EFFECT OF FLUORIDE ON CRYSTAL TEXTURE AND RADIOCALCIUM UPTAKE OF RAT BONE

Physical properties of root cementum: Part 6. A comparative quantitative analysis of the mineral composition of human premolar cementum after the application of orthodontic forces

INTRODUCTION

The aim of this study was to examine quantitatively with electron probe microanalysis (EPMA) the calcium (Ca), phosphorus (P), and fluoride (F) concentrations in human first premolar cementum after the application of light and heavy orthodontic forces.

METHODS

Thirty-six maxillary and mandibular first premolars (18 experimental, 18 control) were extracted from 16 subjects (10 male, 6 female; mean age, 13.9 years; range, 11.7-16.1 years) who were randomly assigned to the light-force or the heavy-force group. In the light-force group, 25 g of buccally directed force was applied to the experimental premolar; in the heavy-force group, 225 g of buccally directed force was applied to the experimental premolar. The contralateral premolar served as the control. The experimental and control premolars were extracted 28 or 29 days after initial force application and prepared for EPMA. The Ca, P, and F concentrations were measured on the buccal and lingual surfaces at the midpoint of the cervical, middle, and apical thirds of the root from the outer to the middle to the inner third of the cementum.

RESULTS

Little change was found in the mineral composition of cementum after the application of light forces; however, there was a trend toward an increase in the mineral composition (Ca, P, and F) of cementum at various areas of periodontal ligament compression. The application of heavy forces caused a significant (P = .000) decrease in the Ca concentration of cementum at certain areas of periodontal ligament tension. The application of both light and heavy orthodontic forces did not appear to influence the F concentrations in cementum.

CONCLUSIONS

Heavy orthodontic forces cause alterations in the mineral content of cementum; light forces cause little change.

Effect of fluoride on root resorption caused by mechanical injuries of the periodontal soft tissues in rats

The present study was carried out to investigate histologically and histometrically the effect of fluoride on root resorption induced by mechanical injuries of the periodontal soft tissues in rats. Resorption lacuna in the root surface of the molar in animals given both mechanical injuries and fluoride administration was significantly smaller in length and area than that in animals given only mechanical injuries. Moreover, resorption lacuna in the former animals contained fewer odontoclasts than that in the latter. The results of the present study might suggest that the administration of fluoride suppressed root resorption induced by mechanical injuries of the periodontal soft tissues.

Histologic and histometric study of the effect of fluoride on the rat mandibular condyle

The effect of fluoride on the rat mandibular condyle was studied histologically and histometrically. The condyles of the rats that received 50 ppm fluoride in the drinking water for 17 weeks did not differ in structure from those of the control rats fed tap water containing 1 ppm fluoride. However, the condyles of the rats given 100 ppm fluoride in the drinking water for the same period showed a significant increase in both the thickness of the cartilage layer (P smaller than 0.02) and the density of cancellous bone (P smaller than 0.01) when compared to the controls. The thickening of the cartilage layer was due to an increase in the number of hypertrophied chondrocytes. The trabeculae of cancellous bone were thicker and consequently the bone marrow spaces were extremely reduced. The trabeculae contained more calcified cartilage in their cores.

Effect of fluoride-containing compounds on the skeletal retention of 80Sr and 45Ca in the rat

A series of three studies was conducted with rats to investigate the influence of various means of fluoride supplementation on radioactive strontium metabolism. The data demonstrated that shortened periods of fluoride exposure of 60 days or less did not alter radioactive strontium metabolism appreciably, but periods of fluoride exposure of four to eight months decreased the skeletal retention of radioactive strontium significantly.