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LECTURE 1: REVIEW OF ANATOMY, STRUCTURE, & FUNCTION OF PERIODONTIUM DR. MANLANGIT GINGIVA...

LECTURE 1: REVIEW OF ANATOMY, STRUCTURE, & FUNCTION OF PERIODONTIUM DR. MANLANGIT GINGIVA PARTS OF THE GINGIVA → the oral mucosa refers to all soft tissues of the mouth → 3 areas: Masticatory Mucosa gingiva, hard palate Lining Mucosa alveolar mucosa, other mucous membranes Specialized Mucosa dorsum of tongue SURFACE CHARACTERISTICS → normal clinical features of gingiva: Color coral pink Papillary Contour pointed, filling the interproximal spaces, blunt for older persons scalloped mesiodistally and slopes coronally Marginal Contour scalloped mesiodistal view, slopping coronally Texture has stipplings Consistency firm, tightly bound to teeth MUCOGINGIVAL JUNCTION and underlying bone → demarcates the boundary between attached gingiva and alveolar mucosa → coral pink color varies according to: → remains in the same position throughout life o pigmentation → not present in the palate since mucosa is firmly bound to bone o vascularity and continuous with gingiva o epithelial keratinization → it is seen in the lingual between floor of the mouth and gingiva STIPPLINGS ALVEOLAR MUCOSA → found in attached gingiva only → located apical to the attached gingiva → gives the “orange peel” appearance → loosely connected and movable → a form of reinforcement as its function → non-keratinized, darker in color because non-keratinized → usually disappears in disease and reappears in health epithelium is translucent, thus, color of underlying tissue is seen → caused by interdigitation of the connective tissue papilla with epithelial ridges INTERDENTAL PAPILLA → occupies the space between two teeth in contact MAIN FUNCTION → important clinically & diagnostically because it is the first to → to protect supporting tissues from oral environment show early signs of periodontal disease → provides little physical support → shape & size depends on tooth contact: Anterior pyramidal Posterior buccal & lingual peaks connected by gingival col → col may be present or absent (in diastemas) GINGIVAL SULCUS → usually 2-3 mm in depth → bounded by tooth, JE, sulcus epithelium Kirsten M. Abarquez | Cebu Doctors’ University | DMD-3B  LECTURE 1: REVIEW OF ANATOMY, STRUCTURE, & FUNCTION OF PERIODONTIUM DR. MANLANGIT CONTINUOUS TOOTH ERUPTION SULCULAR EPITHELIUM → happens throughout life → it is non-keratinized but may undergo keratinization → there are two kinds: → it lines the lateral walls of the sulcus; continuous with oral epithelium Active Eruption movement of teeth in the direction of → it is important because it acts as a semipermeable membrane occlusal plane through which injurious bacteria products pass into gingiva and Passive Eruption exposure of teeth by separation of JE tissue fluid from gingiva seeps into sulcus from enamel and migration onto the cementum or exposure of anatomic BIOLOGIC WIDTH crown due to gingival recession → anatomical parameters: ACTIVE ERUPTION Gingival Sulcus = 1 mm → coordinated with attrition to compensate for tooth tissue worn Junctional Epithelium = 1 mm away by attrition → attrition reduces the clinical crown Alveolar Crest Fibers = 1 mm → ideally, the amount of tooth tissue exposed during active eruption should be equal to tooth wear: Biologic Width = 3 mm o to preserve vertical dimension o as the tooth erupts, cementum is deposited at the apices → this should be the distance from alveolar bone crest to the and furcation of roots margins of the porcelain crown PASSIVE ERUPTION GINGIVAL CONNECTIVE TISSUE → considered pathologic by some authors because it is a result of → composed of lamina propria with collagen and reticular fibers chronic inflammation and sometimes a few elastic and oxytalan fibers → these fibers are embedded in ground substance where blood AREAS OF GINGIVAL EPITHELIUM vessels and nerves are → oral epithelium → has (2) layers: → sulcular epithelium o papillary layer → junctional epithelium o reticular layer JUNCTIONAL EPITHELIUM GINGIVAL PRINCIPAL FIBERS → a cuff-like band of stratified squamous non-keratinized epithelium that is continuous with the sulcular epithelium