Mandibular advancement splints and continuous positive airway pressure in patients with obstructive sleep apnoea: a randomized cross-over trial.

This prospective, randomized, cross-over trial was designed to compare the efficacy of a mandibular advancement splint (MAS) with that of nasal continuous positive airway pressure (nCPAP) in patients with obstructive sleep apnoea (OSA). Twenty-four patients (20 males and four females) with mild to moderate OSA (AHI between 10 and 49 events per hour) were enrolled in the study. Each patient used both MAS and nCPAP, with the initial therapy being allocated at random. Treatment periods lasted for two months with a two-week wash-out interval between. Polysomnography was performed prior to the study and after each clinical intervention. Patient and partner questionnaires were used to assess changes in general health and daytime somnolence. The AHI decreased from 22.2 to 3.1 using nCPAP, and to 8.0 using the MAS (P < 0.001 for both devices) and there was no statistically significant difference between the two treatments. The Epworth Sleepiness Score (ESS) fell from 13.4 to 8.1 with nCPAP, and to 9.2 with MAS (P < 0.001), again with no differences between the use of MAS or nCPAP. The questionnaire data showed an improvement in general health scores (P < 0.001) after both treatments, but daytime sleepiness only improved significantly using nCPAP (P < 0.001). Despite this, 17 out of the 21 subjects who completed both arms of the study preferred the MAS. The splints were well tolerated and their efficacy suggests that the MAS may be a suitable alternative to nCPAP in the management of patients with mild or moderate OSA.

Long-term use of mandibular advancement splints for snoring and obstructive sleep apnoea: a questionnaire survey.

A mandibular advancement splint (MAS) may be an alternative treatment for snoring and obstructive sleep apnoea (OSA). However, there is little subjective or objective information concerning long-term effectiveness, compliance and side effects. A retrospective questionnaire was used to survey these issues plus patient satisfaction and maintenance requirements in 166 patients who could have worn a mandibular advancement splint for over a year. One-hundred and twenty-six (76%) subjects returned the questionnaire, (84 with OSA, 42 snorers), of whom 69 (55%) reported still using the splint regularly, 47 (37%) every night. The most common reported reasons for stopping use were discomfort (29/ 57; 52%) of nonusers), and poor perceived efficacy (12 subjects). Users reported more daytime symptoms, and they and their partners were more likely to observe improvements with splint use. Side effects were reported by 49 subjects, more commonly in nonusers. Sixty-five of 67 current users and 23 of 41 nonusers reported less snoring with splint use (p = < 0.001). Long-term mandibular advancement splint usage appeared less satisfactory than previously reported, however, splints were considered effective by 97% of current users and even by over half of those who had stopped use. Reasons for stopping use included side effects, social circumstances, dental treatment, as well as lack of perceived efficacy.

Changes in airway and hyoid position in response to mandibular protrusion in subjects with obstructive sleep apnoea (OSA).

This prospective clinical study examined the alterations in airway and hyoid position in response to mandibular advancement in subjects with mild and moderate obstructive sleep apnoea (OSA). Pairs of supine lateral skull radiographs were obtained for 13 female and 45 male, dentate Caucasians. In the first film, the teeth were in maximal intercuspation, while in the second the mandible was postured forwards into a position of maximum comfortable protrusion. Radiographs were traced and digitized, and the alterations in the pharyngeal airway and position of the hyoid were examined. Males and females were analysed separately. In males only, correlations were sought between the changes in hyoid and airway parameters, and the initial and differential radiographic measurements. In males, mean mandibular protrusion at the tip of the lower incisor was 5.3 mm, increasing its distance from the posterior pharyngeal wall by 6.9 mm (or 9 per cent). Movement of the hyoid showed extreme inter-subject variability, both in the amount and direction. In relation to the protruded lower jaw, the hyoid became closer to the gonion by 6.9 mm and to the mandibular plane by 4.3 mm. With respect to the upper face, a 1.3-mm upward and 1.1-mm forward repositioning was seen. The percentage alterations in airway dimensions matched or bettered the mandibular advancement. The minimum distances behind the soft palate and tongue improved by 1.0 and 0.8 mm, respectively. Despite their smaller faces, females frequently showed greater responses to mandibular protrusion than males. No cephalometric features could be identified which might indicate a favourable response of the airway to mandibular protrusion. Larger increments of hyoid movement were associated with an improved airway response, but the strength of the correlations was generally low.

