Ultrastructure and function of cementum ppt

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1. Ultra-structure and Function of Cementum Presented by: Dr. Md. Naseem Ashraf 2 nd Year Post Graduate

2. Contents Introduction Development of cementum Molecular factors affecting cementogenesis Physical properties Chemical composition Histology of cementum Classification Cemento-dentinal junction Cemento-enamel junction

3. Contents Functions Cementum resorption and repair Effects of ageing on cementum Cementum in oral environment Role of cementum in periodontal disease Changes in cementum Developmental anomalies Conclusion References

4. Introduction Definition: calcified avascular mesenchymal tissue that forms the outer covering of the anatomic roots Extent: begins at cervical portion of the tooth at the cemento-enamel junction up to the apical foramen First demonstrated microscopically in 1835 by Franke and Rashkow (two pupils of purkinje) Anatomically – part of tooth Functionally- part of periodontium

5. Development of Cementum Initiation HERS- Corono -apical extension of IEE and OEE induces secretion of enamel proteins Facing ectomesenchymal cells of dental papilla differentiate into the odontoblast HERS becomes interupted and ectomesenchymal cells of inner portion of dental follicle comes in contact with the pre-dentin Odontoblasts starts forming pre-dentin Em cells of follicle receive signal from dentin and surrounding HERS cells & differentiate into cementoblasts

6. Physical Characteristics Hardness: less than dentin Colour: Light yellow with dull surface and lighter than dentin Thickness: Variable, thinnest at CEJ and thickest at at apex. Apical foramen is surrounded by cementum Its permeable, (as age progresses permeability of cementum diminishes)

7. Chemical characteristics On dry weight basis, cementum of fully formed teeth contains: Inorganic substances- 45-50% Organic substances and water- 50-55%

8. Inorganic Portion Hydroxyapatite - calciumand Phosphate Trace elements like - Copper - Flourine - Iron - Lead - Potassium - Silica Cementum has highest fluorine content among mineralized tissues

9. Organic portion Collagen: Type I predominant (90%), others include type III (5%), V, XII, XIV Matrix proteins Proteoglycans Osteonectin Osteopontin Osteocalcin Fibronectin Bone sialoprotein

10. Organic portion Protein extracts of mature cementum Promotes cell attachment and migration Stimulates protein synthesis for gingival fibroblasts and PDL cells Bone sialoprotein & osteopontin Differentiation of progenitor cells to cementoblasts

11. Histology of cementum Histology section of cementum shows: A) Cells, fibers, ground substance B) Cemento-enamel junction C) Cemento-dentinal junction

12. Histology of Cementum Cells of cementum The cells associated with cementum are: Cementoblast Cementocytes Cementoclasts

13. Histology of cementum CEMENTOBLASTS Numerous mitochondria Well defined golgi apparatus Large number of granular endoplasmic reticulum Synthesise collagen and protein polysaccharide, which make up the organic matrix of cementum After some cementum is laid down, its mineralisation begins The cells are found lining the root

14. Histology of Cementum CEMENTOCYTES Spider shaped cells, characteristic feature of cellular cementum During the formation of cellular cementum, cemetoblasts become entrapped within their own matrix due to rapid deposition and are called cementocytes Similar to osteocytes , they lie in spaces called as lacunae Haphazardly arranged and widely dispersed In deeper layers of cementum, cementocytes shows definite signs of degeneration such as cytoplasmic clumping, empty lacunae, vesiculation

15. Histology of cementum CEMENTOCLASTS Found in howship’s lacunae Unilocular / multilocular cells Function: resorption of cementocytes Major role: resorption and repair

16. Histology of cementum INCREMENTAL LINES OF CEMENTUM Refered to as incremental lines of salter Represent rhythmic periodic deposition of cementum Appears as dark lines running parallel to root surface Seen in both cellular and acellular cementum but more prominent in acellular cementum Best seen in decalcified sections under light microscope Highly mineralized areas with less collagen and more ground substance

17. Histology of cementum

18. Types of cementum By location: 1) Radicular cementum 2) Coronal cementum By cellularity: 1) Cellular cementum 2) Acellular cementum By the presence of collagen fibrils in the matrix: 1) Fibrillar cementum 2) Afibrillar cementum A /c to development Primary ( p refunctional ) Secondary (functional)

19. Types of Cementum By the origin of matrix fibers: 1) Extrinsic fibers 2) Intrinsic fibers 3) Mixed fibers

20. Types of Cementum ACELLULAR CEMENTUM First to be formed Covers cervical 3 rd or half of the root Does not contain cells Formed before tooth reaches occlusal plane Thickness 30-230 μ m Composed mostly of sharpey’s fibers Contains intrinsic calcified collagen fibrils

