartilage of growing rats in response to mandibular retractive forces.

INTRODUCTION: The mandibular condylar surface is made up of four layers, i.e., an external layer composed of dense connective tissue, followed by a layer of undifferentiated cells, hyaline cartilage and bone. Few studies have demonstrated the behavior of the condylar cartilage when the mandible is positioned posteriorly, as in treatments for correcting functional Class III malocclusion. OBJECTIVE: The aim of this study was to assess the morphologic and histological aspects of rat condyles in response to posterior positioning of the mandible. METHODS: Thirty five-week-old male Wistar rats were selected and randomly divided into two groups: A control group (C) and an experimental group (E) which received devices for inducing mandibular retrusion. The animals were euthanized at time intervals of 7, 21 and 30 days after the experiment had began. For histological analysis, total condylar thickness was measured, including the proliferative, hyaline and hypertrophic layers, as well as each layer separately, totaling 30 measurements for each parameter of each animal. RESULTS: The greatest difference in cartilage thickness was observed in 21 days, although different levels were observed in the other periods. Group E showed an increase of 39.46% in the total layer, reflected by increases in the thickness of the hypertrophic (42.24%), hyaline (46.92%) and proliferative (17.70%) layers. CONCLUSIONS: Posteriorly repositioning the mandible produced a series of histological and morphological responses in the condyle, suggesting condylar and mandibular adaptation in rats.

Prevalence of snoring and high risk of obstructive sleep apnea syndrome in young male soldiers in Korea.

There are little information on prevalence of obstructive sleep apnea syndrome (OSAS) and clinical features in the young military population. The purpose of this study was to estimate the prevalence of snoring and high risk of OSAS in young male soldiers in Korea and to identify the risk factors of OSAS. A total of 665 participants (aged 20-23 yr) who visited the Armed Forces Ildong Hospital for regular physical examination were enrolled. All participants completed the Berlin Questionnaire and underwent a physical examination. The participants with high risk for OSAS completed portable sleep monitoring. The prevalence of snoring and high risk of OSAS in young male soldiers in Korea was 13.5% and 8.1%, respectively. The prevalence of high arched palate, tongue indentation, long uvula, large tonsil and retrognathia was significantly higher in the high risk OSAS group. High arched palate, long uvula or low lying soft palate, tonsil size III or IV, Epworth Sleepiness Scale score > 10 and obesity (BMI > 27 kg/m(2)) were found to independently predict OSAS. For early identification and treatment of young soldiers with OSAS in a military environment, a precise screening by questionnaire and physical examination is needed.

Morphometric evaluation of condylar cartilage of growing rats in response to mandibular retractive forces

INTRODUCTION: The mandibular condylar surface is made up of four layers, i.e., an external layer composed of dense connective tissue, followed by a layer of undifferentiated cells, hyaline cartilage and bone. Few studies have demonstrated the behavior of the condylar cartilage when the mandible is positioned posteriorly, as in treatments for correcting functional Class III malocclusion. OBJECTIVE: The aim of this study was to assess the morphologic and histological aspects of rat condyles in response to posterior positioning of the mandible. METHODS: Thirty five-week-old male Wistar rats were selected and randomly divided into two groups: A control group (C) and an experimental group (E) which received devices for inducing mandibular retrusion. The animals were euthanized at time intervals of 7, 21 and 30 days after the experiment had began. For histological analysis, total condylar thickness was measured, including the proliferative, hyaline and hypertrophic layers, as well as each layer separately, totaling 30 measurements for each parameter of each animal. RESULTS: The greatest difference in cartilage thickness was observed in 21 days, although different levels were observed in the other periods. Group E showed an increase of 39.46% in the total layer, reflected by increases in the thickness of the hypertrophic (42.24%), hyaline (46.92%) and proliferative (17.70%) layers. CONCLUSIONS: Posteriorly repositioning the mandible produced a series of histological and morphological responses in the condyle, suggesting condylar and mandibular adaptation in rats.

