Enamel rod formation in the monkey observed by scanning electron microscopy.

Area of Science:

• Developmental Biology
• Biomineralization
• Microscopy

Background:

• Tooth enamel formation involves ameloblasts secreting rod and interrod enamel.
• The precise structural relationship between rod and interrod enamel during development is not fully understood.

Purpose of the Study:

• To investigate the structural relationship between forming enamel rods and interrod enamel using scanning electron microscopy.
• To elucidate the mechanism behind the formation of enamel crystallites and their orientation.

Main Methods:

• Scanning electron microscopy (SEM) was used to examine permanent tooth buds from monkeys.
• Detailed analysis of the morphology of ameloblasts and the forming enamel surface.

Main Results:

• Mineralizing interrod enamel forms pits around Tomes' processes, restricting enamel rod formation.
• The forming face of enamel rods angles toward the tooth surface, creating a specific site for simultaneous rod and interrod enamel formation.
• Ameloblasts exhibit two secretory surfaces involved in crystallite orientation.

Conclusions:

• The specific arrangement of pits and ameloblast secretory surfaces facilitates simultaneous formation of rod and interrod enamel crystallites at the apical margin.
• This simultaneous secretion is hypothesized to cause the indistinct boundaries observed between rod and interrod enamel in this region.