**Core Concept**
Radiotherapy after tooth extraction is a common practice, but it requires careful consideration of the timing to avoid complications. The underlying principle is that radiotherapy can cause osteoradionecrosis (ORN), a condition where the bone tissue dies due to radiation damage.

**Why the Correct Answer is Right**
Radiotherapy after tooth extraction should be avoided because the extraction site is an area of high risk for ORN. This is because the extraction site has a compromised blood supply, which makes it more susceptible to radiation damage. The lack of blood supply and the presence of bacteria in the extraction site can lead to a cascade of events that ultimately result in bone death. Additionally, the radiation can also damage the surrounding bone and soft tissues, making it difficult for the body to heal.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because there is no specific contraindication for radiotherapy after tooth extraction in patients with a history of periodontal disease.

**Option B:** This option is incorrect because radiotherapy after tooth extraction can be safely administered in patients with a history of dental implants, provided the implant is not in the direct path of the radiation beam.

**Option C:** This option is incorrect because there is no specific contraindication for radiotherapy after tooth extraction in patients with a history of oral surgery.

**Clinical Pearl / High-Yield Fact**
To minimize the risk of ORN, it is recommended to wait for at least 2-3 weeks after tooth extraction before starting radiotherapy. This allows the extraction site to heal and reduces the risk of complications.

**Correct Answer:** D.