The role of lateral cephalometric radiography and fluoroscopy in assessing mandibular advancement in sleep-related disorders.

Mandibular advancement splints are successful in managing obstructive sleep apnoea (OSA) in selected subjects. For these to be effective, some improvement in the dimensions of the oropharyngeal airway must occur. Twenty subjects with proven obstructive sleep apnoea were examined using lateral cephalometric radiography and a fluoroscopic technique. Cephalograms were analysed, and assessed for both skeletal and soft tissue abnormalities known to be present in OSA subjects. On the basis of these, a prediction was made as to whether the subject's oropharyngeal airway would increase during mandibular protrusion. From the fluoroscopic sequences, the narrowest antero-posterior dimensions of the post-palatal and post-lingual airways were recorded as the mandible moved from the intercuspal position into maximal protrusion. The changes in airway size were noted and these were compared with the predictions made from the static films. In nine subjects, fluoroscopy indicated that the airway opened well during mandibular protrusion, seven did not improve and in four the changes were minimal. Post-palatally the mean airway increase was 2.6 mm, whilst behind the tongue a mean improvement of 3.1 mm was seen. In all but two instances, the cephalometric prediction agreed exactly with the outcome demonstrated by fluoroscopy. All subjects whose airways clearly increased were correctly identified by the cephalogram alone. Cephalometric features associated with a good airway response to protrusion were a reduced lower facial height, low maxillomandibular planes angle and a high hyoid position, accompanied by a normal anteroposterior relationship of the jaws, relatively normal mandibular body length and soft palate area. The more abnormal the skeletal and soft tissue dimensions, the poorer the prognosis. Thus, whilst a single radiograph could indicate whether a positive mandibular response to protrusion could be expected, where doubt existed, a fluoroscopic analysis could provide a useful adjunct to diagnosis.

The cephalometric morphology of patients with obstructive sleep apnoea (OSA).

This prospective study analysed the lateral cephalometric radiographs of 59 dentate, white, Caucasian males. Thirty-five patients with proven obstructive sleep apnoea (OSA) formed the experimental group, while 24 subjects with no history of respiratory disease acted as controls. Radiographs were traced and digitized, and both hard and soft tissue features were compared between the groups. The pooled data were then subjected to discriminate analysis. Although conventional cephalometric measurements did not differ between the two groups, significant reductions were found in the lengths of the mandibular body and cranial base and in cranial base angulation in OSA subjects. The width of the oropharynx was significantly narrower in this group, particularly in the post-palatal region. The area of the soft palate was increased although that of the tongue was not. Intermaxillary space length (the distance between the posterior pharyngeal wall and the tip of the lower incisor) was decreased, and thus the area in which the tongue had to function was smaller in OSA subjects. From the discriminant analysis, two four-variable models were derived, both of which provided 100 per cent discrimination between the OSA and normal subjects. For the first model the entire OSA group was used: for the second, only obese OSA subjects (those a body mass index > 25) were chosen. The combination off a short mandible and intermaxillary space, with an enlarged soft palate but decreased pharyngeal airway has relevance to the effective management of OSA. In selected patients, advancement of the lower jaw by a nocturnal mandibular repositioning splint may be indicated. The orthodontist would seem to be in a unique position to assist in both the identification and treatment of these subjects.

A method of studying adaptive changes of the oropharynx to variation in mandibular position in patients with obstructive sleep apnoea.

The aim of this study was to develop a method of studying the effects of mandibular advancement on oropharyngeal airway dimensions in the sagittal plane in conscious, supine patients. Six white, dentate, male patients with proven obstructive sleep apnoea had sagittal fluoroscopic recordings taken in the resting supine position. Images were recorded at four frames per second as the mandible was advanced with the teeth in contact to maximum protrusion and then opened. Software in the fluoroscopic imaging system permitted measurement of the change in mandibular position together with oropharyngeal airway dimensions expressed as the narrowest dimension observable in the post-palatal and post-lingual sites. Plotting of airway dimensions during mandibular advancement enabled estimation of the degree of protrusion associated with maximal airway benefits. Progressive mandibular advancement produced variable adaptive changes in the post-palatal and post-lingual regions of the oropharynx. The amount of airway opening appeared to be related to the horizontal and vertical relationships of the face and to the dimensions of the soft palate. The changes in post-palatal and post-lingual airway dimensions were not always identical, despite the observation that both tongue and soft palate were seen to move in unison, with close contact being maintained between the two structures. Jaw opening resulted in synchronous posterior movement of both tongue and soft palate, with consequent narrowing of oropharyngeal airspace. Fluoroscopy is a simple method of assessing upper airway changes with mandibular advancement in the conscious patient. The technique should facilitate the selection of subjects for whom mandibular advancement would seem advantageous. The nature of the adaptive response is dependent on individual structural variation. It is suggested that, where artificial mandibular advancement with dental devices is considered beneficial, jaw opening should be kept to a minimum.

