American Board of Orthodontics (ABO) Practice Exam

The recommended pilot drill size being 0.2-0.5 mm less than the diameter of the Temporary Anchorage Device (TAD) is based on the need to ensure a tight fit for the TAD within the bone while still allowing for sufficient initial placement.

When placing TADs, creating a pilot hole that is slightly smaller than the TAD aids in achieving optimal stability and retention. This is crucial as it allows for the TAD to grip the surrounding bone effectively, reducing the risk of failure during orthodontic treatment. A pilot hole that is too small may increase the risk of fracture or breakage of the TAD during insertion, while a hole that is equal to or larger than the diameter of the TAD can lead to insufficient engagement and a higher likelihood of mobility.

Therefore, adhering to the guideline of a pilot drill size that is 0.2-0.5 mm less than the TAD size ensures that the device is secure upon insertion, facilitating effective orthodontic anchorage.