In the Bell stage, which cell layers compose the enamel organ?

• A. Outer enamel epithelium only
• B. Inner enamel epithelium, outer enamel epithelium, stellate reticulum, stratum intermedium
• C. Stellate reticulum only
• D. Stratum intermedium only

Answer: (B)

During the Bell stage, the enamel organ is a layered epithelial structure that will form enamel and consists of four cell layers: outer enamel epithelium on the exterior, inner enamel epithelium lining the boundary with the dental papilla, and two middle layers—the stellate reticulum, a network of star-shaped cells, and the stratum intermedium, a band of more flattened cells adjacent to the inner enamel epithelium. The inner enamel epithelium differentiates into ameloblasts that secrete enamel; the outer enamel epithelium provides protection and signaling; the stellate reticulum cushions the organ and helps with diffusion of nutrients; and the stratum intermedium supports metabolism and supplies enzymes needed for enamel formation. All four layers together define the enamel organ at this stage.