What is the bulk of a tooth primarily made up of?

The bulk of a tooth is primarily made up of dentin. Dentin is the second layer of the tooth structure, located beneath the enamel and surrounding the pulp. It is a hard, calcified tissue that provides both strength and support to the tooth. Dentin consists of microscopic tubules, which can transmit sensations, making it sensitive to temperature changes and other stimuli.

Enamel, while critical as the outer protective layer of the tooth, is much thinner compared to dentin and does not constitute the majority of the tooth's mass. Cementum is a specialized calcified tissue that covers the root of the tooth and helps anchor it in the jawbone but is again not a significant portion of the tooth's structure. The pulp is the innermost part of the tooth, containing nerves and blood vessels, and while vital for tooth health, it occupies a much smaller volume than dentin. Thus, dentin is the correct answer as the primary component that forms the bulk of the tooth.