Mandibular posture during sleep in healthy adults

State-Dependent Biomechanical Behavior of Oropharyngeal Structures in Apneic and Control Subjects: A Proof-of-Concept Study

Rationale: Apneic individuals have reduced airway caliber during sleep. The biomechanical changes in upper airway anatomy contributing to this airway narrowing are largely unknown. Objectives: We sought to investigate the state-dependent (wake vs. sleep) biomechanical behavior of the upper airway soft-tissue and craniofacial structures. Methods: Upper airway magnetic resonance imaging was performed in 15 sleep-deprived control subjects (apnea-hypopnea index, <5; 0.3 ± 0.5 events per hour) and 12 sleep-deprived apneic subjects (apnea-hypopnea index, ⩾5; 35.2 ± 18.1 events per hour) during wake and sleep and analyzed for airway measures and soft-tissue/mandibular movement. Results: In the retropalatal region, control subjects showed sleep-dependent reductions (P ⩽ 0.037) in average cross-sectional airway area (CSA), minimum CSA, and anteroposterior and lateral dimensions. Apneic subjects showed sleep-dependent reductions (P ⩽ 0.002) in average CSA, minimum CSA, and anteroposterior and lateral dimensions. In the retroglossal region, control subjects had no sleep-dependent airway reductions. However, apneic subjects had sleep-dependent reductions in minimal CSA (P = 0.001) and lateral dimensions (P = 0.014). Control subjects only showed sleep-dependent posterior movement of the anterior-inferior tongue octant (P = 0.039), whereas apneic subjects showed posterior movement of the soft palate (P = 0.006) and all tongue octants (P ⩽ 0.012). Sleep-dependent medial movement of the lateral walls was seen at the retropalatal minimum level (P = 0.013) in control subjects and at the retropalatal and retroglossal minimum levels (P ⩽ 0.017) in apneic subjects. There was posterior movement of the mandible in apneic subjects (P ⩽ 0.017). Conclusions: During sleep, control and apneic subjects showed reductions in retropalatal airway caliber, but only the apneic subjects showed retroglossal airway narrowing. Reductions in anteroposterior and lateral airway dimensions were primarily due to posterior soft palate, tongue and mandibular movement and to medial lateral wall movement. These data provide important initial insights into obstructive sleep apnea pathogenesis.

Effect of Different Maxillary Oral Appliance Designs on Respiratory Variables during Sleep

This study aimed to analyze the efficacy of maxillary oral appliance (MOA) designs on respiratory variables during sleep. At baseline, 23 participants underwent a sleep test with a portable device for two nights and were categorized as participants with mild obstructive sleep apnea (mild-OSA) (n = 13) and without OSA (w/o-OSA) (n = 10). Three types of MOAs, standard-OA (S-OA), palatal covering-OA (PC-OA), and vertically increasing-OA (VI-OA), were each worn for three nights, and sleep tests with each MOA were performed with a portable device for two nights. Based on the average of the respiratory event index (REI) values for the two nights for each MOA, w/o-OSA participants with an REI ≥ 5.0 were defined as the exacerbation group and those with an REI < 5.0 as the non-exacerbation group. In mild-OSA participants, an REI ≥ 15.0 or REI ≥ baseline REI × 1.5 were defined as the exacerbation group and those with an REI < 15.0 and REI < baseline REI × 1.5 were defined as the non-exacerbation group. The percentage of the exacerbation and non-exacerbation groups with MOA was evaluated in the w/o-OSA and mild-OSA participants. The maxillary and mandibular dental-arch dimension was compared by dentition model analysis. The exacerbation group in w/o-OSA participants (n = 10) comprised 10.0% participants (n = 1) with S-OA, 40.0% (n = 4) with PC-OA, and 30.0% (n = 3) with VI-OA. The exacerbation group in the mild-OSA participants (n = 13) comprised 15.4% subjects (n = 2) with S-OA, 23.1% (n = 3) with PC-OA, and 23.1% (n = 3) in VI-OA. In the model analysis for w/o-OSA, the posterior dental arch width was significantly greater in the exacerbation group than in the non-exacerbation group wearing S-OA (p < 0.05). In addition, the ratio of the maxillary to mandibular dental arch width (anterior dental arch width) was significantly greater in the exacerbation group than in the non-exacerbation group for both PC-OA and VI-OA (p < 0.05). In mild-OSA, the maxillary and mandibular dental arch lengths and the ratio of maxillary to mandibular dental arch width (posterior dental arch width) were significantly smaller in the exacerbation group than in the non-exacerbation group for S-OA (p < 0.05). This study confirmed that wearing an MOA by w/o-OSA and mild-OSA participants may increase the REI during sleep and that PC-OA and VI-OA may increase the REI more than S-OA. The maxillary and mandibular dental-arch dimensions may affect the REI when using an MOA.

