[Effect of extracellular zinc on osteoclastic resorption in dental mineralized tissues].

OBJECTIVE

To investigate the bone resorption caused by osteoclasts and modulating functions of zinc ion on dental slices.

METHODS

Osteoclasts were separated from long-limb bones of neonatal rabbits, cultured with de-activated human tooth slices and glass slices. The cells in the experiment group were treated with 1x10(-14)mol/L-1x10(-4)mol/L zinc+10% (volume fraction) fetal calf serum (FCS)+alphaMEM, while those in the control group were grown in 10%FCS+alphaMEM. Osteoclasts on glass slices were stained by TRAP staining. The absorption pits on tooth slices were observed by inverted phase contrast microscope. The resorbing activity was evaluated with the concentration of calcium in the supernatant liquid of osteoclasts. The ratio between the concentration of calcium in the experiment group and that of the control group was termed the resorption index.

RESULTS

The isolated cells were multinuclear and showed positive in cytoplasma by TRAP staining. Usually, osteoclasts resorbed tooth slices first on the cementum and dentin, which had lower content of mineralized tissue. Compared with those on bone slices, the lacunae on the dental slices appeared less in amount, less in area and shallower in depth. They often showed shallow pits in a large area. Microscopy showed that the number and area of absorption pits formed on treated tissues were less than those on the control tissues. The content of calcium in the supernatant liquid increased at the concentrations of 1x10(-4)-1x10(-14)mol/L zinc, especially in the group of 1x10(-8)mol/L, 1x10(-10) mol/L, 1x10(-14)mol/L zinc on the 3rd day (P<0.05). But they were reversed on the 7th day, except in the group of 1x10(-14)mol/L zinc. At the end of culture, the resorption indexes of 1x10(-4)-1x10(-7)mol/L, 1x10(-9)mol/L, 1x10(-12)mol/L and 1x10(-13)mol/L group were lower than 1, but those of 1x10(-8)mol/L, 1x10(-10)mol/L, 1x10(-11)mol/L and 1x10(-14)mol/L group were higher than 1.

CONCLUSION

The effect of zinc ion on osteoclastic resorption in dental slices is associated with phase and dosage closely.