Sir, the treatment of airway restriction with dental appliances has recently become a fashionable topic. These can range from minor problems such as snoring to life threatening conditions such as sleep apnoea and several different forms of treatment have been recommended.

However, the condition is not well understood and consensus has by no means been reached on either the cause or the cure. This has not prevented a rapid increase in the number of courses encouraging dentists to increase their income by between £23,000 and £33,000 per year. I can imagine that for a focused clinician these claims may not be unrealistic, but should we not be looking more deeply into the cause and the long-term success of treatment?

There are many obvious natural factors associated with sleep apnoea including being overweight, sleeping on the back, leaving the mouth open especially when asleep and having a low muscle tone, all of which are also closely associated with modern lifestyles. Having worked with such patients since the 1980s, it is my belief that both snoring and sleep apnoea could almost be eliminated if sufferers could be taught to sleep on their side with their mouth closed, especially if in addition they could lose some weight and improve their muscle tone. The upper airway is rarely much of a problem and the open mouth posture is usually a habit rather than a need.

The special appliances that are recommended act somewhat empirically by holding the mandible forward and/or open to increase the pharyngeal airway. In a way they act like a functional appliance such as a Bionator but additional measures are sometimes recommended to prevent the patient dropping their jaw out of the appliance. Some do this by opening the bite wider and others by engaging both the upper and lower teeth.

It has been accepted for many years that functional appliances in general have a reciprocal effect on both the mandible and maxilla, reducing the overjet while lengthening the face. Simply put, the drag from the mandible pulls back the maxilla. Many clinicians believe that such changes are limited to children and that the adult facial skeleton is resistant to change, however recent research suggests that long-term wear of sleep apnoea appliances by adults also increases their facial height.1,2 Unfortunately this is exactly the opposite of what is required and must give rise to concern that after several years the resting airway would become smaller. This tendency must be all the greater if the upper and lower jaws are linked together.

There does not seem to be any evidence that these appliances are more effective than a tennis ball sewn into the back of the pyjamas.