This section will discuss features of malocclusion that are expected to develop as a result of premature exfoliation of primary teeth (PEPT), which contribute to greater need for orthodontic treatment.

The most common and obvious consequence of PEPT is enhancement of crowding, rotations, and TSALDs (38,41,85,86). From an orthodontic perspective, mesial drift of the permanent molars leads to loss of arch perimeter, reducing the space in which the permanent teeth can be aligned (44). Bhujel found that the frequency of crowding was 49% in PEPT groups as opposed to 29% in the controls, which was statistically significant (31).

When a primary tooth is lost, there is a tendency for the adjacent teeth to tip into the extraction space (38). As described by Pokorna et al., this is most prevalent when Es are lost prematurely, causing M1s to rotate around their palatal cusp in the maxilla and tip mesially in the mandible (82). The mesial-in rotation in the maxilla may also increase the tendency towards crossbite (83,87).

PEPT is also known to cause deepening of the bite and midline deviations (83,87). This is especially true in cases of premature loss of Cs due to lingual collapse and lateral shifting of incisors (16,20,60).

Eruption of permanent successors can be accelerated for delayed as a result of PEPT (88,89). This can have a great impact on the developing occlusion in the buccal segments. Posen found that age at time of extraction was of the greatest significance; eruption of premolars is delayed in children who lose primary molars prematurely at age 4 to 5 years, while eruption is accelerated if the tooth is lost prematurely between ages 8 to 10 years (88). Between ages 5 to 8 years, there is a gradual decrease in the delay of premolar eruption which shifts to acceleration by age 8 years. Kerr, on the other hand, evaluated premature loss of primary canines and molars and found that earlier tooth loss generally promoted earlier eruption, except in the mandibular premolar region (89).

Due to tooth migration, there may be a reduction in space for eruption of permanent successors or adjacent teeth (41,44). Clinch and Healy found that PEPT and order of eruption play a large role in eruption of permanent dentition (37). When space loss has taken place, if a permanent canine erupts after the premolars, it is often blocked out, and if a maxillary E is lost before eruption of the M1, the second premolar is often blocked out. MacLaughlin et al. found that early loss of mandibular Es caused 20% of second premolars to become impacted or erupt ectopically (90). As previously discussed, Northway et al. found that early loss of maxillary Ds causes blocked out canines, early loss of maxillary Es can cause second premolar impaction, and early loss of mandibular Ds and Es can result in ectopic eruption of second premolars (47).

Many studies have demonstrated that loss of primary molars can affect the Angle molar classification. Generally, after loss of primary molars in the maxilla, the molar relationship tends towards Class II while in the mandible it tends towards Class I or Class III (31,47,82,83). As many molars begin with a flush terminal plane relationship shifting into Class I with continued development, loss of a mandibular primary molar may facilitate the change to Class I. Additionally, premature exfoliation of primary molars seems more likely to cause a Class II molar relationship than Class III.

Pokorna et al. demonstrated that following premature loss of Es, one can expect to find different molar relationships on the left and right side in 68% of patients (82). Loss of Es, rather than Ds, seems more likely to alter the molar relationship. The work of Northway et al. showed agreement in that loss of a mandibular D does not cause a shift towards mesioclussion (47). One can also extrapolate that if M2s erupt before premolars, these shifts in molar relationship following PEPT may be intensified (13).

As a result of space loss and drifting of adjacent teeth, it is possible that TSALDs will be aggravated and permanent teeth will erupt ectopically or become impacted. This is especially true in crowded dentitions. Consequently, it is accepted that PEPT can lead to a need for extractions of permanent teeth and comprehensive orthodontic treatment in the future (70). Pedersen et al. found that PEPT in the maxilla was more likely to result in need for extractions of permanent teeth, whereas in the mandible, it would require orthodontic treatment of longer duration (83). Ronnerman and Thilander found similar results, stating that the tendency was for orthodontic treatment following PEPT to involve premolar extractions in the maxilla versus expansion in the mandible because the maxilla has less leeway space available and more significant mesial migration of M1s (81). As mentioned, Wagner et al. recently showed that 31.4% of children in the control group had a high need for orthodontic treatment as defined by the IOTN. They hypothesized that the need was most likely due to a severe TSALD resulting from space loss and need for interventions to create space, such as premolar extractions (41).