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Welcome to Indian Dental Academy …

Welcome to Indian Dental Academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy has a unique training program & curriculum that provides students with exceptional clinical skills and enabling them to return to their office with high level confidence and start treating patients

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  • 1. CEMENTUM INDIAN DENTAL ACADEMYLeader in Continuing Dental Education www.indiandentalacademy.com www.indiandentalacademy.com
  • 2. CONTENTS• 1. Introduction.• 2. Physical characteristics.• 3. Chemical composition.• 4. Cementogenesis.• 5. Structure & Classification.• 6. Cementodentinal Junction & Intermediate Cementum.• 7. Cementoenamel Junction.• 8. Function.• 9. Hypercementosis.• 10. Clinical Considerations.• 11. Conclusion. www.indiandentalacademy.com
  • 3. INTRODUCTION• Definition:• Cementum is a hard, avascular, mineralized connective tissue covering the anatomic roots of human teeth.• It was first demonstrated microscopically in 1835 by two pupils of purkinje.• It begins at the cervical portion of the tooth at the Cementoenamel Junction and continues to the apex.• Cementum furnishes a medium for the attachment of collagen fibers that binds the tooth to the surrounding structures. www.indiandentalacademy.com
  • 4. PHYSICALCHARACTERISTICS• Cementum is light yellow in colour & can be distinguished from enamel by its lack of luster & its darker hue.• It exhibits a lighter colour than dentin & is also softer and more permeable.• The relative softness of cementum makes it susceptible to abrasion when ever the cemental surface is exposed to the oral environment such as by gingival recession. www.indiandentalacademy.com
  • 5. 3. CHEMICAL COMPOSITION• On a dry weight basis, cementum from fully formal permanent teeth contains about 45% to 50% inorganic substances and 50% to 55% organic material and water.• The inorganic portion consists mainly of calcium and phosphate in the form of hydroxyapatite.• Cementum has the highest fluoride content of all the mineralized tissues.• The organic portion of cementum consists primarily of type I collagen and protein polysaccharides (proteoglycans).• www.indiandentalacademy.com
  • 6. • Other collagans associated with cementum include typeIII, a less cross-linked collagen found in high concentrations during development and during repair and regeneration of mineralized tissues.• Type XII collagen, a fibril-associated collagen with interrupted triple helixes that binds to type I collagen and also to noncollagenous proteins.• Type XII collagen is found in high concentrations in ligamentous tissues including the PDL, and may function in maintaining a mature ligament that can withstand the forces of occlusion. www.indiandentalacademy.com
  • 7. Noncollagenous proteins identified in cementum also areassociated with bone and include the following:• Alkaline phosphatase• Bone sialoprotein• Fibronectin• Osteocalcin• Osteonectin• Osteopontin• Proteoglycans• Proteolipids• Vitronectin & several growth factors.• Bone sialoprotein and osteocalcin appear to be specific to mineralized tissues, except for enamel. www.indiandentalacademy.com
  • 8. • Two apparently unique cementum molecules, an adhesion molecule (cementum attachment protein) and a growth factor (insulin – like growth factor) have been identified, but further studies are warranted to confirm the existence and function of these molecules. www.indiandentalacademy.com
  • 9. 4. CEMENTOGENESIS• Although cementum formation takes place along the entire root, its initiation is limited to the advancing root edge.• At this site, Hertwig’s epithelial root sheath (HERS), which derives from the coronoapical extension of the inner and outer dental epithelium, is believed to send an inductive message, possibly by secreting some enamel proteins, to the facing ectomesenchymal pulp cells.• These cells differentiate into odontoblasts and produce a layer of predentin. www.indiandentalacademy.com
  • 10. • Soon after, HERS becomes interrupted and ectomesenchymal cells from the inner portion of the dental follicle then can come in contact with the predentin. • The next series of events results in formation of cementum on the root surface.www.indiandentalacademy.com
