The value of oral appliances in the treatment of obstructive sleep apnoea.

Oral appliances have long been used to treat snoring and mild to moderate obstructive sleep apnoea. This kind of treatment is considered an alternative, non-invasive treatment option. Mandibular protrusive appliances enlarge and stabilise the oro- and hypo-pharyngeal airway space by advancing the mandible, and stretching the attached soft tissue, in particular the tongue, soft palate, uvula, and the pharyngeal tissues. This article summarises the indications, contraindications, and possible side-effects of using oral appliances. Therapeutic efficacy is influenced by multiple parameters that are clinically difficult to control. One major parameter is the patient`s stomatognathic situation of the patient. Thus oral appliances are restricted to patients whose dental retention is adequate for permanent treatment and who do not suffer from temporomandibular joint dysfunction. Regular follow-up sleep studies and dental evaluations are necessary to ensure adequate permanent treatment.

1. Introduction

Snoring is caused by vibration of the soft tissue during sleep while breathing within extrathoracal respiratory tract. Pathological reasons for the noise include tension loss in the oropharyngeal muscle due to disturbed innervation, degenerative processes, tumours, and changes in the mucous membranes.

In general, the snorer's sleep profile and the cardiovascular situation are undisturbed, thus snoring does not affect a snorer's general health situation, but it can significantly impair social life and marital relation. Heavy snoring might influence general health. If, in addition to snoring, the patient complains about clinical symptoms such as excessive daytime sleepiness, reduced efficiency, morning headache, high blood pressure, and arrhythmias, a sleep-related breathing disorder should be suspected. This disorder has a considerable and even life-threatening medical impact on a patient's general health. The correlation between increased morbidity and morality and moderate and severe expression of obstructive sleep apnoea syndrome has been proved. Therefore, the diagnosis must be made according to a differential diagnostic process [1].

In the West, snoring is a common disorder, with an estimated prevalence of 28% in women and 45% in men in the age average of 30 to 60 years; approximately 5% of these patients suffer from sleep disordered breathing [2]. The main risks for a sleep breathing disorder are an increased body mass index, increased age, and male sex. A family predisposition, hormone status, the anatomy of the extrathoracal airway, the neck circumference and general behavioural factors such as alcohol consumption, use of sedatives, sleeping in a supine position, and a lack of general sleep hygiene can also trigger or cause sleep-disordered breathing. Estrogens seem to have a preventive effect on snoring.

When women go though the hormonal changes they too have a higher incidence of snoring.

With most patients, sleep-disordered breathing is caused by partial or complete obstruction of the upper airways. In rare cases it can also have centrally-placed source of obstruction. A precise, differential diagnosis is required before the onset of oral protrusive appliance treatment, since these devices are effective exclusively in obstructive sleep apnoea syndrome (OSAS).

The diagnostic process in OSAS includes taking the medical history, physical examination, and a cardio-respiratory sleep study. In a cardio-respiratory sleep study, parameters such as the peripheral oxygen saturation and desaturation, pulse, oral and nasal flow, sleep position, paratracheal noises; occasionally additional parameters are recorded. If cardio-respiratory sleep examination fails to provide a precise diagnosis, polysomnography in a sleep laboratory is required [1]. This entails an electric encephalogram, so that the cardio-respiratory parameters can be analysed together with the patient's sleep profile.

2. Treatment with oral appliances

Many treatment approaches exists to eliminate habitual snoring. Surgical are distinguished from non-surgical approaches. Oral protrusive appliances are increasingly used in primary snoring and mild-to-moderate obstructive sleep disordered breathing. An anterior and caudal movement of the mandible during sleep reduces the amount of nasopharyngeal obstructions and snoring in mild to moderate OSA considerably [3]. A mandibular advancement enlarges the pharyngeal airway during sleep thus tightening and stabilising the pharyngeal soft tissue [4]. This manoeuvre reduces airway resistance in accordance to Hagen-Poiseuilles law. Adjustment of the mandibular protrusion and pharyngeal opening is anatomically restricted to a certain degree. An increase in pharyngeal diameter is not proportional to the amount of mandibular protrusion [5].

Mayer-Ewert et al. described the positive effect of a mandibular advancement device, the so-called Esmarch-Orthese, on the respiratory situation during sleep for the first time [6]. The Esmarch-Orthese is designed like a modified function orthodontic appliance, since it moves the mandible into a protruded and fixed position. To date, other appliances, such as tongue-retaining devices, soft palatinal lifters, and functional training devices have not gained medical acceptance because there is still no adequate scientific proof that these appliances treat snoring and obstructive sleep apnoea effectively [7].

