The effect of the consistency of the diet on eruption rates and lengths of incisor teeth in rats.

It is uncertain whether the consistency of the diet affects the eruption of rodent incisors. One study reported that harder diets made incisors shorter and erupt faster, and suggested that the faster eruption was due to the decreased length. Two other studies found no effect on eruption rates. In the present study the impeded and unimpeded eruption rates of these lower incisors were measured, using ether anaesthesia for all procedures. There were two groups of rats fed in alternate periods on standard laboratory pellets and in the intervening periods on the same material ground to a powder. In each period, one group was fed on pellets and the other on powder. The impeded eruption rate was less when the rats were fed on powder than on pellets and the rate declined with time. The unimpeded incisors were not affected by the diet, so the effects on the impeded incisor were direct effects on the tooth and not systemically mediated. The impeded incisors lengthened during the experiment and the lengthening was greater on powder than on pellets. The ratio of the change in impeded eruption rates to the increase in tooth length on changing from pellets to powder was different from the ratio for going from powder to pellets, so the effect of the diet on the impeded eruption rate was not due to the change in length of the teeth. There was a negative correlation between the decline in impeded eruption rates and the lengthening of the incisor with time, suggesting that tooth length can influence eruption rates.(ABSTRACT TRUNCATED AT 250 WORDS)