Palate Expansion

For decades, most dentists believed that palate expansion in adults was impossible; because they assumed that all the expansion occurs by separation of the maxillary bones at the midline suture, like pushing apart two tables, and therefore it must stop when the suture ossifies in the late teenage years.  However the growth in the sutures is not primary. It does not push the bones apart. It responds to forces, including bite forces and mechanical expansion forces by remodeling and thereby adapting to whatever conditions are present. Palates can be expanded in adults, because the maxillary bones unfold and the suture lowers. The expansion can be maintained post-treatment by having a stable natural bite and wearing a retainer that has a stable raised bite surface every night.

NATURAL PALATE EXPANSION 

The upper jawbone and upper dental arch are designed to expand enough to fit around the tongue so the tongue can maintain a resting posture up high in the palate with its tip just behind the upper front teeth. Bite forces (not tongue forces) cause this expansion by spreading apart the two (right and left) maxillary bones, in two directions.

In one direction, the two maxillary bones rotate 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 swing 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. As a result, many 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. The same narrow upper jawbones can be produced in monkeys and other animals by just softening their diets.

Also contributing to the narrowness of our upper jawbones is the vertical facial growth patterns that result from weak jaw muscles. When the jaw muscles are too weak to limit to eruption forces built in to the teeth and their surrounding bones, the face grows long in front, 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 effectiveness of Frankel appliances, which expand palates simply by employing lip bumpers that hold the lips and cheeks away from the teeth.

Also contributing to the narrowness of our upper jawbones in many people is the overbite and the steeply cusped unworn teeth that lock the upper jawbone to a lower jawbone that grows by translating rather than expanding. Bites act like a suture between the upper and lower jawbones, and steeply interdigitated bites have limited adaptive capacity.    

EFFECTS ON THE NASAL AIRWAY - When the upper jawbone cannot expand properly, 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 slightly narrow palates become obligate mouth breathers whenever their nasal passages swell due to colds or allergies. Habitual mouth breathers have enough space for a nasal airway, but they don't use it. 

Mouth breathing causes significant health problems. It prevents the nose from moistening, filtering, and warming the air before it hits the throat - making mouth breathers prone to upper respiratory problems. It 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. Mouth breathing also impairs the effectiveness of respiration, because the nose acts like a little lung. In one study, volunteers who wore nose clips to force mouth breathing for a couple of hours developed 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 vertical instead of horizontal facial growth, 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 a long narrow faces. In humans, lowering the mandible also rotates it backward, so lowering the mandible to create an oral airway passage results in a long, narrow, and retrusive face (recessed chin). 

ENLARGING THE NASAL AIRWAY, - by expanding the palate and upper jawbone, can increase the cross-sectional area of the nasal cavity and restore nasal breathing in adults. Surgically the expansion can be accomplished by distaction osteogenesis maxillary expansion (DOME) or by miniplate assisted rapid maxillary expansion (MARPE). Non-surgically, the expansion can be produced by an oral appliance that delivers light steady mechanical forces transversely across the palate.  The expansion 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 simultaneously 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.   

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 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 loading the upper teeth, 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. The natural bite can be stabilized by shaving down high spots, building up low spots, or using buttons with elastics to shift individual teeth. 

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.

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. 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 composite resin or porcelain veneers. 

THE LOWER TEETH - Stabilizing the natural bite to retain the palate expansion may or may not require directly treating the lower teeth. The lower dental arch is generally V shaped, and it typically advances along with any kind of TMJ treatment, thereby bringing a wider part of the lower dentition opposite the directly widening part of the upper dentition, which can maintain bite stability. However, if the upper and lower teeth are steeply interdigitated, any change in their relative positions can cause uncomfortable collisions between opposing teeth. In such cases, flattening the steeply interdigitated teeth slightly by either reducing the steepest cusps (mountain peaks) or shallowing the deepest valleys with composite resin can greatly facilitate treatment and post-treatment stabilization.

If those dental remedies are not an option, the lower teeth may need to be uprighted to recreate a good interdigitation. In most cases, the lower teeth were tipped inward to interdigitate with narrow upper teeth anyway, and 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 by pulling individual pairs of teeth into proper alignment using orthodontic elastics attached to tiny buttons temporarily glued to the sides of the involved teeth.  

COSTS - Our fee is $2,000 for the basic expansion screw appliance. If more widening or further tooth straightening is needed, a second stage of expansion can be made for half price. If work is needed on the lower teeth to stabilize the bite post-treatment, that would be extra.