September 10, 2019
by David R. Farkouh, BSc, DMD, MSc, FRCDC
Primary teeth have many important roles in the health and development of our young patients. Primary teeth are vital to chewing, speaking, smiling, aesthetics and holding space in the jaws for the developing permanent teeth.1 In some cases when a primary tooth is lost due to trauma, infection or early exfoliation, a malocclusion can result due to the unfavourable movement of adjacent teeth. The use of space maintainers can be utilized to prevent the unwanted movement of teeth that create malocclusions and to allow the appropriate space for the succedaneous tooth to erupt.2
In my interactions with dentists and dental students, space maintainers always seem to be a topic that creates confusion and discomfort. The circumstances in which a space maintainer is required, and how to effectively design the appliance to prevent the creation of a malocclusion seem to be the two most common concerns. The purpose of this article is to guide clinicians in the treatment planning process and to help demystify the topic.
Missing primary incisor(s)
The teeth that are most commonly lost due to trauma in the primary dentition are the maxillary incisors. Young children with oral habits including pacifier use and thumb sucking can create an excessive overjet that make them susceptible to dental trauma. Once the primary canines have erupted, no space loss occurs in the primary incisor area. NO SPACE MAINTAINER is required for the loss of primary incisors.
Missing primary first molar(s)
When the primary first molar (D) is lost prematurely, space maintenance may or may not be required. In determining the need for space loss for a lost D, it is important to identify whether the permanent first molar and the permanent lateral incisor have erupted. If these teeth have not yet erupted in the quadrant of concern, then space maintenance is required. The space maintainer of choice for this scenario is the Band and Loop space maintainer (Fig. 1). Space loss is possible in the area of a lost first primary molar area when the first permanent molar and lateral incisor in the involved quadrant have not yet erupted. Eruption of the first permanent molar6 will move the adjacent second primary molar (E) mesially into the space if a space maintainer is not in place. Similarly, if a space maintainer is not in place prior to the eruption of the permanent lateral incisor in the involved quadrant, there is the potential for the primary canine to be forced distally with the eruption of the permanent lateral incisor. This would result in space loss. If both the permanent first molar and lateral incisor in the involved quadrant have erupted, then a space maintainer is not required for the loss of the first primary molar.
A Band and Loop space maintainer for missing 85 with a band on tooth #46 and the loop in contact with the distal aspect of tooth #84.
Missing primary second molar(s)
In cases where a second primary molar is lost, space maintenance is crucial to prevent malocclusion. The second primary molar serves to prevent the adjacent first permanent molar from drifting mesially. Therefore, the general rule with regards to losing a primary second molar prematurely is that a SPACE MAINTAINER IS ALWAYS REQUIRED. If the first permanent molar has already erupted prior to the loss of the second primary molar than a Band and Loop space maintainer placed on the 6 is the appliance of choice. The dentist is presented with a different challenge when the second primary molar is lost prior to the eruption of the adjacent first permanent molar.
In these cases, some space loss should be expected however preventing as much mesial movement of the permanent first molar is the key. If the permanent molar is partially erupted and the mesial surface of the tooth is exposed in the arch, then a Band and Loop space maintainer can be placed on the first primary molar with the loop directed distally to passively contact the mesial surface of the erupting first permanent molar.
In cases where the first permanent molar is completely unerupted, a distal shoe space maintainer can be used to prevent mesial movement of the 6. This appliance is designed with a band on the D and a loop with a distal shoe placed subgingival to contact the mesial surface of the unerupted first permanent molar. Due to its complexity and invasive nature, this modality is not commonly utilized. Many clinicians choose to wait until the first permanent molar is fully erupted to place a Band and Loop on the tooth, to prevent further space loss while keeping in mind that distalization of the tooth orthodontically will most likely be required in the future. A common example where this treatment is pertinent is in the case of second primary molar loss secondary to the ectopic eruption of the adjacent first permanent molar (Fig. 2).
