Inflammation in rat bone induced by sodium fluoride

Abstract

Sodium fluoride (NaF) and sodium monofluorophosphate (MFP) are compounds that generate fluoride, being able to increase differentiation and proliferation of osteoblast. It has been demonstrated that NaF increases bone mineral density at the level of hip and spine, although there are still controversies regarding the quality of bone. The aim of this study was to evaluate the histopathological characteristics of bone tissue and bone morphometric differences under treatment with NaF and MFP. Experiments were carried out in female rats which were divided in 3 groups (n= 8 per group): control group = water 1 ml/day; NaF group = NaF 80 mmol/day, and MFP group = MFP 80 mmol/day. After that, the tibia and femur were obtained for the following analysis: 1. Histomorphometric analysis of trabecular bone (trabecular bone volume, trabecular thickness and trabecular width) 2. Morphometric analysis of cortical bone (cortical area, cortical width, periosteal and endosteal perimeter); 3. Biomechanical three-point bending test; 4. Histopathological analysis. NaF and MFP showed increased trabecular bone volume. At midshaft level the treatment did not modify the cortical width and the fracture load in a three-point bending test showed no significant differences between groups. Histopathological analysis of the bones of rats treated with NaF showed an immature bone net, numerous active osteoblasts, osteoclasts with greater multinucleation and fibrosis peritrabecular. The animals treated with MFP showed bone with mature appearance and a more organized pattern. The lack of inflammation was a distinctive feature compared with bones of rats treated with NaF. The presence of acute inflammation in bone of rats treated with NaF could explain the lack of therapeutic success with this drug.