Most acids never reach the pulp if there is _____ mm of dentin

• A. 1.0 mm
• B. 0.5 mm
• C. 0.75 mm
• D. 0.25 mm

Answer: (B)

Dentin thickness acts as a diffusion barrier that protects the pulp from acids. The dentinal tubules and the dentinal fluid can allow some diffusion, but as the path length increases, less acid actually reaches the pulp. About 0.5 mm of dentin is the commonly cited minimum that generally prevents acids used in typical procedures from reaching the pulp, thanks to diffusion distance and natural buffering. If there is at least 0.5 mm, the pulp is usually protected; thicker dentin provides even more protection, while only 0.25 mm is typically too thin and may allow harmful diffusion, risking pulpal irritation or injury. When dentin is this thin, clinicians often use protective liners to safeguard the pulp before restoring.