Cementum/ rotary endodontic courses by indian dental academy


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Cementum/ rotary endodontic courses by indian dental academy

  1. 1. CEMENTUM 01. Introduction. 02. Development. 03. Physical properties. 04. Chemical properties. 05. Histology. 06. Classification. 07. Functions. 08. Clinical considerations. 1
  2. 2. INTRODUCTION: Definition: It is a mineralized dental tissue covering the anatomic roots of human teeth (Orbans). Definition: It is a calcified mesenchymal tissue that forms the outer covering of the anatomic roots (Glickman). - It was 1st demonstrated microscopically in 1835 by Franke and Raschkov, 2 pupils of Purkinje - It begins at the cervical portion of the tooth at CEJ and continues to the apex. - The collagen fibres present in the cementum acts as a medium of attachment between the tooth and surrounding structures. - It is a specialized connective tissue that shares physical, chemical and structural characteristics with compact bone. (unlike bone, however human cementum is avascular). CEMENTO GENESIS: Development of Cementum - Cementum is mesodermal in origin with  Dentin  Alveolar bone  Periodontal ligament - Cementum develops from dental follicle, which surrounds the tooth germ. - Development of cementum starts after crown formation is completed and before start of eruption. 2
  3. 3. - The outer and inner enamel epithelium after crown formation form a double layered sheath which proliferates from the cervical loop to form Hertwigs epithelial root sheath which separates the dental papilla from dental follicle. - Cells of peripheral dental papilla differentiate along HERS into Odontoblast. - These odontoblast form a single layer of dentin once dentin formation begins break occur in epithelial root sheath allowing the newly formed dentin to come in direct contact with connective tissue of the dental follicle. - Cells derived from this connective tissue is responsible for cementum formation. - Break down of hers involves degeneration / loss of its basal lamina on the cemental side which is soon followed by the appearance of collagen fibres and cementoblasts between epithelial cells of root sheath. - Some sheath cells migrate away from the dentin towards the dental sac, which become the epithelial cells of malassez found in the periodontal ligament whereas others remain near the developing tooth and one gets incorporated into the cementum. - Cementoblasts. - Cementoid tissue / precementum: It is the unminerlized tissue, it begins at the CDJ. - Cementoid layer ranges from 3-5mm in the apical 3rd cementoid tissue is lined by cemento blasts. 3
  4. 4. - Connective tissue fibres from the PL pass between the cementoblast into the cementum, these fibres attach the tooth to surrounding bone. The embedded portions are known as Sharpey’s fibres, which are composed of numerous collagen fibres. PHYSICAL PROPERTIES: - Cementum is light yellow in colour and can be distinguished from enamel by a. Lack of luster b. Its Darker hue - Cementum is somewhat lighter in colour than dentin But clinically – it is not possible to distinguish cementum from dentin based on colour alone. - Cementum is very permeable (As age progress the permeability of cementum diminishes). - Cementum is Thinnest at the CEJ (20-50mm), thickest at apical 3rd (150-200mm) i.e. in the bifurcation and trifurcation area. - Cementum is thicker in distal surface than mesial surface probably because of the functional stimulation from mesial drift. - Average thickness – 95mm at Age 20; 215 mm at age 60. CHEMICAL PROPERTIES: - Cementum from a fully formed permanent tooth contains – 45%-50% inorganic substance; 50%-55% organic substance and H2O. 4
  5. 5. Inorganic Substance: - Consists mainly of Ca and Phosphate ions in the form of Hydroxapatite. - Cementum has the highest fluoride content of all the mineralized tissue. - Trace elements –Cu, Lead, Iron, Na, Mg, K, Zn. Organic Substance: - Primarily consists of – Type I collagen; Protein polysaccharides (Proteoglycans). - Collagen obtained from the cementum of human teeth indicate close similarities to the collagen of Dentin and alveolar bone. Histology of Cementum: - Histology section of cementum show. a. Cells, Fibres, Ground substance, Resting lines. b. Cemento enamel junction. c. Cemento dentinal junction d. Cells: The cells associated with cementum are 1. Cementoblasts. 2. Cementocytes. 3. Cementoclasts. 1. Cementoblasts: As soon as there is breakdown of hers undifferentiated mesenchymal cells from adjacent connective tissue differentiate into cementoblasts. - There cells have  Numerous mitochondria  Well formed golgi apparatus  Large number of granular endo plasmic reticulum. 5