INTRODUÇÃO: a superfície do côndilo da mandíbula é constituída por quatro camadas: uma externa (constituída de tecido conjuntivo denso), seguida pela camada de células indiferenciadas, cartilagem hialina e osso. Poucos estudos demonstraram o comportamento da cartilagem condilar quando a mandíbula é posicionada posteriormente, como na terapia para correção de Classe III funcional. OBJETIVO: o objetivo desse trabalho foi avaliar os aspectos morfológicos e histológicos do côndilo de ratos, em resposta ao posicionamento posterior da mandíbula. MÉTODOS: foram selecionados 30 ratos Wistar, machos, com cinco semanas de vida, aleatoriamente divididos em dois grupos: grupo controle (GC) e grupo experimental (GE), que recebeu dispositivos para induzir a retrusão mandibular. Os animais foram sacrificados após 7, 21 e 30 dias de experimento. Para a análise histológica, foi realizada a mensuração da espessura condilar total, incluindo as camadas proliferativa, seriada e hipertrófica, assim como cada camada separadamente, totalizando 30 medições para cada parâmetro, de cada animal. RESULTADOS: a maior diferença na espessura da cartilagem foi observada em 21 dias, apesar de serem verificados níveis diferentes nos demais períodos. Em GE, foi possível observar um aumento de 39,46% na camada total, representado pelo aumento na espessura das camadas hipertrófica (42,24%), seriada (46,92%) e proliferativa (17,70%). CONCLUSÕES: o reposicionamento posterior da mandíbula produziu uma série de respostas histológicas e morfológicas no côndilo, e sugerem a ocorrência de uma adaptação condilar e mandibular em ratos.

Ontogenetic changes of craniofacial complex in Turner syndrome patients treated with growth hormone.

OBJECTIVE: The present study assessed changes of craniofacial complex in Turner syndrome (TS) patients treated with growth hormone (GH) during development. The objective was to examine the growth rate and pattern of craniofacial structures and to establish effects of GH on craniofacial development. MATERIALS AND METHODS: The study population consisted of 15 TS patients treated with GH aged 5-18.5 years (13.3 ± 4.4) and corresponding control group of 45 females aged 6.8-18.7 (11.4 ± 2.6). According to the stage of cervical vertebral maturation, subjects were categorized into pre-growth (5 TS and 15 controls) and growth (10 TS and 30 controls) subgroups. The cephalometric analysis comprised angular and linear variables, measured on lateral cephalometric radiographs. RESULTS: The mandibular corpus/anterior cranial base ratio increased significantly only in controls during development. In growth period, ramus/corpus ratio was significantly larger in TS group. SNA and SNB angles were significantly smaller in TS growth subgroup compared to corresponding controls. Among other variables, no statistically significant differences were revealed. CONCLUSIONS: In TS patients treated with GH, growth capacities of cranial base and maxilla are adequate which can be attributed to GH treatment. Shape of mandible is altered due to decreased growth of corpus and overdeveloped ramus. Both maxillary and mandibular retrognathism are becoming more expressed during development. CLINICAL RELEVANCE: Favorable influence of GH on craniofacial complex growth rate and altered growth pattern revealed in this study should be considered while planning both orthodontic treatment and retention.

Prevalence of Snoring and High Risk of Obstructive Sleep Apnea Syndrome in Young Male Soldiers in Korea

There are little information on prevalence of obstructive sleep apnea syndrome (OSAS) and clinical features in the young military population. The purpose of this study was to estimate the prevalence of snoring and high risk of OSAS in young male soldiers in Korea and to identify the risk factors of OSAS. A total of 665 participants (aged 20-23 yr) who visited the Armed Forces Ildong Hospital for regular physical examination were enrolled. All participants completed the Berlin Questionnaire and underwent a physical examination. The participants with high risk for OSAS completed portable sleep monitoring. The prevalence of snoring and high risk of OSAS in young male soldiers in Korea was 13.5% and 8.1%, respectively. The prevalence of high arched palate, tongue indentation, long uvula, large tonsil and retrognathia was significantly higher in the high risk OSAS group. High arched palate, long uvula or low lying soft palate, tonsil size III or IV, Epworth Sleepiness Scale score > 10 and obesity (BMI > 27 kg/m2) were found to independently predict OSAS. For early identification and treatment of young soldiers with OSAS in a military environment, a precise screening by questionnaire and physical examination is needed.

