Palate Expansion

Many modern people have narrow palates, because a strained facial growth pattern has prevented good natural palate expansion. Palates can be expanded, but extensive misinformation about palate expansion has created controversy that has made it difficult for people to understand how it works and when it should be used.

For decades, most dentists believed that palate expansion occurs by separation of the two maxillary bones at their midline suture, and therefore it must stop when that suture ossifies in the late teenage years. Now we know that palates can be expanded in adults by wearing removeable oral appliances that apply light steady forces, which spreads the maxillary bones like unfolding a pair of wings and lowers the suture connecting them, accommodated by remodeling of the midline suture and at the surrounding circum-maxillary sutures. The expansion requires 3-6 months, and it is then maintained by a stable natural bite and nightly wear of a retainer with a raised bite table that employs nocturnal bruxism to broadly load the expanded structure.

NATURAL PALATE EXPANSION - The upper jawbone is a framework of two paired (right and left) maxillary bones which form a structure that expands in response to chewing forces.

In children, the maxillary bones spread apart at their connecting midline suture in two directions. In one direction, the two maxillary bones rotate outward and upward around the mid-palatal suture while lowering that suture and thereby flattening the palate, as seen below. In our ancestors, very strong chewers always had very shallow wide palates.    

In another direction, the two maxillary bones swing out around their connection at the front of the suture, which flattens the midface, as can be seen below. In our ancestors, very strong chewers also had very wide flat faces.  

In adults, jawbone growth slows down about 90%, but then continues slowly. The midline suture stops opening, but it continues remodeling, like all cranial sutures. The palate continues expanding bery slowly by a gradual unfolding, like spreading a pair of bird wings; which lowers the midline suture and is accommodated by remodeling of the midline suture and the surrounding circum-maxillary sutures, which never close.

However, this natural upper jawbone expansion depends on bite forces, which have diminished by about half in the last few centuries. As a result, many modern upper jawbones do not grow wide enough to fit around the tongue. Similar narrow upper jawbones can be produced in animals by just softening their diets.

Also contributing to the narrowness of our upper jawbones is the vertical facial growth that results from weak jaw muscles. Lengthening the front of face tightens the cheeks, which 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 together the jawbones. The upper jawbone can be locked by the bite to a lower jawbone that is composed of one thick piece of cortical bone, which cannot expand, because it grows by being pushed forward from behind. 

EFFECTS ON THE NASAL AIRWAY - When the upper jawbone is narrow, the nasal airway just above it is also 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; due to restriction in the upper premolar area, just beneath the front of the nasal cavity, where airway flow is usually restricted in mouth breathers. 

The narrow nasal airway causes mouth breathing. People with very narrow palates are usually obligate mouth breathers. They have to keep their lips slightly parted to allow an oral airway, because there is not enough room for airway passage through the nose. People with slightly narrow palates usually 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. Habitual mouth breathing can be treated by anything that keeps the mouth closed, including orthodoontic elastics, cervical collars, and mouth taping.

Mouth breathing is a significant health problem. 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 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. Wearing nose clips lowers arterial oxygen levels. Mouth breathing increases airway resistance and decreases sleep quality.

Mouth breathing can sustain 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, making it grow long instead of wide. Monkeys forced to mouth breathe grow long narrow faces. In humans, the mandible is much shorter, so the mouth breathing which lowers the mandible also rotates it backward; - resulting in long, narrow, and retrusive facial growth that pushes the mandible and tongue back toward the cervical spine. 

EFFECTS ON TONGUE POSTURE - When the tongue cannot fit up in the front of the palate, it must find another place to rest. It may reposition down and back into the pharynx, leading to sleep apnea; it may position between the posterior teeth to form a cushion, resulting in a scalloped tongue; or it may reposition down and forward between the front teeth, leading to an anterior open bite. Also, when the palate is too narrow for the tongue, the suction that normally holds the tongue up against the palate during sleep is interrupted, allowing the tongue to drop down and back more easily. 

ORTHOPEDIC PALATE EXPANSION - can spread the maxillary bones and enlarge the nasal cavity by wearing a removeable oral appliance that delivers light steady mechanical forces transversely across the palate most of the time (not just at night) for 3 to 6 months. Because it works by pushing on the teeth, it also tips those teeth to an extent that depends on the mechanics used to provide the expansion 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, or miniplate assisted rapid maxillary expansion (MARPE), 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. A MARPE appliance is shown below.

Palate expansion may 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. Combining expansive forces above and below the palate seems like 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 minimal 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 the interdigitation of upper and lower teeth will return the palatal bones to their pre-treatment positions every day.   

RETENTION - After the expansion, it needs to be stabilized by widely 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 include orthopedic features such as a front flat bite plate for those who had a deep overbite before treatment, springs to continue moving individual teeth, or inclines that promote mandibular advancement.

RESTABILIZING THE BITE - The expansion process always destabilizes the bite to some extent. The bite may then restabilize naturally, especially if combined with mandibular advancement, which brings a wider part of the lower dental arch underneath the widened portion of the upper dental arch. However, if the upper and lower teeth are steeply interdigitated, any change in their relative positions can cause uncomfortable collisions between teeth, and adjusting the bite may be necessary to facilitate post-treatment stabilization.   

If necessary, the lower teeth can be uprighted during palate expansion by including 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 orthodontic elastics attached to tiny buttons glued to the sides of the involved teeth to pull 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 realign the teeth into a complete arch, which is incompressible and thereby functions as a good retainer. If some front teeth are unusually narrow, the gaps can be closed by widening those teeth using veneers or crowns. 

COMBINING PALATE EXPANSION WITH A SLEEP APNEA APPLIANCE - When a patient has both a narrow palate and obstructive sleep apnea, we can combine treatment mandibular advancement and palate expansion by using a 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, depending on the need for springs and other mechanisms for also straightening teeth. If more widening is needed, a second stage of expansion can be made for about half that fee. Springs can be added for straightening teeth for a small additional cost.