  • 11. CURRENT THEORIES INCLUDESTHE FOLLOWING:• Infiltrating dental follicle cells receive a reciprocal inductive signal from the dentin or the surrounding HERS cells and differentiate into cementoblasts.• HERS cells transform into cementoblasts, other reports indicate that during tooth root maturation, cells within the HERS undergo apoptosis, and some cells from the fragmentad root sheath form discrete masses surrounded by a basement membrane, known as epithelial cell rests of Malassez, which persist in the mature PDL. www.indiandentalacademy.com
  • 12. CEMENTOBLASTS• Soon after Hertwig’s sheath breaks up, undifferentiated mesenchymal cells from adjacent connective tissue differentiate into cementoblasts.• Cementoblasts synthesize collagen and protein polysaccharides (proteoglycans), which make up the organic matrix of cementum.• Cementoblasts have numerous mitochondria, a well formed Golgi apparatus, and large amounts of granular endoplasmic reticulum, & these ultrastructural features can be observed in other cells actively producing proteins and polysaccharides. www.indiandentalacademy.com
  • 13. • After some cementum matrix has been laid down, its mineralization begins.• The uncalcified matrix is called cementoid.• Mineralization of cementoid is a highly ordered event and not the random precipitation of ions into an organic matrix.• Under normal conditions growth of cementum is a rhythmic process, and as a new layer of cementoid is formed, the old one calcifies.• The cementoid tissue is lined by cementoblasts. www.indiandentalacademy.com
  • 14. • Connective tissue fibers from the PDL pass between the cementoblasts into the cementum. • These fibers are embedded in the cementum and serve to attach the tooth to surrounding bone. • These embedded portions of collagen fibrils that pass well into the cementum are known as Sharpey’s fibers.www.indiandentalacademy.com
  • 15. 5. STRUCTURE• With light microscope two kinds of cementum can be differentiated:• Acellular & Cellular.• In Acellular cementum, some layers of cementum do not incorporate cells, spiderlike cementocytes in their lecumae.• It may cover the root dentin from the CEJ to the apex but is often missing on the apical third of the root.• In cellular cementum, cementocytes are present in their lacunae and they are present in the apical third of the root. www.indiandentalacademy.com
  • 16. THICKNESS OF CEMENTUM• Cementum is thinnest at the cementoenamel junction (20 to 50 µm) and thickest toward the apex (150 to 200 µm).• The cells incorporated into cellular cementum, cementocytes, are similar to osteocytes.• They lie in spaces designated as lacunae.• A typical cementocyte has numerous cell• Processes (or) canaliculi radiating from its cell body. www.indiandentalacademy.com
  • 17. • These processes may branch, and they frequently anastomose with those of a neighbouring cell. • Most of the processes are directed toward the periodontal surface of the cementum. • The cytoplasm of cementocytes in deeper layers of cementum contains few organelles, the endoplasmic reticulum appears dilated, and mitochondria are sparse.www.indiandentalacademy.com
  • 18. • These characteristics indicate that cementocytes are either degenerating (or) are marginally active cells.• When cementum remains relatively thin, sharpey’s fibers cross the entire thickness of the cementum.• The attachment proper is confined to the most superficial or recently formed layer of cementum.• This would seem to indicate that the thickness of cementum does not enhance functional efficiency by increasing the strength of attachment of the individual fibers. www.indiandentalacademy.com
  • 19. CLASSIFICATION• Cementum is classified according to three factors:• time of formation (primary or secondary)• the presence (or) absence of cells within its matrix (acellular and cellular) and• the origin of the collagenous fibers of the matrix (intrinsic fibers resulting from cementoblast activity (or) extrinsic fibers resulting from the incorporation of periodontal ligament fibers.) www.indiandentalacademy.com
