Meeting Abstract
12.5 Friday, Jan. 4 Morphology of the rabbit periodontal ligament and the effect of reduced bite force SELF, CJ*; HERRING, SW; University of Washington, Seattle; University of Washington, Seattle cjself@uw.edu
The periodontal ligament (PDL) transmits occlusal loads from the teeth. This study was undertaken to describe the morphology of rabbit molar PDL as an example of an evergrowing cheek tooth and to determine the effect of reduced loading on the PDL. Under reduced loading, decreased architectural uniformity and collagen amount were expected. To achieve partial unloading rabbits received a single dose of either botulinum toxin (BTX) or saline into one masseter muscle (n=7-8). After 4 weeks specimens were sectioned horizontally or coronally and stained with picrosirius red. Linearly polarized light was used on coronal sections to measure fiber orientation. Horizontal sections were evaluated under circularly polarized light to quantify collagen content. Values from the left and right sides were averaged. In control PDLs collagen content was 21.6۪±8%, lower than 35% reported in murine molars, which are not evergrowing and thus have relatively short, stable roots (Beertsen et al 1975). Average angle of fiber attachment was 61°, more obtuse than the reported 30° for humans (Raspanti et al. 2000) but similar to rats (61°, Komatsu and Chiba 1997), mice (51°, unpublished), and cows (50°, Pini et al. 2004). Although more comparative data are needed, these findings suggest that relative root length can compensate for low collagen content and that obtuse PDL orientation correlates with horizontal-plane chewing. Nonparametric comparisons of reduced vs. normal bite force groups showed slight reductions in collagen and attachment angle, but these were non-significant, reflecting the small sample size and modest decrease in force. However, there was no trend for variability to increase. PDL uniformity may be related to chewing direction rather than occlusal force. Supported by PHS DE018142.
