Study of the structure and development of periodontium

Abstract

Aim or Purpose: We aimed to analyze the development process of natural periodontal ligament, which provided the oretical foundations the regeneration of periodontal ligament. Materials and Methods: Human third molars were collected with patients' informed consents and approval from the Ethics Committee of Stomatology Hospital, School of Medicine, Zhejiang University. C57 mice at different ages of from 1 week to 2 weeks and 4 weeks were used for study of mandibles. TheInstitutional Animal Care and Use Committee from Zhejiang University approved all animal experiments. The teeth toots were cut into thin disks by making parallel incisions perpendicular to the longitudinal axis of teeth utilizing a diamond saw at a low speed under water cooling. 600, 800, 2000-grit silicon carbide papers were used in order under DI water to polish. Half of the dentin disks were examined using scanning electron microscopy and the other half were examined with immunofluorescence using confocal microscope. The mandibles were cut into slices and examined with immunofluorescence. The type III collagen, type I collagen fibers and hydroxyapatites were stained. Results: The cementum was composed of two types of collagen fibers with different structures, rich in type III collagen and type I collagen respectively. The sharpey fibers were anchored by hydroxyapatite minerals. During the development of periodontal tissue, periodontal ligament fibers grew into intocementum and then mineralized by minerals. Conclusions: Two types of collagen fibers served as different roles in cementum, and the sharpey fibers from periodontal ligament were anchored by hydroxyapatite minerals after grew into tooth, which highlighted attention to this order when repairing tissues.