Which part of the working end is always in contact with the tooth surface?

The correct answer, indicating that the toe-third or tip-third of the working end is always in contact with the tooth surface, reflects an essential aspect of effective dental hygiene practices.

The toe-third or tip-third of an instrument, such as a scaler or curette, is designed to facilitate precise adaptation to the contours of the tooth and optimize plaque and calculus removal. This part of the instrument allows for effective scaling, root planing, or other therapeutic procedures by ensuring that the most functional area is actively engaged with the dental surfaces.

In contrast, other parts of the working end may not provide the same level of effectiveness. The middle portion may not consistently maintain contact during instrumentation, and the entire working end involves both the active and inactive areas, where only the tip-third contacts the tooth. The handle, being the part that the clinician grasps, is never in contact with the tooth surface, as its primary purpose is for maneuvering and control of the instrument rather than for direct application to dental surfaces.

Thus, understanding the specific roles of different parts helps dental professionals enhance their techniques and ensure better patient outcomes.