### Core Concept
The dentogingival unit is a critical anatomical structure in periodontal health, comprising the junctional epithelium and the gingival fibers. It plays a vital role in maintaining the attachment between the tooth and the surrounding gingiva.

### Why the Correct Answer is Right
The junctional epithelium is a specialized epithelial structure that forms the attachment between the tooth and the gingiva, while the gingival fibers provide the mechanical integrity to this attachment. The gingival fibers are composed of both principal and secondary fibers, which are embedded in the connective tissue of the gingiva. The junctional epithelium and gingival fibers work in tandem to maintain the health and function of the periodontal tissues. This attachment is essential for the proper sealing of the gingival sulcus and prevention of bacterial invasion.

### Why Each Wrong Option is Incorrect
**Option A:** Gingival fibers alone do not constitute the dentogingival unit, as they require the presence of the junctional epithelium for proper attachment.

**Option C:** Periodontal ligament (PDL) fibers are crucial for tooth support and are not a component of the dentogingival unit.

**Option D:** This option is incorrect as the dentogingival unit does indeed comprise of gingival fibers and junctional epithelium.

### Clinical Pearl / High-Yield Fact
Mnemonic: "Junctional Epithelium and Gingival Fibers" (JEGF) form the dentogingival unit, which is essential for maintaining periodontal health. Remember that the junctional epithelium is a specialized structure that forms the attachment between the tooth and the gingiva, while the gingival fibers provide mechanical integrity.

### Correct Answer Line
✓ Correct Answer: B. Gingival fibres and junctional epithelium