Periodontal ligament/Bone

The periodontium (the tooth support structure) has four constituent connective tissues, two of which are calcified and two which are non calcified. The two non-calcified (soft) connective tissues are the periodontal ligament (PDL), which fills the periodontal space between the root and the socket wall, and the lamina propria of the gingiva. By convention the boundary between the two is a horizontal line drawn at the level of the alveolar crest. The two calcified tissues are the cementum on the root surface (a bone-like material which can be either acellular or cellular) and the alveolar bone of the socket wall. This bone may also be referred to as the lamina dura (because it appears as a prominent white line on x-ray) or the cribriform plate (because it is perforated with numerous channels containing blood vessels). All four connective tissue elements of the periodontium share the same major matrix element: type I collagen.

There are five slides available covering various aspects of periodontal and alveolar bone structure. Slide 1 is a demineralised section of a tooth in situ showing periodontal structure, bone formation (osteoid) and bone resorption. Slide 2 is also demineralised but is stained with picric acid (rather than H&E) - this highlights the collagen fibres, especially as they insert into bone and cementum. Slide 3 is demineralised but then pre-oxidised before staining with an elastin stain - this stains the oxytalan fibres within the PDL. Slide 4 is a (micro)radiograph of a ground section of a tooth in its socket - this demonstrates the varying degrees of mineralisation within the bone of the socket of the tooth. Slide 5 is a ground section of a tooth highlighting the structural features of cementum.