Journal of Dental Research, Vol 72, 46-50, Copyright © 1993 by International & American Associations for Dental Research Online Journals
Comparison of rates of enamel synthesis in impeded and unimpeded rat incisors
Z. Skobe, J. D. Heeley, J. M. Dobeck, K. S. Prostak, L. Maravelis and D. N. Stern
Forsyth Dental Center, Boston, Massachusetts 02115.
Periodic intubations of rats with solutions of fluoride (F) lead to the
appearance of bands of disrupted pigmentation in continuously erupting
incisors. Distances between fluorotic bands reflect time intervals between
intubations. In this experiment, the periodicity of fluorotic banding was
used for estimation of the rate of enamel synthesis in impeded and
unimpeded rat incisors. Rats kept on a low-F diet and distilled water were
intubated two or four times per week with 2 mg NaF/150 g body weight. In a
group of rats, one of the mandibular incisors was cut at the gingival
margin after two weeks, and intubations were continued for an additional
two weeks. In another group of F-intubated rats, incisors were cut or
notched at the gingival margin twice, six days apart. Control rats either
received the same periodic F intubations or were maintained on the low-F
diet without intubation. Measurements of spacing between fluorotic bands
were identical in impeded and unimpeded teeth, even though the latter
erupted at a faster rate. In an unimpeded mandibular incisors, there was a
significant elongation of the secretory zone and a shortening of the
pigmentation zone, resulting in reduced pigmentation intensity of the
erupted portions of the teeth. The results show that the rate of enamel
synthesis is independent of the eruption rate.
