Dentin consists of approximately 70% inorganic, 20% organic, and 10% aqueous.

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

Answer: (A)

Dentin is a mineralized connective tissue with distinct fractions of its composition: about 70% inorganic material, 20% organic matrix, and 10% water. The inorganic portion is mainly hydroxyapatite crystals, which give dentin its stiffness. The organic matrix is largely collagen type I along with non-collagenous proteins, providing toughness and a scaffold for mineral deposition. Water fills the spaces within the matrix and dentinal tubules, affecting diffusion, permeability, and mechanical behavior. These proportions explain why dentin behaves differently from enamel (more organic content and water, less brittle) and why bonding and demineralization processes interact with it in particular ways. While slight variation exists among sources, this 70/20/10 distribution is the standard way dentin is described, making the statement true.