Effect of Excess Fluoride Exposure on Radiographic and Histopathological Changes in Long Bones of Rabbit

The present study aimed to investigate the effects of excess fluoride exposure on long bones in young rabbits ( Oryctolagus cuniculus ). New Zealand White rabbits ( n = 30) were randomly divided into five equal groups and were provided drinking water containing 0, 50, 100, 200, and 400 µg added fluoride per ml ad lib for a period of 90 days. Blood samples were collected on days 0, 45, and 90 of the experiment, and femur samples were collected for fluoride estimation on day 90 after radiography of long bone before sacrifice. Study revealed significant increase in serum fluoride concentration following oral intake of excess fluoride. Alterations in activities of alkaline phosphatase, aspartate transaminase, alanine transaminase, and concentrations of creatinine and urea nitrogen in blood plasma were also recorded in animals receiving excess fluoride, though changes revealed inconsistent pattern. Radiographic changes in long bones in fluoride exposed rabbits included widening of metaphysis, thinning of cortical region, and a variety of osteopenic changes like osteoporosis and osteomalacia that were more prominent in animals receiving 200 ppm or more than 200 ppm fluoride in drinking water. Important changes in histomorphology of growth plate in long bones recorded in excess fluoride (> 100 ppm) exposed rabbits included irregular thickening of epiphyseal growth plate with haphazard orientation of chondrocytes forming nodular protrusion into metaphysis. Fluoride exposure induced both osteogenesis and osteoporosis to a degree varying with dose of fluoride exposure.