Chapter 15

Results of Premature Loss of Deciduous Teeth

Deciduous teeth may be lost prematurely by trauma, premature resorption of their roots, decay, or by extraction. One of the most feared effects of premature loss is the migration of neighboring teeth into the space created. The successor of a prematurely lost tooth may find its space in the dental arch reduced or even fully lost. Although substantial loss of space in the dental arch will occur in many cases, it does not always happen by any means. The fear of the effects of premature loss of deciduous teeth is not always realistic. Loss from trauma is limited mainly to the maxillary incisors.

Resorption of roots of teeth, which normally should not yet be shed, may occur in crowded dental arches. Such resorption is mainly encountered in the mandibular and maxillary deciduous lateral incisors and canines. Once in a while it is seen in a maxillary second deciduous molar, when its distal root forms an obstacle to the eruption of the far mesially located adjacent first permanent molar.10 Whether the deciduous molar will be shed prematurely depends, among other things, on the amount of root material that becomes resorbed.

Premature resorption of the root of a deciduous tooth usually occurs because the eruption of a permanent one is not only associated with the resorption of the root of its predecessor, but also with the one of an adjacent deciduous tooth. This is seen most frequently in the maxilla at the lateral deciduous incisor and in the mandible at the deciduous canine. A relatively large crown of an erupting maxillary central permanent incisor may lead not only to loss of the central deciduous incisor, but also of the lateral one. In the mandible, no median structure between the left and the right sides of the jaws is present after the first year of life. Crowding in the mandibular incisor region prior to emergence can result in an asymmetrical eruption pattern. Lack of space may be concentrated unilaterally and result in premature loss of one deciduous lateral incisor or one deciduous canine. The latter is the deciduous tooth that is most frequently lost as a result of premature root resorption in the mandible. In the maxilla, lack of space in the incisor region cannot be concentrated unilaterally in a corresponding manner, as the presence of the median intermaxillary suture acts as a barrier against a migration to the other side.

Further, deciduous canines are also the deciduous teeth most frequently lost due to premature extraction. Such extractions are intended to create space for a more favorable emergence of the lateral permanent incisors or to achieve a spontaneous improvement of the already emerged and malpositioned incisors. However, this procedure is indicated only under special conditions and should not be performed without careful consideration of the different aspects involved. Extraction of the deciduous canines may lead to situations that result in a less favorable subsequent development of the dentition than would otherwise have been the case.

Decay is the most common cause for premature loss of tooth material of deciduous molars. The mesiodistal crown dimension can become reduced and the available arch length may decrease.27^, 77 Decayed deciduous molars may loose their crowns partially or completely. Toothache or infections (alveolar fistulae) may lead to removal of roots and crown or of what has remained of them. Complete loss of deciduous molars due to decay, followed by extraction, occurs more than twice as often in the mandible as in the maxilla.20^, 42^, 77^, 99 Deciduous canines are more caries resistant than deciduous molars and rather seldom disappear for that reason. Deciduous incisors have only about half the infraoral lifetime as the other deciduous teeth and as such are less affected by decay.

The main results of premature loss of deciduous teeth are migrations of neighboring teeth toward the evoked diastema. These migrations depend on the tooth lost,19^, 20^, 40 the local conditions of occlusion,20^, 26^, 56 and the sagittal relation between the two dental arches. The most important variable involved seems to be the spatial condition within the dental arch.25^, 26^, 83 Also, the influence of the tongue and buccal musculature plays a role.20^, 42 Finally, the time of premature loss is essential.25^, 26 Premature loss long before the normal time of exfoliation seems to have a retarding effect on the eruption of the successor. Loss of a deciduous molar shortly prior to its normal time of exfoliation seems to have an accelerating effect on the eruption and emergence of its successor.34

In general, premature loss of deciduous teeth in subjects with an excess of dental arch space has a negligible effect or none at all on the subsequent development of the dentition and the ultimate location of the permanent teeth. In situations with no extra space available in the dental arches, premature loss of deciduous teeth may lead to several complications. Premature loss of deciduous teeth in crowded dental arches has almost always a distinctly unfavorable effect. As a rule, crowding will increase considerably.