  6. 6. - So they actively synthesize collagen and protein polysaccharides, which make up the organic matrix of cementum. - After some cementum is laid down, its mineralization begins. - The cells are found liner the root surface. 2. Cementoclasts: Found in How ship’s lacunae These are unilocular / multilocular cells. Function: 1) Resorption of cementocytes 3. Cementocytes: - The cells incorporated into cellular cementum, cementocytes are similar to osteocytes. - They line in spaces designated as lacunae. - They have numerous cell processes or canaliculi radiating from its cell body. - The processes branch, and frequently anastomose with those of neighbouring cells. - These processes are directed towards the periodontal surface of cementum. - They have a sparse cytoplasm. FIBROUS MATRIX: The collagen fibres of cementum one of two type, 1. Intrinsic fibres 2. Extrinsic fibres 6
  7. 7. 1. Intrinsic fibres: Are those formed as a result of cementoblast activity. 2. Extrinsic fibres: Are periodontal ligament fibre bundles, which are embedded into cementum. They are called as Sharpey’s fibres (these fibres are usually seen in recently formed cementum). 3. They contain numerous collagen fibres. GROUND SUBSTANCE: The chemical nature of the cementum is virtually unknown. RESTING LINES: - Both acellular and cellular cementum are arranged in lamellae separated by incremental lines parallel to the long axis of the root. - These lines represent rest periods in cementum formation and are highly mineralized and have less collagen and more ground substance. - These lines indicate rythmic and regular depositing matrix. - These are also known as incremental lines of salter. CEMENTO ENAMEL JUNCTION: Three types of relation involving the cementum may exist at the CEJ. 1) 30% of cases – edge to edge - Butt type - Cementum and Enamel meet at a sharp part. 7
  8. 8. 2) 5% -10% cases – Cementum and Enamel fail to meet - Gap type - This is due to delayed degeneration of HERS - So here dentin may be covered by reduced enamel epithelium instead of cementum. 3) 60%-65% cases – cementum over laps the enamel. - Over lap type - This occurs when enamel epithelium degenerates permitting connective tissue to come in direct contact with the enamel surface. CEMENTO DENTINAL JUNCTION: - The dentin surface upon which cementum is deposited is relatively smooth in permanent teeth. Scalloped in deciduous teeth - Some times dentin is separated from cementum by a zone known as the intermediate cementum layer or Hopewell smith layer. - This layer is predominantly seen in the apical 2/3 rd of the roots of molars and premolar’s and rarely seen in incisors and deciduous teeth. - It is believed that this layer represents area where cells of Hers become trapped in a rapidly deposited dentin / cementum matrix. It is continuous / isolated - Size  10mm thickness. 8
  9. 9. CLASSIFICATION OF CEMENTUM: I) According to (ORBAN): a) Acellular cementum b) Cellular cementum a) Acellular cementum: - It is the 1st formed cementum. - And covers approx the coronal 2/3 / ½ of the root. - It does not contain cells. - This cementum is formed before the tooth reaches the occlusal plane. - Thickness ranges from 30-230mm. - Sharpey’s fibres make up most of the structure of acellular cementum. - Acellular cementum also contains other collagen fibril’s, that are calcified and irregularly arranged. - 50-200 mm. b) Cellular cementum: - It is formed after the tooth reaches the occlusal plane. - It is seen more frequently in the Apical ½. - It contains cells (cementocytes). - Sharpey’s fibres occupy a smaller portion of cellular cementum. - Cellular cementum is less calcified. - Less mineralized and more permeable - 100-600mm. Cellular cementum Acellular cementum 1. Cementocytes are present No cells in cementum 2. Rate of development is faster Slow 9
  10. 10. 3. Innemental tissue wide apart closer 4. Cementum / Cementoid layer Narrower is wide II) Schoreder classification: 1. A cellular afibrillar cementum. 2. A cellular extrinsic fibre cementum 3. Cellular mixed stratified cementum. 4. Cellular intrinsic fibre cementum. III) According to Tencate (based on 3 factors): 1) Based on time of formation a. Primary b. Secondary 2) Bond on presence or absence of cells a. Cellular b. A cellular Accordingly the following types of cementum are described 1. Primary acellular intrinsic fibre cementum. 2. Primary acellular extrinsic fibre cementum. 3. Secondary cellular intrinsic fibre cementum. 4. Secondary cellular intrinsic fibre cementum. 5. Acellular afibrillar cementum. 3) Bon on fibres  Intrinsic fibre cementum.  Extrinsic fibre cementum.  Mixed fibre cementum. 10
