Anatomy of the Periodontium part I By Dr.Ghayath Aljawady
University of Mosul college of Dentistry Oral and Maxillofacial Dept. Periodontics unitOUTLINE
Introduction Definitions Components of the Periodontium GingivaINTRODUCTION
Knowledge of the anatomy of the periodontal tissue and their associated structures is essential to understand periodontal diseases and their treatment. It is derived from (perio) and (odont) Perio - Around Odont - ToothDEFINITIONs Periodontology: is the fundamental dental science that deal with scientific study of the periodontium in health and disease. Periodontium:The tissues that surround and support the teeth . Periodontics: the art and science of studying the periodontium. Periodontist: specialist in periodontics
COMPONENT OF PERIODONTIUM
The Gingiva The periodontal ligament The cementum The Alveolar Bone Gingiva: fibrous mucosal surrounding the teeth and covering the coronal portion of the alveolar process. The gingiva is one of the soft tissues that line the oral cavity. It consists of an epithelial layer and an underlying connective tissue layer called the lamina propria. All the soft tissue in the mouth are Known as the oral mucosa, it is divided into three different types:
Masticatory mucosa: Is a tissue that is firmly attached to the underlying bone and covered with parakeratinized or keratinized epithelium. The gingiva and the tissue covering the hard palate are examples. Lining mucosa: Loosely attached to their underlying structures and covered with non-keratinized epithelium. Lips, cheeks, floor of the mouth. Specialized mucosa: Covers the dorsal surface of the tongue
Types of gingiva:
Marginal gingiva (free or unattached) Attached gingiva (firmly attached to underlying tooth and bone) Inter-dental gingiva( located between adjacent teeth.Clinical features
Microscopic features Marginal gingiva:1) Is the most coronally positioned portion of the gingiva.2) It is not attached to the tooth, and it creates the soft tissue wall of the gingival sulcus.3) In health, is knife-edged in contour, firm in consistency, and smooth in texture. 4) It extends apically to the free gingival groove, approximately 1 mm wide.
Gingival sulcus:Shallow crevice or space around the tooth bounded by surface of tooth on one side and the epithelium lining the free margin of the gingiva on the other. V –shaped. Depth of Gingival Sulcus :Ideal conditions - zero.Clinically - 2 – 3 mm. Histologic -1.8 mm with variations from 0 to 6 mm.
Attached Gingiva: 1) It is firmly bound to the underlying tooth and alveolar bone. 2) Gingiva is tapered in contour, stipple in texture, and firm in consistency. 3) Varies in width from one area of the mouth to another and from one patient to another. 4) Bound coronally by the free gingival groove and apically by the mucogingival junction.
Attached Gingiva is: More in maxilla than mandible with least width in 4, palatal sur.in maxilla blends imperceptibly with equally firm,resilient palatal mucosa. On lingual aspect, AG terminates at the junction with the lingual alveolar mucosa, which is continuous with the mucous membrane lining the floor of mouth. The width increases with age. Depends on teeth involved, the buccolingual position in the arch , location of the frenum or muscle attachment. It provides gingival tissue that can withstand the mechanical forces of brushing and tension applied on mucosa
Interdental gingiva: Its that part of the gingiva that occupy the inter-proximal space, created by adjacent teeth in contact. Therefore, shape determined by contact relationship with teeth, and width of proximal surfaces. If the contours are flat, interproximal contacts, the gingiva will be narrow and short. If the proximal contours are more convex with a small coronally positioned contact area, the interdental gingiva will be broad and high.