21. Types of Cementum

22. Types of Cementum

23. Types of Cementum CELLULAR CEMENTUM Secondary formed cementum Contains cementocytes Formed after tooth reaches the occlusal plane Less calcified than acellular cementum Thicker than acellular cementum Sharpey’s fibers occupies a smaller portion

24. Types of Cementum

25. Based on nature and origin of organic matrix 2 sources of collagen extrinsic intrinsic Extrinsic fibers-known as sharpey’s fibers-embedded portion of Principle fibers of PDL Formed by fibroblast Intrinsic fibers- belong to cementum Formed by cementoblast Cementoblast also forms non- collagenous proteins like glycoproteins, proteoglycans etc

26. Schroeder Classification- 1986

27. Acellular Afibrillar Cementum Contains neither cells nor intrinsic or extrinsic fibers Product of cementoblast , found at coronal cementum Thickness 1-1.5 micrometer Lacks collagen and hence plays no role in attachment Deposited on enamel and dentine in close proximity to CEJ

28. Acellular Extrinsic Fiber Cementum Composed of densely packed bundles of sharpey’s fibers & lacks cells Product of fibroblast and cementoblast Found in cervical third of root-may extend apically Thickness between 30-230 micrometer Only type of cementum seen in single rooted teeth Cementoid is not found Main function is anchorage- specially in single rooted teeth

29. Cellular Mixed Stratified Cementum Composed of extrinsic and intrinsic fibers and cells Co-product of fibroblast and cementoblast Appears in apical third of roots, apices and in furcation areas Thickness 100-1000 micrometers Intrinsic fibers are uniformly mineralised but the extrinsic fibers are variably mineralised with some central unmineralised zones

30. Cellular Intrinsic Fiber Cementum Contains cells and intrinsic fibers Formed by cementoblast and fills resorption lacunae Majority of fibers are organised parallel to the root surface Cells have phenotype of bone forming cells Very minor role in attachment Corresponds to cellular cementum and is seen in middle to apical third and inter- radicular cementum

31. Intermediate cementum Ill defined cementum near CEJ of certain teeth Contains cellular remnants of Hertwig's epithelial root sheath Embedded in calcified ground substance Thickness is 10 micrometers

32. Cemento-Dentinal Junction Interface between cementum and dentine In deciduous teeth- scalloped In permanent teeth- smooth Areas of dentine adjacent to CDJ appears granular in ground section due to colaescing and looping of terminal portion of dentinal tubules and is called TOMES GRANULAR LAYER During RCT obturating material must end near CDJ No increase or decrease in width with age(2-3 micrometer)

33. Cemento-enamel Junction

34. Cemento-enamel Junction Functions: Provide medium for attachment to collagen fibers of the PDL Cementum is harder than alveolar bone and is avascular and doesn’t show resorption under masticatory or orthodontic forces Thus during orthodontic forces tooth integrity is maintained and alveolar bone being elastic in nature changes its shape, fulfilling orthodontic requirement Functions as covering for root surface Cementum has the property of continuous deposition thus it repairs damage such as fracture or root resorption Cementum can aid in maintaining the teeth in functional occlusion if deposited in apical aspect in patients with chronic bruxism- passive eruption

35. Cementum Resorption and Repair Permanent teeth doesn’t undergo the process of physiologic resorption as does the counterpart However the cementum of erupted as well as unerupted teeth is subject to resorptive changes that may be of microscopic proportion or sufficiently extensive to present a radiographically detectable alteration in the root contour Local conditions 1) Trauma from ocllusion 2) Orthodontic movement 3) Cysts and Tumours 4) Pressure from malaligned erupted teeth 5) Peri-apical disease and Periodontal disease Systemic Conditions Paget’s disease Hypothyroidism Heridity fibrous osteodystrophy Calcium deficiency

36. Cementum Resorption and Repair Cementum resorption appear microscopically as bay like concavities in the root surface Multi-nucleated giant cells and large mononuclear macrophages are generally found adjacent to cementum undergoing active resorption Several sites of resorption coalesce to form a larger area of destruction Resorptive process may extend into underlying dentin and even into pulp, but its usually painless Cementum resorption is not necessarily continuous and may alternate with periods of repair and deposition of new cementum The newly formed cementum is demarcated from the root by a deep stained irregular line, termed as reversal line, which delineates the border of the previous resorption

37. Cementum Resorption and Repair Repair of cementum is a process to heal the damage caused by resorption or cemental fracture Cementum repair requires the presence of viable connective tissue If epithelium proliferates in the area of resorption then repair will not take place Repair can occur in both vital and non-vital teeth Repair can be Anatomical Functional

