1979 Volume 29 Issue 2 Pages 90-102
Human incisors, fixed in 10% formalin, were exposed to disinfected (Calpis) or live (Yakult) lactobacillus drink at 37°C and the structural changes of the natural surface and the outer enamel layer were observed.
The natural surfaces of the enamel exposed to the lactobacillus drinks became white and the degree of whitenss increased day by day. The changes however were not as distinct by scanning electron microscopy and electron probe X-ray microanalyser. It was found that the peripheries of the terminal enamel rods on the natural surfaces were dissolved by exposure to the disinfected lactobacillus drink for 10 days and by exposure to the live lactobacillus drink for 24 hours.
On the other hand, in the outer enamel layer the demineralized zone migrated to the subsurface enamel layer as days went by and the uppermost surface of the enamel was recognized as a highly mineralized zone, indicative of remineralization. On exposure to live lactobacillus drink for 10 days a highly mineralized zone was observed in the outer enamel layer and inside the mineralized zone a demineralized zone was found. By scanning electron microcopy the crystallites of the enamel rods were needle-like in structure and their arrangement was relatively sparse in the demineralized zone. The cores of the enamel rods were dissolved at the incremental lines of Retzius.
In the ground enamel and dentin exposed to the lactobacillus drinks demineralization occured from their surfaces and the highly mineralized zones as shown in the intact enamel were not observed.
