The periodontal curette is a type of hand-activated instrument used in dentistry and dental hygiene for the purpose of scaling and root planing. The periodontal curette is considered a treatment instrument and is classified into two main categories: universal curettes and Gracey curettes. Periodontal curettes have one face, one or two cutting edges and a rounded back and rounded toe. They are typically the instrument of choice for subgingival calculus removal. typically used during nonsurgical periodontal therapy of a patient? dental hygiene care. The goal of nonsurgical periodontal therapy is to eliminate inflammation and return the patient? periodontium back to health. One of the ways this can be achieved is by minimizing the bacterial challenge to the patient.