## Core Concept
Chemotherapeutic plaque control methods involve the use of chemical agents to prevent or reduce the accumulation of dental plaque, thereby helping to prevent gingivitis and periodontal disease. These methods are an adjunct to mechanical plaque control methods like brushing and flossing.

## Why the Correct Answer is Right
The correct answer, chlorhexidine, is a well-known antiseptic used in dentistry for its effectiveness against a wide range of bacteria. It works by binding to the tooth surface and mucous membranes, thereby reducing the accumulation of plaque and preventing gingivitis. Chlorhexidine is available in various forms, including mouthwashes, gels, and varnishes.

## Why Each Wrong Option is Incorrect
- **Option A:** While essential oils have been studied for their potential antimicrobial properties, they are not as commonly used or as effective as chlorhexidine for chemotherapeutic plaque control.
- **Option B:** Hydrogen peroxide is used in dentistry for its bleaching properties and as an antiseptic, but it is not the primary agent used for chemotherapeutic plaque control.
- **Option C:** Fluoride is primarily used for the prevention of dental caries and does not play a significant role in chemotherapeutic plaque control.

## Clinical Pearl / High-Yield Fact
A key point to remember is that chlorhexidine is particularly useful for patients at high risk of periodontal disease or those who have difficulty with mechanical plaque control. However, it can cause side effects such as tooth staining and alteration of taste.

## Correct Answer: D. Chlorhexidine.