Premolars

Premolars are often ideal for the relief of both anterior and posterior crowding, the first and second premolars have similar crown forms, which means that an acceptable contact point can be achieved between the remaining premolar and the adjacent molar and canine. The choice between first or second premolar depends on a number of factors: for example, the degree of crowding, the anchorage requirements, the overjet and overbite.

In Class I cases where crowding exists and the

Fig. 5 Premolars had previously been extracted as part of orthodontic treatment in adolescence. Crowding returned in the lower labial segment (a), which was relieved by removal of a lower incisor and fixed appliance treatment. A bonded retainer was fitted at the completion of treatment (b)

Fig. 5 Premolars had previously been extracted as part of orthodontic treatment in adolescence. Crowding returned in the lower labial segment (a), which was relieved by removal of a lower incisor and fixed appliance treatment. A bonded retainer was fitted at the completion of treatment (b)

Fig. 6 A Kesling set up of the case in Figure 5, removing the lower left central incisor and replacing the remaining incisors and canines.

This showed the anticipated tooth positions and occlusion with the upper arch

Fig. 6 A Kesling set up of the case in Figure 5, removing the lower left central incisor and replacing the remaining incisors and canines.

This showed the anticipated tooth positions and occlusion with the upper arch

Fig. 7 A lower premolar has been transplanted to replace the upper left central incisor which had a poor prognosis

Fig. 7 A lower premolar has been transplanted to replace the upper left central incisor which had a poor prognosis

Fig. 8 A severely crowded case, where unusually, four canines were extracted. The resulting occlusion gave acceptable contacts between first premolar and lateral incisors and improved the arch form. (a-c) Pre treatment, (d-f) Post treatment

canines are mesially angulated, loss of first premolars may produce spontaneous improvement in the alignment of the canines (Fig. 9). Any excess extraction spaces may close with time, although a study by Berg et al., showed space closure to be greatest in the first 6 months following extraction.18 In carefully selected cases reasonable alignment can sometimes be achieved. However cases amenable to this type of treatment are rare and fixed appliances especially when second premolars have been extracted invariably produce better results.

Second premolars are the third most commonly developmentally absent teeth after third molars and upper lateral incisors.19 Where deciduous molars are retained beyond their normal exfoliation dates, a radiograph should be taken to confirm the presence and position of the permanent successor. In uncrowded arches deciduous molars with good roots are often retained, as space closure in these cases can be difficult (Fig. 10).

Second premolars can become impacted either due to early loss of deciduous molars or severe crowding. Ectopic second premolars usu ally erupt lingually or palatally and should be considered for extraction if they are completely excluded from the arch (Fig. 11).

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