A STUDY OF THE INORGANIC CARBON DIOXIDE IN INTACT HUMAN ENAMEL

¹ Eastman Dental Dispensary, Rochester, N. Y.

1. Differences in the CO₂ content of superficial and inner portions of intact human enamel are reported for unerupted and erupted permanent teeth of different ages. The concentration of CO₂ increases from the surface toward the dentin in all tooth groups. This pattern of distribution appears to be developmental. The CO₂ content of the outermost and subsurface enamel increases after the completion of calcification in unerupted teeth, and decreases progressively with age in erupted teeth. The CO₂ distribution in the bulk of the enamel does not change after mineralization.

2. The loss in weight on ashing at 525° C. is greater in the outermost than in immediately underlying enamel. However, the pattern of distribution of CO₂, based on either dry or ashed weight, is similar.

3. No marked differences were found in the calcium or inorganic phosphorus distribution with age or enamel depth. CO₂:P molar ratio ranged from a low of 0.05 at the outer surface of enamel to a high of 0.115 near the dentinoenamel junction.

4. Preliminary experiments show that a portion of the CO₂ in enamel may be removed by exposure to weak acids. Loss of CO₂ from the surface enamel of erupted teeth may therefore be the result of preferential dissolution.