What does gray density on CBCT most commonly represent?

• A. Dentin, marrow space, soft tissue
• B. Air
• C. Bone
• D. Metal

Answer: (A)

In CBCT, grayscale values reflect how dense a structure is, but the scale is machine-dependent and not the same as true Hounsfield units. The mid-range gray tones you see most often correspond to non-metallic tissues like dentin, marrow spaces, and soft tissue. Air shows up as very dark (near black), while metal tends to be very bright with possible artifacts. Cortical bone can appear quite white, but the typical mid-gray range you encounter across many dental CBCT scans is dominated by dentin, marrow space, and surrounding soft tissues, making gray density most representative of those tissues.