## Core Concept
Periochip is a type of **chlorhexidine**-based product used in periodontology. Chlorhexidine is a disinfectant and antiseptic that is used to control dental plaque and gingivitis. It works by binding to the tooth surface and mucous membranes, thereby reducing the accumulation of plaque and preventing the growth of bacteria.

## Why the Correct Answer is Right
The correct answer, **Chlorhexidine**, is right because periochip is indeed a biodegradable, sustained-release chip that contains chlorhexidine digluconate. This chip is inserted into the periodontal pocket to provide a localized delivery of chlorhexidine, which has antimicrobial properties. Chlorhexidine's mechanism of action involves disrupting the bacterial cell membrane, ultimately leading to the death of the bacteria. This helps in reducing the bacterial load in the periodontal pocket, which is beneficial in the treatment of periodontal diseases.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because it does not correspond to chlorhexidine.
- **Option B:** This option is incorrect because it also does not correspond to chlorhexidine or any known component of periochip.
- **Option C:** This option is incorrect for similar reasons; it does not accurately represent the composition of periochip.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **chlorhexidine** is widely used in dentistry for its antimicrobial properties. It is available in various formulations, including mouthwashes, gels, and chips like periochip. Chlorhexidine can cause side effects such as tooth staining and alteration of taste; however, its efficacy in reducing plaque and gingivitis makes it a valuable tool in periodontal therapy.

## Correct Answer Line
**Correct Answer: D. Chlorhexidine.**