## Core Concept
The question targets the knowledge of periodontal plaque control methods, specifically focusing on the most effective mechanical device for cleaning concave interdental surfaces of teeth or root concavities. This involves understanding the design and functionality of various dental hygiene tools.

## Why the Correct Answer is Right
The correct answer, **. Interdental brushes**, is effective for cleaning concave interdental surfaces because of their unique design. Interdental brushes have a small, cylindrical or tapered brush head that can be inserted into the interdental spaces, allowing for effective removal of plaque and debris from these areas. Their shape and size enable them to adapt well to concave surfaces, making them particularly useful for cleaning root concavities and areas where regular toothbrushes cannot reach.

## Why Each Wrong Option is Incorrect
- **A. Periodontal probe**: This is a diagnostic tool used to measure pocket depths and assess the health status of the periodontium. It is not designed for removing plaque or debris.
- **B. Cotton points**: While cotton points can be used for applying medication or for minor cleaning, they are not effective for removing plaque from concave interdental surfaces.
- **D. Wooden wedges**: These are used primarily for isolating teeth during dental procedures or for drying areas. They do not have a role in plaque removal.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **interdental brushes** are especially useful for patients with tight interdental spaces or those with concavities on their roots, as these areas are difficult to clean with standard toothbrushes. Effective use of interdental brushes can significantly improve oral hygiene and prevent periodontal disease.

## Correct Answer: C. Interdental brushes