In vitro study of the effects of copper ion on osteoclastic resorption in various dental mineralized tissues

Abstract

To investigate the effects of copper ion on osteoclastic resorption in various dental mineralized tissues. Osteoclasts were separated from long-limb bones of neonatal rabbits, and cultured with de-activated human tooth slices and glass slices. The cells in the experiment group were treated with (1 x 10(-14))-1 x (10(-4)) mol/L copper + 10% (volume fraction) fetal calf serum (FCS) + alpha-MEM, while the cells in control group cells were grown in 10% FCS + alpha-MEM. 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 control group was termed as the resorption index. The isolated cells were multinuclear and TRAP positive in cytoplasma. Osteoclasts resorbed teeth slices first on the cementum and dentin. Compared with those on bone slices, the lacunae on the dental slices numbered less, with smaller volume and shallower in depth. Microscopy showed that the number and area of absorption pits formed on treated tissues were less than those on control tissues. The content of calcium in the supernatant liquid decreased in the concentrations of 1 x 10(-14) mol/L - 1 x 10(-4) mol/L copper, especially in the group of 1 x 10(-10) mol/L copper at 3rd day (P < 0.05) and 1 x 10(-4) mol/L, 1 x 10(-10) - 1 x 10(-12) mol/L copper at 7th day (P < 0.05). Their resorption index was lower than one. Extracellular copper ion can inhibit osteoclastic resorption on dental slices.