Craniofacial morphology/phenotypes influence on mandibular range of movement in the design of a mandibular advancement device

Background

The mandibular opening path movements have different directions according to the craniofacial morphology of the patient but always downward and backward, therefore increasing the collapse of the upper airway. The aim of this work is to determine if there is a relationship between the craniofacial morphology and the mandibular movement to help understand the impact on the mandibular position.

Methods

52 students with full permanent dentition aged 19 to 23 years (mean 21.3 SD 1.7; 29 females and 23 males), participated in the study. Each subject had a lateral cephalometric radiograph taken. The opening angle was determined for two levels of vertical openings at 5 and 10 mm.

Results

The opening angle showed a greater variability between subjects ranging from 63.15 to 77.08 for 5 mm angle and from for 61.65 to 75.72 for the 10 mm angle. Differences of facial phenotypes was evident when comparing the individual dissoccluding angle of the low angle horizontal pattern and high angle vertical pattern.

Conclusions

The opening angle is related to craniofacial morphology with higher vertical anterior and shorter anteroposterior faces having a more horizontal path of mandibular movement than shorter vertical anterior and longer anteroposterior subjects who have a more vertical path.

Mandibular movement analisys by means of a kinematic model applied to the design of oral appliances for the treatment of obstructive sleep apnea

BACKGROUND

Mandibular advancement devices (MADs) are one of the treatment options used for the obstructive sleep apnea syndrome (OSAS). At present, MADs are designed with standard titration systems, without considering each patient's anatomical characteristics of the temporomandibular joint and mandible shape. The main objective of this study is to evaluate if a variability in mandibular morphology will influence the displacement of the jaw with a MAD. Such knowledge will be of help to find optimal mandibular positions with MAD even when opening the mouth.

METHODS

By using a mandibular movement model, the movement patterns of different points on the chin have been analyzed. The influence of different skeletal mandibular shapes on these movements have also been studied. The results show differences in the movement patterns of the lower front teeth depending on its distance to the center of the condyle, with a more horizontal direction in those in which there is a greater distance.

RESULTS

Variations in mandibular morphology imply differences in movement patterns of the analyzed points of the mandible. Consequently, MADs should be designed according to each patient's anatomy to avoid mandibular retrusion in those areas that may narrow the upper airways.

CONCLUSIONS

This study may help to understand why not all patients move their lower jaws forwards equally with the same degree of mandibular protrusion measured in relation to the teeth. These results might also partially explain why airway obstruction is more severe in certain untreated sleep apnea subjects than in others when opening their mouth during sleep.

Validation of midsagittal jaw movements to measure sleep in healthy adults by comparison with actigraphy and polysomnography

OBJECTIVE

In a device based on midsagittal jaw movements analysis, we assessed a sleep-wake automatic detector as an objective method to measure sleep in healthy adults by comparison with wrist actigraphy against polysomnography (PSG).

METHODS

Simultaneous and synchronized in-lab PSG, wrist actigraphy and jaw movements were carried out in 38 healthy participants. Epoch by epoch analysis was realized to assess the ability to sleep-wake distinction. Sleep parameters as measured by the three devices were compared. This included three regularly reported parameters: total sleep time, sleep onset latency, and wake after sleep onset. Also, two supplementary parameters, wake during sleep period and latency time, were added to measure quiet wakefulness state.

RESULTS

The jaw movements showed sensitivity level equal to actigraphy 96% and higher specificity level (64% and 48% respectively). The level of agreement between the two devices was high (87%). The analysis of their disagreement by discrepant resolution analysis used PSG as resolver revealed that jaw movements was right (58.9%) more often than actigraphy (41%). In sleep parameters comparison, the coefficient correlation of jaw movements was higher than actigraphy in all parameters. Moreover, its ability to distinct sleep-wake state allowed for a more effective estimation of the parameters that measured the quiet wakefulness state.

CONCLUSIONS

Midsagittal jaw movements analysis is a reliable method to measure sleep. In healthy adults, this device proved to be superior to actigraphy in terms of estimation of all sleep parameters and distinction of sleep-wake status.

A pilot study of upper airway management using a remote-controlled artificial muscle device during propofol anesthesia

STUDY OBJECTIVE

To test the hypothesis that the jaw closure using a pneumatic actuator device affect airway collapsibility and resistance during propofol anesthesia.

DESIGN

Prospective, randomized study.

SETTING

University-affiliated hospital.

PATIENTS

Six male subjects were included in the present study.