38. Cementum Resorption and Repair Anatomic Repair : The root outline is re-established as it was before cemental resorption. It generally occurs when the degree of destruction is low Cementum resorption is repaired by cellular and acellular cementum Functional Repair : in cases of large cemental resorption or destruction, repair doesn’t re-establish the same contour as before To maintain the width of PDL, the adjacent alveolar bone grows and takes the shape of defect, this is done to improve the function of tooth, hence called functional repair

39. Effect of Ageing on Cementum With ageing the surface of cementum becomes more irregular. This is caused by calcification of some fiber bundles where they were attached to cementum Cemental width may increase with increasing age (5-10 times) Increase in width is greater apically and lingually In ageing, a continuous increase of cementum in the apical zone may result in obstruction of apical foramen

40. Exposure of Cementum to oral environment Cementum becomes exposed to oral cavity in cases of gingival recession and a consequence of loss of attachment in pocket formation Cementum is sufficiently permeable to be penetrated by micro-organisms, organic and inorganic substances in such cases Bacterial invasion of the cementum occurs commonly in periodontal disease Caries of cementum can also develop

41. Role of Cementum in Periodontal disease DCNA Vol.24 Issue 4 (1980)- Joseph J. Aleo

42. Changes in Cementum Associated with Periodontal Disease Structural Changes Partial demineralization Repreciation of dissolved minerals Decrease or loss of cross banding of collagen Sub-surface condensation of organic material of exogenous origin Chemical Changes Increase in calcium and phosphate levels Increase in fluoride content Decrease in sodium levels

43. Changes in Cementum Associated with Periodontal Disease Cytotoxic changes Effects on cell proliferation Hatfield and Bomhammers - inhibitory substance penetrates the exposed cementum that prevents growth of epithelial cells in tissue cultures Presence of endotoxins - limits fibroblast proliferation – detrimental to the arrest of disease Cementum bound endotoxins – 50 times more toxic Destructive physical changes – cavitation , partial demineralisation Effect on cell attachment Cultured human gingival fibroblasts do not attach to diseased tooth ( Aleo etal 1975)

44. Changes in Cementum Associated with Periodontal Disease Inhibitory principle of matrix- Morris (1975) Disease inhibited development of implanted marrow whereas demineralised healthy tooth did not Demineralised diseased roots showed more inhibition-toxins must have seeped into root matrix during pocket formation and demineralization removed the toxin allowing development of marrow According to inhibitory principle of matrix-phenol extraction usually required to remove toxins from bacterial cell wall is not necessary to make diseased cementum receptive cell attachment

45. Changes in Cementum Associated with Periodontal Disease In early and moderate periodontitis- acellular cementum is affected (coronal half of the root) Damage extends to cellular cementum in most advanced periodontal conditions and furcally positioned lesions These surfaces are almost always covered by cellular cementum during successful regeneration, whether this is adequate is unclear (McNeil and Sommerman-1999)

46. Role of Cementum Molecules in Periodontal Regeneration Growth factors and adhesion molecules present in cementum are also active towards cells of gingiva, PDL and alveolar bone (Narayanan and Bartold-1996; Bartold etal-2000) Its possible that these growth factors present have the potential to participate in the regeneration of these tissues But its not significant as growth factors remain bound within cementum matrix Even if inflammatory component releases them, their relative concentrations are likely to be less than those available from blood and inflammatory cells Therefore contributions of cementum molecules towards regeneration of other periodontal tissues are likely to remain marginal

47. Chemical Modifications of Cementum Addition of zinc to cultures relieved endotoxin induced depression of cellular proliferation Chelation of zinc enhanced cellular toxicity of endotoxin- Aleo Studies analyzing effect of zinc on cellular attachment are still underway Register & Burddick - tested effects of partial demineralization by acid on attachment (Dog models) Results-production of cementum pins- reattachment with cementogenesis- repair of chronic interproximal defects- complete alveolar bone repair over labial defects by 1 year

48. Related Studies

49. Dynamic v/s Stable (is it still a controversy?)

50. Developmental Anomalies of Cementum Enamel Projections If amelogenesis does not stop before the start of root formation, enamel may continue to form over portions normally covered by cementum Enamel Pearls This consist of globules of enamel on root surface in cervical regeneration (act as plaque retentive areas)

