In which scenario would a biopsy be immediately indicated?

The immediate indication for a biopsy occurs when there are unexplained persistent lesions. This scenario suggests that there is a lesion that has not resolved over time and does not have an identifiable cause. Persistent lesions could potentially indicate a more serious condition, such as malignancy or other pathological processes, which necessitate definitive diagnosis through histological examination.

In contrast, while the other scenarios may raise concerns, they do not inherently require a biopsy. Significant intraoral swelling could result from a variety of causes, including infections, which might resolve with appropriate treatment. Radiographic changes in vital teeth often warrant observation or other non-invasive diagnostics before opting for a biopsy. A symptomatic response to restorative treatment may indicate an issue related to the restoration itself but does not specifically point to the need for a biopsy unless accompanied by unexplainable persistent lesions. Thus, unexplained persistent lesions necessitate immediate investigation through biopsy for accurate diagnosis and management.