Lead acetate as a vital marker for the analysis of bone growth

Quantitative evaluation of newly formed bone in the alveolar wall surrounding the root during the initial stage of experimental tooth movement in the rat

By using a chronological lead-labelling technique and computer image analysis the volume of this newly formed bone was evaluated. Rat maxillary first molars were moved mesially by a fixed, closed coil-spring appliance for 6 days using three different magnitudes of initial tensile force (27, 60 and 136 g). Sham-treated rats wearing an inactivated appliance were used for the control study. All animals were injected twice intraperitoneally with lead-disodium EDTA, 3 hr before the beginning and 3 hr before the end of treatment. The unit volumes of newly formed bone (mm3/mm2) were assessed with reference to lead-labelling lines in the alveolar walls of the root socket by computer image analysis. In the control group, two distinct lead-labelling lines indicated continuous bone formation on the mesial side of the root sockets, but only a jagged line was found on the distal side. After experimental mesial tooth movement, only a single lead line could be found on the mesial/pressure side of the root sockets; on the distal/tension side, a wide layer could be detected between the two lead lines. The volume of newly formed bone on the distal/tension side in the experimental groups was significantly greater than that in the control group. However, there was no significant difference in the volumes of newly formed bone among the three experimental groups. The study demonstrates that the volume of newly formed bone in the alveolar walls during the initial stage of tooth movement can be quantified and that the magnitude of the tensile force of tooth movement may not influence directly the volume of newly formed bone in the alveolar wall on the tension side.

Mechanism of induction of hypercalcemia and hyperphosphatemia by lead acetate in the rat

The present study is an investigation of the mechanism of hypercalcemia and hyperphosphatemia induced by the intravenous injection of lead acetate (Pb-Ac). A total of 118 male rats were injected with 30 mg/kg of Pb-Ac, or with 16.5 mg/kg of sodium acetate as the control. The levels of serum calcium, phosphorus and lead were then determined at various time periods after the injections. Serum calcium and phosphorus levels increased with time after Pb-Ac injection and the maximum values of calcium (17 mg%) were found after 1 h and of phosphorus (13.5 mg%) after 30 min. Both calcium and phosphorus levels reverted to the normal range after 12 h. The maximum net rates of increase of calcium and phosphorus were found immediately after Pb-Ac injection. At that time, deposition of lead at the calcifying sites of bone and incisor dentin was demonstrated by a histochemical examination. In other experiments the changes in the calcium and phosphorus contents in the medium after shaking bone powder in serum with Pb-Ac in an in vitro system were studied. It was confirmed that the calcium and phosphorus were displaced from the bone mineral, the extent of the displacement being correlated with the concentration of the Pb-Ac added to the medium, and that these displacements were very rapid reactions. These results suggest that hypercalcemia and hyperphosphatemia following Pb-Ac injection results from a direct action of lead on the bone mineral.

Effects of repeated ingestion of large quantities of acetylsalicylic acid on membranous bone growth and dentin apposition in young monkeys

Four daily doses of ASA were administered by mouth to young growing monkeys which received six injections of lead acetate every seven days as an intravital stain to indicate sites of bone and dentin mineralization. Microscopic evaluation of the inhibitory effects on membranous bone growth and dentin apposition was made. Four doses of ASA at 325 mg/kg inhibited membranous bone growth as well as the remodeling of the Haversian canal systems for about 16-18 days, with incomplete recovery during the experimental period. No comparable effect on dentinogenesis was observed. This preliminary study indicates that four doses of ASA at this level caused a toxic effect directly on membranous bone growth but not on dentin apposition.

Effects of tetracyclines on membranous bone growth and dentin apposition in young rhesus monkeys

Various tetracyclines were administered by different routes to young monkeys that received multiple injections of lead acetate as an intravital stain of calcification sites. Microscopically, the tetracyclines inhibited membranous bone growth, but they did not affect dentin apposition.

Preliminary study of inhibitory effects of tetracyclines on membranous bone growth in rhesus monkeys

Various doses and forms of tetracycline were administered to young monkeys that received multiple injections of lead acetate as a vital marker of the calcification sites. The effects of these tetracyclines on membranous bone growth were assessed histologically ; retarded bone growth occurred under some conditions.

Effects of some staining agents on dentin apposition in young rabbits

Alizarin red S, trypan blue, chlortetracycline, and 45Ca were administered to young rabbits that received multiple injections of lead acetate as marker. Inhibiting effects of these agents on dentin apposition were studied. No evidence of toxicity of chlortetracycline or 45Ca was detected. Alizarin at 100 mg/kg reduced the rate of dentin apposition, and 150 mg/kg caused severe retardation. Trypan blue at 50 to 100 mglkg showed no adverse effects, but 350 mglkg arrested dentinogenesis completely.