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Are oral appliances a substitute for nasal positive airway pressure?
  1. R P Millman,
  2. C L Rosenberg
  1. Departments of Medicine and Plastic Surgery, Rhode Island Hospital, Brown Medical School, Providence, Rhode Island, USA
  1. Correspondence to:
    Dr R P Millman, Division of Pulmonary, Sleep and Critical Care Medicine, Rhode Island Hospital, 593 Eddy Street (APC-4), Providence, RI 02903, USA;
    rmillman{at}Lifespan.org

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A simple non-adjustable oral appliance is no substitute for nasal positive airway pressure in patients with obstructive sleep apnoea.

Although positive airway pressure (PAP) devices have become the mainstay of treatment for obstructive sleep apnoea, not all patients can or will use PAP on a nightly basis. Many patients find taking a bulky PAP unit on business or vacation trips a burden. In this issue of Thorax Smith and Stradling attempt to show that a simple non-adjustable oral appliance may be used in place of PAP on a short term basis.1 Unfortunately, in only nine of the 50 patients entered into the study was their sleep apnoea controlled with the appliance.

This low success rate of 18% does not concur with the published literature which has reported a success rate of 81% in patients with mild and 60% in patients with moderate sleep apnoea.2 Part of the difference between this study and the previous literature may be related to the type of device used and side effects from the device. Smith and Stradling employed a device that had previously been shown to be effective in controlling snoring.3 It consists of two customised sports-type mouth guards fused together to place the mandible in a forward position set at approximately 75% of maximum mandibular protrusion. The device covers both the teeth and the gums, so it differs from more commonly used devices such as the Herbst and the Klearway which cover only the teeth and are adjustable, allowing gradual advancement of the mandible to a forward position at night to open the pharynx and prevent snoring and sleep apnoea.

The difference in appliance configuration probably contributed to the low success rate. Thirty one of the subjects studied by Smith and Stradling gave up the device due to intolerable side effects such as sore gums, excessive salivation, and painful masseter muscles or temporomandibular joints. This contrasts markedly with other experiences with the appliance. We previously reported a study of 19 patients who had failed with nasal CPAP and changed to treatment with the Herbst mandibular advancement device.4 At the time of the follow up sleep studies no patient reported pain or discomfort while wearing the removable Herbst appliance. Tegelberg and colleagues reported 45 patients randomised to treatment with an oral appliance adjusted to 50% of maximum mandibular protrusion.5 Only one patient withdrew from treatment for side effects—specifically, the patient developed recurrent aphthous ulcers related to an allergic reaction to the acrylic polymer. Fritsch et al randomised patients to treatment with either a Herbst appliance or an appliance developed at their centre (Monobloc) initially set at 75% maximum mandibular protrusion.6 Although side effects were common with the two appliances (mucosal dryness, tooth discomfort, and excessive salivation), all the symptoms were mild and none of the subjects discontinued treatment because of side effects. Mehta and colleagues randomised 28 patients to treatment either with a control oral plate that did not advance the mandible or with a mandibular advancement split that advanced the mandible to the most protrusive position that the patient could comfortably maintain.7 Twenty one of the 24 patients completed the protocol. Side effects, which included excessive salivation, gum irritation, mouth dryness, jaw discomfort, and tooth grinding were mild to moderate and lasted a maximum of 3 weeks. None of the patients stopped using their device because of the side effects. Furthermore, two randomised crossover studies of PAP and oral appliances have shown that mandibular advancement was better tolerated in mild to moderate sleep apnoea and preferred to nasal PAP.8,9

Even in those patients who were able to tolerate their mandibular advancement device, Smith and Stradling found that their sleep apnoea was not well controlled with the appliance. One reason may have been that the patients did not have their appliances suitably adjusted. The authors arbitrarily chose a specific mandibular protrusion and then studied the patients at that setting. Setting a mandibular position for an oral appliance may not be that simple. Kato et al reported a dose-dependent effect of mandibular advancement on the severity of sleep apnoea.10 Clinical protocols in patients with adjustable Herbst or Klearway appliances involve a slow advancement of the mandible until snoring and daytime sleepiness have resolved. At this point patients using an appliance are sent for repeat polysomnographic evaluation to see if further adjustments need to be made to the appliance. In our clinic patients on nasal CPAP who would like to use an appliance for vacation or business trips are not allowed to switch to an appliance unless it is adequately controlling their sleep apnoea. One could argue that giving an appliance with an arbitrarily fixed mandibular protrusion to a patient with sleep apnoea is akin to arbitrarily switching a patient with an appliance to an arbitrary PAP pressure of, for example, 8 or 10 cm H2O.

The response of a patient to an oral appliance may also be affected by pharyngeal anatomy; this is not mentioned by Smith and Stradling. Patients with large tonsils, for example, may not respond to an oral appliance because of the degree of baseline pharyngeal obstruction. In a series of patients who had failed uvulopalatopharyngoplasty and who then went on to oral appliance therapy, we reported one patient in whom an oral appliance did not control his sleep apnoea.11 On initial testing he had a baseline apnoeic/hypopnoeic index (AHI) of 43 episodes/hour. Since he could not tolerate nasal CPAP he was fitted with a Herbst appliance. The repeat AHI with the Herbst appliance in place was 56 episodes/hour. Because he was significantly symptomatic he underwent a uvulopalatopharyngoplasty, following which the AHI was 29 episodes/hour. He was then tried on the appliance again and a repeat sleep study indicated control of his sleep apnoea with an AHI of 8 episodes/hour.

In summary, Smith and Stradling have shown that, in their hands, their appliance was not a good alternative to PAP therapy. Their results were hampered by significant side effects from the appliance and poor control of the sleep apnoea. Although it is possible that their results could be extended to bite-block type appliances, it is difficult to extrapolate the results to more sophisticated adjustable mandibular devices.

A simple non-adjustable oral appliance is no substitute for nasal positive airway pressure in patients with obstructive sleep apnoea.

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