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.
Figure 1: Space maintainers like this “lingual holding arch” prevent the permanent six-year molars (on which the bands are mounted) from moving forward in the mouth into the spaces created by the missing primary molars (see arrows). Forward drifting of the six-year molars can block the normal eruption pathway of the (permanent) bicuspid teeth.
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.
| 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. |
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