High magnification in situ viewing of wound healing in oral mucosa.

Microscope endoscopy is a technique which allows high resolution, non-invasive examination of soft tissues. This study employed microscope endoscopy to examine the process of healing following exposure of the oral mucosa to carbon dioxide laser radiation. On the wound boundaries, cellular debris and the laser-induced char layer were shed as epithelial migration occurred. Wounds healed by secondary intention, with complete epithelial closure by 72 hours. A marked vascular response was evident from 6 to 48 hours following wounding, a time period coincident with the known pattern of blood vessel activation and infiltration of the wound site by leukocytes. The use of microscope endoscopy as an adjunct to biopsy and other invasive diagnostic methods in the assessment and follow-up of soft tissue pathology may have value in clinical practice.

The importance of a multidisciplinary approach to the assessment of patients with obstructive sleep apnoea.

Obstructive sleep apnoea may present with a wide range of symptoms resulting in a variety of referral pathways. A multidisciplinary approach to examination and diagnosis helps to determine the most appropriate treatment plan for each individual. The subject is seen by each member of the team, appropriate investigations undertaken and a further meeting arranged at which all opinions are discussed. A reasoned treatment regime is produced, taking into consideration the patient's wishes and overall medical condition. This paper describes the team approach currently employed in the Department of Thoracic Medicine at The Prince Charles Hospital, Brisbane, Australia. The thoracic physician and ENT surgeon work in close collaboration with their dental colleagues: an orthodontist, prosthodontist and a maxillofacial surgeon. An outline of the examination and investigations made by each is described and the multidisciplinary approach is illustrated by a description of the management of five subjects with suspected obstructive sleep apnoea.

The importance of a multidisciplinary approach to the assessment of patients with obstructive sleep apnoea.

Obstructive sleep apnoea may present with a wide range of symptoms resulting in a variety of referral pathways. A multidisciplinary approach to examination and diagnosis helps to determine the most appropriate treatment plan for each individual. The subject is seen by each member of the team, appropriate investigations undertaken and a further meeting arranged at which all opinions are discussed. A reasoned treatment regime is produced, taking into consideration the patient's wishes and overall medical condition. This paper describes the team approach currently employed in the Department of Thoracic Medicine at The Prince Charles Hospital, Brisbane, Australia. The thoracic physician and ENT surgeon work in close collaboration with their dental colleagues: an orthodontist, prosthodontist and a maxillofacial surgeon. An outline of the examination and investigations made by each is described and the multidisciplinary approach is illustrated by a description of the management of five subjects with suspected obstructive sleep apnoea.

Ultrasonography of masseter muscle size in normal young adults.

The present study was planned to determine the relationship between linear dimensions of human masseter muscle cross-section and cross-sectional area (CSA), and to assess symmetry between the two sides in normal young adults. Cross-sectional images of the masseter muscle were measured bilaterally by real-time ultrasound imaging in 39 healthy dentate subjects, 19 males and 20 females, aged 21-47. From stored images, CSA and two linear measurements of muscle cross-section were obtained (the shortest and the longest distance through the muscle group). Correlation and regression analyses were performed to examine the relationship between CSA and the linear dimensions (both individually and with the linear dimensions multiplied). Symmetry of CSA between the two sides of the face was examined using the paired t-test. The significance of correlation coefficients (r) and the difference between the slopes of the regression lines were also examined. Masseter CSA was larger in males than in females. All correlation values between CSA and linear measurements were significant but muscle CSA was most accurately predicted when the linear measurements were multiplied (r = 0.97; P < 0.001). Although the correlation in this regard was high, the linear dimensions consistently overestimated the actual CSA by approximately 25%. Males showed more symmetry of CSA than females. The range of values for symmetry of masseter CSA was too large to assess abnormal asymmetry in patients with unilateral symptoms.

