Journal of Dental Research, Vol 66, 1583-1586, Copyright © 1987 by International & American Associations for Dental Research Online Journals
Root surface caries subsequent to gingivectomy in rats inoculated with Streptococcus sobrinus (mutans) and Actinomyces viscosus
A. R. Firestone, C. Graves, P. W. Caufield and F. F. Feagin
We studied the effect of oral infection with cariogenic micro-organisms on
alveolar bone loss and root surface caries subsequent to gingivectomy in
rats. Thirty-six rats were fed diet MIT 200 (67% sucrose); one-half, the
controls, had antibiotics added to the diet. At ages 18, 19, and 21 days,
the experimental group was orally infected with streptomycin-resistant
Streptococcus sobrinus (mutans) 6715 and Actinomyces viscosus M-100. At age
30 days, all animals were subjected to a gingivectomy on maxillary and
mandibular left quadrants. The experimental group was re-inoculated at age
36 days. Animals were killed seven weeks after surgery. Jaws were stained,
and planimetric measurements of exposed root surface area and caries on
lingual/palatal surfaces of 1st and 2nd molars were made from video images
with a computer/digitizer. Compared with the non-operated contralateral
quadrants, gingivectomy significantly increased exposed root surface area
in the maxilla and in the mandible in both the control and experimental
groups. Oral inoculation significantly increased exposed root surface in
mandibular (but not maxillary) quadrants which had received a gingivectomy,
but had no effect on non-gingivectomized quadrants. There was no caries in
the control group, whereas ten rats in the experimental group had root
surface caries lesions, all in quadrants which had received a gingivectomy.
This rat model should prove useful in further studies of root surface
caries.
