The Susceptibility of ‘Young’ and ‘Old’ Human Enamel to Artificial Caries in vitro

A laboratory artificial caries technique has been used to compare the susceptibility of ‘young’ and ‘old’ enamel to an identical acid attack. Results showed that the lesions in old enamel were more demineralized than those in young enamel. A well-defined surface zone was usually absent in the old specimens, and furthermore the old enamel was obviously thinner than the young enamel. Fluoride analysis of the outer 80 μm of enamel showed young enamel to be richer in fluoride than old enamel, but still the old enamel exhibited a minor concentration gradient. The results indicate that old enamel should not necessarily be regarded as more resistant to acid attack than young enamel.