Cementum

The cementum is a specialised calcified substance covering the root of the tooth. The cementum is a part of the periodontium that attaches the teeth to the alveolar bone by anchoring the periodontal ligament. This presentation covers the anatomy and pathologies associated with the cementum.

1. CEMENTUM Presented by – Shraddha Kode

2. INTRODUCTION Calcified avascular mesenchymal tissue that forms the outer covering of the anatomic root (Newman et al, 2006) Latin: ‘ caementum ’ Meaning: “quarried stone”. 2 main types- Acellular (Primary) Consist of calcified Cellular (Secondary) interfibrillar matrix and collagen fibrils

3. SIMILARITIES WITH BONE Diseases that affect the bone, often alter cementum’s properties as well. Eg . Paget’s disease results in hypercementosis , hypophosphatasia results in no cementum formation, etc . Composition is similar to that of bone Differences are Avascular Lack Haversian canals Not innervated Exhibits little or no remodeling Less readily resorbed – therefore permits orthodontic movement

4. PHYSICAL CHARACTERISTICS 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.

5. CHEMICAL COMPOSITION 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 ).

6. CLASSIFICATION Based on location Radicular cementum – it accounts for the bulk of cementum Coronal cementum – it is cementum over enamel in humans it is thin and poorly developed but it is better developed in herbivorous animals. Based on time of formation Primary cementum formed before tooth eruption. Secondary cementum formed after tooth eruption.

7. 3. Based on it’s cellularity Acellular cementum – which lacks embedded cells. Cellular cementum – in which cells are located within the mineralized matrix . 4. Based on the presence or absence of collagenous fibrils Afibrillar cementum – it lacks dense array of collagen fibrils although rare isolated fibrils will be present. Fibrillar cementum – Contains well defined densely packed collagen fibrils in it’s matrix.

8. 5. Based on the origin of collagenous fibrils Extrinsic fibers-, which are formed due to cementoblasts activity. Intrinsic fibers – incorporation of the periodontal ligament fibers.

9. Acellular Cementum Cellular Cementum Location Coronal 2/3 rd Apical 1/3 rd Function Attachment Protection , maintaining teeth in functional occlusion - minor role in attachment. Cellularity Not Present Present Structure Microscopically - structure less EM – Striation are seen Laminated appearance Fiber arrangement Extrinsic fibers – Parallely arranged perpendicular to root surface Intrinsic fibers – parallel to root surface Extrinsic fibers – larger, haphazardly arranged. Mineralisation Fully mineralised extrinsic fibers Intrinsic fibers – mineralised uniformly Exrrinsic fibers – less mineralised Speed of formation Slow and constant Rapid and irregular Mode of secretion by cells Unipolar Multipolar Cementoid Absent Present

10. ACELLULAR CEMENTUM CELLULAR CEMENTUM

11. Classification by SCHROEDER in 1986 ACELLULAR AFIBRILLAR CEMENTUM (AAC) No cells no extrinsic intrinsic collagen fibres Product of cementoblasts Found as coronal cementum in humans Thickness of 1 to 15 Am

12. ACELLULAR EXTRINSIC FIBRE CEMENTUM (AEFC) Composed of densely packed bundles of Sharpey’s fibres Lacks cells Product of fibroblasts and cementoblasts Cervical third of roots in humans Thickness – 30 and 230 Am

13. CELLULAR MIXED STRATIFIED CEMENTUM (CMSC) Composed of extrinsic intrinsic fibres and cells Produced by fibroblasts and cementoblasts Apical third of roots and in furcation areas Thickness – 100 to 1000 gym

14. CELLULAR INTRINSIC FIBRE CEMENTUM (CIFC) Contains cells No extrinsic fibres Formed by cementoblasts Fills resorption lacunae

15. INTERMEDIATE CEMENTUM First layer of cementum is actually formed by the inner cells of the HERS and is deposited on the root’s surface is called intermediate cementum or Hyaline layer of Hopewell-Smith Deposition occurs before the HERS disintegrates

16. Intermediate cementum is situated between the granular dentin layer of Tomes and the secondary cementum that is formed by the cementoblasts (which arise from the dental follicle) Approximately 10  m thick and mineralizes greater than the adjacent dentin or the secondary cementum

17. SHARPEY’S FIBRES C onnective tissue fibers from PDL pass between the cementoblasts into the Cementum. T hese fibers are known as “ SHARPEY’S FIBERS ” T hey are embedded in the cementum & serve as an attachment for the tooth to surrounding bone

18. Hertwig’s Epithelial Root Sheath and Root formation

19. MINERALISATION

20. INCREMENTAL LINES OF SALTER In both acellular and cellular cement incremental lines run roughly parallel with the root surface. These lines represent “Rest Periods” in cementum formation. These are formed by fiber-free amorphous substance and represent intervals between successive deposition of cement and are called incremental Lines of Salter. Histochemical study indicates that the incremental lines are highly mineralized areas with less collagen and more ground substance.

