4: Development and Morphology of the Primary Teeth

CHAPTER 4 Development and Morphology of the Primary Teeth

This chapter presents a brief review of the development of the teeth. An accurate chronology of primary tooth calcification is of clinical significance to the dentist. It is often necessary to explain to parents the time sequence of calcification in utero and during infancy. The common observation of tetracycline pigmentation, developmental enamel defects, and generalized hereditary anomalies can be explained if the calcification schedule is known. A brief discussion of the morphology of the primary teeth is also appropriate before considering restorative procedures for children.

A complete review is available in the reference texts on oral histology, dental anatomy, and developmental anatomy listed at the end of the chapter. Furthermore, contemporary scientists are rapidly gaining knowledge of tooth development at the molecular level. We suggest that readers with a special interest in the molecular events of tooth development study the listed references by Smith1 and by Miletich and Sharpe.2

LIFE CYCLE OF THE TOOTH

INITIATION (BUD STAGE)

Evidence of development of the human tooth can be observed as early as the sixth week of embryonic life. Cells in the basal layer of the oral epithelium proliferate at a more rapid rate than do the adjacent cells. The result is an epithelial thickening in the region of the future dental arch that extends along the entire free margin of the jaws. This thickening is called the primordium of the ectodermal portion of the teeth and what results is called the dental lamina. At the same time, 10 round or ovoid swellings occur in each jaw in the position to be occupied by the primary teeth.

Certain cells of the basal layer begin to proliferate at a more rapid rate than do the adjacent cells (Fig. 4-1A). These proliferating cells contain the entire growth potential of the teeth. The permanent molars, like the primary teeth, arise from the dental lamina. The permanent incisors, canines, and premolars develop from the buds of their primary predecessors. The congenital absence of a tooth is the result of a lack of initiation or an arrest in the proliferation of cells. The presence of supernumerary teeth is the result of a continued budding of the enamel organ.

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Figure 4-1 Life cycle of the tooth. A, Initiation (bud stage). B, Proliferation (cap stage). C, Histodifferentiation and morphologic differentiation (bell stage). D, Apposition and calcification.

(Adapted from Bath-Balogh M, Fehrenbach MJ: Illustrated dental embryology, histology, and anatomy, ed 2, Philadelphia, 2006, Saunders.)

Jan 14, 2015 | Posted by in Pedodontics | Comments Off on 4: Development and Morphology of the Primary Teeth
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