The mandibular protrusive appliances used for treating snoring and OSAS vary in their effectiveness, manufacture, material, ability to adjust mandibular protrusion, need of dental retention, durability, wearing comfort, expected side effects, efficacy, and expense (Table 1 (Tab. 1)) [7]. Table 1 lists different parameters to distinguish the devices. The efficacy of two splints appliances fixed on the teeth of the upper and lower jaw has been proved [8]. The connection system keeps the mandibular protrusion. Together with the splint's material thickness it determines the bite opening. The connection system should allow minor jaw movements and can be placed in anterior, buccal, interocclusal or palatinal position within the appliance (Figures 1 (Fig. 1), 2 (Fig. 2), 3 (Fig. 3) and 4 (Fig. 4)). Thus preventing the overly rigid use of the temporomandibular joints. Mandibular advancement must be adjusted directly on the patient. There is a vital clinical advantage that the patient can adjust the mandible protrusion himself according to need and his subjective tolerance.

Table 1

Classification of oral appliances for the treatment of snoring

Figure 1

An example of various frequently-used two-splint appliances: IST® according to Hinz

Figure 2

An example of various frequently-used two-splint appliances: TAP® according to Thornton

Figure 3

An example of various frequently-used two-splint appliances: Klearway™ according to Lowe

Figure 4

An example of various frequently-used two-splint appliances: ISTplus® according to Hinz

3. Efficacy of mandibular protrusion appliances

To evaluate the efficacy of oral appliance treatment, parameters such as snoring noise, cardiovascular situation, and daytime sleepiness must be considered.

Although oral appliances reduce habitual snoring considerably in some cases, snoring can persist during appliance use cause for this it are body position, alcohol, weight gain, and allergies [3]. The data presented in the literature reveals great divergence regarding the therapeutic effectiveness of oral appliances. Treatment improvement varies from 40% to 83% when one considers the reference parameter RDI (respiratory disturbance index) and/or AHI (Apnea -hypopnea index) [8]. The difference can be sufficiently explained by different patient selection, inclusion criteria, indications, and the polygraphic and polysomnographic control examinations employed. Oral protrusive appliances affect daytime systolic blood pressure and the diastolic pressure during 24-hour blood pressure recording. The consistent application of an oral protrusive appliance during sleep reduces those blood pressure values significantly in patients with OSAS [9]. Application of a protrusive device reduces daytime sleepiness significantly. There has so far been present no systematically-controlled study examining the specific influence of the treatment modality in affecting in daytime sleepiness and sleep profile.

4. Side-effects

Concerning side-effects caused by oral appliances, we must differentiate between discomfort and long term effects. At the beginning of treatment, patients may complain about increased salivation, tenderness in the masticatory muscle and temporomandibular joint, and occlusion disturbances. These findings generally occur during the adaptation period. Due to dental anchorage, direct and reciprocal forces caused by the mandibular protrusion are transferred onto the teeth. These forces can lead to a retrusion of the upper front teeth and a protrusion of the lower front teeth as well as to an anterior and lateral bite opening. In general, the extent of dental-side effects depends mainly on the extent of mandibular protrusion, the dental and periodontal situation at the onset of the treatment, and the length of time the appliance is used by the patient. Although side-effects appear frequently during oral appliance treatment; they are usually mild and clinically acceptable. Severe occlusion disturbances can occur in individual cases [10]. If side-effects do occur, continuation of the treatment must be re-evaluated. Two splint appliances covering the entire dental arch of the clinical crowns seem to be superior to those fixed with clamps because of fewer dental side-effects. Dental side-effects can be reduced significantly via functional load on the teeth, e.g. by chewing hard chewing gum. To date, structural changes in the temporomandibular joint by mandibular protrusion during sleep have not been described in the literature. Mandatory for permanent treatment with an oral protrusion appliance is sufficient dental anchorage. Removable dentures, periodontal diseases, acute infections, temporomandibular dysfunction, as well as epilepsy are regarded as contraindications for this kind of treatment. A dental based contraindication was diagnosed in about 30% of those patients revered from the sleep-laboratory to a dentist for oral appliance therapy [11], [12].

The main advantages of oral appliances are the relative simplicity of the treatment, its non-invasiveness, its reversibility, and cost-effectiveness. An appliance is easy to transport, to clean and maintain, and it require no electricity. In comparative studies of oral appliances and cpap (continuous positive airway pressure), patients subjectively prefer oral appliance treatment, particularly in mild cases [13]. Upon closer examination, however, oral appliance compliance seems lower than expected [14]. Poor dental status and excess body-mass reduce patient compliance.

5. Summary

In summary, mandibular protrusive appliances remove or fundamentally reduce snoring's frequency and volume. Prior to initiating oral appliance use, however, the presence of characteristic of sleep apnoea syndrome must be examined by performing a sleep study. Oral appliances are indicated in snoring and mild-to-moderate OSAS only. From the dental point of view, adequate dental anchorage and a healthy stomatognathic situation is required to guarantee adequate mandibular protrusion during sleep and to reduce dental side effects.

Treatment efficacy should be evaluated in regular sleep studies with the patient wearing the appliance. Dental follow-ups are necessary with permanent use to monitor occlusion, the bite, and to ensure correct appliance fit. Other less invasive treatment such as better sleep hygiene, positioning training, and weight reduction must be considered to minimise side-effects.