Space Invaders by Dr. Jarod Johnson

Space maintenance is a critical, often misunderstood segment of pediatric dentistry. With the prevalence of dental caries estimated to be 42 percent in primary teeth, we can expect to encounter tooth loss and the subsequent need for space maintenance in our practices.1 Space maintenance is important to consider when premature loss of a primary tooth could affect the available space for developing permanent teeth. Figs. 1-3 (above) show sequelae of the early loss of primary molars.

There are multiple situations in which clinicians must consider the use of space maintenance and select appropriate appliances. This article will review the types of space maintainers available, as well as the materials and techniques used to achieve successful outcomes in the primary and mixed dentitions.

The basics
When evaluating patients for space maintenance, it’s important to consider each child’s growth and development. It’s widely accepted that most space loss occurs within the first six months of tooth loss. In addition to determining if a space maintainer is indicated because of tooth position in the arch, eruption timing is important to consider. As a general rule, loss of a primary tooth before age 7 will delay the eruption of the permanent successor, because bone will fill in over the erupting tooth. Early loss after age 7 tends to speed up the eruption of the succedaneous tooth, especially in cases where bone is less dense because of apical pathology associated with the lost tooth. Generally, expect a tooth to take six months to move through each millimeter of bone as detected by a bitewing radiograph.2,3

Incisors: Primary incisors lost because of trauma or caries do not require space maintenance after the eruption of the primary canines. Replacement for aesthetics is the strongest indication for an appliance; language development and nutrition remain controversial.2

Canines: Unilateral loss of a canine can give rise to a midline shift, so it’s advisable to extract the contralateral canine to prevent this from occurring. Some clinicians will also choose to place a lower lingual holding arch in the mandible to prevent “dumping” of the mandibular incisors.2,3,4

Primary first molars: Loss of a primary first molar before the eruption of the first permanent molars is an indication for space maintenance.2,3 Loss of a primary first molar after the eruption of the permanent molar (given that two teeth posterior to the space loss are in occlusion) will result in approximately 1-1.5mm of space loss. It can be argued that this amount of space loss is clinically insignificant.5 In cases where minimal crowding is present, there is a benefit to holding the leeway space.

Primary second molars: The primary second molar is a key tooth in the development of the dental arch. Loss before the eruption of the permanent first molar will result in significant space loss; in these cases, a distal shoe is the appliance of choice to prevent mesial migration of the permanent molar and subsequent impaction of the second premolar.2,3 Loss of a primary second molar after the eruption of a permanent molar can be treated with a nance or band and loop in the maxilla; a band and loop, if the four lower incisors are not present (Figs. 4 and 5); or a lower lingual holding arch in the mandible.4

Direct space maintainers (prefabricated): Chairside space maintainers can be used for cases where space maintenance is indicated because of one missing tooth. They’re commonly utilized as the band and loop, distal shoe, and reverse band and loop appliance. Their use allows appliances to be cemented on the same day that the extraction occurs without any previous impression. However, they can be prone to more problems than lab-fabricated space maintainers. Figs. ?6a–b show the apical movement of a band resulting in tissue irritation.

After removal of the tooth:

1. Select a band from the kit ligate with floss, and try the band onto a tooth. Try different bands on the tooth until a fit is adequate (Figs.?7 and 8).
2. Select the desired attachment for the band (Fig. 9).
3. Trim the attachment with a wire cutter.
4. Insert the attachment into the band (Fig. 10).
5. Adjust the appliance intraorally, remove, and secure the attachment into place using the instrument (Fig. 11).
6. Dry the teeth, then cement the band using luting cement (Fig. 12).
7. Remove excess cement.

Indirect space maintainers (lab-

fabricated): Lab-fabricated space maintainers have higher durability and better adaptation, and can be used in more situations than prefabricated appliances. They can be designed as band and loop, reverse band and loop, distal shoe, lower lingual holding arch, nance, transpalatal arch and removable appliances. One disadvantage is they require two visits—the first to obtain an impression, and a subsequent delivery visit.