51. Developmental Anomalies of Cementum Hypercementosis Refers to prominent thickening of cementum It may be localised to one tooth or may involve the entire dentition (Paget’s disease) Occurs as generalised thickening of the cementum, with nodular enlargement of cementum in apical third of root Etiology of Hypercementosis Spike-like type of hypercementosis : results from excessive forces from orthodontic appliances or occlusal forces Generalised type-occurs in teeth without antagonist

52. Developmental Anomalies of Cementum Cementoblastoma Only neoplasm of cementum Cementum like tissue is deposited around the roots of teeth as irregular or rounded mass Age less than 25 Involves commonly- mandibular molars and pre-molars Tooth usually as vital pulp Attached to roots and causes its resorption, involves pulp canal and also causes slow expansion of cortical plate Enlargement produced is usually asymptomatic

53. Developmental Anomalies of Cementum Cementicles Are small, globular masses of cementum found in approx 35% of human roots. May not be always attached to the cementum surface but may be located free in Pdl . These may result from microtrauma , when extra stress on sharpey’s fibers causes a tear in the cementum. Are more commonly found in apical & middle third of root and in root furcation areas May develop from calcified epithelial rests; around small spicules of cementum or alveolar bone traumatically displaced into the periodontal ligament; from calcified Sharpey's fibers; and from calcified, thrombosed vessels within the periodontal ligament

54. Developmental Anomalies of Cementum Cementoma Benign cementoblastoma/cemental dysplasia Represents an unusual reaction of bone Caused due to occlusal trauma Present usually at apex of mandibular incisor Almost exclusiely found in black persons Age-20 to 40 years Causes expansion of jaw

55. Developmental Anomalies of Cementum Concrescence Form of fusion which occurs root formation has been completed Thought to arise as a result of crowding or traumatic injury of the teeth with resorption of interdental bone so that the two roots are in approximate contact and fused by deposition of cementum between them May occur before or after tooth has erupted

56. Developmental Anomalies of Cementum Cementopathia In 1923, Gottlieb reported a fatal case of influenza and he attributed it as atrophy of bone Characterised by loss of collagen in PDL and their replacement by loose connective tissues and bone resorption resulting in widened PDL space Gottlieb attributed this condition to inhibition of continuous cementum formation which he considered essential for cementum formation He then termed the disease as cementopathia

57. Developmental Anomalies of Cementum Hypophosphatasia This is a hereditary disease characterised by total absence of cementum It results in early loss of teeth It occurs due to deficiency of enzyme alkaline phosphatase (ALP )in serum and tissues

58. Developmental Anomalies of Cementum Ankylosis Fusion of alveolar bone and cementum with obliteration of PDL space is termed as ankylosis Occurs in cases of cemental resorption, may represent a form of abnormal repair May develop after chronic apical inflammation, tooth re-plantation and occlusal trauma Results in resorption of root and gradual replacement with bone tissue

59. Cemental tears The detachment of a fragment of cementum is described as a cemental tear. Cemental tears have been reported in the periodontal literature associated with localized, rapid periodontal breakdown.

60. Conclusion Cementum is an important tissue of the periodontium, attachment apparatus of the tooth and helps in tooth movements Cementum deposition is continuous process but this tissue is rather static as compared to the surrounding dynamic tissue therefore it hast be taken into account while performing various dental procedures Although the morphogenesis and the established structure of the various cementum varieties have been described by many researchers, knowledge of cementum physiology still lags behind what is known about the other dental and periodontal tissues. The interest in cementum, however, has never been given up by researchers, and the ultimate goal of true periodontal regeneration after treatment for periodontitis has revived vigorously the interest in this unique mineralized tissue

61. References Carranza’s clinical periodontology (10th & 11th edition) Orban’s –Text Book Of Oral Histology And Embryology 11th edition Mallar KB, Girish HC, Murgod S, Yathindra Kumar BN. Age estimation using annulations in root cementum of human teeth: A comparison between longitudinal and cross sections . J Oral Maxillofac Pathol 2015;19:396-404 Alistair D King, Tamer Turk, Canan Colak , Selma Elekdag -Turk, Allan S. Jones, Peter Petocz Ali M. Physical properties of root cementum: Part 21.Extent of root resorption after the application of 2.5 degrees and 15 degrees tips for 4 weeks: A microcomputed tomography study . Am J Orthod Dentofacial Orthop 2011;140:e299-e305 Higgins D, Kaidonis J, Townsend G, Hughes T, Austin J. Targeted sampling of cementum for recovery of nuclear DNA from human teeth and the impact of common decontamination measures. Investigative Genetics 2013, 4:18 Boscchardt D, Selvig K. Dental Cementum: The dynamic tissue covering the root surface. Periodontology 2000. Vol. 13, 1997, 41-75