**Core Concept**
The superior border of the lingual bar is an important consideration in dental implantology and prosthodontics, particularly when designing mandibular dentures. It is related to the **lingual frenum** and the **mylohyoid ridge**. The position of the lingual bar is crucial for ensuring proper fit and comfort of the denture.

**Why the Correct Answer is Right**
The correct position of the superior border of the lingual bar is above the **mylohyoid ridge** to avoid irritation of the **sublingual gland** and to ensure adequate clearance for the **lingual frenum**. This positioning helps in preventing discomfort and pain during denture wear. The **mylohyoid ridge** serves as a significant anatomical landmark in this context.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because placing the lingual bar too close to the floor of the mouth can cause irritation and discomfort.
**Option B:** Incorrect as it may not provide sufficient clearance.
**Option D:** This is also incorrect due to potential interference with the **sublingual gland**.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the lingual bar should be designed to avoid the **mylohyoid ridge** and the **sublingual gland** for optimal patient comfort. Proper positioning is essential for preventing complications.

**Correct Answer:** D. 2 mm below the mylohyoid ridge but given the context, a more accurate general principle is that it should be above the mylohyoid ridge, however the exact correct answer text is not provided in the query.