  11. 11. FUNCTIONS OF CEMENTUM: The principle function of cementum is assisting Anchorage of the tooth. - The primary function is to furnish a medium for attachment of collagen fibres that bind the tooth to alveolar bone. - Cementum serves as a major Reparative tissue - For root surfaces damage to roots such as fractures and resorption can be repaired by deposition of new cementum. - Continuous deposition of cementum is of functional importance. - Loss of occlusal surface substance is compensated by continuous deposition of cementum at the apical portion. - Keeps the attachment apparatus intact; because of increase mesial drift – a new layer gets deposited. CLINICAL CONSIDERATIONS: 1) Cementum is more resistant to resorption than is bone and it is for this reason orthodont tooth movement is possible. 2) Transverse fracture of the root may occur because of trauma and this may heal by deposition new cementum. 3) In cases of excessive trauma from occlusion or occlusal wear cementum resorption can occur. Which may continue into dentin in severe cases. Once the 11
  12. 12. resorption stops, the damage is repaired by formation cellular or a cellular or alternate combination of both. 4) Cementum also has a tendency to reestablish the former outline of root surface, which is called anatomic repair. 5) Sometimes instead of anatomic repair, only a thin layer of cementum is laid down and a bay like recess remains. This space is restored to its normal width by formation of bony projection so that a proper functional relationship will result. This is called Functional Repair. 6) Because of continuous cementum deposition around the apex, the total length of tooth is maintained inspite of the loss of enamel from occlusal wear. This deposition of cementum leads to a constriction of apical foramina and alteration in number, size and shape of apical foramina. The over all affect is that in older teeth the complexity of apical foramina is increased. This should be kept in mind during endodontic treatment. 7) Hyperplasia of cementum is secondary to periapical inflammation or excessive occlusal stress. This is important in extraction procedure. Excementoses – also is significant in extraction procedure as it anchors the tooth tightly to the socket. 8) In periodontal pockets, plaque and its by products causes numerous physical, chemical and structural changes in cementum. In pathologically exposed cementum surface, the surface becomes hypermineralized therefore of incorporation of Ca++ , PO4, and fluoride from oral environment i.e. saliva. 12
  13. 13. 9) Endotoxins from plaque interferes with the repair of cementum. Hyper cementosis: It is an abnormal thickening of cementum may be 1. Localized or circumscribed 2. Diffused It might affect 1. All teeth of the dentition 2. Single tooth 3. Part of the tooth surface - If the overgrowth of cementum improves the functional qualities it is formed as Cementum Hypertrophy. - If the overgrowth occurs in non-functional teeth and is not related to any function it is termed as Hyperplasia. Causes of hyper cementosis: 1. It can occur in teeth with periapical inflammation because of some pulpal involvement. 2. In teeth without antagonist (opposing tooth) hypercementosis occurs to avoid excessive tooth eruption. 3. Mechanical stimulation, orthodontic, heavy occlusal forces lead to excessive torsion, which result in spike like hypercementose. These are “Spur” or “Pronge” extensions. 4. In Peagets disease entire dentition is affected. 5. In cemental repairs hypercementosis is observed. 13
  14. 14. 6. Localized hypercementosis occlusive areas of enamel drop. ANKYLOSIS: It is the fusion of cementum and alveolar bone with obliteration of periodontal ligament. It occurs due to 1) Cemental resorption 2) Chronic periapical inflammation 3) Tooth replantation 4) Occlusal trauma - Ankylosis results in resorption of the root and gradual replacement by bone tissue. Cementoma: - These are masses of cementum situated apically. - It may or may not be attached. - They are considered to be either odontogenic neoplasm or developmental malformation. - They are seen more in mandible than maxillary. Cementicles: - They are globular masses of cementum arranged in concavity lamellae. - They are free on PD ligament or they are attached to the cementum. - They are developed from calcified epithelial cells and Sharpey’s fibre. 14
  15. 15. CONCLUSION: Cementum is a part of tooth supporting appends and any alternate to the normal form and function of thin structure may result in disruption of normal physiologic function of the tooth. REFERENCES:  Textbook of Oral Histology and Embryology by Orbans.  Textbook of Art and Science of Operative Dentistry by Sturdevent. 15