Endogenous tooth stains can include fluorosis.

• A. True
• B. False
• C. Not applicable
• D. Sometimes

Answer: (A)

Endogenous stains come from within the tooth, not from something on the surface. Fluorosis happens during tooth development when excessive fluoride disrupts enamel formation, leading to intrinsic discoloration of the enamel that can appear as white mottling or brown staining. Because the stain is inside the tooth structure, polishing the surface won’t fully remove it, which is exactly what makes it endogenous. So fluorosis is a classic example of an endogenous tooth stain, making the statement true.

Not applicable wouldn’t fit, since this is a straightforward intrinsic stain caused by developmental factors, and “sometimes” isn’t precise because the condition, when present, represents a consistent endogenous change.