Preclinical Paediatrics · MU Sofia

17. Histogenesis of the periodontium.

Covers the development of the periodontium, starting with the four main components: gingiva, periodontal ligament, cementum and alveolar bone. It traces how the periodontal ligament forms from the dental follicle, including the differentiation of follicular cells into cementoblasts, osteoblasts and fibroblasts and the origin of Sharpey's fibres. It then describes alveolar bone formation and the staged growth of ligament fibres, ending with the histology of the ligament and the intermediate plexus.

Inside: 2 sections · 4 labelled pictures · 14 flashcards · 7 min

Topic 17 of 40 in the MU Sofia syllabus for Preclinical Paediatrics (Dental Medicine, Year 3). The free AceMed note covers it in 2 sections, about 1,065 words (7 min of reading), with 14 flashcards.

In this note

  1. HISTOGENESIS OF PERIODONTIUM
  2. Elongation and growth of fibers

HISTOGENESIS OF PERIODONTIUM

Periodontium is a complex set of structures that helps to support the tooth and consists of four principle components:

  • Gingiva
  • PDL
  • Cementum
  • Alveolar Bone

Tissues form a specialized fibrous joint and are thought to be of ectomesenchymal origin

PERIODONTAL LIGAMENT

PDL is a fibrous connective tissue between the alveolar bone and cementum covering the root and connects it with gingiva. The PDL occupies the periodontal space and is composed of:

  • Fibres
  • Cells
  • Intercellular Substance
  • Has many mesenchymal cells (Cells of dental follicle differentiate into collagen forming cells) that, if stimulated, differentiate into osteoblasts, cementoblasts and fibroblasts (form the ligament, cementum and alveolar bone)
  • Some cells of ligament invade the tooth root sheath as it breaks apart. Other cells of ligament area form delicate fibres, which appear along with the forming roots near the cervical region of the crown
  • Thickness of PDL varies from too to tooth and its position in relation to the tooth
  • Thinness portion of PDL is near the middle of root
  • Width of PDL shows a progressive decrease with age

DEVELOPMENT OF PDL

  • During initial stage of root formation, Dental follicle is the dental germ element which is responsible for periodontal ligaments development Fibroblasts
  • Under the influence of Hertwig’s Root Sheath, follicular cells show increased proliferation and differentiate into:
  • Cementoblasts→ innermost cells of follicle
  • Osteoblasts→ outermost cells of follicle (forming alveolar bone)
  • Fibroblasts→ centrally located (form periodontal ligament) synthesis of collagen + removal of collagen fibres due to remodeling ↓ digestives vacuoles
  • The inner cell’s package of fibroblasts produces the fine fibrils oriented around the regions of cementogenesis
  • Initially PDL fibres are oriented parallel to the root. At this stage, almost no or only a thin layer of cement was posted over
  • Cementum matrix has specific receptors molecules that attract fibres
  • Attachment of the fibres is done by adhesins and specific receptors on the fibres. The fibres are then inserted into the cementum matrix perpendicular to the dentin. After attachement of fibres to the dentin, they are coated with a cementum matrix and remain switched on in cementum as extrinsic or Sharpei’s fibres
  • Fibroblasts produce the PDL fibres by getting embedded in the developing cementum and alveolar bone
  • All developing fibres of periodontal ligament run obliquely in the coronal direction from tooth to bone
  • Changes as tooth erupts. Part of PDL fibres present in cementum and alveolar bone are called the Sharpey’s Fibres

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