An orthodontic tooth positioner is not used to perform which of the following tasks?

An orthodontic tooth positioner is a specialized dental appliance primarily used in orthodontics to help maintain teeth in their new positions after braces or other corrective treatments have been removed. It effectively helps to align the teeth, stabilize them in their new positions, and can also be used for minor adjustments of tooth positioning.

The role of the tooth positioner does not include separating teeth before banding. This task typically involves other appliances or techniques, such as orthodontic separators, which are specifically designed to create space between the teeth prior to the placement of bands. Therefore, the correct answer reflects that the primary function of a tooth positioner is not to assist in this preparatory step but rather to facilitate the final adjustments and stabilization of teeth after orthodontic treatment.