**Core Concept**
Relining of complete dentures is a procedure to re-contour the denture base and improve its fit to the underlying tissues. It involves adding a new layer of material to the existing denture base, usually to accommodate changes in the shape or size of the oral tissues. This is often necessary due to resorption, inflammation, or other alterations that compromise the denture's stability and comfort.

**Why the Correct Answer is Right**
The presence of abused soft tissues is a critical indication for relining of complete dentures. Abused tissues can lead to chronic inflammation, pain, and discomfort, making it difficult for the patient to wear the denture. Relining the denture can help reduce pressure on the affected areas, alleviate pain, and improve the overall fit and stability of the denture. This is essential in preventing further tissue damage and promoting healing.

**Why Each Wrong Option is Incorrect**
**Option A:** Immediate denture construction at 3-6 months after original construction may be necessary due to changes in the underlying tissues, but it is not a specific indication for relining. Immediate dentures are constructed immediately after tooth extraction to prevent the shrinkage of the alveolar ridge.

**Option B:** A patient's inability to afford a new denture is not a valid medical indication for relining. Denture relining is a clinical procedure aimed at improving the fit and comfort of the denture, not a financial solution.

**Option D:** While the construction of new dentures with multiple appointments can cause physical and mental stress, this is not a direct indication for relining. Relining is a specific procedure to address changes in the oral tissues, not a solution to the stress associated with denture construction.

**Clinical Pearl / High-Yield Fact**
When assessing a patient for denture relining, it's essential to evaluate the underlying tissues for signs of abuse, such as chronic inflammation, pain, or discomfort. This can help identify patients who may benefit from relining to improve the fit and stability of their dentures.

**✓ Correct Answer:** C. Abuse soft tissues are present.