**Core Concept**
Immediate denture treatment is a procedure where a patient receives a denture on the same day as tooth extraction. This approach aims to maintain the patient's facial aesthetics and chewing function during the healing period. However, it poses several challenges due to the altered anatomy and compromised oral tissues.

**Why the Correct Answer is Right**
The correct answer is related to the challenges associated with immediate denture treatment. One major disadvantage is the difficulty in achieving proper denture fit and stability due to the swelling and altered anatomy of the underlying tissues. This is because the gums and surrounding tissues undergo significant changes in the first few weeks after tooth extraction, making it challenging to achieve a precise fit of the denture. Additionally, the altered anatomy can lead to difficulties in achieving proper denture retention and stability.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while immediate denture treatment can be more costly than conventional denture treatment, it is not the primary disadvantage. Immediate denture treatment may require additional procedures, such as bone grafting or tissue augmentation, which can increase costs.
**Option B:** This option is incorrect because while immediate denture treatment can cause discomfort and irritation, it is not the primary disadvantage. The discomfort is usually temporary and can be managed with proper follow-up care and adjustments to the denture.
**Option C:** This option is incorrect because while immediate denture treatment can lead to difficulties in achieving proper denture fit and stability, it is not the primary disadvantage. The altered anatomy and compromised oral tissues can lead to a range of challenges, including difficulties in achieving proper denture fit and stability.

**Clinical Pearl / High-Yield Fact**
One key consideration when planning immediate denture treatment is to ensure that the denture is designed to accommodate the expected changes in the underlying tissues. This can involve using a temporary or interim denture that can be adjusted and refined as the tissues heal.

**Correct Answer: D. Altered anatomy and compromised oral tissues making it difficult to achieve proper denture fit and stability.**