This lesson will outline the important anatomy required to understand the pathophysiology of periodontal disease.
In order to understand how the periodontium is affected during periodontal disease, it is essential to understand the basic structures and functions of each of the periodontal tissues.
The Periodontium is a term which refers to network of tissues found around the tooth; each of which is specialised. This lesson will give an overview of the anatomy and the functions of;
The gingivae is composed of 3 different types of epithelium;
Sulcular epithelium (SE) is made up of non-keratinised SSE, and lines the gingival sulcus. Despite being very close to the tooth, it doesn’t attach to the tooth surface. There are no rete ridges present. The sulcular epithelium is apically bound to Junctional epithelium.
Junctional epithelium (JE) is made up of non-keratinised SSE and is responsible for attaching the gingivae to the tooth. This is through a specialised type of attachment involving cell adhesion molecules called hemidesmosomes, and the basal lamina produced by epithelial cells. JE is thickest coronally, comprised of 20-30 cells thick and tapers apically to one cell thin. JE attaches most apically to the cemento-enamel junction in clinically healthy individuals.
Junctional epithelium is structured differently to sulcular epithelium, resulting in different characteristics. The JE is more permeable than sulcular epithelium, meaning that fluids, immune cells and antimicrobial products are able to enter the oral cavity. However, permeability is bidirectional, meaning pathogens such as bacteria and their products can target this area. This results in the adjacent connective tissue space becoming infiltrated with immune cells such as Neutrophils, Lymphocytes and Plasma cells if disease occurs.
Oral epithelium (OE) is made up of keratinised SSE and is the visible part of the gingivae. It forms a physical impermeable barrier to the oral bacteria. The basal layer of the epithelium forms folds into the connective tissue, which increases the surface area contact between connective tissue and epithelium. This is known as rete ridges.
The connective tissue of the gingivae is called the lamina propria. The lamina propria can be subdivided into the papillary and reticular layer. An important component of the gingival connective tissue is the gingival fibres; these are collagen fibre bundles which lie ground substance, fibroblasts, blood/lymph vessel and neural tissue. The fibre bundles are grouped based on the origin, insertion and location. The four main bundles are;
Alveolar bone is the ridge of bone which holds the teeth in their place, forming the tooth sockets, also known as the alveolar process.
The socket walls are made up of dense bone called compact bone which is a weight bearing structure. This bone also forms the buccal and lingual/palatal plates of the jaw bones. The compact bone is where the periodontal ligaments can insert. On radiographs, this bone produces a dense radiopacity around the tooth, called the lamina dura.
Between the sockets and the jawbone is cancellous bone, which is made up of trabeculae. Trabeculae bone is the main site of calcium exchange. Optimised to provide the greatest amount of support for minimal mass.
The alveolar bone is a dynamic tissue capable of rapid remodelling, which is mediated by its cellular components. This includes osteoblasts, osteocytes and osteoclasts.
The periodontal ligament is a fibrous connective tissue which connects the cementum with the alveolar bone. Its functions include;
The structure of the periodontal ligament is composed of an extracellular matrix, consisting of many fibres such as collagen, and ground substance featuring cells, blood vessels and nerves. The collagen fibres in the PDL are arranged into bundles, and named based on their location and orientation, including;
Cementum is an avascular mineralised tissue which overlies the root dentine. It’s believed Cementum is continually deposited through life and can be subdivided based on its cellular content; including cellular and acellular cementum.
This cementum forms during root formation and tooth eruption. The PDL has fibres which insert to the acellular cementum and mineralise, called Sharpeys fibres. This results in attachment between the PDL and cementum. Acellular cementum is characteristically more calcified than the cellular.
This cementum lies over the acellular cementum. Its cells, called Cementocytes, lie in lacunae similar to bone, and appears histologically more irregular than the acellular component. This layer is thicker in the apical region of the root than the coronal.
Periodontium means the structures found around the tooth.
The periodontium is divided into;
Berkovitz BK. Periodontal ligament: structural and clinical correlates. Dental update. 2004 Jan 2;31(1):46-54.
Clerehugh V, Tugnait A, Genco RJ. Periodontology at a Glance. Somerset: John Wiley & Sons, Incorporated; 2009.
Sodek J, Mckee MD. Molecular and cellular biology of alveolar bone. Periodontology 2000. 2000 Oct;24(1):99-126.
