Anatomy, Histology, & Function of the Periodontium PDF

Anatomy, Histology, & Function of the Periodontium Oral Mucosa Consists of 3 main zones: 1. Masticatory mucosa: gingiva + hard palate 2. Specialized mucosa: dorsum of the tongue 3. Lining mucosa: alveolar mucosa + oor of the mouth Periodontium - Periodontium: per...

Anatomy, Histology, & Function of the Periodontium Oral Mucosa Consists of 3 main zones: 1. Masticatory mucosa: gingiva + hard palate 2. Specialized mucosa: dorsum of the tongue 3. Lining mucosa: alveolar mucosa + oor of the mouth Periodontium - Periodontium: peri= around, odontos= tooth - Normal Periodontium provides necessary support for natural teeth to maintain in function Periodontium is composed of 4 components: 1. Gingiva 2. Periodontal ligament (PDL) 3. Cementum 4. Alveolar bone Gingiva The part of the oral mucosa that covers the alveolar processes of the jaws and surrounds the necks of the teeth Divided into: 1. Marginal gingiva 2. Attached gingiva 3. Interdental gingiva 1. Marginal gingiva - Unattached gingiva - The border of the gingiva that surrounds teeth like a collar - Free gingival groove: - a shallow depression that separate attached from unattached gingival - Presents in 50% of the cases 2. Attached Gingiva - It is continuous with the marginal gingiva - It is rm, resilient, and tightly bound to the underlying periosteum of alveolar bone - It is demarcated by the mucogingival junction - The width of the attached gingiva: - Is another important clinical parameter - It is the distance between the mucogingival junction (MGJ) and the bottom of the gingival sulcus or periodontal pocket - It should not be confused with the width of keratinized gingiva - The width of the attached gingiva on the facial aspect di ers in di erent areas of the mouth - Greatest in the incisors - Narrower in the posterior teeth 1 of 9 fi fl ff ff  3. Interdental Gingiva - It occupies the gingival embrasure, which is the interproximal space beneath the area of tooth contact - It can be pyramidal, or it can have a “col” shape - In the Pyramidal: the tip of one papilla is located immediately beneath the contact point - Col shape: a valley-like depression that connects a facial and lingual papilla and that conforms to the shape of the interproximal contacts The shape of the interdental gingiva depends on: 1. The presence or absence of a contact point 2. The distance between the contact point an the osseous crest 3. The presence or absence of gingival recession If diastema present: The gingiva is rmly attached to the interdental bone to form a smooth, rounded surface with NO papillae Gingival Sulcus - Is the shallow crevice or space around the tooth - Bounded by the surface of the tooth on one side and the epithelium lining the free margin of the gingiva on the other side - It is V shaped, and it permits the entrance of a periodontal probe - The clinical determination of the depth of the gingival sulcus is an important diagnostic parameter - The histologic depth of a sulcus does NOT need to be exactly equal to the depth of penetration of the probe (probing depth) - Probing depth of a clinically normal gingival sulcus is (0-3mm) ≠ (NOT Pocket Depth) Gingival Crevicular Fluid (GCF) - A diagnostic biomarker of the biologic state of the periodontium in health and disease - Reduces in health, increases in in ammation - The main route of di usion is through the basement membrane, through the intracellular spaces of the junctional epithelium, and then into the sulcus - Contains components of connective tissue, epithelium, in ammatory cells, serum, and microbial ora inhabiting the gingival margin or the sulcus (pocket) The functions of the GCF are: 1. Cleanse material from the sulcus 2. Contain plasma proteins that may improve adhesion of the epithelium to the tooth 3. Possess antimicrobial properties 4. Exert antibody activity to defend the gingival 2 of 9 fl ff fl fi fl  Gingiva Microscopic features Gingiva Composition: 1. EP.: Strati ed squamous epithelium: predominantly cellular in nature 