**Core Concept**
Radiation therapy can cause damage to the bone and soft tissues, leading to chronic changes and impaired healing. This is due to the ionization of DNA and cellular damage from radiation, which can disrupt the normal bone remodeling process and lead to fibrosis and necrosis.

**Why the Correct Answer is Right**
Osteoradionecrosis (ORN) is a severe complication of radiation therapy, characterized by the death of bone tissue due to radiation-induced damage. This can lead to exposed bone, chronic pain, and infection. The risk of ORN is particularly high in areas that have received high doses of radiation, such as the mandible. The mechanism of ORN involves the disruption of the normal bone remodeling process, leading to a lack of osteoblasts and an accumulation of osteoclasts, resulting in bone necrosis.

**Why Each Wrong Option is Incorrect**
**Option A:** Alveolar osteitis, also known as dry socket, is a common complication of tooth extraction, but it is not directly related to radiation therapy. It is caused by the exposure of the bone and nerve endings after extraction.

**Option C:** Prolonged healing is a possible complication of tooth extraction in patients who have undergone radiation therapy, but it is not the greatest danger. Prolonged healing can be managed with appropriate wound care and pain management.

**Option D:** Fracture of the mandible is a possible complication of tooth extraction, but it is not directly related to radiation therapy.

**Clinical Pearl / High-Yield Fact**
Patients who have undergone radiation therapy to the head and neck region are at increased risk of osteoradionecrosis, particularly if they require tooth extractions. It is essential for clinicians to take a thorough medical history and assess the patient's radiation therapy history before proceeding with extractions.

**✓ Correct Answer: B. Osteoradionecrosis**