A morphometric examination of the periodontal ligament vasculature of the marmoset molar

Abstract

Although many investigators have studied the vascular morphology of the animal and human periodontal ligament, there is an absence of a definitive systematic assessment of the periodontal vascular distribution. Descriptions of the macroscopic and microscopic vascular architectural arrangements of the mandible and periodontal ligament have tended to be qualitative rather than quantitative. A light microscopic morphometric investigation was undertaken to establish and evaluate the periodontal ligament vascular distribution of the marmoset monkey mandibular second molar to obtain further species information. Eight marmoset mandibles were histologically processed and serially sectioned horizontally at 8 microns from the cervical to the apical region of the second molar. These animals had been subjected to various diet regimes over varying periods. In the pilot study, 20 vertical sections per molar root were sampled for two second molars from two animals. As a result of a statistical evaluation of the pilot study, it was determined that six equidistant sections per molar root was an adequate sample for the major study. These sections were stained with Miller's, Verhoeff's iron haematoxylin or Pollack's trichrome. Two hundred and thirty photomicrographs were projected onto a digitizing tablet of a semiautomatic tracing device at a magnification of 6,t00x to compute vascular and periodontal ligament areas. Appropriate standard descriptive statistics were employed using the B.M.D.P. (Biomedical) statistical software package to determine the vascular distribution of the periodontal ligament. In addition, a general linear mixed model on a logit scale was used to determine a stylized periodontal vascular distribution model for each of the three lateral thirds of the periodontal ligament. Ten randomly selected photomicrographs were re-anaìysed to test the repeatability of the method. The findings demonstrated that the existence of statistical differences between lateral thirds of the periodontal ligament necessitated the analysis of these regions separately. No significant difference at the one percent level was found for any of the variables examined to test the repeatability of the method. The lateral vascular distribution was such that the middle third had the greatest vascular volume (13.l percent), followed by the alveolar ligament third (8.9 percent) with the least to be found in the ligament third near tooth root (2.6 percent). The overall periodontal vascular volume for the marmoset mandibular second molar obtained from the data was 8.3 I 0.4 percent (mean 1 2 standard errors) whereas that derived from the stylized periodontal ligament model was 7.5 percent. These two overall percentage vascular volume figures were so similar that it was reasonable to conclude that the statistical model of the vascular distribution was an acceptable representation of the data. The vertical vascular distribution was zone dependent. However, in general, an increase was demonstrated from the cervical to the apical regions. A consistent finding for all lateral thirds of the ligament, at any depth of the ligament and in all quadrants, was that the percentage vascular volume for the tooth on the right side of the mandible was greater than that on the left. In zone 1, the alveolar ligament third, quadrants 1,2,3 and 4 were found to be statistically different from each other at the one percent level with the lingual surface having an appreciably greater vascular volume. The remaining three quadrants were similar in their vascularity, although the vascular volume on the buccal was greater than that on the mesial which, in turn, was greater than that on the distal. A detectable statistical difference between mesial, distal or single roots was not evident, nor was there any statistical evidence of differences between animals due to their respective diets . The intraspecies and interspecies vascular configurations and distributions are discussed with particular emphasis placed on the possible functions of the periodontal ligament vasculature. some of the previous periodontal vascular distribution findings reported in the literature have been supported by the present observations.