MDSA Pty Ltd

Custom Made Dental Sleep Appliance- Bringing peace to the home

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Oral Appliances.

Currently there are in excess of 200 different types of appliances available. Universally they all have similar effect of repositioning and holding the mandibular (lower jaw) in a protruded position during sleep. This concept was first published and reported back in the early 1980's ( Pancherez et al , Clarke et al, Halstrom et al, Lowe et al ). Earlier patents and published evidence confirmed the efficacy of this.

By holding the lower jaw forward tends to also bring the tongue forward and exert tension on the muscles of the tongue making it more rigid and less floppy overcoming obstruction of the throat.

Of these 200 appliances they tend to fall into 5 categories, defined by their individual design application.

Combined Splints.PNG

The real question is which is best for each patient and which have medical evidence to support their claims.

Unfortunately as most research studies define the appliance used in the generic of MAS or MAD all appliances tend to reference any study published as applicable to their product.

Why? It’s essential to select the right oral appliance for each patient to ensure compliance and improved patient outcomes.

Studies have shown that changes occur in the upper airway at several levels when the mandible is pulled forward.

A study by Isono et al (1) used video endoscopy to examine the effects of advancing the mandible on the pharyngeal airway of 13 patients with OSA who were under general anesthesia with total muscle paralysis. They found that advancing the mandible widened the retropalatal airway as well as that at the base of the tongue. They applied negative pressures to the airway and showed that a more negative pressure was required to cause collapse of the airway when the mandible has been advanced. In their discussion, they postulated that one of the mechanisms by which mandibular advancement stabilizes the soft palate and retropalatal airway is through tension transmitted along the palatoglossus muscles to the soft palate.

A study by Schwab et al (2) using MRI on snorers while they were awake showed that advancing the mandible resulted in a greater increase in the lateral than the A-P dimension of the airway. CPAP produces a similar change (3).

Wearing an appliance will also prevent the mouth from falling open during sleep. A study by Meurice et al (4) showed that upper airway collapsibility was increased in normal subjects while awake when their mouths were opened.

Therefore, wearing a dental appliance that advances the mandible stabilizes the upper airway by:

1. pulling the base of the tongue forward,

2. pulling the soft palate forward and putting the walls of the upper airway under tension

3. keeping the mouth from falling open during sleep.

These are primarily passive mechanical effects that can be explained by applying simple physical principles to what is known about the anatomy of the upper airway.

The critical anatomic relationships in terms of improving the sleeping airway with mandibular advancement are as follows:

It is important to keep the mouth closed. If the mouth is opened more than 10mm tensile forces that are produced by advancing the mandible are directed partly downwards towards the feet. This increases the longitudinal tension in the pharynx and promotes collapse.

However, there are situations in which combining advancement of the mandible with a slight increase in the opening of the jaw will help to further stabilize the soft palate without promoting collapse of other portions of the upper airway.

It is tension that stabilises the structures in the upper airway. When you are awake, upper airway muscles are activated to produce this tension.

When you are asleep, these muscles become less active and tension is lost.

CPAP restores this tension by applying an intraluminal pressure. When the anatomy is favorable, mandibular advancement can be as effective as CPAP in tensing and stabilizing the structures of the upper airway.

Study by Oshima et al (5) demonstrates that mandibular advancement in properly selected patients with OSA results in a decrease in genioglossal EMG activity during sleep as has been observed in patients with OSA who use CPAP (6).

CPAP applies pressure to the inside of the upper airway that stretches the tissues and prevents their collapse.

This pressure also acts as a counter-pressure to the pressure exerted by the tissues surrounding the upper airway. Advancing the mandible decompresses these same tissues. Either way, the net pressure in the tissues surrounding the upper airway is lowered resulting in widening of the upper airway.

CPAP accomplishes these goals by applying pressure to the inside of the upper airway.

When the anatomy is favorable, mandibular advancement with a dental appliance can achieve the same goals.


1.Isono S, Tanaka A, Sho Y, Konn A, Nishino T: Advancement of the Mandible Improves Velopharyngeal Airway Patency. J Appl Physiol 1995; 79:2132-2138

2.Schwab RJ, Gupta KB, Duong D, Schmidt-Nowara WW, Pack AI, Gefter WB: Upper Airway Soft Tissue Structural Changes with Dental Appliances in Apneics. Am J Respir Crit Care Med 1996; 153 (part 2 of 2 parts): A719

3.Schwab RJ, Pack AI, Gupta KB, Metzger LJ, Oh E, Getsy JE, Hoffman EA, Gefter WB: Upper Airway and Soft Tissue Structural Changes Induced by CPAP in Normal Subjects. Am J Respir Crit Care Med 1996; 154:1106-1116

4.Meurice J, Marc I, Carrier G, Series F: Effects of Mouth Opening on Upper Airway Collapsibility in Normal Sleeping Subjects. Am J Respir Crit Care Med 1996; 153:255-259

5.Oshima T, Tsai WH, Hadjuk EA, Remmers JE: Mandibular Protrusion Decreases Genioglossal EMG. Am J Crit Care Med 1998; 157(3):A655

6.Strohl KP, Redline S: Nasal CPAP Therapy, Upper Airway Muscle Activation and Obstructive Sleep Apnea. Am Rev Resp Dis 1986; 134:555-558