INTERVENTION

We used pressure-flow relationships to evaluate critical closing pressure (PCRIT) and upper airway resistance in different conditions of body and head position. Anesthesia was induced and maintained with a propofol infusion, targeting a constant blood concentration of 1.5 to 2.0μg/mL to establish an adequate depth of anesthesia, with patients breathing spontaneously through a nasal mask. An air-inflatable pneumatic actuator was used to achieve jaw closure. Nasal mask pressure was intermittently reduced to evaluate upper airway collapsibility (passive PCRIT) and upstream resistance under 4 different conditions: (1) neutral occlusion at 0-cm head elevation (baseline), (2) jaw closure at 0-cm head elevation, (3) neutral occlusion at 6-cm head elevation, and (4) jaw closure at 6-cm head elevation. PCRIT and upstream resistance under each condition were compared using 1-way analysis of variance. P<.05 was considered significant.

MEASUREMENTS

The pressure and inspiratory flow at the subjects' nose mask were recorded. Polysomonographic parameters (electroencephalograms, electrooculograms, submental electromyograms, and plethysmogram) were also recorded.

MAIN RESULTS

The combination of 6-cm head elevation with jaw closure using the pneumatic actuator decreased upper airway collapsibility (PCRIT≈-3.0 cm H2O) compared to the baseline position (PCRIT≈-1.2 cm H2O; P=.0003).

CONCLUSION

We demonstrated that jaw closure using an air-inflatable pneumatic actuator device can produce substantial decreases in upper airway collapsibility and maintain upper airway patency during propofol anesthesia.

The study of grinding patterns and factors influencing the grinding areas during sleep bruxism

OBJECTIVE

The purpose of this study is to investigate the grinding patterns and discuss the factors influencing the position relationship between intercuspal position (ICP) and grinding area during sleep bruxism.

METHODS

Lateral condylar inclination, inclination of lateral incisal path and freedom in long centric of thirty subjects were measured. The grinding patterns during sleep bruxism were recorded with a bruxism recording device, BruxChecker. The position relationship between ICP and the grinding area was examined. Spearman's rank correlation coefficient was used for correlation analysis between grinding area and free factors (grinding patterns, freedom in long centric and discrepancy between lateral condylar inclination and inclination of lateral incisal path).

RESULTS

All 12 subjects with 0mm-freedom in long centric exhibited that ICP of both sides located within the grinding areas. 4 subjects showed that ICP of both sides located outside the grinding areas. There is a significant correlation between 0mm-freedom in long centric and ICP within the grinding areas (p <0.01).

CONCLUSIONS

Freedom in long centric has a significant effect on position relationship between intercuspal position and the grinding area.

Diagnosis and treatment for obstructive sleep apnea: Fundamental and clinical knowledge in obstructive sleep apnea

PURPOSE

This review article covers the diagnosis and treatment of obstructive sleep apnea (OSA) from a dental perspective. It addresses the issue of when and how to screen for and then, if indicated, refer the patient for a more comprehensive.

STUDY SELECTION

Our focus in this article was on identifying current unanswered questions that relevant to OSA problems that dental scientists have to pursue and on providing valuable information on that problems, consequently the previous studies which investigated or reviewed the diagnosis and treatment of OSA were included. In addition, we included studies on jaw movements during sleep and on the use of a lateral cephalometric film related to the diagnosis and treatment of OSA.

RESULTS

The role of portable sleep monitoring devices versus full laboratory polysomnography is discussed. This review also describes what is known about the efficacy of mandibular advancement devices and when and how they fit in to a treatment program for a patient with obstructive sleep apnea. Finally some basic research is presented on jaw movements during sleep and how a lateral cephalometric film can be used to assess the changes of the airway with body posture and head posture.

CONCLUSION

This article provides the valuable suggestions for the clinical questions in the diagnosis and treatment of OSA.

Mandible behaviour interpretation during wakefulness, sleep and sleep-disordered breathing

The mandible movement (MM) signal provides information on mandible activity. It can be read visually to assess sleep-wake state and respiratory events. This study aimed to assess (1) the training of independent scorers to recognize the signal specificities; (2) intrascorer reproducibility and (3) interscorer variability. MM was collected in the mid-sagittal plane of the face of 40 patients. The typical MM was extracted and classified into seven distinct pattern classes: active wakefulness (AW), quiet wakefulness or quiet sleep (QW/S), sleep snoring (SS), sleep obstructive events (OAH), sleep mixed apnea (MA), respiratory related arousal (RERA) and sleep central events (CAH). Four scorers were trained; their diagnostic capacities were assessed on two reading sessions. The intra- and interscorer agreements were assessed using Cohen's κ. Intrascorer reproducibility for the two sessions ranged from 0.68 [95% confidence interval (CI): 0.59-0.77] to 0.88 (95% CI: 0.82-0.94), while the between-scorer agreement amounted to 0.68 (95% CI: 0.65-0.71) and 0.74 (95% CI: 0.72-0.77), respectively. The overall accuracy of the scorers was 75.2% (range: 72.4-80.7%). CAH MMs were the most difficult to discern (overall accuracy 65.6%). For the two sessions, the recognition rate of abnormal respiratory events (OAH, CAH, MA and RERA) was excellent: the interscorer mean agreement was 90.7% (Cohen's κ: 0.83; 95% CI: 0.79-0.88). The discrimination of OAH, CAH, MA characteristics was good, with an interscorer agreement of 80.8% (Cohen's κ: 0.65; 95% CI: 0.62-0.68). Visual analysis of isolated MMs can successfully diagnose sleep-wake state, normal and abnormal respiration and recognize the presence of respiratory effort.