can have a pyramidal or Col shape. PYRAMIDAL SHAPE- In this the papilla is located immediately beneath the contact point. It is present in anterior teeth COL SHAPE It is valley like depression that connects the facial and lingual papilla and conforms to the shape of interproximal contact and present in posterior teeth Its epithelium is non keratinised and same as junctional epithelium
Microscopic (Histological) Features
The gingiva consist of central core of connective tissue covered by stratified squamous epithelium. Gingival Epithelium:1) Oral (outer) Epithelium.2) Sulcular Epithelium3) Junctional Epithelium
Oral Epithelium: Keratinized or parakeratinized consist of four layers: 1) Stratum basale,Basal cell layer (The deepest cells) 2) Spinosum cell layer 3) Stratum granulosum cell layer 4) Stratum corneum(Keratinized, para, or nonkeratinized) cell layer
O.E.have also melanocytes,langerhans & non-specific cells that are stellate cells Melanocyte;pigment containing cells ,it synthesize melanin, melanin granules that phagocytosed & contained within other cells of epith. & c.t.called melanophages or melanophores Langerhanse ;immune cells that react with Ag,its belong to mononuclear phagocyte system(reticuloendothelial system)as modified monocyte derived from bone marrow
Merkel cells; located in deeper layer of epith.harber nerve ending & connected to adjacent cells by desmosoms ,its identified as tactile perceptorsCell mem.of epith.cell that face B.M.has a no.of electron dense thicker zones appearing at various intervals along cell mem.,tonofilament of cytoplasm converge toward these structure…..hemidesmosom,it involve in attachment of epith.to B.M.,pair of adjacent H.D.form desmosom b/w adjacent cells
ous epithelium
Sulcular Epithelium: It lines the gingival sulcus facing the tooth similar to oral epithelium except the 2nd layer (it lacks granular cell layer) It is a thin ,non-keratinized stratified, squamous epithelium, without retepegs It extend from the coronal limit of the junctional epithelium to the crest of the gingival marginIt is extremely important, because it may act as a semipermeable membrane through which injurious bacterial products pass into the gingiva and through which tissue fluid from the gingiva seeps into the sulcus.
Junctional Epithelium: J.E.derived from reduced enamel epith.(ameloblast+outer E.epith.)its 0.25-1.35mm in coronoapical dimension & about 0.15mm wide Larger cells,wider intercellular space & less desmosoms. Basal cells of J.E.connected to E.through structure semilar to B.M.or its continuation of it with hemidesmosoms.
The junctional epithelium is attached to the tooth surface (epithelial attachment) by means of an internal basal lamina and to the gingival connective tissue by an external basal lamina that has the same structure as other epithelial-connective tissue attachments elsewhere in the body.
The internal basal lamina consists of a lamina densa (adjacent to the enamel) and a lamina lucida to which hemidesmosomes are attached. Organic strands from the enamel appear to extend into the lamina densa. The junctional epithelium attaches to afibrillar cementum present on the crown (usually restricted to an area within 1 mm of the cementoenamel junction) and root cementum in a similar manner.
The attachment of the junctional epithelium to the tooth is reinforced by the gingival fibers, which brace the marginal gingiva against the tooth surface. For this reason, the junctional epithelium and the gingival fibers are considered a functional unit, referred to as the dentogingival unit.
Connective Tissue: Is known as the lamina propria. Divided into two layers: (1) the papillary layer adjacent to epithelium, (2) reticular layer, contiguous with the periosteum.Lamina propria consist of:Collagen fibersIntercellular ground substance:- CellsBlood vesselsNerves
Gingival Fibers There are functions: 1) To brace the marginal gingiva firmly against the tooth. 2)To provide the rigidity necessary to withstand the forces of mastication without being deflected away from the tooth surface. 3)To unite the free marginal gingiva with the cementum of the root and the adjacent attached gingiva.
The gingival fibre are arranged in 4 groups:
1 DENTOGINGIVAL FIBRES This are embedded in the cementum 2 ALVEOLAR CREST FIBRE It arise from the alveolar crest and It run coronary into the gingival 3 CIRCULAR FIBRES It circle the tooth in ring like 4 TRANSCEPTAL FIBRES It runs from tooth to tooth coronal to the alveolar septumThe most prominent cells found in the gingival connective tissue: 1. Plasma cells 2. Fibroblasts 3. Mast cells 4. Lymphocytes
Vascular Supply: Blood supply are derived from 3 sources Blood vessels in the periodontal ligament Blood vessels from the alveolar process (emerge from alveolar crest) 3) Supraperiosteal arterioles The lymphatic drainage usually follows the blood supply, the major portion of the lymph drainage from the gingiva going to the submandibular lymph nodes.