What is the purpose of a hand reamer in dental procedures?

A hand reamer is specifically designed to widen the canals during endodontic procedures, which is essential for root canal treatments. Its primary function is to enlarge the root canal space, allowing for better access to the infected or necrotic pulp tissue. By widening the canals, the dentist can effectively clean and shape the root canal system, preparing it for filling material afterward. This step is crucial for ensuring that all infected tissue is removed and that the canal is adequately sized to facilitate proper sealing.

The other options do not align with the function of a hand reamer. For instance, cleaning teeth and polishing surfaces are actions typically carried out using different instruments, such as scalers or polishing cups. Filling cavities is a restorative procedure that involves different tools and materials, not the reaming action facilitated by a hand reamer. Thus, the primary purpose of a hand reamer in dental procedures is to widen the canals, making it an essential instrument in endodontics.