Palate Expansion

For decades, most dentists believed that palate expansion in adults was impossible; because they assumed that it occurs by separation of the maxillary bones at the midline suture, and therefore it must stop when the suture ossifies in the late teenage years.  Now we know that palates can be expanded at any age using light steady forces; which unfold the maxillary bones and lower the ossified suture, accompanied by adaptive remodeling in the suture and throughout the midface. The expansion can be maintained post-treatment by stabilizing the natural bite and nightly wear of a retainer with a stable raised bite table that employs the forces of nocturnal bruxism to broadly load the expanded structure until it stabilizes.

NATURAL PALATE EXPANSION - The upper jawbone and upper dental arch are designed to grow by expanding until they become wide enough to fit around the tongue so the tongue can rest up high in the palate where it belongs, with its tip just behind the upper front teeth. The upper jawbone is a framework of two paired (right and left) maxillary bones. In children, they expand by spreading apart, primarily in response to bite forces.

In one direction, the two maxillary bones spread by rotating outward and upward around the midpalatal suture while lowering that suture and thereby flattening the palate, as seen from left to right in the illustration below. In our ancestors, very strong chewers always had very shallow wide palates.    

In another direction, the two maxillary bones spread by swinging out around their front-most connection, as can be seen from left to right in the illustration below, which flattens the midface.  In our ancestors, very strong chewers also had very flat faces.

However, this natural upper jawbone expansion depends on bite forces, and the forces we apply with our jaw muscles have diminished radically in the last couple of centuries. Our jaw muscles are about half as strong as they were just a couple of hundred years ago before liquids and processed foods came to provide most of our nutrition. This weakening of the jaw muscles is one cause of narrow palates, as evidenced by the fact that the same types of narrow upper jawbones can be produced in monkeys and other animals by just softening their diets. As a result of our soft diets, many modern upper jawbones do not receive enough bite forces to fully expand. Instead of growing wide enough to fit around the tongue, they only grow wide enough to fit around the thumb or a pacifier.

Also contributing to the narrowness of our upper jawbones is the vertical facial growth that results from weak jaw muscles. When the jaw muscles are too weak to limit the eruption forces of the teeth and their surrounding bones, their eruption excessively lengthens the front of face, which tightens the cheeks, which creates a force that pushes inward on the molars and premolars. The role of the tight cheeks in maintaining a narrow palate can be seen in the ability of Frankel appliances to expand palates simply by holding the lips and cheeks out and away from the teeth.

Also contributing to the narrowness of our upper jawbones in many people is the deep or steep overbite and tightly interdigitated steeply cusped teeth that lock the upper jawbone to the lower jawbone. The front half of the lower jawbone, the portion holding the teeth, is made of one thick piece of cortical bone, which cannot expand. It only grows by being pushed forward from behind. In the facial growth process, the bite acts like a suture between the upper and lower jawbones. When the upper jawbone is locked by the bite to a lower jawbone that cannot expand, the upper jawbone cannot expand either, and its horizontal growth gets redirected vertically.   

EFFECTS ON THE NASAL AIRWAY - When the upper jawbone cannot expand sufficiently and remains narrow, the nasal airway just above it also remains narrow; because the roof of the upper jawbone (the palate) is the floor of the nose. Typically, the upper dental arch becomes V-shaped instead of U-shaped; and the upper premolar area, where the narrowing is most common, is the floor of the anterior portion of the nasal cavity, where airway flow is usually restricted. 

MOUTH BREATHING - The narrow nasal airway is a common cause of mouth breathing. People with very narrow palates are usually obligate mouth breathers, and they keep their lips parted to allow an oral airway. People with palates that are just wide enough to accomodate a nasal airway become obligate mouth breathers whenever their nasal passages swell slightly due to colds or allergies. Habitual mouth breathers have enough space for a nasal airway, but they don't use it. 

Mouth breathing prevents the nose from moistening, filtering, and warming the air before it hits the throat - making mouth breathers prone to upper respiratory problems. It also prevents the release from the paranasal sinuses of nitric oxide into the lungs; which has antibacterial properties, a vasodilating effect, and a role in endothelial health. It also impairs the effectiveness of respiration, because the nose acts like a little lung. Volunteers who wear nose clips to force mouth breathing develop lowered arterial oxygen levels. Sleep studies show that mouth breathing increases airway resistance and decreases sleep quality.

Mouth breathing sustains itself by the way it alters facial growth. Lowering mandibular posture to create space for an oral airway passage causes the face to grow vertically instead of horizontally, which prevents the nose from growing wide enough to allow normal nasal breathing. In monkeys forced to mouth breathe by experimentally plugging their nostrils, lowering the mandible to create an oral airway passage made it grow straight downward, resulting in long narrow faces. In humans, the mandible is much shorter, so lowering the mandible also rotates it backward, resulting in long, narrow, and retrusive faces (recessed chin). 