Supine position related obstructive sleep apnea in adults: pathogenesis and treatment

The most striking feature of obstructive respiratory events is that they are at their most severe and frequent in the supine sleeping position: indeed, more than half of all obstructive sleep apnea (OSA) patients can be classified as supine related OSA. Existing evidence points to supine related OSA being attributable to unfavorable airway geometry, reduced lung volume, and an inability of airway dilator muscles to adequately compensate as the airway collapses. The role of arousal threshold and ventilatory control instability in the supine position has however yet to be defined. Crucially, few physiological studies have examined patients in the lateral and supine positions, so there is little information to elucidate how breathing stability is affected by sleep posture. The mechanisms of supine related OSA can be overcome by the use of continuous positive airway pressure. There are conflicting data on the utility of oral appliances, while the effectiveness of weight loss and nasal expiratory resistance remains unclear. Avoidance of the supine posture is efficacious, but long term compliance data and well powered randomized controlled trials are lacking. The treatment of supine related OSA remains largely ignored in major clinical guidelines. Supine OSA is the dominant phenotype of the OSA syndrome. This review explains why the supine position so favors upper airway collapse and presents the available data on the management of patients with supine related OSA.

Computerized cephalometric study of the pharyngeal airway space in patients submitted to orthognathic surgery

INTRODUCTION

Pharynx is a muscular organ with is sustained by craniofacial bones. It is divided into nasal, oral and hipopharynx, and can be considered as a tube that serves both respiratory and digestive systems. Its anatomical morphology permits that factors facilitate its obstruction, leading to the sleep apnea syndrome. One of the treatment consists of surgical mandibular advancement, increasing pharyngeal dimensions. The aim of this study was evaluate the cephalometric changes in the pharyngeal airway space after orthognathic surgery procedures for correction of mandibular prognathism.

MATERIALS AND METHODS

Pre and post-operative cephalometric analysis was performed on 19 patients submitted to mandibular setback by mandibular bilateral sagittal split osteotomy associated with maxillary advancement by Le Fort I osteotomy, using the Dolphin Imaging 10.0 software.

RESULTS

Results did not reveal statistically significant changes in the upper (nasopharyngeal), middle (oropharyngeal) and lower (hypopharyngeal) airway spaces, but showed increase in the nasal pharynx due the maxillary advancement and a lower position of the hyoid bone due the mandibular setback.

DISCUSSION

Maxillomandibular orthognathic surgery for correction of mandibular prognathism does not seem to statistically significantly change the pharyngeal airway space, but it increases the maxillary airway.

CONCLUSION

It seems to be important to consider the double jaw surgery in cases of mandibular prognathism, aiming prevention of a possible reduction of whole upper airway.

Added value of a mandible movement automated analysis in the screening of obstructive sleep apnea

In-laboratory polysomnography is the 'gold standard' for diagnosing obstructive sleep apnea syndrome, but is time consuming and costly, with long waiting lists in many sleep laboratories. Therefore, the search for alternative methods to detect respiratory events is growing. In this prospective study, we compared attended polysomnography with two other methods, with or without mandible movement automated analysis provided by a distance-meter and added to airflow and oxygen saturation analysis for the detection of respiratory events. The mandible movement automated analysis allows for the detection of salient mandible movement, which is a surrogate for arousal. All parameters were recorded simultaneously in 570 consecutive patients (M/F: 381/189; age: 50±14 years; body mass index: 29±7 kg m(-2) ) visiting a sleep laboratory. The most frequent main diagnoses were: obstructive sleep apnea (344; 60%); insomnia/anxiety/depression (75; 13%); and upper airway resistance syndrome (25; 4%). The correlation between polysomnography and the method with mandible movement automated analysis was excellent (r: 0.95; P<0.001). Accuracy characteristics of the methods showed a statistical improvement in sensitivity and negative predictive value with the addition of mandible movement automated analysis. This was true for different diagnostic thresholds of obstructive sleep severity, with an excellent efficiency for moderate to severe index (apnea-hypopnea index ≥15h(-1) ). A Bland & Altman plot corroborated the analysis. The addition of mandible movement automated analysis significantly improves the respiratory index calculation accuracy compared with an airflow and oxygen saturation analysis. This is an attractive method for the screening of obstructive sleep apnea syndrome, increasing the ability to detect hypopnea thanks to the salient mandible movement as a marker of arousals.

