Teeth
The tooth can be divided into two main areas: the crown and the root.
Most of the hard tissue in teeth is dentine, a special calcified tissue, derived from mesenchyme. The dentine in the root is covered by a layer of cementum, calcified tissue derived from mesenchyme. The tooth is then connected to bone by the periodontal ligament, which has wide bundles of collagen fibres, and is embedded in bony ridge called alveolar ridge.
Teeth is made up of three layers, enamel, dentine and a pulp cavity. The crown is protected by layer of enamel, a very hard, highly mineralised tissue, which is derived from ectoderm. Cementum, dentine and enamel differ from bone, in that they are not vascularised. Enamel also does not have collagen as its main consituent. It is made up of crystals or prisms of calcium phosphate. The centre of tooth is made up of a pulp cavity that extends down through the roots as a root canal. This region contains the nerve and blood supply to the tooth.
Gums, or gingiva is the name for the oral mucosa that covers the tooth. At the gingival crevice (or sulcus), the cells in the epithelium of the gum adhere to the tooth enamel via a basement membrane. If bacteria calcify here, and accumulate, they can disrupt this seal, and the periodontal tissues can become infected and inflamed.