2. C.T: Connective tissue: - less cellular - Mainly collagen bers + ground substance Strati ed squamous epithelium The gingival epithelium is Strati ed squamous epithelium composed of 3 di erent areas: 1. Oral or outer epithelium (OE) 2. Sulcular epithelium (SE) 3. Junctional epithelium (JE) 1. Outer/oral Epithelium (OE) - Epithelium covers the crest and outer surface of the marginal gingiva and the surface of the attached gingiva - Thickness: 0.2 to 0.3 mm - It is (keratinized or parakeratinized), or combinations of both Outer/Oral epithelium composed of Four layers: 1. Stratum basale (basal layer) 2. Stratum spinosum (prickle cell layer) 3. Stratum granulosum (granular layer) 4. Stratum corneum (corni es layer) 3 of 9 fi fi fi fi fi ff  2. Sulcular Epithelium (SE) - It lines the gingival sulcus - It is a thin (non-keratinized) strati es squamous epithelium - Extends from coronal limit of junctional epithelium to the crest of gingival margin - Function: Acts as a semipermeable membrane - Bacterial products pass —> gingiva - Gingival tissue uid —> sulcus 3. Junctional Epithelium (JE) - Consists of a collar-like band of strati ed squamous (nonkeratinizing) epithelium - The length of the junctional epithelium ranges from 0.25 to 1.35 m - Formed by the con uence of the oral epithelium and the reduced enamel epithelium during tooth eruption Biological Width (BW) - Is the distance established from the junctional epithelium and connective tissue attachment to the root surface of a tooth = 2.04 mm (a) Histological sulcus= 0.69 mm (b) Epithelial attachment= 0.97 mm (c) Connective tissue attachment=1.07 mm (d) Biological width (b+c) Microscopic Features: The gingival epithelium main function: - To protect the deep structures, while allowing for a selective interchange with the oral environment - This is achieved via the proliferation and di erentiation of the Keratinocytes 1. Proliferation: by mitosis in the basal layer, in which a small proportion of cells remain as a proliferative compartment while a larger number begin to migrate to the surface 2. Di erentiation: involves the process of “keratinization” Gingiva Keratinization 1. Orthokeratinized epithelia: Complete keratinization leading to the production of an super cial layer similar to that of the skin, with no nuclei in the stratum corneum and a well- de ned stratum granulosum 2. Parakeratinized epithelia: Retained nuclei in stratum corneum 3. Non-keratinized epithelia: Has neither granulosum nor corneum strata, whereas super cial cells have viable nuclei 4 of 9 ff fi fi fi fl fl fi fi ff  The Cellular components of gingival epithelium: - Keratinocyte: The principal cell type of the gingival epithelium - Other cells: - Langerhans cells: Phagocytic function - Merkel cells: Harbors nerve endings - Melanocytes: Melanin production Connective Tissue: Major components: - 3 types of C.T bers: collagen, reticular, & elastic - Collagen bers (Type I) (60% by volume) - Fibroblasts cells (5%) - Vessels, nerves, and matrix (about 35%) - Ground substance lls the space between bers & cells C.T known as the lamina propria: 1. Papillary layer: subjacent to the epithelium 2. Reticular layer: contiguous with the periosteum of the alveolar bone Gingival Fibers Functions 1. To brace the marginal gingiva rmly against the tooth 2. To provide the rigidity necessary to withstand the forces of mastication 3. To unite the free marginal gingiva with the cementum of the root and the adjacent attached gingiva Gingival Fibers Arrangments A. Gingivodental bers: extend from the cementum i) To the crest of the gingiva ii) to outer surface iii) to the periosteum of the labial plate B. The circular bers encircle the tooth in ringlike fashion: (4) are shown in cross-section C. The transseptal bers: located interproximally, form horizontal bundles that extend between the cementum of the approximating teeth Connective tissue Gingival cells Fibroblasts Osteoclasts Plasma cells Macrophages Odontoclasts Undi erentiated Mast cells Polymorphonuclear Ectomesenchymal cells Osteoblasts