Palate expansion can provide important overall health benefits for people with narrow faces and limited nasal airway flow, because the roof of the mouth is the floor of the nose. If the palate is too narrow, the nasal airway may be too narrow to allow normal nasal breathing. The result is mouth breathing. Some people with very narrow palates are obligate mouthbreathers and can never breathe entirely through the nose. Their mouths are always slightly open. Other people with slightly narrow palates or nasal obstructions such as enlarged turbinates or a deviated septum only mouthbreathe when their nasal passages swell due to colds or allergies.
One problem with mouthbreathing is that it prevents the nose from moistening, filtering, and warming the air before it hits their throats. The incoming air acts like a harsh dry wind. As a result, mouthbreathers are prone to upper respiratory problems.
A second problem with mouthbreathing is that it can impair blood oxygenation. Nasal breathing helps oxygenate the blood. A study in which normal nasal breathers wore nose clips to force them to mouthbreathe for a few hours found that they developed lowered blood oxygen. More recent studies indicate that nasal breathing may release nitric oxide that helps regulate pulmonary blood flow.
A third problem with mouthbreathing is that it can impair normal facial growth, because it causes the jaw muscles to automatically attain a lowered jaw posture to allow an oral airway passage. Postural forces control the shapes acquired by bones. The lowered jaw posture produced by mouthbreathing causes the front of the face to lengthen and narrow. Monkeys forced to mouthbreathe develop long narrow faces.
Palatal expansion can cure mouthbreathing by widening the roof of the mouth and thereby also widening the floor of the nose. Expanding the palate a few millimeters has been likened to developing a third nostril.
Palatal expansion occurs more rapidly in children, but it can also be accomplished in adults at any age. For decades, traditional orthodontists only performed rapid palatal expansion, because they believed that the palate could only be expanded by completely separating the two sides of the midline palatal suture, therefore it had to be performed before most of the craniofacial sutures close at the end of the second decade, or it would require surgery to cut the suture. However, we now know that even adult palates can be expanded gradually by wearing an by oral appliance that supplies light steady outward force on the sides of the palate. The process usually takes 3 to 6 months, depending on the type of appliance used. The oral appliance must be worn most of the time, but it need not be worn all the time.
Expansion screws appliances are the most effective way to widen a palate. They employ a powerful turnbuckle located in the middle of the appliance, and the patient is given a key that turns it. With each turn of the screw, the two sides of the palate are driven slightly further apart. The patient uses the key to maintain light steady pressure on the upper teeth. Traditional expansion screw wideners were called Schwartz, Haas, or Hyrax appliances. One expansion screw widener called a DNA appliance is aggressively marketed as epigenetic, although there is no evidence that it actually affects genetics. Often an expansion screw can be added to an existing oral appliance which is then split down the middle and used as a palate widener.
Bent wire wideners (such as quad helix appliances, coffin spring appliances, bionators, and crozats) employ a framework of wires and springs that are soldered to thin metal bands that are usually glued to the teeth. Bent wire wideners have been used to widen palates since 1881 (Dr. Walter Coffin). They can be relatively unobtrusive, but their main disadvantage is that they tend to do more tipping of teeth and less expansion of the underlying basal bones, such as the pillars of the nasal cavity. Frankel appliances are bent wire appliances that expand the palate by including a plate that holds the cheeks out away from the teeth and therefore reduces the forces inward on the teeth.
ALF (advanced lightwire functional) appliances are simple low force bent wire appliances that are now aggressively marketed to dentists as having almost magical properties. For example, the advocates claim, "By focusing on the form and function of the neuro- and viscera-cranium, the gentle action of the ALF appliance provides a safe sensory stimulus within the mouth that allows for a greater range of neurological regulation to occur, especially through the cranial nerves and the automotic nervous system." In reality they are not different from other bent wire wideners, except that the wire is lighter and they must be worn for longer time periods. Light gentle forces are more biologically compatible than heavy forces such as those produced by expansion screws, but they also produce more tipping of teeth and less movement of the bony bases.
Because their forces are gentle, ALF appliances are promoted as being compatible with cranial osteopathy, which is discussed extensively in CRANIAL AND CRANIOSACRAL under TREATMENTS.