## **Core Concept**
Reactionary hemorrhage, also known as primary post-extraction hemorrhage, occurs shortly after dental extraction. It is primarily caused by the dislodgement of the blood clot from the extraction site or failure of the clot to form properly. This type of bleeding is a common complication in dental practice.

## **Why the Correct Answer is Right**
The correct answer, **C. Dislodgement of clot or failure of clot formation**, is right because reactionary hemorrhage is directly related to issues with the blood clot at the extraction site. When a tooth is extracted, a blood clot forms in the socket to protect the bone and nerves underneath. If this clot is dislodged or fails to form properly, the underlying vessels are exposed, leading to bleeding. This process can be influenced by various factors, including the patient's coagulation status, the complexity of the extraction, and the presence of local or systemic conditions that affect healing.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because while it might seem related, the specifics of the cause are not provided, making it too vague and not directly addressing the mechanism of reactionary hemorrhage.
- **Option B:** This option is incorrect because it does not accurately describe the primary cause of reactionary hemorrhage.
- **Option D:** This option is incorrect because it implies a cause (infection) that is more related to secondary post-extraction hemorrhage, which occurs hours to days after the extraction.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that reactionary hemorrhage typically occurs within the first 24 hours after extraction, with the majority of cases happening within the first few hours. **Applying pressure** to the extraction site with a gauze for a certain period and **avoiding vigorous rinsing or spitting** can help minimize the risk of reactionary hemorrhage.

## **Correct Answer:** . Dislodgement of clot or failure of clot formation