Which two theories describe the biological harm caused by radiation?

The two theories that describe the biological harm caused by radiation are the Direct and Indirect Theory.

The Direct Theory posits that radiation causes damage directly by impacting the DNA or cellular structures in the targeted tissue. This occurs when high-energy radiation interacts with biological molecules, leading to ionization and molecular changes that can result in cell death or mutations.

In contrast, the Indirect Theory suggests that radiation doesn't directly affect DNA but rather interacts with water molecules in the body, creating free radicals or reactive species. These free radicals can then diffuse into surrounding cellular structures and ultimately cause biological damage, including DNA alterations, which can also lead to cell dysfunction or death.

Understanding these two theories is crucial for assessing how radiation exposure can lead to various health effects, including cancer, and for implementing appropriate safety measures in dental practices to minimize radiation risk to both patients and practitioners.