Thornton Adjustable Positioner (TAP)
by Dr Peter Mendelsohn
I attended a course entitled 'Snoring, apnoea and the Dentist' in March as a representative of the British Snoring and Sleep Apnoea Association.
The course was run by Dr W Keith Thornton who is a dentist in private practice in Dallas, Texas. He is also Visiting Faculty, Department of Oral and Maxillofacial Surgery, Bylor College of Dentistry and Director or Oral Appliance Therapy at Sleep Medicine Associates of Texas.
He has developed his own oral appliance, known as the Thornton Adjustable Positioner (TAP), and has now treated over 300 patients during the last three years. His interest is in snoring and Obstructive Sleep Apnoea (OSA). I learnt some interesting facts from a man who has a great deal of experience in this field.
Dr Thornton began by discussing the various sleep states and went on to discuss a condition half way between snoring and sleep apnoea called Upper Airway Resistance Syndrome (UARS) which manifests in excessive daytime sleepiness. UARS is caused by a partial obstruction of the airway. Here there is night-time arousal due to increased respiratory effort. There is no oxygen desaturation which is an important diagnostic factor distinguishing UARS from OSA.
Then he spoke about Obstructive Sleep Apnoea which is concerned with the periodic collapse of the pharyngeal airway whilst sleeping. This causes progressive asphyxia which increasingly stimulates breathing efforts against the collapsed airway, typically until the person is awakened. This leads to excessive daytime sleepiness (often a contributory factor in road traffic accidents), inability to concentrate, memory and judgement impairment (again, often a contributory factor in accidents in the workplace), irritability and depression.
The medical effects of OSA include a strain on the cardiovascular system leading to arrhythmia (irregular heart beat), hypertension (increased blood pressure), stroke and sudden death. According to one study 45% of patients with stable treated congestive heart failure have sleep apnoea.
I picked up some interesting points relating to sleep and to OSA which are often not mentioned:
- In Rapid Eye Movement sleep (REM) there is penile erection. This can be used to diagnose physiologic or psychological impotence.
- Very often with OSA there is a lack of libido - again this may be physiological or psychological.
- The effects of alcohol on airway muscle tone can last for up to 7 days before returning to normal. According to Dr Thornton, one drink for the apnoeic can be equivalent to 7 or 8 for the normal person. This can be related to driving where the tendency to fall asleep can be greatly increased with only a little alcohol in the susceptible individual.
- When a person falls asleep the lower jaw muscles relax causing the mouth to fall open thereby minimising the space available for airflow. The soft tissue infringement on this space manifests in snoring.
Dr Thornton then went over the treatment options for snoring and OSA:
Laser assisted Uvulopalatoplasty (LAUP) and uvulopharyngopalatoplasty (UPPP) are treatment modalities for severe snoring.
These work by removing the obstruction. The problem here is that reported success rates are variable. Some studies show a 50% success rate. Success has been identified as 50% reduction of the symptoms post-operatively.
A careful diagnosis has to be made as it is ineffective with symptoms due to vibrating tissue at the tongue base. Removal of soft tissue from the palate will do nothing to cure the symptoms in this case.
- Avoid alcohol, tobacco and sleeping tablets.
- Weight gain may be a consequence rather than a cause of OSA but for those who are overweight losing weight can help resolve the condition.
- Sleep position should not be supine (on one's back). Sleeping on the side is a preferable position.
- Pharmacological options include protripyline and theophyline but because these drugs cannot be used for all patients, the search for the ideal drug continues. Moreover, some patients cannot tolerate, or simply refuse, this option.
- Continuous positive airway pressure (CPAP). The major concern with nasal CPAP therapy is long-term compliance, because continued use of the device requires considerable patient commitment. When studies were performed that covertly monitored actual CPAP use, compliance was found to be less than what was self-reported by the patients. There is also the problem of transporting the machine when away from home.