Leucocytes (PMNs) Cementoblasts Lymphocytes 5 of 9 ff fi fi fi fi fi fi fi fi  Gingiva Clinical Features - Color - Contour - Consistency - Texture A. Color - Gingival Color: Generally described as "coral pink“ - Produced by: - Vascular supply - Thickness and degree of EP. Keratinization - Pigment-containing cells - The alveolar mucosa is red, smooth, and shiny rather than pink and stippled B. Contour - Depends on: 1. Teeth shape 2. Teeth alignment 3. Location and size of proximal contact 4. Facial and lingual gingival embrasures dimensions C. Consistency - Normal gingiva - Firm and resilient - The gingival bers contribute to the rmness of the gingival margin D. Texture - The gingival texture is Similar to orange peel —> “stippled” - Attached gingiva is stippled - Marginal gingiva is not stippled - It is absent in infancy, appears in some children at about 5 years of age, increases until adulthood, and frequently - Begins to disappear in old age - The reason behind alternating elevations and depressions in the gingiva is due to the papillary layer projections in the the C.T causing elevations. 6 of 9 fi fi  Periodontal Ligament: - Is the connective tissue that surrounds the root and connects it with the bone - It is continuous with the connective tissue of the gingiva and communicates with the marrow spaces through vascular channels in the bone - the average width is about 0.2 mm - Composed mainly of bundles of type I collagen brils - PDL bers classi ed into several groups: 1. Alveolar crest bers 2. Horizontal bers 3. Oblique bers 4. Periapical bers 5. Interradicular bers - Also contains cell rests of Malassez (M) 4 types of Cells 1. Connective tissue cells: include broblasts, cementoblasts, and osteoblasts 2. Epithelial rest cells 3. Immune system cells 4. Neurovascular cells - Fibroblasts: Most common in PDL - Synthesize collagen - Can phagocytose “old” collagen bers - Regulate “Collagen turnover” PDL Functions: 1. Formative and remodeling 2. Nutritional and sensory 3. Nerves and vessels protection 4. Occlusal forces transmission to the bone 5. Resistance to the impact of occlusal forces 6. Teeth to the bone and gingiva attachment 7 of 9 fi fi fi fi fi fi fi fi fi fi  Cementum - Is the calci ed mesenchymal tissue that forms the outer covering of the anatomic root Two types of cementum: A. Acellular (primary) - Deposite during tooth eruption - Located in all areas of the root B. Cellular (secondary) - Deposites after tooth eruption - Located in the apical third of the root and furcations Fibers in the cementum are either: - Intrinsic: produced by cementoblasts - Extrinsic: produced by PDL broblasts Cemento-enamel Junction (CEJ) - Normal variations in tooth morphology at CEJ: A: Space between enamel & cementum with dentin (D) exposed B: End-to-end relationship of enamel & cementum C: Cementum overlapping enamel 8 of 9 fi fi Alveolar bone - Is the portion of the maxilla and mandible that forms and supports the tooth sockets The alveolar process consists of: 1. Cortical bone/compact bone —> External plate 2. Alveolar bone proper —> The inner socket wall of thin, compact bone, seen as the lamina dura in radiographs 3. Cancellous trabeculae between these two compact layers act as supporting alveolar bone Composition: Cells and intercellular matrix - Osteocyte, Osteoblasts, Osteoclasts - Organic matrix consists mainly (90%) of collagen type 1 with small amounts of osteocalcin, osteonectin, bone morphogenetic protein, phosphoproteins, and proteoglycans All bone surfaces are covered by connective tissue: - Outer surface —> periosteum - Internal surface —> endosteum Blood supply - Superior/inferior Alveolar Artery Lymphatic System - All drains to the Submandibular L.N. except: - Lower incisors buccal and lingual gingiva —> submental L. N. - Third molars —> Jugulodigastric L.N. Periodontium Nerve Supply - Innervation periodontium through branches of the trigeminal nerve - Infra-orbital n. - Posterior Superior Alveolar n. - Great Palatine n. - Alveolar n. - Mental n. - Long buccal n. - Lingual n. 9 of 9