The purpose of this investigation was to study the effect of the different stages in the development of the child on the quality and the degree of calcification of the enamel and the dentili and to describe the characteristics of the developmental periods as revealed by the changes recorded within these structures.
Mode of Tooth Growth.—The hard tissues of the teeth, the enamel and the dentin, grow by the formation of a layer of new substance on the old (fig. 1). Such activity is termed appositional, or additive, growth, as distinguished from proliferative, or multiplicative, growth. The former is the result of cellular secretion; the latter is the result of cellular division.The appositional type of growth results in the formation of concentric layers, or rings, and is well illustrated in the trunk of the tree. The cambium, under the bark, is analogous to the formative layers