Functional treatment of snoring based on the tongue-repositioning manoeuvre

Orofacial biofunction comprises muscular and physical effects, which may contribute to stabilization of the oropharyngeal airway. The tongue-repositioning manoeuvre (TRM) provides physical stabilization of the tongue and the soft palate together with, as a prerequisite, a nasal breathing mode. The aim of the present study was to evaluate the influence of a TRM treatment concept on primary snoring. The TRM was used to achieve a closed biofunctional rest position of the orofacial system and to re-educate the nasal breathing pattern. Pressure indicating oral shields were used for home exercises as a biofeedback instrument and to support nocturnal mouth closure. Treatment was undertaken on 125 consecutive primary snorers [101 males, mean age 52.4 years, range 34-75, mean body mass index (BMI) 28.1, range 18.9-38.5, and 24 females, mean age 55.2 years, range 36-70, mean BMI 26.8, range 22.7-31.9]. Bed partner ranking was performed, and snoring was judged using a 10-cm visual analogue scale (VAS). The VAS score was 8.4 (range 6-10) before treatment and decreased to 4.1 (range 0-10) after treatment [mean observation time 4.6 months (1-10)]. Analysis of variance showed a significant influence of treatment in subjects with a normal body weight (BMI 18.5-25). The data provide evidence that dynamic stabilization of the orofacial system with the TRM in conjunction with nocturnal wear of an oral shield is beneficial for reducing the symptoms in primary snorers with a normal BMI.

Impact of orthodontic appliances on sleep quality

INTRODUCTION

Many young patients are asked to wear headgear or functional appliances during sleep as part of their orthodontic treatment. The objective of this clinical study was to assess the impact of these appliances on sleep quality.

METHODS

Twenty-two subjects (8 boys, 14 girls) between 10 and 15 years of age wearing either a headgear or a removable appliance for 3 to 12 months were enrolled in a sleep study. Each subject participated in 2 overnight sleep studies with and without the appliance. There was a 1-week interval after an adaptation night. The studies were performed at the Sleep Research Laboratory at Toronto Western Hospital in Canada. Each subject served as his or her own control. Twelve subjects had an extraoral headgear appliance, and 10 had intraoral functional (5 Fränkel, 5 Twin-block) appliances. No subject reported any sleep or medical disorder. The primary outcome variable was sleep efficiency.

RESULTS

Sleep efficiencies were 90.7% (SD, 7.9) and 91.6% (SD, 4.3) with and without the appliances, respectively. When sleep quality was compared with and without appliances, analysis of variance (ANOVA) showed no significant difference in sleep efficiency or other sleep variables such as sleep onset latency, rapid eye movement onset latency, rapid eye movement percentage, short-wave sleep percentage, or respiratory disturbance index. Sex and body mass index were not confounding variables. In addition, the use of extraoral or intraoral appliances did not affect sleep quality.

CONCLUSIONS

In young orthodontic patients, there appears to be no difference in sleep quality with or without the overnight use of these appliances after they have been worn for a minimum of 3 months.

Influence of breathing route on upper airway lining liquid surface tension in humans

We have recently demonstrated that the severity of sleep-disordered breathing in obstructive sleep apnoea hypopnoea syndrome (OSAHS) can be reduced by lowering the surface tension (gamma) of the upper airway lining liquid (UAL). Morning xerostomia (related to oral breathing during sleep) is reported by most OSAHS patients. In the present study we examine relationships between breathing route, oral mucosal 'wetness' and the gamma of UAL. We studied eight healthy subjects (age, 25 +/- 5 years [mean +/- S.D.]; body-mass index, 23 +/- 2 kg m(-2)) during a 120 min challenge of both nasal-only breathing (mouth taped) and oral-only breathing (nose clip), each on a separate day (randomized). Both oral mucosal 'wetness' (5 s contact gravimetric absorbent paper strip method) and the gamma ('pull-off' force technique) of 0.2 microl samples of UAL obtained from the posterior pharyngeal wall were measured at 15 min intervals (mouth tape removed and replaced as required). Upper airway mucosal 'wetness' increased during 120 min of nasal breathing from 4.0 +/- 0.4 (mean +/- S.E.M.) to 5.3 +/- 0.3 microl (5 s)(-1) but decreased from 4.5 +/- 0.4 to 0.1 +/- 0.2 microl (5 s)(-1) with oral breathing (both P < 0.001, repeated-measures ANOVA, Tukey's multiple comparison test, post hoc test). Concurrently, the gamma of UAL decreased from 59.3 +/- 2.2 to 51.8 +/- 0.98 mN m(-1) with nasal breathing but increased from 64.4 +/- 2.7 to 77.4 +/- 1.1 mN m(-1) with oral breathing (P < 0.001). For the group and all conditions studied, gamma of UAL values strongly correlated with upper airway mucosal 'wetness' (correlation coefficient, r2 = -0.34, P < 0.001; linear regression). We conclude that oral breathing increases and nasal breathing decreases the gamma of UAL in healthy subjects during wakefulness. We speculate that nasal breathing in OSAHS patients during sleep may promote a low gamma of UAL that may contribute to reducing the severity of sleep-disordered breathing.