  • 20. Accordingly, the following types ofcementum are described:• Accordingly, the following types of cementum are described:• Primary acellular intrinsic fiber cementum• Primary acellular extrinsic fiber cementum• Secondary cellular intrinsic fiber cementum• Secondary cellular mixed fiber cementum• Acellular afibrillar cementum.• Two other types of cementum are named depending on location and patterning, namely, intermediate and mixed stratified cementum. www.indiandentalacademy.com
  • 22. 6. CEMENTODENTINALJUNCTION• The dentin surface upon which cementum is deposited is relatively smooth in permanent teeth.• The cementodentinal junction in deciduous teeth, however, is sometimes scalloped.• The attachment of cementum to dentin either case is quite firm although the nature of this attachment is not fully understood. www.indiandentalacademy.com
  • 23. INTERMEDIATE CEMENTUM• Intermediate cementum (IC) is described as a highly calcified amorphous layer found at the cementodentinal junction in mammalian roots.• Intermediate cementum was first described in 1878 by Bodecker as the “interzonal layer” between dentin and cementum. www.indiandentalacademy.com
  • 24. • In 1920 Hopewell-Smith described a thin homogeneous layer devoid of any identifiable histologic elements between the granular layer of Tomes and the internal acellular layer of cementum.• He speculated that this layer acted as a barrier to the external passage of medicaments placed in the root canal in the treatment of pulpless teeth. www.indiandentalacademy.com
  • 25. • Bencze in 1927 is credited with the first use of the term “intermediate cementum” (he actually called it the “intermediary layer of cementum”) in his description of an ill-defined area between cementum and dentin that had microscopic characteristics unlike either tissue. www.indiandentalacademy.com
  • 26. – The cells of the root sheath have a further function:- they are involved in the formation of a structureless highly mineralized layer some 10 µm thick on the surface of the root dentin.– This layer has variously been described as dentin (the hyaline layer of Hopewell – Smith) and as intermediate Cementum, but a study of its development suggests that it is neither and instead may be a form of enamel. www.indiandentalacademy.com
  • 27. – As the large collagen fibers of mantle dentin form, they are deposited slightly away from the basement membrane supporting the root sheath , leaving a gap filled with ground substance and a very fine fibrillar material.– The basement membrane supporting the root sheeth breaks up.– The root sheath cells develop profiles of Rough endoplasmic reticulum and actively secrete a distinct class of enamel proteins closely related to the amelogenin family into this gap. www.indiandentalacademy.com
  • 28. – The mineralisation of mantle dentin does not involve this layer, which mineralizes both later and separately, largely because of its distinct matrix. – Thus the dentin of the root surface is covered by an epithelial product of the root sheath cells that is more mineralized than other dentin.www.indiandentalacademy.com
  • 29. – It has been proposed that its function is to ‘cement’ cementum to the dentin as well as provide the initial attachment of ligament fibrils to the tooth.– Other functions are i) a permeability barrier between cementum and dentin (i.e.. between the external root surface and the inernal [pulpal] root surface), ii) a precursor for cementogenesis in root development, and iii) a precursor for cementogenesis in would healing. www.indiandentalacademy.com
  • 30. – In studies of ligament repair new cementum may be deposited on denuded dentin, but in histologic section there is always an artifactual split between the newly deposited cementum, and the dentin, suggesting a week union between these two tissues in the absence of this hyaline layer.– Because it seems to have a cementation function, is of epithelial origin, and lies between the dentin and primary cementum, the term ‘intermediate epithelial cement layer’ is also proposed. www.indiandentalacademy.com
  • 31. 7. CEMENTOENAMELJUNCTION• The relation between cementum and enamel at the cervical region of teeth is variable.• In approximately 30% of all teeth, cementum meets the cervical end of enamel in a relatively sharp line.• In about 10% of the teeth, enamel & cementum do not meet.• Presumably this occurs when enamel epithelium in the cervical portion of the root is delayed in its separation from dentin. www.indiandentalacademy.com