Predictive value of molar bite force on Class II functional appliance treatment outcomes.

Sagittal intermaxillary changes brought about by functional appliances show large inter-individual variation. One factor that may in part explain these differences is the masticatory musculature and its functional capacity. The aims of this study were to investigate changes in maximal molar bite force during functional appliance treatment and to assess the influence of pre-treatment maximal molar bite force on treatment outcomes with functional appliances used in Class II malocclusion children. Twenty-five children (17 males and 8 females), aged 9-13 years, with a Class II malocclusion and increased overjet were treated with functional appliances for 1-2 years. Dental casts, lateral cephalograms, maximal molar bite force, and finger force measurements were performed before (T1) and after (T2) treatment. These same measurements were also performed 1-2 years before treatment (T0); the intermediate period before starting treatment served as the control. Multiple regression analyses were used to determine possible correlations between initial maximal molar bite force and dental or cephalometric changes during treatment. Maximal molar bite force, which increased pre-treatment (T0-T1), decreased during functional appliance treatment (T1-T2). Children with a weaker T1 maximal molar bite force showed a larger overjet reduction, greater improvement in molar relationship, greater reduction in ANB angle, and greater augmentation in SNB angle from T1 to T2. Treatment of children with Class II malocclusions with functional appliances seems to lead to more favourable treatment outcomes in those with a weaker maximal molar bite force. This was observed both as regards improvements in dental sagittal relationships, namely overjet and molar Class, as well as skeletal changes due to a decrease in ANB and an increase in SNB angles.

Effects of hypodontia on craniofacial structures and mandibular growth pattern.

INTRODUCTION: This study was performed to examine craniofacial structures in persons with hypodontia and to reveal any differences, that may occur, when agenetic teeth are only found in the maxilla, the mandible or in both jaws. The groups consistent of 50 children (33 girls, 17 boys) aged between 9 and 13.5 years were analyzed and assigned to three subgroups. Group 1 = upper jaw hypodontia. Group 2 = lower jaw hypodontia. Group 3 = hypodontia in both jaws. MATERIALS AND METHODS: Eleven angular and three index measurements from lateral encephalographs and two linear measurements from dental blaster casts were calculated. All data was statistically analyzed, parameters with p < 5% were investigated for each subgroup respectively. RESULTS: In comparison with standards the study group showed bimaxillary retrognathism and a reduction of the lower anterior facial height. Moreover both overbite and overjet significantly increased. Other values laid within the normal ranges. Evaluating results of the subgroups, differences in the means of SNA, SNB and overjet between the groups were observed.Analysis of the mandibular growth pattern revealed, that neither vertical nor horizontal patterns are dominant in hypodontia patients. CONCLUSIONS: In certain dentofacial parameters differences between persons with hypodontia and such with full dentition exist. According to our findings agenetic teeth may have a negative influence on the saggital development of a jaw and the lower face and may be responsible for increased overbites. This should receive attention in orthodontic treatment of hypodontia patients.

[Relationship between masseter muscle electromyographic activities and the position of the mandible].

OBJECTIVE: To investigate the changes in electromyographic activities of the temporal and masseter muscles at different positions of the mandible. METHODS: Twenty orthodontic patients with Angle Class II malocclusion and mandibular retrusion (ANB<6°) aged 10-14 years were enrolled in this study. All the patients were treated with Forsus fixed functional appliance combined with MBT straight-wire appliance. The electromyographic activities of the temporal (T) and masseter (M) muscles before, during and after functional treatment were evaluated by assessing the average integrated electromyogram (EMG) and T/M ratio at clenching status in different mandibular positions. RESULTS: After functional forward positioning of the mandible, the electromyographic activities of the temporal and masseter muscles decreased and T/M ratio increased significance at the clenching status (P<0.05). CONCLUSION: The appliance insertion and activation is associated with a decreased EMG activity of the temporal and masseter muscles, and the T/M ratio is correlated to the position of the mandible.

