**Core Concept:** Mechanical removal of dental plaque is essential for maintaining oral hygiene and preventing periodontal diseases. The most effective mechanical devices for cleaning interdental surfaces of teeth include interdental brushes, floss, dental picks, and water irrigators (e.g., oral irrigators).

**Why the Correct Answer is Right:**

Interdental brushes are considered the most effective mechanical device for cleaning interdental surfaces of teeth among the provided options. These brushes are small, cylindrical, and have a soft bristles, which allow them to effectively clean the interdental spaces, including the tightest areas where flosses cannot reach. Interdental brushes are specifically designed to remove plaque and prevent periodontal diseases caused by bacterial colonization in these spaces.

**Why Each Wrong Option is Incorrect:**

A. Floss: While floss is effective for cleaning interproximal surfaces, it is less effective in cleaning the interdental spaces due to its thin and flexible design. Floss may also cause gingival bleeding and inflammation when used inappropriately.

B. Dental picks: Dental picks are stiff and narrow instruments primarily used for removing calculus (hardened plaque) from the root surfaces. They are not suitable for cleaning interdental spaces effectively.

C. Water irrigators (oral irrigators): Although water irrigators are effective for removing plaque and debris, they are less effective in cleaning the interdental spaces compared to interdental brushes. The narrow nozzle of an oral irrigator does not reach and clean the interdental spaces efficiently.

**Clinical Pearl:**

Interdental brushes are the most effective mechanical device for cleaning interdental surfaces of teeth, ensuring improved oral health and preventing periodontal diseases. Proper use of floss, dental picks, and water irrigators (oral irrigators) is essential for adjunctive cleaning and maintaining oral hygiene.

**Correct Answer:** Interdental brushes (Letter A)