Palate Expansion

Until the last couple of decades, many dentists believed that palate expansion in adults was impossible; because they assumed that all the expansion occurs in the midline suture, and therefore it must stop when the suture ossifies in the late teenage years.  Now we know that both the ossified suture and the maxillary bones that it connects stay adaptable, along with the alveolar ridges surrounding the teeth and the bony buttresses that brace the upper jawbone against the rest of the cranium.  As a result, palate expansion can be produced at any age.  

NATURAL PALATE EXPANSION 

The upper jawbone and upper dental arch are designed to grow wide enough to fit around the tongue so the tongue can rest up high in the palate with its tip just behind the upper front teeth.   The upper jawbone is a framework of two paired (right and left) maxillary bones, and they expand by spreading apart, like unfolding a pair of wings, in two directions.

In one direction, the two maxillary bones spread away from each other by rotating outward and upward due to growth at the midpalatal suture, seen from left to right in the illustration below.  As biting forces drives these two maxillary bones upward, they also flatten the palate.  In our ancestors, very strong chewers always had very shallow wide palates.    

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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.

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However, this natural upper jawbone expansion depends on jaw muscle strength, and our jaw muscles have weakened by about half in the last couple of centuries due to our soft food diets.  As a result, many upper jawbones do not fully unfold and remain narrow. 

There are three causes of this failure of the upper jawbone to expand.  One cause is clearly weak chewing, because the same changes can be produced in monkeys raised on soft diets.  Another cause is a steeply interdigitated bite that locks the upper teeth to the lower teeth, which are planted in a jawbone that grows by translating rather than expanding.  The lower jawbone cannot be expanded, because it is one piece of cortical bone, and it responds to mechanical forces by bending.  Another cause is the vertical growth pattern which results from the lowered tongue posture, because it tightens the cheeks and thereby causes them to push inward on the sides of the upper jawbone.   This force is so significant that the upper jawbone can be expanded in people with long faces just by wearing an oral appliance (Frankel), which has lip bumpers that hold the lips and cheeks away from the teeth. 

When the upper jawbone cannot expand properly, the nasal airway is narrow; because the roof of the upper jawbone (the palate) is the floor of the nose. People with very narrow palates are usually obligate mouth breathers.  When their faces are at rest, their lips are slightly 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, because mouth breathing is easier.  

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; 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.  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 also sustains itself by the way it alters facial growth.  Mouth breathing lowers mandibular posture to create space for an oral airway passage, which 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, the mandible grows straight downward, resulting in a long narrow face.  In humans forced to mouth breathe by an insufficient nasal airway, the mandible grows by rotating down and back, resulting in a long, narrow, and retrusive face (recessed chin). 

TREATMENT 

Treatment that expands the upper jawbone also enlarges the nasal airway.  The necessary mechanics push the maxillary bones outward by pushing on the teeth, which can also displace those teeth to a degree that depends on the mechanics used. Bent wire appliances, such as quad helix appliances, bionators, Crozats, and ALF (advanced lightwire functional) appliances; employ a framework of wires and springs soldered to metal bands; and they can be relatively unobtrusive, so they are easily worn in adults; but they 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 incorporating TADs (temporary anchorage devices), which are tiny lag screws temporarily implanted in the palate, into palate expanders that must be glued in place to ensure that almost all of the movement occurs in the bones rather than the teeth.   

Although the palate expansion devices usually come with instructions to perform two turns weekly, the palate can be expanded most effectively by 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.  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 shift the palatal bones back to their pre-treatment positions every day.  

OUR PALATE EXPANSION APPLIANCES are traditional expansion screw appliances that we have redesigned for adults by using a thin metal expansion framework and avoiding bulk in the front of the palate where it could interferes with tongue posture and speech.   Whether finger springs or orthopedic inclines are added depends on patient needs.  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.  At the end of treatment, you'll need to wear a retainer at night on a long-term basis.  That retainer can have various orthopedic features, like a front flat bite plate, and also various orthodontic features, like minor tooth straightening with clear aligners.

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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.

RETENTION - After the expansion process, the palatal width needs to be maintained by wearing a removeable retainer every night and restoring a stable bite, which functions as an effective retainer during the day.   

GAPS BETWEEN TEETH - can result from palate widening. If the teeth were crowded before treatment due to insufficient space, simply straightening the teeth can close the gaps and align the teeth into a structural arch, which is incompressible and thereby helps retain the expansion.  In people with some 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.      

RESTORING A STABLE BITE - is important at the end of the active phase of treatment, because a stable bite acts like a daytime retainer.  Stabilizing the bite 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 can maintain bite stability.  However, if the 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 temporarily bonding composite resin into the deepest valleys can greatly facilitate treatment.

If flattening is not an option, the lower teeth may need to be uprighted to recreate a steep interdigitation. In most cases, the lower teeth were tipped inward to interdigitate with narrow upper teeth anyway.  The lower teeth 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.