When should a prophy angle NOT be used?

A prophy angle should not be used when there is excessive tooth decay present. The main reason for this is that a prophy angle is designed for polishing and cleaning the surfaces of the teeth after plaque and calculus have been removed. If there is significant decay, using a prophy angle could potentially cause further damage to the tooth structure. The polish may not allow for the effective treatment of the decay, and the removal of any softened enamel or dentin could exacerbate the situation instead of promoting oral health.

In cases of extensive decay, it is important to address the decay through restorative methods rather than merely polishing the tooth, as this does not deal with the underlying problems. This ensures that the integrity of the tooth is maintained and is unable to lead to more severe issues such as infection or significant tooth loss.

Using a prophy angle after scaling, on patients with healthy gums, or on individuals with ongoing orthodontic treatment is typically appropriate, as these scenarios involve maintenance of oral health rather than addressing active decay or structural weaknesses in teeth.