and Dentogingival cementum apical to CEJ, to lateral and completely encircles the tooth coronal direction into the lamina propria of gingiva → also known as epithelial attachment or epithelial cuff → triangular Alveologingival from alveolar crest to lamina propria → made of 15-20 cells and tapers to 1-2 cells at the apical end coronally → length =.025 - 1.35 mm Circular Group encircles the tooth → function: o provides a seal at the base of the sulcus Transseptal horizontal fibers → may be located in enamel, enamel & cementum, or cementum Dentoperiosteal on vestibular surfaces; from tooth, passes only depending on the stage of tooth eruption or gingival over alveolar crest and blend with fibers of recession periosteum → the most permeable of all gingival epithelia; permits the exit of Semicircular from mesial or distal surface of tooth tissue fluid & inflammatory cells from connective tissue to sulcus extending around vestibular or oral surface → also allows entry of bacterial products from the outside in to insert on opposite side of same tooth Transgingival from proximal root surfaces radiating through JUNCTIONAL EPITHELIAL CELLS embrasures and blends with fibers on oral or → are for adherence to tooth surface unlike keratinized cells which vestibular surfaces cannot adhere Intergingival fibers which run parallel to dentition on → this is important following injury to JE and its epithelial vestibular or oral surfaces attachment FUNCTION Kirsten M. Abarquez | Cebu Doctors’ University | DMD-3B  LECTURE 1: REVIEW OF ANATOMY, STRUCTURE, & FUNCTION OF PERIODONTIUM DR. MANLANGIT Dentogingival provide gingival support Cratered Papillae Alveologingival attach gingiva to bone Circular Group maintain contour and position of free marginal gingiva Transseptal maintain relationships of adjacent teeth, protect interproximal bone Periostogingival attach gingiva to bone Interpapillary provide support for interdental gingiva Transgingival secure alignment of teeth in arch Intergingival provide support and contour of attached GINGIVAL CLEFTS gingiva Intercircular stabilize teeth in arch V-Shaped Stillman’s Cleft SHAPE AND CONTOUR Blunted Slit-Like Stillman’s Cleft Bulbous PERIODONTAL LIGAMENT → fibrous connective tissue fibers which attaches tooth to alveolar bone → function: o support the tooth o maintain physiologic relationship between bone and cementum THICKNESS Rolled, Life-Saver Shaped → between 0.1 to 0.25 mm depending on age and stage of eruption → thicker in adolescents than the elderly → thinner on teeth without antagonists → thinner on impacted teeth PRINCIPAL FIBERS OF THE PDL Alveolar Crest Group originates from crest of alveolar process and inserts into the cervical cementum crest of alveolar process to cervical cementum Horizontal Group at right angles with tooth’s long axis Kirsten M. Abarquez | Cebu Doctors’ University | DMD-3B  LECTURE 1: REVIEW OF ANATOMY, STRUCTURE, & FUNCTION OF PERIODONTIUM DR. MANLANGIT Oblique Group from cementum to bone in diagonal o less mineralized than bone (65%) direction → thickness of cementum: o deposited throughout life Apical Group around the tooth apex o most rapid in apex area, to compensate continuous tooth Interradicular Group over crest of interradicular septum in eruption and to compensate attrition multirooted teeth o between ages 11-70, there is 3x increased thickness SHARPEY’S FIBERS CLASSIFICATION OF CEMENTUM → terminal end portions of the periodontal ligament fibers which → location: are embedded in cementum on one end and bone on the other o radicular end o coronal → normally, periodontal fibers follow a wavy course → cellularity: o acellular CELLS IN THE PERIODONTAL LIGAMENT o cellular → collagen presence/absence Undifferentiated have the ability to become o fibrillar Mesenchymal Cells fibroblasts, cementoblasts, osteoblasts o afibrillar and is why the PDL has a formative function ACELLULAR CEMENTUM Fibroblasts major cell, produces collagen, and → formed before tooth reaches occlusal plane also resorbs collagen fibrils by → made mostly of Sharpey’s fibers secreting collagenase (which increases → incremental lines are “rest periods” during cementum formation during periodontal