What is the angle between the blade and tooth when a Gracey curette is parallel to the surface being treated?

When a Gracey curette is positioned parallel to the surface being treated, the angle between the blade and the tooth is typically about 70 degrees. This specific angle is designed for optimal instrumentation, allowing for efficient scaling and root planing while minimizing tissue trauma.

The design of the Gracey curette, with its angled blade, facilitates access to specific surfaces of the teeth. By positioning the curette at a 70-degree angle, the clinician can effectively engage the tooth surface and remove plaque and calculus deposits. This angle is crucial for achieving proper adaptation of the curette to the tooth anatomy, ensuring thorough cleaning and maintaining the integrity of surrounding periodontal tissues.

Other angles, such as 90 degrees, would indicate a perpendicular approach, which is not suitable for the curved surfaces of the root and may result in ineffective debridement. Lower angles, like 60 degrees or 80 degrees, may not provide adequate engagement and could potentially lead to inadequate removal of deposits or damage to the soft tissues surrounding the tooth. Thus, maintaining approximately a 70-degree angle enhances clinical performance and patient outcomes in periodontal therapy.