Method: Human dentine blocks were demineralized with acetic acid (IRB-UW08-052). After demineralization, six blocks received 38% SDF solution (SDF group) whereas the other 6 blocks received distilled water (Control group). The blocks were placed in 24-well plates, inoculated with Streptococcus mutans, and incubated at 37℃ anaerobically for 7 days to form biofilm on the dentine caries lesions. Knoop microhardness testing was used to measure the microhardness of the lesions after biofilm challenge. Scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy were used to study the calcium and phosphate content, and the organic (collagen I content using log [amide I: phosphate]) of the lesions, respectively.
Results: The Knoop hardness values of the outer 125 µm of the dentine caries lesions in SDF group was higher than the control group (0.34±0.08 vs. 0.14±0.02; p<0.01). SEM-EDS results showed calcium and phosphate weight-percent were higher in SDF group than the control group in outer 25 µm (Calcium: 20.3±8.0% vs. 6.0±4.1%, p<0.01; Phosphate: 9.3±2.8% vs 4.2±3.1%, p<0.05). The log [amide I: phosphate] of the lesions in SDF group was lower than the control group (0.65±0.26 vs. 1.10±0.28; p<0.05).
Conclusion: The study results show that SDF can increase the microhardness and reduce the minerals loss and collagen I breakdown of dentine caries lesion generated by Streptococcus mutans.
Study supported by University of Hong Kong (Grant #200802159003).