  • 32. • In such cases there is no cementoenamel Junction. Instead a zone of the root is devoid of cementum and is, for a time, covered by reduced enamel epithelium.• In approximately 60% of the teeth , cementum overlaps the cervical end of enamel for a short distance.• This occurs when the enamel epithelium degenerates at its cervical termination, permitting connective tissue to come in direct contact with the enamel surface. www.indiandentalacademy.com
  • 33. www.indiandentalacademy.com
  • 34. 8. FUNCTIONS• The primary function of cementum is to furnish a medium for the attachment of collagen fibers that bind the tooth to alveolar bone.• This is demonstrated in some cases of hypophosphatasia, a rare heredity disease in which loosening and premature loss of anterior deciduous teeth occurs.• The exfoliated teeth are characterized by an almost total absence of cemetum. www.indiandentalacademy.com
  • 35. • Cementum serves as the major reparative tissue for root surfaces.• Damage to roots such as fractures and resorptions can be repaired by the deposition of new cementum.• Cementum can also be viewed as the tissue that makes functional adaptation of teeth possible.• For example, deposition of cementum in an apical area can compensate for loss of tooth substance from occlusal wear. www.indiandentalacademy.com
  • 36. 9. HYPERCEMENTOSIS• Hypercementosis is an abnormal thickening of cemetum.• It may be diffuse or circumscribed.• Etiology: • accelerated elongation of a tooth • inflammation about a tooth • tooth repair and • osteitis deformans (or) paget’s disease of bone. www.indiandentalacademy.com
  • 37. • 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, it is termed hyperplasia.www.indiandentalacademy.com
  • 38. • Localized hypercementosis may sometimes be observed in areas in which enamel drops have developed on the dentin. • The hyperplastic cementum covering the enamel drops occasionally is irregular and sometimes contains round bodies that may be calcified epithelial rests.www.indiandentalacademy.com
  • 39. • The same type of embedded calcified round bodies frequently are found in localized areas of hyperplastic cementum & are designated as excementoses.• A thickening of cementum is often observed on teeth that are not in function.• Hyperplasia of cementum in non functioning teeth is characterized by a reduction in the number of Sharphey’s fibers embedded in the root. www.indiandentalacademy.com
  • 40. 10. CLINICAL CONSIDERATIONS• Cementum is avascular and is more resistant to resorption than is bone, and it is for this reason that orthodontic tooth movement is made possible.• When a tooth is moved by means of an orthodontic appliance, bone is resorted on the side of the pressure, and new bone is formed on the side of tension. www.indiandentalacademy.com
  • 41. • The difference in the resistance of bone and cementum to pressure may be the fact that bone is richly vascularized, whereas cementum is avascular.• Thus degenerative processes are much more easily effected by interference with circulation in bone, whereas cementum with its slow metabolism is not damaged by a pressure equal to that exerted on bone. www.indiandentalacademy.com
  • 42. REPAIR OF THE CEMENTUM • Anatomic Repair: • In this type of repair the former outline of the root is restablished by cemental deposition. • Functional Repair: • In some teeth the resorbed area is covered only by a thin layer of cementum. The depression that exists is filled by the growth of adjacent alveolar bone. This kind of repair is called functional repair. www.indiandentalacademy.com
  • 43. • In periodontal pockets, plaque and its by- products can cause numerous alterations in the physical, chemical and structural characteristics of cementum.• Endotoxin originating from plaque can be recovered from exposed cementum & it is believed that they may interfere with healing during periodontal therapy.• Consequently in periodontal theropy, various procedures (mechanical and chemical) have been proposed that are intended to remove this altered www.indiandentalacademy.com cemental surface.