Mandibular Advancement Devices (MADs) work by altering the position of the mandible (lower jaw) which reverses the tendency of the lower jaw to fall back allowing the tongue to block the airway. The airway is opened by bringing the jaw forward, bringing the hyoid bone up and the tongue forward.
There are three basic categories:
- The TRD uses suction, caused by placing the tongue into a cup or bubble positioned between the anterior (front) teeth, to hold the tongue in an anterior position while the patient is sleeping. The suction prevents the tongue from falling back and being drawn downward by the negative pressure of inspiration. It is effective as long as the suction seal is maintained, which usually is less than half the night. A patent nasal airway must be present for this treatment to be effective.
- The fixed MAD moves the mandible forward several millime- tres, while passively bringing the tongue with it, keeping the pharyngeal air space patent (open) during sleep. The optimum amount of anterior advancement of the mandible is the range between 50% and 100% of patient's maximum protrusive (forward) movement. This forward position can he maintained by using a one-piece, or fixed, appliance that holds the maxilla (upper jaw) and mandible (lower jaw) together. Anterior breathing holes may be necessary for some patients to allow oral respiration, especially for those with restricted nasal flow.
- A more ideal design for the appliance is the non-fixed MAD, which involves the construction of separate devices for the maxilla and mandible. A separate appliance for each makes fitting easier and makes it more difficult to dislodge, because removal of the appliance is in a different path to mouth opening. Connecting the upper and lower appliance is accomplished with a single hook and latch in the anterior region (Thornton Adjustable Positioner or TAP).
Because of their versatility and ease of adaptation, the TAP is more effective than the one-piece appliance, especially for patients who actively grind their teeth at night. Some patients may not be able tolerate the rigid fixation of their jaws with the one-piece design. The objective of the design of the TAP was to restrict all backward movement while still allowing the patient to move the mandible forward and side to side, as well as to open the mouth if necessary. The advantages of oral appliance therapy are simplicity, reversibility, and cost-effectiveness. In time it may become the primary treatment in patients who are unable to tolerate nasal CPAP or who are poor surgical risks. It is readily accepted by most patients and can supplement other treatments in the small percentages of instances in which the dental devices alone do not bring sufficient relief.
An advantage of the non-fixed MADs is the ability to systematically pinpoint the exact mandibular position that benefits each patient the most. When using a fixed MAD one is forced to pick an arbitrary forward position and gamble on what results might be achieved. The position at which each patient experiences maximum benefit is unique to that individual and, at this time, cannot be determined before constructing the appliances. Also with fixed MADs the tongue is normally restricted often impinging on the airway.
Most of the clinical experience has been with the TAP. More than 300 of these have been delivered during the past three years to patients with chronic, heavy snoring who have been observed not to breathe for short periods during sleep, or for whom the sheer noise has disrupted their homes and even their relationships. A significant number of these patients had already tried several options, including everything from inexpensive devices and other home remedies purchased at the pharmacy to CPAP and to surgery, which included uvulopalatopharygoplasty; laser- assisted uvolopalatoplasty and correction of a deviated septum.
Although no blind controlled study has been completed, the clinical results warrant further investigation into the effectiveness and limitations of the Thornton Adjustable Positioner. In the follow-up survey of 208 of 300 patients who had worn the appliance for over six months, only four said that they felt the appliance had not improved their snoring problem and 81% were still wearing it an average of 25 days a month. Three of the 300 patients had not been able to use the appliance; none of them had specific complaint regarding pain or discomfort, only that it was difficult mentally to sleep with something in their mouth. A temporary bite change occurred in almost all patients which lasted an average of 15 to 30 minutes immediately after removal of the appliance.
To summarise the TAP is:
- easy to use
- comfortable to wear
- avoids the necessity for surgery and the potential complication associated with it
- not permanent
- low cost
For further details on the appliance please contact: Dr. Peter Mendelsohn at The Carnaby St. Dental Practice, 31 Carnaby St., London W1V 1PQ. Telephone: 0207 734 6421