Introduction The Need For Efficient Space Closure

Although space closure is sometimes needed in non-extraction cases, the subject is generally discussed relative to premolar extraction cases. Space closure is carried out in the same manner in both groups, and although the subject of orthodontic extractions has been controversial in the past, it is now accepted that extraction of four premolars is beneficial in some cases. The 7 mm of space provided in each quadrant may be used to benefit the patient in one or more of the following ways:

• Relief of crowding, to achieve stable alignment of the dentition

• Retraction of upper anterior teeth to correct the overjet in Class 11/1 cases

• Retraction of lower incisors to assist correction of Class III cases

• Retraction of upper and lower incisors to improve facial profile or occlusion in bimaxillary proclination cases

• Mesial movement of molars, increasing space for third molar eruption.

In maximum anchorage cases, most of the space will be used to relieve crowding (Fig. 9.1) or to retract incisors (Fig. 9.2).

However, in minimum anchorage cases, where crowding or protrusion is minimal, less than 7 mm of space in each quadrant will be needed for relief of crowding or incisor retraction. In these cases, there will be a need to close the residual spaces by mesial movement of first and second molars, providing more space for eruption of third molars (Fig. 9.3).

Reciprocal space closure of premolar space (Fig. 9.4) will be appropriate in many cases, especially where residual spaces are small. But in other cases it is necessary to vary the treatment mechanics and to control the anchorage balance, either to retract incisors (Fig. 9.5) or to mesialize molars (Fig. 9.6).

Consequently, in an efficient orthodontic practice, there is a need for a reliable method of space closure, which will allow control of anchorage balance.

Fig. 9.4 Reciprocal space closure.

Fig. 9.5 Incisor retraction.

Fig. 9.6 Mesial molar movement.

Fig. 9.4 Reciprocal space closure.

Fig. 9.5 Incisor retraction.

Fig. 9.6 Mesial molar movement.

Fig. 9.3 Mesial movement of molars may be needed to close residual space in minimum anchorage cases. This will provide more space for eruption of third molars.

Normal space closure I " Too rapid space closure

Fig. 9.7 Closing loop archwires were part of traditional edgewise treatment mechanics. They were individually made for each patient, and had a limited range of action before the omega loop came into contact with the molar tube.

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