The four zones of the incipient lesion, described by Silverstone, are:

Question

A) Outer zone, body of the lesion, dark zone, and translucent zone
B) Surface zone, body of the lesion, dark zone, and translucent zone
C) Light zone, body of the lesion, dark zone, and translucent zone
D) None of the above

Answer 1

B
Explanation: B) The translucent zone, the deepest zone, is seen in approximately 50% of the carious lesions examined. In this zone, which is the advancing front of the lesion, slight demineralization occurs, resulting in a 1% pore space, compared with 0.1% for intact enamel. In contrast, the dark zone occurs in approximately 95% of carious lesions and has a pore volume of 2% to 4%. When teeth showing no dark zone are placed in a remineralizing solution, the dark zone becomes visible in its expected position between the translucent zone and the body of the lesion. On the basis of this finding, it is suggested that this dark zone is where remineralization can occur; and, that a wider dark zone requires a greater amount, or a longer period, of remineralization of the lesion.
Peripheral to the dark zone is the main body of the lesion. In this zone, pore volume ranges from approximately 5% on the fringes of the lesion to about 25% in the center.13 Despite this considerable amount of demineralization, the remaining crystals still maintain their basic orientation on the protein matrix. Finally, the surface zone has a near-normal pore space of approximately 1%. The surface zone and the dark zone are the remineralization zones of the incipient lesion. Thus, surface and subsurface remineralization of pore space with calcium and other minerals is possible until cavitation occurs with the complete breakdown of the enamel matrix.