[Evaluation of the repair process in mechanically injured rat bone stimulated by sodium fluoride with non-toxic doses].

The influence of sodium fluoride on the course of repair process in the mechanically injured rat bone was studied. Thirty six male Wistar rats aged 5 months, weighing 460-540 g were investigated. The animals lived under standard conditions and were fed ad libidum with the standard LSM food including 0.7 mg/kg of fluorine on the average. The animals randomly divided into 3 groups that comprised study and control groups, 6 rats each. The rats in the first group were given water with 20 mg (1.05 mmol) of sodium fluoride per kg of body weight for 24 h over a period of 2 weeks--group Ia. In the second group--IIa--animals were given water with sodium fluoride at a dose of 1.5 mmol/kg b.w./24 h for a period of 4 weeks. In the third group--IIIa--the animals were given sodium fluoride in a dose of 1.5 mmol/kg b.w./24 h for a period of 6 weeks. The rats from the control groups I, II and III were given water without sodium fluoride for the period of 2, 4 and 6 weeks, respectively. At the beginning of the experiment a hole was drilled in both femoral bones in rat under barbiturate anaesthesia. According to the protocol the rats underwent ether euthanasia after 2, 4 and 6 weeks after surgery and the following samples were collected: blood from the heart for biochemical studies and both femoral bones for biochemical and histological studies. The following parameters were evaluated in blood serum: fluorine, calcium, magnesium contents, serum concentrations of urea, creatinine, bilirubin and activity levels of enzymes: aspartate aminotransferase, alanine aminotransferase, cholinesterase, base phosphatase. Fluorine, calcium magnesium and zinc contents were estimated in bone samples. The concentration of fluorine ions in animal serum after 2, 4 and 6 weeks of experiment increased significantly as compared with the corresponding controls. The highest fluorine concentrations were observed in serum of rats supplemented with NaF for 6 weeks. The fluorine concentrations in the bone tissue and fresh and dried granulation tissues in all studied groups also revealed statistically significant increase as compared to the controls. The rats fed with sodium fluoride for the period of 6 weeks revealed statistically significant increase of serum magnesium concentration as compared to the remaining study groups. Bone magnesium concentrations in animals fed with NaF for the period of 2 and 6 weeks were higher as compared to the corresponding control groups, with the highest differences observed after 6 weeks of experiment. Animals fed with sodium fluoride for the period of 6 weeks revealed increased serum calcium concentrations as compared to the study groups after 2 and 4 weeks of experiment. Similar results were achieved in bone tissue samples (Fig. 1 and 2, Tab. 1-6). Basing on the achieved results in biochemical studies and histological pictures it should be assumed that laboratory animals fed with sodium fluoride in doses recognised as non-toxic reveal intensified healing process within mechanically injured bones. The use of sodium fluoride led to accelerated chondrogenesis process in the area of insufficiently perfused bone, osteogenesis including temporary callus formation and mineralization of the new bone, as well as remodelling into mature lamellar bone. The greatest differences in the repair dynamics for both groups occurred between the second and fourth week of experiment. These results could be the base of clinical studies on application of the sodium fluoride in the acceleration of fracture healing.