Cementum - PDF

CEMENTUM Dr Sandeep Gupta Oral Pathologist  INTRODUCTION 2 Is mineralized dental tissue covering the anatomic roots of human teeth. Beginsat cervical portion of the tooth at the cementoenamel junction & continues to the apex. Furnishes a medium for th...

CEMENTUM Dr Sandeep Gupta Oral Pathologist  INTRODUCTION 2 Is mineralized dental tissue covering the anatomic roots of human teeth. Beginsat cervical portion of the tooth at the cementoenamel junction & continues to the apex. Furnishes a medium for the attachment of collagen fibers that bind the tooth to surrounding structures. Makes functional adaptation of the teeth possible. 3 THICK CEMENTUM ON ROOT APICES IN AN ELDERLY PERSON 4  PHYSICAL CHARACTERSTICS 5  Hardness is less than that of dentin.  Light yellow in color.  Can be distinguished from enamel by its lack of luster & its darker hue.  Semi-permeable to a variety of materials.  CHEMICAL COMPOSITION 6  Contains 45% to 50% inorganic substances & 50% to 55% organic material & water.  Cementum has the highest fluoride content of all the mineralized tissues.  Organic portion consists primarily of type I collagen & protein polysaccharides (proteoglycans).  Inner dental epithelium Outer dental epithelium Hertwig’s epithelial root sheath Stratum intermedium  Prior to the beginning of root formation, the root sheath forms the epithelial diaphragm The outer & the inner enamel epithelium bend at the future cementoenamel junction into a horizontal plane, narrowing the wide cervical opening  The proliferation of the cells of the epithelial diaphragm is accompanied by the proliferation of the cells of the connective tissues of the pulp, adjacent to the diaphragm The free end of diaphragm does not grow into the connective tissue but the epithelium proliferates coronal to the epithelial diaphragm  Connective tissue of the dental sac surrounding the root sheath proliferates & invades the continuous double epithelial layer dividing it into network of epithelial strands  Epithelial Cell Rests of Malassez The epithelial rests appear as small clusters of epithelial cells which are located in the periodontal ligament adjacent to the surface of cementum. They are cellular residues of the embryonic structure known as Hertwig's epithelial root sheath.  13 Cellular components of cementum  CEMENTOBLASTS 14  Soon after Hertwig’s sheath breaks up, undifferentiated mesenchymal cells from adjacent connective tissue differentiate into cementoblasts.  Synthesizecollagen & protein polysaccharides which make up the organic matrix of cementum.  Have numerous mitochondria, a well-formed golgi apparatus, & large amounts of granular endoplasmic reticulum. 15 16 ULTRASTRUCTURE OF CEMENTOCYTE NEAR CEMENTUM SURFACE. 17 Cementocytes  CEMENTOID TISSUE 19  The uncalcified matrix is called cementoid.  Mineralization of cementoid is a highly ordered event & not the random precipitation of ions into an organic matrix.  Fibers are embedded in the cementum & serve to attach the tooth to surrounding bone. Their embedded portions are known as Sharpey’s fibers. 20  TYPES OF CEMENTUM 21  Cementum can be differentiated into: acellular & cellular cementum.  Acellular cementum does not have spiderlike cementocytes incorporated into it.  Acellular cementum is found at the coronal half whereas the cellular cementum is found at the apical half.  Cementum is thinnest at the cementoenamel junction & thickest toward the apex.  Cementocytes are either degenerating or are marginally active cells. Acellular cementum 23 CELLULAR CEMENTUM 24  Schroeder’s classification 25 Acellular afibrillar cementum Contains neither cells nor extrinsic or intrinsic collagen fibers, except for mineralized ground substance. Coronal cementum.(1-15um) Acellular extrinsic fiber cementum Composed almost entirely of densely packed bundles of Sharpey’s fibers. Cervical third of roots. (30- 230um)  Cellular mixed stratified cementum - Composed of extrinsic & intrinsic fibers & may contain cells. Co-product of cementoblasts & fibroblasts. Apical third of roots, apices & furcation areas. (100-1000um)  27 Cellular intrinsic fiber cementum Contains cells but no extrinsic collagen fibers. Formed by cementoblasts. It fills resorption lacunae. Intermediate cementum Poorly defined zone near the cementodentinal junction. Contains cellular remnants of Hertwig’s sheath embedded in calcified ground substance.  INCREMENTAL LINES 28  Incremental lines of Salter  29  Are highly mineralized areas with less collagen and more ground substance than other portions of the cementum.  The thickness of cementum does not enhance functional efficiency by increasing the strength of attachment of the individual fibers.  CEMENTODENTINAL JUNCTION 30  Smooth in permanent teeth.  Scalloped in deciduous teeth.  Dentin is separated from cementum by a zone known as the intermediate cementum layer.  This layer is predominantly seen in apical two-thirds of roots of molars & premolars. 31  CEMENTOENAMEL JUNCTION 32  In 60% of the teeth, cementum overlaps the cervical end of enamel for a short distance.  In 30% of all teeth, cementum meets the cervical end of enamel in a relatively sharp line. edge to edge  In 10% of the teeth, enamel & cementum do not meet. RELATION OF CEMENTUM TO ENAMEL AT THE CEMENTOENAMEL JUNCTION 33  CLINICAL CONSIDERATIONS 34 Cementum is more resistant to resorption than is bone, & it is for this reason that orthodontic tooth movement is made possible. It is because bone is richly vascularized, whereas cementum is avascular. Cementum resorption can occur after trauma or excessive occlusal forces.  In most cases of repair, there is a tendency to re- establish the former outline of the root surface by cementum. This is called anatomic 35 repair.  However, if only a thin layer of cementum is deposited on the surface of a deep resorption, the root outline is not reconstructed, & a bay like recess remains.  In such areas the periodontal space is restored to its normal width by formation of a bony projection, so that a proper functional relationship will result. the outline of the alveolar bone in these cases follows that of the root surface. This is called functional repair.  HYPERCEMENTOSIS 36  Is an abnormal thickening of cementum.  May affect all teeth of the dentition, be confined to a single tooth, or even affect only parts of one tooth.  If the overgrowth improves the functional qualities of the cementum, it is termed cementum hypertrophy.  If the overgrowth occurs in non-functional teeth or if it is not correlated with increased function, its termed hyperplasia.  37  Extensive hyperplasia of cementum is occasionally associated with chronic periapical inflammation.  Hyperplasia of cementum in non-functioning teeth is characterized by a reduction in the number of Sharpey’s fibers embedded in the root.  Knob like projections are designated as excementoses. Thank You