Loss of deciduous molars prior to the emergence of first permanent molars as a rule has a larger negative effect than premature loss after the first permanent molars have attained occlusion. In the former case, the crowns of the second premolars are relatively far away from the occlusal plane and as such play a lesser role in the prevention of mesial drift of the first permanent molars than when they are situated more occlusally. Further, a first permanent molar tends to emerge earlier and more mesially when the adjacent deciduous molar is no longer present.26^, 86 Premature loss of deciduous molars prior to the emergence of the second permanent molars will result in a more mesial migration of the first permanent molars than in the reversed situation.53^, 103 Further, in cases with premature loss of deciduous molars, the emergence of the second permanent molars in those quadrants is advanced.86

In general, early premature loss of deciduous teeth has a larger negative impact on the subsequent development of the dentition than late premature loss. Migrations that occur as a result of premature loss mainly take place within the first 6 months following the loss.83 In the maxilla, the migrations are more extensive and occur more rapidly than in the mandible.20^, 78^, 85 Furthermore, in the maxilla, the migrations are mainly limited to mesial displacements of the permanent first molars, while in the mandible, the teeth mesial to the diastema tend to move distally in addition.78 However, frequently the loss of space is limited and often negligible.19^, 26^, 40^, 53^, 56^, 80^, 90 In many cases, the initial reduction of space is substantially regained during the later part of the mixed dentition period.58

The results of premature loss of deciduous teeth are predictable; however, this is not always a simple task. Many variables have to be taken into account in such a prediction procedure. The variables involved and the reasoning behind them will be treated mainly on the basis of schematic drawings. Most attention in this respect will be paid to the loss of the second deciduous molars, as these are the key teeth in premature loss. The effects of premature loss of the first deciduous molars is comparable to those of the second ones however, they are less severe.20^, 40 On the basis of the information supplied about premature loss of the second deciduous molars, the effect of the premature loss of the first molars can be estimated.

In the maxillary anterior region, premature loss is usually caused by trauma. In the deciduous dentition, one or two maxillary central incisors are most frequently involved. An intruding movement of a maxillary central deciduous incisor may result in a displacement of the superiorly located crown of the corresponding central permanent incisor. Delayed emergence or no spontaneous emergence at all of the latter may be the result. The situation is even worse when the inclination of the permanent tooth germ becomes changed. As a result, the crown may attain an abnormal position, usually a more or less horizontal one with its incisal edge directed ventrally. The formation of the tooth is completed in the original setting. The crown may become misshapen. However, in most instances, trauma takes place after root formation of the permanent central incisor has already commenced. The deviation in the tooth will then be located at the root.

No—or only slight—displacement of the central permanent incisor occurs when the trauma does not involve an intruding movement of its predecessor. This is frequently the case when the deciduous central incisor is lost in an accident, as often happens in the last phase of the complete deciduous dentition stage. Then the consequences of the trauma are generally limited to a more labial eruption and emergence of the central permanent incisor involved and a considerable delay in its piercing of the gingival tissue—often more than one year.48 The presence of the maxillary central deciduous incisors is not essential in the maintenance of space for their successors in the dental arch. Further, maxillary central deciduous incisors do not play a role, like the lateral ones, in the increase of the transverse intercanine distance (Fig. 15-1A). A maxillary lateral deciduous incisor is most frequently lost prematurely by too early resorption of its root in association with the eruption of the adjacent central permanent incisor. As has been explained, this type of premature loss usually takes place only in cases of crowding. It often occurs bilaterally (Fig. 15-1B). After premature loss of a maxillary lateral deciduous incisor, the deciduous canine on that side will not become displaced laterally during the eruption of the maxillary central permanent incisor in the way explained in Chapter 4. In cases of bilateral premature loss of maxillary lateral deciduous incisors, the intercanine distance does not increase. After unilateral premature loss, both maxillary central permanent incisor crowns will migrate in the direction where the extra space in the dental arch has become available. This movement will result in a discordance of the medians of the two dental arches. The maxillary and mandibular contact points between the central incisors or the midpoints of the central diastema will no longer match. The dentition shows midline deviation. The eruption of a maxillary lateral permanent incisor may be associated with premature loss of the adjacent deciduous canine in a similar way as indicated above (Figs. 15-1C and D). Unilateral premature loss will be followed by migration of the four maxillary permanent incisors toward the site of the loss. A midline deviation will result. Later, insufficient space will be available for the permanent canine in the dental arch, which will emerge in a buccal position and become located outside the dental arch. Bilateral premature loss of deciduous canines in crowding usually will lead to buccal position of both maxillary permanent canines.

Premature loss of mandibular deciduous incisors may occur under comparable circumstances. However, traumata seldom involve mandibular deciduous incisors. Premature loss of a mandibular lateral deciduous incisor usually takes place unilaterally (Fig. 15-2A) and often is associated with an asymmetrical position and emergence of the four mandibular permanent incisors. The same holds true for unilateral loss of a mandibular deciduous canine (Fig. 15-2C). Bilateral loss of mandibular lateral deciduous incisors (Fig. 15-2B) or canines />