REGIONAL DIFFERENCES IN MOLECULAR CROSS-LINKING OF PERIODONTAL-LIGAMENT COLLAGEN OF RAT INCISOR, BY POLARIZING MICROSCOPY

Collagen, a naturally birefringent biopolymer and key structural compo nent of the periodontal ligament (PDL), is altered substantially with regard to its molecular cross-linked structure by the dietary lathyrog en, beta-amino-proprionitrile (beta-APN). Our purpose in studying beta -APN-fed animals was to team if the strength of birefringence of perio dontal collagen, measured microscopically by the Senarmont compensator method, correlates with the molecular changes known to occur in these lathyritic animals, and to explore this technique for the periodontal ligament. Five experimental animals were fed a diet containing 0.25% beta-APN for two weeks, and 3 control animals were fed normal rat chow . Tissues were decalcified and the mandibular incisors were cut in cro ss section at 4 mu m and stained with eosin Y. The Senarmont compensat or, an attachment for the polarizing microscope, was used to measure p hase retardation. Ten measurements were taken from each of the three s ides (mesial, lateral and lingual) of the triangularly shaped incisor sections. The collagen fibers of the beta-APN-fed rats had lower value s of phase retardation than the controls (p < 0.001), indicating reduc ed molecular organization. In addition, minor but significant regional differences were revealed, supporting the method for structural studi es on the periodontal collagen.