Effectiveness of the jaw-thrust maneuver in opening the airway: a flexible fiberoptic endoscopic study

OBJECTIVE

A prospective study was carried out to find the exact site of obstruction in sleep model and to quantitatively evaluate the effect of Jaw-thrust maneuver (JTM) in opening the obstructed airway using flexible fiberoptic endoscope.

METHODS

Twenty-eight ASA physical status I or II patients with snoring symptom undergoing elective surgery were included. The patients were held in supine position without hyperextension of the neck. Having induced anesthesia, the base of the tongue and laryngeal inlet and/or epiglottis were visualized using endoscope. The patients' epiglottides were classified as leaf-shaped, curved (concaved or omega-shaped) and floppy types. We graded the airway opening at the level of epiglottis into six grades and obstruction at the tongue base level into four grades. The grades during inspiration (GrIns), expiration (GrExp) and after JTM (GrJTM) were recorded and compared with Pearson chi-square test.

RESULTS

The strictly curved (Omega-shaped or concaved) epiglottis supplied a salvage pathway for airflow that resisted collapsing with the posterior movement of the tongue base in 2 patients. When we compared GrIns with GrExp for epiglottis the difference was statistically significant (chi(2) = 0.001), but the difference for tongue base was not (chi(2) = 0.152). After JTM, GrJTM for both epiglottis and tongue base were significantly better than GrIns and GrExp (chi(2) < 0.001).

CONCLUSION

Tongue base was the principal site of obstruction although during the respiratory cycle the position of epiglottis changed prominently and increased the obstruction in inspiration. JTM alone significantly relieved the obstruction at the tongue base and epiglottis levels and increased the retroglossal airway.

Influences of head positions and bite opening on collapsibility of the passive pharynx

A collapsible tube surrounded by soft material within a rigid box was proposed as a two-dimensional mechanical model for the pharyngeal airway. This model predicts that changes in the box size (pharyngeal bony enclosure size anatomically defined as cross-sectional area bounded by the inside edge of bony structures such as the mandible, maxilla, and spine, and being perpendicular to the airway) influence patency of the tube. We examined whether changes in the bony enclosure size either with head positioning or bite opening influence collapsibility of the pharyngeal airway. Static mechanical properties of the passive pharynx were evaluated in anesthetized, paralyzed patients with sleep-disordered breathing before and during neck extension with bite closure ( n = 11), neck flexion with bite closure ( n = 9), and neutral neck position with bite opening ( n = 11). Neck extension significantly increased maximum oropharyngeal airway size and decreased closing pressures of the velopharynx and oropharynx. Notably, neck extension significantly decreased compliance of the oropharyngeal airway wall. Neck flexion and bite opening decreased maximum oropharyngeal airway size and increased closing pressure of the velopharynx and oropharynx. Our results indicate the importance of neck and mandibular position for determining patency and collapsibility of the passive pharynx.

Postural cephalometric analysis and nasal resistance in sleep-disordered breathing

OBJECTIVES

The study was designed to compare upright and supine cephalometric measurements in snorers and to evaluate the effects of mandibular position and nasal resistance on pharyngeal dimensions. Anthropometric, rhinomanometric, and cephalometric measurements were used to investigate predictors of apnea-hypopnea index.

STUDY DESIGN

Prospective, cross-sectional.

METHODS

Forty consecutive habitually snoring men waiting for nasal surgery (mean age, 44 y; mean body mass index, 28 kg/m2) underwent an overnight polysomnographic, anterior rhinomanometric, and cephalometric analysis in upright and supine positions.

RESULTS

Nasal resistance correlated positively with minimal pharyngeal airspace at the level of tongue. The opening of jaws after voluntary relaxation of the mandibular position on lying down correlated with decrease in pharyngeal airway measurements at both velopharyngeal and tongue-base levels. In stepwise multiple regression analysis the overall patient model explained 68% of the variation in apnea-hypopnea index with body mass index as the largest predictor. In the nonobese patients, the model explained 86% of variation in apnea-hypopnea index with change in anteroposterior position of the lower jaw in upright and supine measurements and combined nasal resistance after mucosal decongestion as independent determinants. In selected skeletal subtypes the models predicted 83%, 79%, 61%, and 90% of the variation in apnea-hypopnea index.

