A. Long et al., A QUANTITATIVE STUDY ON THE MYELINATED FIBER INNERVATION OF THE PERIODONTAL-LIGAMENT OF CAT CANINE TEETH, Journal of dental research, 74(6), 1995, pp. 1310-1317
The periodontal ligament is richly innervated with mechanosensitive af
ferent nerve fibers, and the location of the mechanoreceptive terminal
s within the ligament is of functional significance. In this study, we
have obtained quantitative information on mechanoreceptor distributio
n in the lower canine teeth of the cat. Using light microscopy, we qua
ntified the number of myelinated axons in the periodontal ligament at
1 mm, 3 mm, and 5 mm from the tooth root apex. Grouped axons and axons
which were isolated in the cemental half of the ligament (and therefo
re putative mechanoreceptors) were identified. The mean total number o
f axons was 1290 (n = 20) at 1 mm from the apex, 1290 at 3 mm, and 814
at 5 mm. The distribution of axons around the tooth root circumferenc
e was found to be non-uniform. Near the root apex, the highest numbers
of grouped axons were located distally and mesially, and in the middl
e region of the root, the highest numbers were found mesially. The hig
hest numbers of isolated axons at the apical levels were located dista
lly, and in the mid-root region, mesially. At all levels, the lingual
region was the most sparsely innervated by both groups. There was a po
sitive correlation between the number of grouped axons and the width o
f the ligament in the same region, but this correlation was much weake
r for isolated axons, suggesting that their distribution does not resu
lt only from the volume of tissue. Variations in the number of axons a
nd, to a lesser extent, the dimensions of the periodontal ligament wer
e considerable. However, these variations were less between left and r
ight teeth of the same animal than between teeth in different animals,
reinforcing the use of the contralateral tooth as a control for exper
iments in which these variables are quantified.