Advances in Dental Research, Vol 3, 183-187, Copyright © 1989 by International & American Associations for Dental Research
Scanning electron microscopy of trypsin-treated enamel from fluorosed rat molars
T. B. Kardos, A. R. Hunter and M. J. Hubbard
Fluoride-induced pitting and porosity of teeth have long been observed, but
little progress has been made in determining their origin. We have
observed, in the trypsin-treated surfaces of enamel, pits that disappear on
completion of maturation, following the removal of the protein matrix and
full mineralization. Since these pits were considered to be similar to
those seen in fluorotic teeth, this scanning electron microscope (SEM)
study was undertaken to determine the effect of fluoride on these transient
developmental pits during enamel matrix maturation. A group of 20
eight-day-old rats was given daily intraperitoneal injections of NaF (20
mg/kg [9 mg F-/kg] body weight) for five days. Twenty control animals
received intraperitoneal injections of isotonic saline. Maxillary and
mandibular molars were dissected from the 13-day-old animals, washed in
HEPES buffered (Ca2+/Mg2+) free basal medium, Eagle's (BME), incubated in
3% trypsin/BME for 5-10 min at room temperature, then indirectly sonicated
in BME for 2-4 min. Clean crowns were fixed in 2.5% glutaraldehyde for
three hr, dehydrated, critical-point-dried, and sputter-coated for SEM.
Pits in the surfaces of developing enamel were observed in all groups. In
control teeth, the pitting was restricted to the cervical margin, whereas
in teeth from the fluoride-treated animals, pits were observed on some
cuspal surfaces in addition to the cervical margin. These results confirmed
that pits in trypsin-treated surfaces of developing enamel are a transient
developmental event and showed that, in the presence of a high dose of
fluoride, the maturation of enamel is modified with retention of the pits.
