Amelodentinal junction

At a larger order of size, enamel has a prismatic structure, the enamel prism or rod representing the most obvious histologically defined entity. In cross-section its dimensions are approximately the same as those of an ameloblast but it is extremely long and may extend from the amelodentinal junction to the enamel surface. Adjacent prisms are approximately parallel but show local changes of direction. The prisms are formed as the result of the activity of ameloblasts, and one ameloblast may contribute to several prisms, while each prism receives material from more than one cell. In the outermost layer of fully formed human enamel the prisms merge into each other and a thin surface layer is produced. This layer resembles reptile enamel which is less than 1 mm thick and is not prismatic but continuous. 

Figure 32.5 The pattern of mineralization in the enamel of an incisor tooth. The partially mineralized matrix is shown stippled and the final mineralization, moving outwards from the amelodentinal junction, is shown black...

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