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A palatal expander is a device in the field of Orthodontics which is used to widen the upper jaw (maxilla) so that the bottom and upper teeth will fit together better. This is a common orthodontic procedure. Although the use of an expander is most common in children (8%-18%), it can be and has successfully been used in adults, although the effects of expansion are slightly more uncomfortable. Also, depending on the amount of correction and age of the patient, it may result in surgical separation of the maxilla. Use of a palatal expander is most often followed by braces to straighten out all the teeth.
Contents
- History
- Indications for a Palatal Expander
- Rapid Palatal Expansion
- Effects
- Slow Expansion
- Implant Supported Expansion
- Surgically Assisted Rapid Palatal Expansion SARPE
- Side Effects of a Palatal Expansion
- Amount of expansion
- References
It is believed that expansion therapy should be started in patients either before or during their peak growth spurt. For obtaining maximal skeletal changes, the therapy is initiated at a very early age. Expansion therapy performed after the peak growth spurt will lead to more dental changes than skeletal which leads to tipping of buccal teeth. There are different types of expansion techniques that can be used in patients such as Rapid maxillary expansion, slow maxillary expansion, implant-based maxillary expansion and SARPE.
History
Westcott first reported placing mechanical forces on maxilla in 1859. Emerson C. Angell was the person to publish a paper in 1860 in Dental Cosmos about palatal expansion. He placed a screw in a 14-year-old girl between the maxillary premolars for 2 weeks. When she came back, he noticed results of expansion in her upper arch. In 1877, Walter Coffin developed the Coffin Spring for the purpose of arch expansion. In 1889, J. H. McQyillen who was the President of the American Dental Association at that time, opposed Angell's idea about arch expansion. Goddard in 1890 and Landsberger in 1910 revisited the expansion. Goddard standardized the expansion protocol where he expanded twice a day for 3 weeks.
Andrew Haas reintroduced his expansion device to United States in 1956 called Haas Expander. He was also one of the first people to report lowering of mandible with bite opening and increase in nasal width and gain in arch perimeter. Robert M. Ricketts introduced the Quad Helix in 1975 which was a modification of the W Spring. Biederman introduced the tooth-borne Hyrax Expander in 1968. Cohen and Silverman were first ones to introduce the Bonded type of expander in 1973.
Indications for a Palatal Expander
Some most notable indications for the need of a palatal expander include:
- Posterior cross bite
- Crowding of the teeth
- Most cases of malocclusion
- Rhinologic and respiratory ailments
- Impacted maxillary canine
- Cleft lip
- Cleft palate
Rapid Palatal Expansion
Rapid palatal expansion (RPE) or Rapid Maxillary Expansion (RME) is an expansion technique where expansion of 0.5mm to 1mm is achieved everyday until the posterior crossbite is relieved.The expander works by turning a key inside the center of the expander. The turn of this key will push the arms of the expander.
For stability purposes, the RPE usually remain in the patient's mouth anywhere between 3–6 months, but this time may vary between patients. This is often known as "six month retention period" during which the bone fills the gap in the maxilla that was created by the expansion process. To prevent any type of relapose, a retainer is given to the patient to keep the teeth in proper alignment.
RPE can be tooth supported, bone supported or both tooth and bone supported.
Effects
The expansion process usually results in a large gap between the patient's 2 top front teeth, often known as Diastema. This gap is closed naturally and the teeth may overlap which leads to braces being needed. Some may develop a large space while others do not develop a space at all. It usually takes a week or two for one to adjust to eating and speaking after first receiving the rapid palatal expander. This process requires patients to turn the expansion screw themselves to tighten up the expander. For expansion that is not managed by the patient and on the lower jaw, a Bionator appliance may be a more suitable alternative
Although it may vary from person to person, most usually feel slight pressure on their teeth. It usually takes a week or two for one to adjust to eating and speaking after first receiving the rapid palatal expander. When the palatal expander is first removed, patients usually report that their mouth feels extremely big and spacious.
Slow Expansion
Slow expansion techniques expands maxilla at a much slower rate compare to the rapid maxillary expansion technique. In slow expansion technique, a patient is ordered to turn the screw 4 times which amounts of 1mm per week. Patient is instructed to turn the jackscrew at the same rate for next 8–10 weeks to achieve the desired expansion. This slow rate of expansion allows skeletal and dental changes to happen in a 1:1 ratio. This means that equal amount of dental and skeletal expansion is achieved, compared to RME technique where mostly skeletal expansion is achieved initially.
Slow expansion has also been advocated to be more physiologic to the tissues of the maxilla and it causes less pain. Some studies have reported that diastema in slow type of expansion also happens less due to the interdental fibers having chance to close the space as the maxilla is being expanded.
Implant-Supported Expansion
Implant supported expansion technique involves the forces being applied directly to the maxillary bone instead of the teeth. This technique involves placing anywhere from 2-4 mini-implants in the palatal vault area of maxilla to anchor the RME appliance to the screws. The patient is then asked to turn the jackscrew with the rapid approach over next two weeks. A disadvantage of this type of technique is their invasiveness and higher risks of infection.
Surgically Assisted Rapid Palatal Expansion (SARPE)
For more information, please see SARPE
Once a patient reaches maturity (puberty) the palate halves or the Intermaxillary suture fuses together into a single palate tissue. If the patient suffers with a constricted maxillary arch, a palatal expander would need to be used. However, with the matured palate, the palatal expander would need to be surgically inserted onto the mid-palatal suture. Typically, the patient would be under the care of an oral-maxiofacial surgeon and the surgical procedure would commence.
The mid-palatal suture is first cut open into two parts. The center of the midpalatal suture is then inserted into the open slit. Once fully inserted, the mid-palatal suture of the patient is then closed by the surgeon. The orthodontist will then finish the procedure by connecting the palatal expanders band rings to the patients maxillary molars.
Side-Effects of a Palatal Expansion
One of the limits of expansion is the Zygomatic buttress. It is known that this anatomical bony complex limits the maxillary expansion posteriorly. Maxillary expansion does tend to open up Circumaxillary sutures, Circumzygomatic sutures, intermaxillary sutures and midpalatal sutures. Expansion also tends to happen more anteriorly than posteriorly.
Amount of expansion
Each patient presents with different malocclusion and will need different amount of expansion. It is a general rule to expand the maxilla to a point where the lingual cusp of maxillary molar teeth touch the buccal cusp of mandibular molar teeth. Studies done decades ago by Kerbs (1964), Stockfisch (1969) and Linder Aronson (1979) showed that about one-third to one-half of the expansion was lost before the expansion was eventually stabilized.