What are Space Maintainers?
Space maintainers are recommended when baby molar teeth are missing or are lost prematurely, for example if the patient has large, unfixable cavities. The goal of space maintainers is to prevent movement of the adjacent permanent first molars (six-year molars), and loss of space for adult (permanent) bicuspids and canines. If the permanent first molars are not held in their proper position, they can drift forward and prevent the bicuspid teeth from being able to move into the mouth on their normal path. The first bicuspids can also move forward and block the normal pathway of movement of the permanent canines into the mouth. It is not necessary to place a space maintainer if any of the front (anterior) six primary teeth in either jaw is lost prematurely.
A congenital disorder known as hypohydrotic ectodermal dysplasia is accompanied by the absence of several teeth, including permanent teeth. Hypodontia is the dental term for congenitally missing teeth. If all the teeth are missing, the term is anodontia.
When a back baby (primary) teeth is lost prematurely or is congenitally missing, there is a risk of the permanent six-year molars drifting forward in the mouth and blocking the eruption pathway of the permanent bicuspid teeth. The first bicuspids can also move forward and block the eruption pathway of the permanent canine teeth.
Space maintainers are prescribed to hold the six-year molars in their normal position, as well as to preserve the normal eruption pathway of the bicuspids and permanent canines.
The use of removable dentures as space maintainers is less common in children, but may be prescribed if several teeth are missing and the child’s appearance is affected.
Fixed space maintainers are the most common type of space maintainer. The term “fixed” means the device is adhered with dental cement and is not meant to be removable by the patient. This makes them more reliable at effectively achieving their goal. It also means they must be removed by the dentist at some point.
Types of Fixed Space Maintainers
The type of fixed space maintainer your dentist recommends is based on the number of missing teeth and their location in the mouth. The most common types of fixed space maintainers are described below.
TransPalatal Arch (TPA) appliance
This is a type of fixed space maintainer used in the upper jaw when primary molar teeth have been lost prematurely on both sides of the dental arch. TPA appliances are formed from two metal bands joined across the palate with a rigid wire, which is soldered to the bands. Making the device involves fitting the metal bands onto the child’s abutment teeth and making an impression (mold). The bands remain in the impression, which is then filled with dental plaster to produce a cast. The TPA device is made in a laboratory, on the casts of the child’s teeth.
When cemented onto the abutment teeth, TPA appliances can be effective at preventing forward movement of those teeth; however they do not always prevent forward tipping of the abutment teeth, and space can still be lost as a result. This is especially true if the child habitually uses their tongue, a finger, or thumb to place pressure on the TPA wire. Sometimes a small button will be attached to the center wire of the TPA appliance, which rests on the child’s palate to prevent tipping of the abutment teeth to which the device is cemented. The device is then called a Nance appliance.
TPA appliances are typically left in place until permanent teeth move in to the spaces created by the missing teeth.
Distal shoe space maintainers
This type of space maintainer is used when the patient is too young for six-year molars to be present in the mouth yet. A distal shoe is placed on a baby molar, and has a projection that extends through the gums to the front surface of the un-erupted six-year molar, correctly guiding its eruption pathway into the mouth.
Band and loop space maintainers
This type of device is used when one or more baby molars are lost from only one side of the dental arch, and the six-year molar is present behind them. They feature a metal band around the six-year molar, with a wire arm soldered to it that rests against the back surface of the next remaining tooth forward.
Lingual holding arch
This type of space maintainer is used when one or more baby molars are lost from both sides of the dental arch, and the six-year molars are present behind them. They feature metal bands around the six-year molars, with a wire bent in the shape of the dental arch soldered to the bands and resting on the tongue-side surfaces of the patient’s front teeth.
Other types of space maintainers exist and are commonly used, but are generally variations on these basic themes.
The process of creating and placing space maintainers
If the primary molar tooth or teeth is/are already missing, and no loss of space has occurred, stainless steel bands are fit onto the six-year molar(s) that will anchor the space maintainer.
An impression of the dental arch are made with the band(s) in place on the tooth.
The band(s) are removed from the teeth and placed in the impression, and a stone cast of the teeth will be poured into the impression.
When the stone cast hardens, a wire or wires are positioned onto the casts in such a way that they can prevent the molar(s) from moving. Once in place, the wires are soldered to the bands.
The solder joint(s) are smoothed and polished.
The space maintainer is carefully removed from the stone cast and disinfected.
A second appointment is needed to cement the space maintainer onto the anchoring tooth or teeth.
Some advantages and benefits of Space Maintainers
Some advantages and benefits of space maintainers include:
Space maintainers prevent undesirable movement of the permanent molar and bicuspid teeth.
Space maintainers preserve space in the dental arch for the bicuspid and permanent canine teeth to move into.
Space maintainers preserve the shape of the arc along which the teeth are positioned in the jaw (dental arch).
|Relative cost of procedure ($ – $$$$$)||$$-$$$ (Depends on type of space maintainer.)|
|Time commitment (average)||1 to 2 visits; 1 hour for extraction plus placement of directly fabricated device (rarely used) + 0 to 30 minutes to place lab-made device.|
|Temporary discomfort potential||Low (device itself)|
|Cosmetic results (how it looks)||Generally not a factor|
|Wear properties||Generally not a factor|
|Irreversible pulpitis/infection potential||Low|
|Fracture resistance||Not applicable|
|Tooth reduction (amount required)||None|
|Corrosion, metal sensitivity/allergy potential||Low. Some possibility for minor galvanic corrosion if placed on a tooth with a silver filling. Generally not a factor.|
|Soft tissue irritation potential||Above average if difficult to clean around.|
Potential disadvantages and risks of Space Maintainers
Some disadvantages and risks of space maintainers include:
It may be difficult for the patient to clean the teeth and gums around space maintainers.
If the patient’s oral hygiene is not good, the gums may become inflamed around the space maintainer. In some cases, the gums may grow around the space maintainer, requiring surgical removal (usually a minor procedure).
Patients can develop tooth decay (caries) if plaque is not effectively removed from around the device.
In general, a space maintainer will need to be removed by a dentist at a later date
A space maintainer may loosen or break.
Young patients may have difficulty cooperating with the impressions and cementation procedures necessary to correctly place a space maintainer.
Sedation may be recommended if the patient is especially young, or has special needs. Sedation of children has its own risks which should be fully understood and carefully considered before undergoing treatment. It may be that “crooked teeth”, poor dental arch form, malocclusion, or any other complications that may result from the premature loss of primary molar teeth can more safely be addressed when the patient becomes older.
Frequent monitoring and adjustment of certain types of space maintainers (like the distal shoe type) may be recommended to be sure the device itself is not preventing normal movement of the permanent six-year molar(s) into the mouth.
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