Final answer:
The contra/right angle attachment for a slow speed hand-piece is principally used for crown preparation in dentistry, to shape the tooth with precision at right angles to the surface. Option C.
Step-by-step explanation:
The contra / right angle attachment for a slow speed hand-piece in dentistry is typically used for crown preparation.
This type of attachment allows the dentist to have better access and visibility when shaping the tooth for a crown. It provides the ability to work at right angles to the tooth's surface which is essential for precise crown preparation. The design of the tooth, as suggested by LibreTexts™, with a polycrystalline calcite matrix contributes to the grinding efficiency, and similarly, the design of dental attachments ensures that the dentist can achieve the necessary shape and smoothness for procedures such as crown preparation.
It is not commonly used for scaling and root planing, which is a procedure for cleaning the surfaces of the teeth and their roots and is often performed with different instruments. It is also not used for extraction, which requires forceps and elevators, nor is it used in orthodontic treatment, which involves adjusting the positions of teeth and may involve different types of dental equipment.