Calculus - a hard deposit of calcified plaque which is found around the neck of the tooth. When it is above the free gingival margin (supra-gingival) it is white and chalky. When it is below (sub-gingival) it is dark and hard.

    Candidiasis - an infection caused by Candida albicans, a normal commensal of the mouth; also called "thrush";

    Capsule - a fibrous casing surrounding an organ or gland; also a coating for some bacteria which protects them, from the bodies immune system. It is only the variety of Pneumococcus sp. which has a capsule which is able to pass the immune barrier and cause pneumonia

    caries - the demineralisation, and breakdown of tooth structure by plaque acids.

    Cariogenic - likely to cause caries. Sugar is cariogenic because it supports the growth of plaque

    Carious plaque - types of plaque which are associated with caries .

    Carnivorous - an animal whose diet consists of animal tissue.

    CEJ - see cemento-enamel junction.

    Cell junctions - sites on the cell membrane where cells attach to neighbouring cells. There are three main types. 1. adhering junctions, which anchor cells to each other to resist separation. They may form a belt of adhesions between cells (as between muscle cells) or spot attachments like desmosomes which hold epithelial cells together. 2. tight junctions have no space between the membranes and allow no leakage between cells. They are found between cells of a secreting glands and between endothelial cells of blood vessels to prevent fluid leaking out. 3. gap junctions are channels which allow transfer of small molecules like ions, sugars and amino acids, between cells.

    Cemento-enamel junction- the junction between the enamel covering the crown of the tooth and the cementum covering its root. Often referred to as the CEJ.

    Cementoblasts - cells of mesenchyme origin, induced by proteins from cells of ectodermal origin, to form a layer of cementum around the roots of teeth.

    Cementum - a thin layer of bone-like material covering the roots of teeth and sometimes the enamel surface, containing both extrinsic and intrinsic fibres.

    Central nervous system - the brain and spinal cord. The nerves which leave the spinal cord and brain comprise the peripheral nervous system.

    Chemotaxis - the movement of cells in response to chemical messengers. The movement of neutrophils and macrophages into damaged tissues is brought about by signals released by damaged tissues, and bacterial products.. The term applies to the movement of any organism attracted by a specific chemical, which may be a suitable nutrient.

    Cholinergice - cell receptors specific for the neurotransmitter acetyl choline. Cholinergic receptors are found at neuromuscular junctions of muscle fibres and at all the synaptic junctions of the parasympathetic nervous system. They are also found at the pre- ganglionic synapse of the sympathetic nervous system.

    Chondroitin sulphate - the major glycosaminoglycan of cartilage , the other being keratan sulphate.

    Chromosomes - structures in the nucleus of a cell which appear visible during cell division. Each chromosome (humans have 24) is a tightly coiled string of DNA wound round a protein.

    Clearance - the removal by swallowing, of substance in the mouth. Clearance is dependent on the completeness of swallowing and the rate of flow of saliva.

    Clones - a family of cells, or organisms, which are all identical to a single parent. They are produced by asexual reproduction. When a B lymphocytes has recognised a foreign antigen, it provides millions of identical daughter cells in order to produce the specific antibodies in large quantities.

    Clotting - see blood clotting

    Code - the code of nucleotides is written in "words" of three letters using an"alphabet" of four "letters". These four components of the code are adenine, thymine, cytosine, and guanine.

    Collagen - the most common protein found in the body. It has a fibrous structure and makes up the main organic component of bone and dentine, and the fibres of tendons and ligaments.

    Collagenase - an enzyme produced by fibroblasts which breaks down collagen fibres. The fibroblast recycles the component amino acids, and secretes new collagen fibres. This process of remodelling occurs throughout life. Osteoclasts also secrete collagenases in order to remove bone matrix. Several bacteria are able to secrete collagenases and are thus able to break down and penetrate through collagen fibres in the periodontal ligament.

    Colonies - communities of organisms which have taken up residence in a habitat .

    Competency - the ability of a cell to respond to messengers which could cause it to differentiate into a more specialised cell. Some cells, like pericytes remain competent throughout life, whereas others, such as the oral epithelium, are only able to form an tooth bud during the 12th to 16th week of foetal development.

    Composite - a material made from two or more different types of material which contribute different properties. For example bone is a combination of a resilient fibres of collagen in a brittle matrix (hydroxyapatite).

    Compressive strength - ability to withstand a crushing force.

    Condylar process - the vertical extension of the mandible which ends in the condyle head, the moveable part of the temporomandibular joint.

    Connective tissue - one of the four main types of collections of cells (tissues) which consists of cells in a matrix of ground substance and fibres. Some connective tissues support structures like blood vessels and glands. Others are more structural, like bone, tendons and cartilage.

    Contralateral - the opposite side as distinct from ipsilateral. Often used to refer to the teeth, joint or muscles on the opposite side from the chewing side.

    Coronoid process - the vertical extension of the mandible anterior to the condyle to which the temporal muscle attaches.

    Cortical-bone - the outer layer of bone which is dense and made up of lamellae.

    Covalent bond - a strong bond between atoms formed by sharing outer electrons. When an atom has 8 outer electrons it is stable. Those which naturally have 8, like neon and argon gasses are quite unreactive. The carbon atom has 4 outer electrons and therefore needs 4 extra electrons to be stable. Four hydrogen atoms make a good partnership for carbon,(CH4, C2 H6 ... etc) hence hydrocarbons,(saturated with hydrogen atoms) are quite stable, insoluble and unreactive. One oxygen atom (outer shell has 6 electrons) and two hydrogen atoms (H2O) also makes a stable arrangement, although not as stable as the hydrocarbon, family as the water molecule is a little unbalanced, providing hydrogen bonds and other unusual properties of biological importance, such as its ability to hold other molecules in a solution.

    Cusps - peaks or raised areas of a tooth which usually fit into a fossa on the opposing tooth.

    Cytokines -chemical messengers that allow neighbouring cells to communicate with each other. They are paracrine messages as distinct from endochrine or hormonal messengers. There are several main families of cytokines including growth factors , neurotransmitters, , lymphokines and many others. The method of communication involves detection of the chemical message, a ligand , by receptor proteins (for example an integrin on the cell membrane of the receiving cell. The result of the message is a shift in the level of gene expression or the expression of new genes and altered cell behaviour. Cytokines are complex as they sometimes inhibit and/or facilitate the actions of each other.

    Cylasm - the contents of the cell, not including thenucleus.

    Cytoskeleton - a system of fine filaments which cross the cell in all directions, helping toand keep or change its shape. There are three main types of filaments; in order of decreasing size they are, microtubules, microfilaments and intermediate filaments.

    Cytotoxins - products released by bacteria which are toxic to other living cells.