CONCLUSIONS

In the nonobese patients nasal resistance and change in mandibular position on lying down were found to be independent contributing factors to the apnea-hypopnea index. Further research on supine cephalometry and relaxed mandibular position may improve prediction of sleep-disordered breathing in snorers.

Neurobiological mechanisms involved in sleep bruxism

Sleep bruxism (SB) is reported by 8% of the adult population and is mainly associated with rhythmic masticatory muscle activity (RMMA) characterized by repetitive jaw muscle contractions (3 bursts or more at a frequency of 1 Hz). The consequences of SB may include tooth destruction, jaw pain, headaches, or the limitation of mandibular movement, as well as tooth-grinding sounds that disrupt the sleep of bed partners. SB is probably an extreme manifestation of a masticatory muscle activity occurring during the sleep of most normal subjects, since RMMA is observed in 60% of normal sleepers in the absence of grinding sounds. The pathophysiology of SB is becoming clearer, and there is an abundance of evidence outlining the neurophysiology and neurochemistry of rhythmic jaw movements (RJM) in relation to chewing, swallowing, and breathing. The sleep literature provides much evidence describing the mechanisms involved in the reduction of muscle tone, from sleep onset to the atonia that characterizes rapid eye movement (REM) sleep. Several brainstem structures (e.g., reticular pontis oralis, pontis caudalis, parvocellularis) and neurochemicals (e.g., serotonin, dopamine, gamma aminobutyric acid [GABA], noradrenaline) are involved in both the genesis of RJM and the modulation of muscle tone during sleep. It remains unknown why a high percentage of normal subjects present RMMA during sleep and why this activity is three times more frequent and higher in amplitude in SB patients. It is also unclear why RMMA during sleep is characterized by co-activation of both jaw-opening and jaw-closing muscles instead of the alternating jaw-opening and jaw-closing muscle activity pattern typical of chewing. The final section of this review proposes that RMMA during sleep has a role in lubricating the upper alimentary tract and increasing airway patency. The review concludes with an outline of questions for future research.

The effect of posture and a mandibular protruding device on pharyngeal dimensions: a cephalometric study

The objectives were to evaluate the impact of body posture on cephalometric measures and the level and the extent to which treatment with a mandibular protruding device (MPD) affects pharyngeal width. The study was composed of 77 patients: 50 were diagnosed with obstructive sleep apnea (OSA) and 27 snored. After each patient underwent a baseline medical (including a somnographic registration), dental and stomatognathic examination, an MPD that would protrude the mandible 75% of the maximal protrusion range was fabricated. In a radiographic examination, four cephalograms were taken: two in the upright position with and without the MPD and two in the supine position with and without the MPD. The cephalometric measures focused on the pharyngeal structures. MPD treatment significantly increased the relative pharyngeal area (at the level of the oropharynx and the hypopharynx) by a mean of +89.6 mm2 (P < 0.01) in the upright posture. The relative pharyngeal area, however, was reduced by more than 50% in the supine position compared with the upright position, independent of MPD treatment. In the supine position, compared with upright, most pharyngeal measures decreased significantly; the hyoid was significantly lower and displaced posteriorly, and the area of the velum increased by a mean of +201.2 mm2 (P < 0.001). We conclude that the MPD significantly increased most pharyngeal measures except the linear distance between the hyoid bone and the third vertebra and decreased the area of the velum.

Recent Developments in Oral Appliance Therapy of Sleep Disordered Breathing

Oral appliances are increasingly gaining a place in the treatment of sleep disordered breathing caused by upper airway obstruction. This review of publications since 1995 documents substantial progress in the scientific basis for this therapy. Imaging by several techniques has shown that mandibular advancing oral appliances open the airway in awake and anaesthetized subjects, creating the presumption that this effect is maintained in sleep. Three controlled cross-over treatment trials have shown that patients consistently prefer oral appliance over continuous positive airway pressure therapy, especially when the treatment effect is strong. Appliance design and use indicates a preference for adjustable mandibular advancing appliances. Complications of therapy appear to be infrequent, but evidence for safety of long-term use is still limited. Oral appliance therapy can be an effective therapy for sleep disorders caused by upper airway obstruction. Considering the accumulated evidence, it is no longer tenable to label oral appliance therapy an OexperimentalO procedure.

