National Dental Assisting Examining Board (NDAEB) Practice Exam

What are the structural units of enamel called?

1. Enamel Rods

2. Enamel Prisms

3. Enamel Follicles

4. Enamel Tubules

The correct answer is: Enamel Prisms

The structural units of enamel are referred to as enamel prisms. Enamel prisms are also commonly known as enamel rods, but the term "prisms" emphasizes their unique, elongated, and hexagonal structure that reflects the organization of enamel at the microscopic level. Enamel is the hardest tissue in the human body, and its toughness is attributed to the highly organized arrangement of these prisms. Each prism consists of tightly packed hydroxyapatite crystals, and their arrangement contributes to the overall strength and durability of enamel. The prisms run from the enamel surface to the dentin-enamel junction, providing structural integrity. In contrast, other terms like enamel follicles, which refer to structures associated with the development of enamel, or enamel tubules, which are more associated with dentin, do not accurately describe the units that compose enamel itself. Hence, the focus on the term "prisms" effectively captures the essential structural characteristics of enamel's organization.