An ex-vivo study of caries arrested  with silver diamine fluoride

Method: Twelve carious primary upper central incisors were collected from 6-year-old children. Six teeth had arrested caries after 24-month biannual SDF applications and 6 had active caries when there was no topical fluoride treatment. The mineral density and crystal characteristics were assessed by micro-computed tomography (micro-CT), and transmission electron microscopy (TEM).

Result: Micro-CT examination revealed a superficial opaque band approximately 150 µm in depth in the arrested cavitated dentinal lesion. This band was limited in the active carious lesion. Needle-shaped crystallites could be seen under TEM in the fine particles collected from the surface of the arrested dentinal lesion. Lattice spacing and intersection characteristics of hydroxyapatite could be identified at high magnification. The arc-shaped selected area electron diffraction (SAED) patterns suggested that the c-axes of the hydroxyapatite platelets had a preferential orientation. In contrast, crystallites could barely be recognized in the active dentinal lesion; only rounded crystallites were found at high magnification. The crystallites were generally smaller than those observed in the arrested dentinal lesion. SAED of these structures were devoid of arc-shaped patterns, suggesting a more random crystallite arrangement.

Conclusion:

A highly remineralised zone with well aligned hydroxyapatites was found on the arrested cavitated dentinal lesion of primary teeth which had received topical SDF applications.