Obstructive sleep apnoea: a review of the orofacial implications

Obstructive sleep apnoea is a complex multifactorial condition produced by a combination of anatomical and physiological factors. There is a significant associated mortality and morbidity to obstructive sleep apnoea. There is an at least 25 per cent increased mortality from cardiovascular disease when obstructive sleep apnoea patients are compared to age and gender matched healthy people. Obstructive sleep apnoea sufferers also have a much higher industrial and motor vehicle accident rate. Management of the condition should be undertaken by a multidisciplinary team including respiratory physicians, sleep laboratory technicians, otorhinolaryngologists, oral and maxillofacial surgeons and dental specialists. The diagnostic and therapeutic interactions of team members are the key to successful treatment. The treatment regime utilises nasal continuous positive airway pressure devices, mandibular advancement splints and soft and hard tissue surgery. This review provides the dental practitioner with an introduction to obstructive sleep apnoea with particular emphasis on the orofacial aspects.

Changes in mandibular position and upper airway dimension by wearing cervical headgear during sleep

We previously reported that the wearing of cervical headgear induced forward displacement of the mandible in awake subjects. However, it was unclear whether such mandibular displacement also occurred during sleep. The purpose of this study was to examine changes in mandibular position and oropharyngeal structures that were induced by the wearing of cervical headgear during sleep. Ten healthy adults (7 male and 3 female) who gave their informed consent were included in this study. A pair of lateral cephalograms was taken with the patient in the supine position with and without cervical headgear at end-expiration during stage 1 to 2 non-rapid-eye-movement sleep. The Wilcoxon signed-rank test was used for a statistical analysis. The amount of jaw opening was significantly decreased by the wearing of the cervical headgear (P <.05), although no significant anteroposterior mandibular displacement was induced. The sagittal dimension of the upper airway was significantly reduced (P <.05); however, no significant changes were observed in the vertical length of the upper airway. Although the hyoid bone and the third cervical vertebra moved significantly forward by the wearing of the cervical headgear (P <.05), the relationship among the mandibular symphysis, the hyoid bone, and the third cervical vertebra did not change. These results suggest that cervical headgear significantly reduced the sagittal dimension of the upper airway during sleep, although there was no significant anteroposterior displacement of the mandible.

Sleep bruxism in patients with sleep-disordered breathing

The aim was to test the hypothesis of a direct association between sleep-disordered breathing and sleep bruxism. The frequency of masseter contraction (MC) episodes and rhythmic jaw movements (RJM) was measured in patients with mild and moderate obstructive sleep apnoea (OSA). The diagnosis of sleep bruxism was made from a combination of questionnaire, clinical observation and all-night polysomnographic recording which included masseter electromyography. A total of 21 patients (19 males/two females, mean age 40.0 years+/-9.2 SD) were randomly selected from a provisional diagnosis of snoring and OSA by a sleep physician. In the patients with mild OSA [n=11, mean apnoea hypopnoea index (AHI)=8.0+/-4.1 SD, body mass index (BMI)=29.1+/-5.0], the diagnosis of sleep bruxism was made in six out of 11 patients (54%); similarly, four out of 10 patients (40%) with moderate OSA (n=10, mean AHI=34.7+/-19.1, BMI=30.6+/-5.0) were identified as bruxists. Although the combination of clinical, subjective estimation and nocturnal electromyographic recording of masseter muscle might provide a more solid base for the diagnosis of sleep bruxism, the result is biased by the variation in the bruxing activity. MC episodes were associated with the termination of apnoea or hypopnoea episodes in only 3.5% of the mild group and 14.4% of the moderate group (p<0.05). It appears that sleep bruxism is rarely directly associated with apnoeic events, but is rather related to the disturbed sleep of OSA patients.

Mandibular posture during sleep in patients with obstructive sleep apnoea

Vertical mandibular posture is thought to be related to narrowing of the upper airway, because mouth opening is associated with an inferior-posterior movement of the mandible and the tongue which influences pharyngeal airway patency. To test whether the mandibular posture is related to the occurrence and/or termination of obstructive sleep apnoea (OSA), the vertical mandibular position was recorded intraorally using a magnet sensor during a standard sleep study in seven patients with OSA. Measurements were recorded during sleep both in the supine and lateral recumbent positions. The percentage of total sleep time spent with mandibular opening greater than 5 mm was significantly larger (p<0.001) in patients with OSA (69.3+/-23.3%) compared with our previous results obtained from healthy adults without OSA (11.1+/-11.6%). The stage of sleep affected the vertical mandibular posture during sleep in the supine position, but not in the lateral recumbent position in patients with OSA. In non-rapid eye-movement sleep, mandibular opening increased progressively during apnoeic episodes and decreased at the termination of apnoeic episodes. In contrast, no significant change in mandibular posture occurred in apnoeic episodes during rapid eye-movement sleep. It was concluded that the vertical mandibular posture is more open during sleep in patients with OSA than in healthy adults and that mandibular opening increases progressively during apnoeic episodes and decreases at the termination of those episodes.