Interaction of Fluoride and Molybdenum on Dental Morphology in the Rat

Eleven replications of a 2 by 2 factorial design were completed to study the main effects and the interaction of fluoride and molybdenum on dental morphology in the rat. This design permitted the measurement of within-litter effects by the treatments, which were administered twice daily from postnatal days 4 through 19, inclusively. The rats were destroyed at 21 days. The left maxillary first molars were sectioned along the maximum' mesiodistal diameter, and various morphologic features were measured by means of a calibrated eyepiece graticule at magnifications of X25, X44, and X125. None of the treatments altered the size of the tooth, as determined by the maximum mesiodistal diameter, but fluoride and the interaction of fluoride and molybdenum altered the widths of the fissures and the thickness of the enamel and the dentin lining the fissures. For the particular levels of fluoride and molybdenum used in this study, the interaction did not enhance the effect of fluoride alone, but instead depressed and reversed it. The possible significance of the findings have been discussed, and several suggestions for future investigation have been made.