Space Maintenance in the Primary Dentition
Management of premature tooth loss in the primary dentition requires careful thought by the clinician, because the consequences of proper or improper space maintenance may influence dental development well into adolescence.1 Early loss of primary teeth may compromise the eruption of succedaneous teeth if there is a reduction in the arch length. On the other hand, timely intervention may save space for the eruption of the permanent dentition. The key to space maintenance in the primary dentition is in knowing which problems to treat.2
Premature tooth loss in this age group is best thought of in terms of anterior (incisors and canines) and posterior (molars) teeth. The causes and treatment of missing teeth differ in these two regions. Anterior tooth loss is due primarily to trauma and tooth decay. Injuries to the primary incisors are common because a child of this age is learning to walk. Although the prevalence of dental decay appears to be declining, a small number of children still suffer from early childhood caries and rampant decay and experience most of the dental disease.3 These decay patterns result in tooth loss in both the anterior and posterior regions. The majority of posterior tooth loss is due to dental caries; rarely are primary molars lost to trauma. If no space loss has occurred immediately after tooth loss, space maintenance is appropriate because the permanent successor will not erupt for several years. If space loss has occurred, a comprehensive evaluation is required to determine whether space regaining or no treatment is indicated. This type of evaluation and decision-making is described in the discussions of the mixed dentition (Chapters 30 and 35) because most attempts at regaining space are made at that time.
Missing primary incisors are usually replaced for four reasons: space maintenance, function, speech, and aesthetics. This reasoning requires examination. Some dentists think that early removal of a primary incisor results in space loss because the adjacent teeth drift into the space formerly occupied by the lost incisor. However, this does not seem to be true in most clinical situations. There may be some redistribution of space between the remaining incisors, but there is no net loss of space. Intuitively, this makes sense because there is no apparent movement or drifting of teeth when developmental spacing is present in the primary dentition.
Poor masticatory function has also been proposed as a reason for replacing missing primary incisors. Concerns have been expressed about a child’s ability to eat after four maxillary incisors have been removed as a result of early childhood caries. Feeding is not a problem, and when given a proper diet, the child continues to grow normally.
Some investigators have cited slowed or altered speech development as a justification for replacing missing maxillary incisors. This may be valid if the child has lost a number of teeth very early and is just beginning to develop speech. Many sounds are made with the tongue touching the lingual side of the maxillary incisors, and inappropriate speech compensations may develop if these teeth are missing. However, if the child has already acquired speech skills, the loss of an incisor is not particularly important.4
Probably the most valid reason for replacing missing incisors is aesthetics. Aesthetic concerns are voiced by some parents but not by others. If parents do not indicate a desire to replace missing anterior teeth, certainly no treatment is appropriate. If the parents do wish to replace the missing teeth, either a fixed lingual arch or a removable partial denture with attached primary teeth can serve as a prosthetic replacement (Figure 25-1). The dentist should present both alternatives and let the parents make an educated decision.
FIGURE 25-1 A fixed (as shown here) or removable partial denture can be used to replace missing anterior teeth in the primary dentition. In most cases the partial denture is placed for aesthetic reasons rather than to prevent space loss in the anterior dental arch.
Loss of a primary canine as a result of either trauma or decay is rare. Because it is so rare, there is some debate about whether space loss will occur if the tooth is not replaced. From a conservative point of view, a band-and-loop space maintainer (see later discussion in this chapter) or a removable partial denture may be placed if the patient is cooperative. Either of these appliances will have to be remade when the permanent lateral incisor erupts because the permanent lateral incisor will require more space than the primary lateral incisor and will interfere with space maintenance. If a space maintainer is not placed in the maxilla, a midline shift to the affected side should be anticipated when the permanent incisors erupt. In the mandible, lingual movement of the incisors and movement of the midline to the affected side may occur. A lingual arch may be appropriate after the permanent incisors erupt to stabilize the midline shift.
Therefore space maintenance during the primary dentition years is aimed primarily at the replacement of primary molars. Loss of interproximal contact as a result of decay, extraction, or ankylosis of an adjacent tooth results in space loss because of mesial and occlusal drift of the tooth distal to the newly created space. There is also evidence that the tooth mesial to the affected molar will drift distally into the space.5,6 Thus loss of space or arch length can occur from both directions (Figure 25-2).
FIGURE 25-2 Premature loss of the primary first molar results in loss of space from both directions. The primary mandibular second molar drifts mesially, and the primary canine drifts distally, but predominantly there is movement from the anterior in the posterior direction for the mandibular arch. A, Arch perimeter has been lost on both sides. B, Panoramic radiograph shows the canine and two premolars attempting to erupt into the limited space on the patient’s right. The left mandibular second premolar is missing.
Space maintenance begins with good restorative dentistry. The dentist should strive for ideal restoration of all interproximal contours. Early restoration of interproximal caries ensures that no space loss occurs. In some instances, however, large carious lesions may make ideal restoration of the tooth impossible, and space loss is inevitable. Even if the pulpal tissues have been compromised, pulp therapy should be initiated and the tooth maintained, if at all possible, because the natural tooth is still superior to the best space maintainer available; it is functional, the correct size, and exfoliates appropriately. In cases of ankylosis, the tooth should be maintained until space loss is imminent; it is then extracted and the space maintained. Ankylosed teeth usually show limited vertical change in the primary dentition years.