Removable appliances: Removable appliances can be used to replace missing teeth. One advantage is that the removable appliance can prevent supraeruption of opposing teeth and restore function.2 The appliance is prone to being lost, and must be worn to be effective. Removable appliances should be considered in special circumstances, or at times when a fixed appliance cannot be made (i.e., band and loop spanning more than two teeth). Figs. 13–15 show the use of a removable appliance. A removable space maintainer on the mandibular arch was used to prevent mesial migration of #19, which was close to eruption and could be palpated under tissue. A lower lingual holding arch was placed after #19 was able to be banded, and the removable appliance discarded. Removable appliances require motivated patients and families.

Impression materials
Alginate: A commonly used impression material for space maintainers, alginate is an irreversible hydrocolloid that will obtain adequate detail for the purposes of fabrication of space maintainers. When working with children it’s advantageous to use a fast-setting material that has a working time of between 1 minute and 15 seconds to 2 minutes, instead of a regular-setting material with a working time of between 3 and 4½ minutes.4 This will allow the child to be more comfortable during the time required for the impression.

Compound: Compound (Fig. 16)—one of the oldest impression materials in dentistry—has been used primarily for edentulous impressions, but can also be used for capturing impressions for space maintenance. It’s made of rosin, copal resin, carnauba wax, stearic acid and talc.6 Compound can be heated by flame or a hot water bath, then inserted into the mouth to set and capture an impression. The lower setting time can be advantageous when treating patients who are uncooperative, pre-cooperative or have gag reflexes. Special consideration must be given to loose teeth and existing appliances; compound will set beneath undercuts and could cause iatrogenic damage.

• Water can be heated by a hot water bath or an electric kettle (Fig. 17)
• If an electric kettle is used, place a paper towel in an alginate bowl to protect the bowl (Fig. 18).
• Heat the compound in a water bath or alginate bowl (Fig. 19).
• After heating, compound is adapted to an appropriate tray, and then reheated (Fig. 20).
• The tray is ready for insertion into the mouth (Fig. 21). Temperature should be evaluated to ensure that the patient is not burned.
• The impression is then poured in stone. After the stone sets, the cast can be heated with warm water to soften the compound and allow for the release of the impression.

Care should be taken to keep the compound/tray interface from heating such that compound does not remain on the impression, and adequate timing should be given such that the compound does not break teeth off the cast.

Vinyl polysiloxane (VPS): VPS comes in a variety of viscosities and has a higher range setting time (3–8 minutes) than alginate and compound impression materials.6 VPS is also more expensive, and generally is not necessary to obtain an impression for a space maintainer; alginate is adequate for most situations. One scenario where VPS may be advantageous as an impression material is when performing treatment under general anesthesia. Using a putty form such as Exaflex can allow for a detailed impression that can be poured multiple times. This can help safeguard against a broken or lost dental cast.

Fig. 22, p. 73, shows the above-mentioned impression materials.

Impression technique
There are various ways of sending impressions to the lab, which may request the impression in different ways. It may want an impression accompanied by the loose bands that were fit to the teeth, or the bands poured up in the cast. A lab can also fit bands to a cast if they’re not fit clinically. It is best to contact the laboratory to determine the preferred method for sending casts.

Separators can be utilized to create space to fit bands. Fig. 23 on p. 73 shows a separator is in place between the left permanent first molar and left primary second molar. The right side has space interproximal because the separator was removed. It’s recommended that radiopaque separators are used; they can be placed using floss before the appointment. After two days, space should be sufficient to create adequate room to fit bands. The separator should be removed, bands ligated with floss and fit determined (Figs. 24 and 25). Bands should be fit to the abutment teeth and adjusted using a band pusher to fill in the remaining space (Figs. 26 and 27). If bands are to be poured into cast, they should remain on the teeth during the impression process. If bands are to be sent along with the cast, they should be removed before the impression. Separators should be replaced if used until the appliance is delivered.