MECHANICALLY ASSISTED PALATE EXPANSION - can increase the cross-sectional area of the nasal cavity and thereby restore nasal breathing. In adults, the process can be performed rapidly by distaction osteogenesis maxillary expansion (DOME) or by miniplate assisted rapid maxillary expansion (MARPE); or it can performed slowly and non-surgically by an oral appliance that delivers light steady mechanical forces for 3 to 6 months transversely across the palate. The appliance does not simply separate the two maxillary bones like pushing apart two tables. The ossified suture does not widen, but it remodels in response to the maxillary bones unfolding like a pair of wings, which lowers the suture; and the rest of the midface adapts by remodeling its structural elements to accommodate the altered pattern of delivery of jaw muscle forces.

Pushing on the teeth to expand the palate and upper jawbone can increase the size of the nasal cavity, however it also tips those teeth to an extent that depends on the mechanics used to provide the forces. Bent wire appliances, such as quad helix appliances, bionators, Crozats, and ALF (advanced lightwire functional) appliances tend to do more tipping of teeth and less expansion of the bones. Expansion screw appliances; such as Schwartz, Haas, Biobloc, Homeoblock, DNA, RNA, and Hyrax appliances; employ a powerful turnbuckle which can significantly move the maxillary bones, but they still cause some tipping of teeth. Recently some orthodontists have been using fixed (glued in) palate expanders with TADs (temporary anchorage devices), which are tiny lag screws temporarily implanted in the palate, to maximize movement of the bones and minimize the tipping of the teeth. They make palate expansion more effective, but they must be kept very clean.

Palate expansion can be enhanced by a chiropractic treatment called nasal release or nasal specific technique; which employs a little balloon expanded inside the nasal cavity to push out the nasal cavity. The forces cause palpable pressure but no pain. Combining expansive forces above the below the palate is likely the most efficient way to expand the palate.

OUR PALATE EXPANSION APPLIANCES are traditional expansion screw appliances that have a thin metal expansion framework and avoid bulk in the front of the palate, where it would interfere with tongue posture and speech. Whether finger springs or orthopedic inclines are added depends on patient needs.  

 

Although palate expansion devices usually come with instructions to perform two turns weekly, we recommend making frequent turns that are as small as possible, because light steady forces shape bones. If the expansion produces pain, you are going too fast and triggering localized inflammation, which prevents smooth remodeling of bone. You can make the smallest turn possible every time you put your appliance back in.

You can take your appliance out for meals and important social functions, but it cannot be worn only at night, unless the bite is very flat or continually adjusted to fit the expansion; because the interdigitation of upper and lower teeth will return the palatal bones to their pre-treatment positions every day, especially when chewing.  

RETENTION - After the expansion process, the palatal width needs to be maintained by widely and evenly loading the upper dental arch in the newly expanded alignment, both in the natural bite and in the retainer worn every night. The retainer can also have various orthopedic features, like a front flat bite plate for those who had a deep overbite before treatment or inclines that promote mandibular advancement.

RESTABILIZING THE BITE - The expansion process always destabilizes the bite to some extent temporarily. The bite may restabilize naturally, especially if combined with a little mandibular advancement, which brings a wider part of the lower dental arch underneath the expanded portion of the upper dental arch and thereby keeps the opposing teeth in close proximity for effective biting and chewing. However, if the upper and lower teeth are steeply interdigitated, any change in their relative positions can cause uncomfortable collisions between opposing teeth, and shallowing the bite table by filling in deep valleys or low areas with composite resin filling material and/or shaving down prematurely contacting mountain peaks can greatly facilitate treatment and post-treatment stabilization.   

In some cases, the lower teeth may need to be uprighted. They can be uprighted during palate expansion by making the palatal expander include flanges that reach down along side the inner edges of the lower teeth, or they can be uprighted after palate expansion by wearing a small unobtrusive removeable "spring" type of appliance, a series of clear aligners, or using orthodontic elastics attached to tiny buttons temporarily glued to the sides of the involved teeth to pulling individual pairs of teeth into proper alignment.  

GAPS BETWEEN TEETH - result from palate widening. If the teeth were crowded before treatment, simply straightening the teeth can close the gaps and align the teeth into an arch, which is incompressible, thereby functioning as a good retainer. In people with front teeth that are unusually narrow, the gaps can be shifted to the sides of those teeth and then closed by widening those teeth using veneers. 

COMBINING PALATE EXPANSION WITH A SLEEP APNEA APPLIANCE - When a patient has both a narrow palate and obstructive sleep apnea, we can combine treatment for sleep apnea with palate expansion by using an upper palate expansion appliance to which the telescopic components and the lower member of the mandibular advancement appliance can be added every night. The process requires dexterity, but most people have no trouble with it.

COSTS - Our fee is $2,500 - $3500 for the basic expansion screw appliance. If more widening or further tooth straightening is needed, a second stage of expansion can be made for about half of that fee. If work is needed on the lower teeth to stabilize the bite post-treatment, that would be extra.