21. PERMEABILITY OF CEMENTUM Cellular and acellular cementum are very permeable and permit the diffusion of dyes from the pulp and external root surface. In cellular cementum, the canaliculi in some areas are contiguous with the dentinal tubuli The permeability of cementum diminishes with age

22. CEMENTOENAMEL JUNCTION 3 TYPES 60% to 65% - cementum overlaps the enamel 30% - edge-to-edge butt joint exists 5% to 10% - cementum and enamel fail to meet (Gingival recession may result in accentuated sensitivity because the dentin is exposed)

23. Normal variations in tooth morphology at the cementoenamel junction

24. FUNCTIONS 1- Acts as a medium for attachment of collagen fibers of PDL ( Sharpey’s fibers ). 2- The continuous formation of cementum keeps the attachment apparatus intact . 3- Cementum deposition apically compensate for the attrition . 4- It is a major reparative tissue ( as in case of fracture or resorption of root)

25. CEMENTUM IN DISEASE HYPERCEMENTOSIS Hypercementosis is characterized by cementum formation beyond the physiologic limits of the tooth . This excessive amount of cementum might lead to an abnormal thickness of the apex that becomes round-shaped and/or with the root appearance altered macroscopically

26. CONCRESCENCE Union of two adjacent teeth by cementum . CAUSE - developmental union by cementum Traumatic injury or crowding of teeth with resorption of the interdental bone repaired by cementum

27. CEMENTICLES Abnormal,calcified bodies in the periodontal ligament Generally they seem to form first on cellular debris, such as the epithelial root sheath remnants. Usually ovoid or round Appearance similar to denticles Size ranges from 0.1- 0.4 mm. Formed as a response to local trauma or hyperactivity Appear in increasing numbers in the aging person

28. FREE CEMENTICLES ATTACHED CEMENTICLES EMBEDDED CEMENTICLES

29. CEMENTAL SPIKES It is uncommon condition characterized by occurrence of small spikes or out growth of cementum on root surface . It may occur due to occusal trauma. Exact mechanism of formation is not known - calcification of Sharpey’s Fibres ???

30. CEMENTAL CARIES Hazen described it as soft progressive lesion found any where an root surface that has lost connective tissues attachment and is exposed to oral environment . Micro-organisms appear to invade the cementum along sharpey’s fibers or between bundles of fibers. Since cementum is formed in concentric layers, micro-organisms spread in lateral direction between various layers. Once it involves dentin the process is identical to dentin caries.

31. ANKYLOSIS Fusion of cementum and alveolar bone with obliteration of periodontal ligament It occurs due to:- Cemental resorption Chronic periapical inflammation Tooth replantation Occlusal trauma

32. HYPOPHOSPHATASIA A rare familial disease, characterized by incomplete bone mineralization. First described by Rathbun ( 1948 ). Characterized by low levels of serum kidney and bone alkaline phosphatase and elevated levels of phosphoethanolamine in serum and urine ( Watanabe et al, 1993 ). Skeletal abnormalities ( rickets, osteomalacia , poor cranial bone formation ) and premature loss of the primary teeth are common findings.

33. BENIGN CEMENTOBLASTOMA It is neoplasm of functional cementoblasts which forms large masses of cementum or cementum like tissues on tooth root . Associated tooth is vital Slow growing and causes expansion of cortical plates. Radigraphic features A tumor appears to attached to roots . Well circumscribed dense radiopaque mast surrounded by thin radiolucent border.

34. CENTRAL LESIONS Cemento-osseous dysplasia (osseous dysplasia) 1 Focal cemento-osseous dysplasia 2 Periapical cemento-osseous dysplasia (osseous dysplasia, cemental dysplasia, cementoma ) 3 Florid cemento-osseous dysplasia Cementifying fibroma (cemento-ossifying fibroma , ossifying fibroma ) Familial gigentiform cementoma (True cementoma )

35. CONCLUSION Specialized tissue evolved for special function Functionally part of the dynamic unit of Periodontium Anatomically part of the root Regeneration of cementum  Regeneration of periodontium