Tooth movement following third molar removal.

The mandibular dental arches of 45 young adults (mean age = 24.3 years) were analyzed by measuring study casts taken immediately before and twelve weeks after the removal of impacted third molar teeth. Arch length and width were measured at predetermined points on the study casts. The results showed significant buccal movement of mandibular second molar teeth following surgery (p < 0.01). Bilateral mesioangular impactions were associated with larger increases in mandibular arch width following surgery than unilateral mesioangular impactions or other classes of impaction (p < 0.05). The greatest amount of tooth movement was observed in cases where mandibular second molars had a pre-operative lingual inclination. It is hypothesised that mesioangularly impacted mandibular third molars can produce sufficient force to displace the adjacent second molar teeth in a lingual direction and when the adjacent third molar is removed this movement is reversed by functional forces.

A microcomputer system for physiological data collection and analysis.

The ability to monitor and record activity within the masticatory system is of importance to both general practitioner and research worker. Recent developments in physiological data collection and analysis at the Department of Anatomy, University of Queensland, have achieved that objective in a simple and cost-effective manner. Recording, printing, plotting, and a wide range of analysis procedures can be undertaken utilizing relatively inexpensive available computers.

Acoustic myography in the assessment of human masseter muscle.

The feasibility of examining electro-mechanical activity of the human masseter muscles using non-invasive recording techniques was examined in six healthy dentate adults (aged 34-57 years). Electrical activity of the muscle was examined by surface electromyography (EMG) and the mechanical activity, in the form of muscle sounds, was examined by acoustic myography (AMG). Bilateral recordings of EMG and AMG were made simultaneously using composite probes which were placed on the skin over the masseter muscles. A standardized pressure was applied to the probes via adjustable rods attached to a safety helmet. Pressures were monitored by strain gauges placed between the ends of the rods and the probes. With the subject seated, recordings of AMG and EMG were obtained during maximal jaw clenching for 4 s and the raw signals were stored on a computer. Of three maximal contractions performed, the last two were used in the analysis. The raw amplified signals underwent frequency analysis by fast Fourier Transform. Total activity was also assessed after amplification, full-wave rectification and integration, and repeatability of the results was assessed. The AMG frequency range was 6-15 Hz and was similar to values for other human skeletal muscles. The integrated values for EMG and AMG were repeatable on both sides of the face (IEMG, right r = 0.99, left r = 0.99; IAMG right r = 0.70, left r = 0.71). Simultaneous recordings of AMG and EMG from the masseter muscles may be useful for assessing electro-mechanical muscle function but further validation studies are required before the technique can be used clinically.

Determination of occlusal facial height in oral reconstructive procedures.

A review is provided of the methods that have been employed for the determination of occlusal facial height in oral reconstructive procedures. Details are provided in relation to a modified form of the patient's own assessment of a preferred vertical dimension of occlusion (PVDO) in dentate subjects exhibiting overclosure, edentulous subjects and in those patients requiring full mouth oral rehabilitation.

Clinical evaluation of restoration margins by an endoscopic microscope.

A method is presented for high magnification, clinical examination and recording of the marginal fit of dental restorations. An endoscopic microscope used in conjunction with video recording facilities affords acceptable colour records of restorative procedures for monitoring purposes. The suggestion is made that the concept of 'fit' in the clinical context has not been adequately addressed. The technique described has other clinical and research implications.

A comparative study of the occlusal plane in dentulous and edentulous subjects.

A study was conducted in dentulous and edentulous subjects to determine the location of occlusal plane as related to the maxillomandibular space. The results from both the dentulous and edentulous groups indicate a close angular affinity between the occlusal and maxillary planes. In the dentulous group, significant associations were found between the angulation of the occlusal plane to the maxillary plane and the height and length of the maxillomandibular space. The occulsal plane to the maxillary plane and the height and length of the maxillomandibular space. The occlusal plane in the long-and-low type of maxillomandibular space tends to be more parallel to the maxillary plane, while the occlusal plane in the short-and-high types of maxillomandibular space tends to be more steeply angulated to the maxillary plane. The occlusal plane deviates away from a mean angulation to the maxillary plane when the height and length of the maxillomandibular space tend to be toward the opposite extremes of the normal range.