Method: Dentin beams 3 x 6 x 0.5 mm were prepared from mid-coronal dentin of extracted human third molars. One group of 12 specimens was left mineralized as controls. A second group of 12 beams was acid-etched on each side by 37% PA for 15 sec. A third group of 12 beams was completely demineralized in 10% phosphoric acid for 18 hrs. After extensive water rinsing, the dry mass of the disks was measured and then they were incubated individually in medium at 37°C with shaking. After 1 week, they were rinsed and their dry masses re-measured.
Result:
|
Mineralized beams |
Acid-etched beams |
Completely demineralized beams |
Loss of dry mass |
-0.54a ± 0.23 |
-3.56b ± 0.37 |
-6.45c ± 1.52 |
N |
12 |
12 |
12 |
Values are % loss of dry mass. Groups identified by different letters are p<0.05.
Conclusion: We were surprised that acid-etched mineralized dentin lost 3.56% of its dry mass in one week. The depth of demineralization layers apparently released more peptide fragments per unit mass than is possible with completely demineralized beams. It is likely that some hydrolyzed peptide fragments remain trapped in completely demineralized beams that are 500 µm thick.