**Core Concept**
Full mouth disinfection (FMD) therapy is a comprehensive approach to managing periodontal disease, focusing on the eradication of pathogens throughout the entire oral cavity. This treatment aims to eliminate periodontal pathogens, reduce inflammation, and promote a healthy periodontal environment.

**Why the Correct Answer is Right**
FMD therapy involves a thorough cleaning of the teeth, roots, and surrounding tissues, as well as the use of antimicrobial agents to kill periodontal pathogens. The treatment targets the entire oral cavity, including areas not directly affected by periodontal disease, to prevent the spread of infection and promote healing. This approach is based on the understanding that periodontal pathogens can be present in various forms, including biofilms, and that a comprehensive treatment is necessary to eliminate these pathogens.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because FMD therapy is not primarily focused on treating gum recession or improving the appearance of the gums.
**Option B:** This option is incorrect because FMD therapy is not a substitute for regular oral hygiene practices, but rather a supplementary treatment to enhance periodontal health.
**Option C:** This option is incorrect because FMD therapy is not limited to treating only the teeth and gums, but rather involves a comprehensive approach to managing periodontal disease.

**Clinical Pearl / High-Yield Fact**
A key aspect of FMD therapy is the use of antimicrobial agents to target periodontal pathogens, which can be present in various forms, including biofilms. This approach highlights the importance of a comprehensive treatment strategy in managing periodontal disease.

**Correct Answer: D. Eradication of periodontal pathogens throughout the entire oral cavity.**