  • 44. CARIES OF CEMENTUM • Caries of cementum also called as Senile Carious lesions (or) root surface caries are those associated with the aging process. • They are located almost exclusively on the root surfaces of the teeth, but sometimes they are associated with partial denture clasps due to advanced gingival recession. www.indiandentalacademy.com
  • 45. • Teeth with Hypercementosis (or) with extensive excementoses, are of practical significance because the extraction of such teeth may necessitate the removal of bone.• These can anchor the tooth so tightly to the socket that the Jaw (or) parts of it may be fractured in an attempt to extract the tooth.• This possibility indicates the necessity for taking x-rays before any extraction. www.indiandentalacademy.com
  • 46. TOOTH RESORPTION -DEFINITION • According to the Glossary – Contemporary Terminology for Endodontics (1998), “Resorption is defined as a condition associated with either a physiologic or a pathologic process resulting in the loss of dentine, cementum and/or bone”. www.indiandentalacademy.com
  • 49. 3. COMBINED INTERNAL AND EXTERNALRESORPTION4. TRANSIENT APICAL BREAKDOWN• Aetiology for External Resorption:• 1, Replantation of tooth• 2. Orthodontic forces• 3. Eruption of neighbouring teeth• 4. Root fracture• 5. Trauma• 6. Necrotic pulp• 7. Root Planing• 8. Pathology like cysts, Ameloblastoma, Giant cell tumour, Fibrous osseous lesions• 9. Hereditary www.indiandentalacademy.com
  • 50. AETIOLOGY FOR CERVICALEXTERNAL RESORPTION• Bleaching• Trauma• Root planning• Hereditary• Orthognathic surgery www.indiandentalacademy.com
  • 51. EXTERNAL SURFACERESORPTION• It is a transient phenomenon in which the tooth undergoes spontaneous destruction and repair.• It is found in all the teeth and considered to be a normal physiological response.• It is a self-limiting process and does not require any treatment. www.indiandentalacademy.com
  • 52. • External inflammatory root resorption:- It is described as a bowl shaped defect which penetrates the dentine• This occurs following irritation or injury of the periodontium due to trauma, periodontal infection or orthodontic treatment www.indiandentalacademy.com
  • 53. External Replacement Resorption:The primary cause is due to laxative injury.This is continuous process by which the teeth is gradually resorbed and replaced by bone.It differs from Ankylosis because of the presence of intervening inflamed connective tissue. www.indiandentalacademy.com
  • 54. ANKYLOSIS– This is primarily associated with luxation injury like Avulsion.– Ankylosis is an union of tooth and bone with no intervening connective tissue following external resorption. www.indiandentalacademy.com
  • 55. TREATMENT– The treatment of external resorption varies with the etiologic factor.– If the external resorption is caused by the extension of pulpal disease into the supporting tissues, root canal therapy will usually stop the resorptive process. www.indiandentalacademy.com
  • 56. – External resorption produced by excessive forces from orthodontic applicances can be stopped by reducing these forces.– In patients with external resorption due to replantation of teeth, preparation of the root canal and obturation with calcium hydroxide paste may stop the resorptive process. www.indiandentalacademy.com
  • 57. 11. CONCLUSION• -Cementum is best considered in functional terms as two tissues, with one providing attachment and the other adaptation to tooth wear and movement.• -Cementum is thinnest at the cementoenamel junction and the relative softness of the cementum makes it susceptible to abrasion thereby exposing the underlying sensitive dentin.• -Therefore whenever the cemental surface is exposed to the oral environment such as by gingival recession, proper treatment procedures has to be followed to prevent the increased sensitivity experienced by the patient. www.indiandentalacademy.com
  • 58. BIBLIOGRAPHY• 1. Oral Histology – Ten Cates, 5th and 6th edition• 2. Orban’s Oral Histology and Embryology – S.N. Bhaskar, Eleventh Edition.• 3. Pathways of the Pulp – 8th Edition – Stephen Cohen, Richard C. Burns.• 4. Textbook of Oral Pathology – William G. Shafer.• 5. Endodontic Practice – Louis I. Grossman, Eleventh Edition.• 6. OOO Journal, 1995; 79; 624-33. www.indiandentalacademy.com