Bands that are to be poured in the cast can be secured with staples, superglue or wax (Figs. 28 and 29). If one can place staples in the mesiodistal dimension, they will be less likely to interfere with soldering. Staples in the buccolingual direction can be cut with wire cutters after the cast is poured. Superglue should be placed after the alginate is dried on the mesial and distal of the band, using caution to avoid placing glue on the intaglio surface of the band. After the impression is poured, staples can be cut, the cast trimmed and stone removed from around the bands (Figs 30 and 31).

Postoperative instructions
After delivery, it’s important to advise parents that space maintainers also need proper upkeep. Appliance care at home will increase the longevity of the appliance and ensure that fewer dental urgencies occur. It’s good to review the post-cementation instructions below with parents. Appliances can be evaluated at recall appointments or even monthly, if patients with an appliance have an account balance that is due.

• Avoid chewy, sticky, crunchy foods. Chewy and sticky foods can dislodge appliances, and crunchy foods can get wedged underneath and cause irritation.
• Don’t let children play with the appliance with their hands or tongues. If the appliance gets bent or damaged, it may need to be replaced.
• If the appliance is loose and can be removed from the mouth, remove it. If the appliance cannot be removed (if it’s attached to another tooth), push the appliance back on the tooth and do not let the child bite on it, which could cause damage. In both situations, call our office as soon as possible.
• Children may experience discomfort for a day or two after an appliance is placed. Over-the-counter analgesics such as acetaminophen or ibuprofen can be beneficial during this period.
• Transient changes in speech may be noticed with some appliances. Children will adapt to the appliance, and no lasting impact on speech has been found to occur.
• Keep the child’s appliance clean by continuing normal oral hygiene practices. If the child is experiencing significant discomfort in the area of the appliance, contact our office.
• Continue making regular dental visits so the appliance can be verified for fit, and removed at the proper time.

Conclusion
It’s my opinion that the best space maintainer is the natural tooth. In many situations, it would be advisable to maintain the primary tooth pulpal therapy (pulpectomy or pulpotomy), to allow for growth and development to occur so a space maintainer can be avoided. Studies have shown that space maintainers fail 57.5–63 percent of the time, most commonly from cement loss or solder breakage.7, 8 While space maintenance can’t always be avoided, it’s important to remember that extractions are the only “permanent” procedure we do in dentistry.

1. National Institute of Dental and Craniofacial Research. Dental Caries (Tooth Decay) in Children (Age 2 to 11). NIH. May 28, 2014. Available at: http://www.nidcr.nih.gov/DataStatistics/FindDataByTopic/DentalCaries/DentalCariesChildren2to11.htm. Accessed October 18, 2016.
2. Casamassimo, Fields, McTigue, Nowak. Pediatric Dentistry: Infancy Through Adolescence. St Louis: Elsevier Saunders; 2013.
3. Dean J, Avery D, McDonald R. Dentistry for the Child and Adolescent. 9th ed. St Louis: Mosby; 2011.
4. American Academy of Pediatric Dentistry. The Handbook of Pediatric Dentistry. 4th ed. Chicago: American Academy of Pediatric Dentistry; 2011.
5. Tunison W, Flores-Mir C, ElBadrawy H, Nassar U, El-Bialy T. Dental Arch Space Changes Following Premature Loss Of Primary First Molars: A Systematic Review. Pediatric Dentistry. 2008;30(4):297-302.
6. Powers J, Sakaguchi R. Craig’s Restorative Dental Materials. 12th ed. St Louis: Mosby Elsevier; 2006.
7. Sasa I, Hasan A, Qudimat M. Longevity of band and loop space maintainers using glass ionomer cement: a prospective study. Eur Arch Paediatr Dent. Jan 2009;10(1):6-10.
8. Qudeimat M, Fayle S. The longevity of space maintainers: a retrospective study. Pediatr Dent. 1998;20:267-272.