Tooth #26 is ectopically erupting such that it is causing external resorption of the distal aspect of tooth #65.
Missing multiple primary molars
In situations where both primary molars in a quadrant are lost, it is important to consider a bilateral space maintainer. If the first permanent molar has not yet erupted and the primary molars in that quadrant are both lost, then the dentist has no choice but to wait until the first molar erupts to initiate space maintenance. However, if the first permanent molars are present both in that quadrant and in the adjacent quadrant in the same arch, then a bilateral space maintainer should be considered. A Band and Loop space maintainer is not used in these situations because the loop would span too large of a space to be stable.
In the maxillary arch a Transpalatal Arch Appliance (Fig. 3) or a Nance Appliance (Fig. 4) are appropriate bilateral space maintainers. These appliances work by anchoring the first permanent molars on each side of the arch to prevent them from moving mesially. These appliances also prevent tipping and rotation movements of the first permanent molars.3 The Nance Appliance uses a pad of acrylic in contact with the anterior palate to help prevent mesialization of the first permanent molars.3 Two negative characteristics of this appliance include irritation of the mucosa underneath the acrylic pad, due to it being hard to clean for the patient, and its potential interference with speech. It is important to note that these appliances are also appropriate in cases where both primary molars are lost bilaterally in the maxillary arch (i.e. teeth 54, 55, 64 and 65 are missing).
An example of a Transpalatal Arch Appliance with band on teeth #16 and #26.
An example of a Nance Appliance with bands on teeth #16 and #26 and an acrylic pad in contact with the anterior palate.
In the mandibular arch the appliance of choice is the Lower Lingual Holding Arch (Fig. 5). This appliance is designed such that there are bands placed on teeth #36 and #46, attached by a wire that sits on the lingual aspects of the mandibular teeth. These can be designed with either a removable or soldered lingual wire. Ideally a Lower Lingual holding Arch is placed once the permanent mandibular incisors have erupted. However, they can be placed before the incisors have erupted. In these circumstances, the incisors have the potential to erupt lingual to the wire and therefore the wire would have to be bent to accommodate the incisors. Once a Lower Lingual Holding Arch has been placed it will maintain the arch length in the mandible.
An example of a Lower Lingual Holding Arch with bands on teeth #36 and #46.
When considering a space maintainer for a lost or soon to be extracted primary tooth, it is important to have a radiograph of the area to determine the location of the succedaneous tooth. If the tooth is about to erupt, then space maintenance is not warranted. If the succedaneous tooth is congenitally missing, then space maintenance may or may not be indicated and a referral to an orthodontist should be considered.
To ensure that a space maintainer will fit properly, it is important to fit bands on the teeth that will be holding the appliance in place. By fitting bands on to the molars prior to taking an impression, the dentist ensures that the fit will be exact.
Alternatively, a good lab technician can fit bands on the teeth from a good impression. A simple alginate impression can be used to take an accurate record of the patient’s arch. In the case of a Band and Loop space maintainer, a sectional arch alginate impression can be taken. Conversely, if a bilateral appliance is being fabricated then a full arch impression is required. Keeping the impression moist and pouring it up as soon as possible will help minimize the impression material from warping and resulting in an ill-fitting appliance. In addition, the impression should be taken prior to the tooth being extracted when possible. If tooth loss occurs prior to the fabrication of a space maintainer then the appliance should be placed as soon as possible.
Space maintainers are a fundamental tool in preventing space loss and in some cases preventing future orthodontic treatment. Choosing the correct space maintainer appliance for each patient’s needs will lead to good results and happy patients. If a dentist is ever unsure of the need for space maintenance or is uncomfortable with placing one, then a referral to an orthodontist or pediatric dentist is warranted.
About the Author
Dr. David R. Farkouh is a staff pediatric dentist in the Department of Dentistry at The Hospital for Sick Children in Toronto, Canada. Dr. Farkouh also maintains a private practice specializing in pediatric dentistry in Toronto, Canada. Dr. Farkouh is the pediatric editor of Oral Health.
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