Tongue movements in patients with skeletal Class III malocclusions evaluated with real-time balanced turbo field echo cine magnetic resonance imaging.

INTRODUCTION: The aim of this study was to evaluate the position and movements of the tongue in patients with skeletal Class III malocclusion. METHODS: Sixty-six patients (31 male, 35 female) with Class III malocclusion were divided into 3 groups according to cephalometric analysis. The first group comprised 23 patients (13 male, 10 female) with mandibular prognathism, the second group comprised 21 patients (9 male, 12 female) with maxillary retrognathism, and the third group comprised 22 patients (9 male, 13 female) with both maxillary retrognathism and mandibular prognathism. Twenty-two skeletal Class I patients (10 male, 12 female) were also included as the control group. RESULTS: Dentofacial morphology affects the position and the movements of the tongue during deglutition. Contact of the anterior portion of the tongue with the rugae area of the hard palate decreased in the Class III malocclusion groups. The posterior portion of the dorsal tongue was positioned more inferiorly, and the root of the tongue was positioned more inferiorly and anteriorly in patients with Class III malocclusion than in the control group. The tip of the tongue was also in a more anterior position in the Class III groups. When the deglutition stages were evaluated, we observed that the manner of bolus transfer was different in patients with skeletal Class III malocclusion than in those with skeletal Class I malocclusion. CONCLUSIONS: Tongue posture is affected by dentofacial structures, and adaptive changes occur in the tip, dorsum, and root of the tongue. Deglutitive tongue movements in patients with skeletal Class III malocclusion are also different from those with skeletal Class I malocclusion.

Tongue movements in patients with skeletal Class II malocclusion evaluated with real-time balanced turbo field echo cine magnetic resonance imaging.

INTRODUCTION: The aim of this study was to evaluate the deglutitive tongue movements in patients with skeletal Class II malocclusion. METHODS: Fifty-nine patients (26 male, 33 female) with skeletal Class II relationship were divided into 3 groups according to cephalometric analysis. Group 1 (n = 19) had mandibular retrognathism, group 2 (n = 20) had maxillary prognathism, and group 3 (n = 20) had both mandibular retrognathism and maxillary prognathism. Twenty-two skeletal Class I patients (10 male, 12 female) were also included as the controls. RESULTS: In the mandibular retrusion group, the posterior portion of the dorsal tongue moved downward at stage 2 and upward at stage 3; the root of the dorsal tongue was in an inferior and anterior position at stage 2. In patients with both mandibular retrognathism and maxillary prognathism, the middle portion of the dorsal tongue was positioned superiorly at stage 3 relative to stage 1; the tongue tip was retruded at stage 3 relative to stages 1 and 2. In the control group, the middle portion of dorsal tongue was positioned superiorly at stage 3 relative to stages 1 and 2; the posterior portion of the tongue moved upward at stage 2 and downward at stage 3, and tongue-tip retrusion was observed at stage 2 relative to stage 1. Contact of the anterior portion of the tongue with the rugae area of the hard palate decreased in the Class II malocclusion groups relative to the control group. The middle portion of the dorsal tongue was positioned more superiorly in patients with Class II malocclusion during all stages of deglutition. The root of the tongue was more inferior and anterior, and the tongue tip was retruded in patients with Class II malocclusion compared with the control group. The posterior portion of the dorsal tongue was more inferiorly positioned in patients with mandibular retrusion than in the other Class II groups or the controls. In the third stage of deglutition, this portion of the tongue had a superior position in groups 2 and 3 relative to the control group. CONCLUSIONS: Dentofacial morphology affects the position and movements of the tongue during deglutition, and adaptive changes occur in the tip, dorsum, and root of the tongue. Deglutitive tongue movements in patients with a skeletal Class II relationship are different from those with a skeletal Class I relationship.