disease) Osteoblasts forms bone CELLULAR CEMENTUM → formed after tooth reaches occlusal plane Cementoblasts forms cementum → has cementocytes houses in lacunae Osteoclasts/Odontoclasts cannot be distinguished from each → has incremental lines other, remodels alveolar bone Epithelial Cells from HERS, cell rests of Malassez CELLS OF THE CEMENTUM FUNCTIONS OF THE PERIODONTAL LIGAMENT Cementoblasts produce collagen fibers Cementocytes found only inside lacunae in cellular cementum Mechanical/Physical attaches tooth to bone, cushion forces (by the fluid content of Cementoclasts indistinguishable from osteoclasts; for extensive vasculature); fibers transmit root resorption forces to bone ROOT RESORPTION important in maintaining normal → seen through scanning electron microscope bone apposition → physiologic resorption happens in deciduous teeth only Formative through the cells in the PDL Nutritive from blood vessels ANKYLOSIS → fusion of cementum and alveolar bone obliteration of PDL Sensory nerves provide pain & tactile → occurs in teeth with cementum resorption, which suggests sensation abnormal repair → may occur after chronic periapical inflammation, tooth CEMENTUM replantation, occlusal trauma, embedded teeth → the tissue that covers the anatomic root of a tooth → main function: EXPOSED CEMENTUM o for attachment of periodontal fibers to teeth → in gingival recession, is permeable and thus, bacteria, organic → inorganic content: substances, inorganic ions can penetrate o hydroxyapatite 45-50% → cemental caries may develop → inorganic content comparison: o less mineralized than enamel (97%) o less mineralized than dentin (70%) Kirsten M. Abarquez | Cebu Doctors’ University | DMD-3B  LECTURE 1: REVIEW OF ANATOMY, STRUCTURE, & FUNCTION OF PERIODONTIUM DR. MANLANGIT CEMENTUM REPAIR OTHERS → if epithelium will grow into the area of resorption, there will be → alveoli are the spaces which houses tooth roots no repair → the interdental septum is the bone between roots ENAMEL-CEMENTUM RELATIONSHIP CELLS FOUND IN THE BONE 5-10% space between enamel and cementum with dentin Osteoblasts bone formation exposed Osteoclasts bone resorption 30% end-to-end relationship of enamel and cementum Osteocytes both 60-65% cementum overlapping the enamel REMODELLING & REPAIR OF ALVEOLAR BONE DEVELOPMENTAL ANOMALIES PHYSIOLOGIC MESIAL DRIFT → these are associated with cementogenesis: → continuous migration/mesial direction o enamel projections → bone resorption occurs on inner wall of alveolus on mesial side o enamel pearls of tooth o hypercementosis → bone formation occurs on the distal side o cementicles → mild compression or pressure causes bone resorption → tension causes bone formation HYPERCEMENTOSIS → also known as cementum hyperplasia SUPPORTING (BASAL) BONE → other causes of hypercementosis: → resorption caused by reduced functional requirement o may occur in teeth without antagonist to keep up with the → loss of occlusal function leads to disuse atrophy speed of excessive tooth eruption o teeth with periapical irritation due to pulpal disease to DISUSE ATROPHY compensate destroyed fibrous attachment → if there is increase in functional demand, bone density will increase but if the demand goes beyond physiologic tolerance CEMENTAL SPIKES of bone, the density will decrease → form of hypercementosis → clumping of cementicles, calcification of Sharpey’s fibers, DEFECTS IN THE ALVEOLAR PROCESS excessive tension from ortho appliance or occlusal forces Dehiscence → dipping of the crestal margin, exposing root Note! If the entire dentition has hypercementosis, the patient has surface Paget’s disease. Fenestration → hole in the cortical plate over the root ALVEOLAR BONE → no communication with the crestal margin MAJOR PARTS OF THE ALVEOLAR BONE → alveolar bone proper → supporting bone o outer cortical plates; compact bone o cancellous, trabeculae spongy bone ALVEOLAR BONE PROPER → also called inner cortical plate → “lamina dura” → “cribriform plate” → made of lamellar bone → where Sharpey’s fibers are embedded → made of a thin layer of lamella of bone SUPPORTING BONE → surrounds the alveolar proper Kirsten M. Abarquez | Cebu Doctors’ University | DMD-3B