Figure 2. Light micrograph of the ESEF, HME, and cell layer samples prepared according to the divisions shown in Fig. 1a. The length of the ESEF sample is approximately 1 mm. (a) The ESEF sample contained cells from the inner enamel epithelium, stratum intermedium, odontoblasts, and dental papilla cells. (b) The secretory ameloblast sample contained no outer enamel epithelium, which is not shown in the magnified micrograph. (c) HME sample was scraped approximately 30 µm by means of a sharp dental excavator. Approximately 22% of the sample weight was HME, based upon the assumption that the collagen in the sample was derived from dentin. (d) Odontoblast cell layer sample was prepared by scraping with a blunt, small spatula from the cells on predentin as shown in the Fig. Key for panels: a, ESEF; b, secretory ameloblast cell layer; c, HME; d, odontoblast cell layer. Key for abbreviations: IE, immature enamel; PD, predentin; OB, odontoblast; D, dentin; AB, ameloblast; EDJ, enamel-dentin junction.