CONTENTS

1. YENEPOYA DENTAL COLLEGE CEMENTUM in HEALTH & DISEASE

2. CONTENTS • INTRODUCTION • CEMENTUM IN HEALTH • TYPES OF CEMENTUM • CLASSIFICATION • COMPOSITION • PERMEABILITY OF CEMENTUM • FUNCTION OF CEMENTUM • CEMENTO ENAMEL JUNCTION • CEMENTODENTINAL JUNCTION • THICKNESS OF CEMENTUM • CEMENTUM IN DISEASE • HYPERCEMENTOSIS • ANKYLOSIS • CEMENTUM RESORPTION & REPAIR • EXPOSURE OF CEMENTUM IN ORAL ENVIRONMENT

3. INTRODUCTION • Periodontium is the functional unit of tissues supporting the tooth. • It consists of four principal components: • Gingiva • Periodontal ligament • Cementum • Alveolar bone Cemetum- Its a calcified avascular mesenchymal tissue that forms the outer covering of anatomic root. It provides anchorage mainly to the principal fibres of periodontal ligament.

4. CEMENTUM IN HEALTH

5. TYPES OF CEMENTUM There are two main types of cementum: Acellular(primary) cementum Cellular(secondary) cementum Both consist of a calcifed interfibrillar matrix and collagen fibrils. Two main sources of collagen fibres in the cementum are: Sharpey’s fibres(extrinsic)-which are the embedded portion of principal fibres of periodontal ligament and are formed by the fibroblast Intrinsic fibres-Fibres that belongs to the cementum matrix and are produced by cementoblast

6. Acellular cementum it is the first cementum formed, it covers approximately the cervical third or half of the root. It does not contain cells. It is formed before the tooth reaches the occlussal plane and its thickness ranges from 30-230 micronmeter. Sharpey’s fibres make up most of the structure of acelluler cementum which has a principal role in suppoting the tooth. Most fibres are inserted at approximately right angles into the root surface and penetrate deep into the cementum. But others enter from several different direction Acellular cementum also contains intrinsic collagen fibrils that are calcified and irregularly arranged or parellel to the surface

8. Cellular cementum It is formed after the tooth reaches the occlusal plane, is more irregular and contain cells(cementocytes) in individual spaces(lacunae) that communicate with each other through a system of anastomosing canaliculi. It is less calcified tahn the acellular type. Sharpey’s fibres occupy smaller portion of cellular cementum and are seperated by other fibres that are arranged either parallel to the root surface or at random. Sharpey’s fibres may be completely or partially calcified or may have a central uncalcified core surrounded by a calcified border Both cellular and acellular 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 more mineralized than adjacent cementum ‘

10. CLASSIFICATION Based on location,morphology and histological appearence Schroeder has classified the cementum as follows: Acellular afibrillar cementum(AAC)- It contains neither cells nor extrinsic or intrinsic collagen fibres, apart from a mineralized ground substance. It is a product of cementoblast and in humans is found in coronal epithelium. Its thickness ranges from 1-15micronmeter. Acellular extrinsic fibre cementum(AEFC)-It is composed of densely packed bundles of Sharpey’s fibres and lack cells.It is a product of fibroblast and cementoblast and in humans is found in the cervical third of roots but may extend further apically.Its thickness ranges from 30-230micronmeters

11. Cellular mixed stratified cementum(CMSC)- It is composed of composed of extrinsic (sharpey’s )and intrinsic fibers and contains cells.It is a co product of fibroblast and cementoblasts.In humans it appears primarily in the apical 3rd of the roots and apices and in furcation areas.Its thickness ranges from 1oo -1ooo micro meter. Cellular intrinsic fiber cementum(CIFC)- Contain cells but no extrinsic collagen fibers.It is formed by cementoblasts.In humans it fills resorption lacunae. Intermediate cementum- It is poorly defined zone near the cemento-dentinal junction of certain teeth that appears to contain cellular remnants of Hertwig’s sheath embedded in calcified ground substance.

12. COMPOSITION Cementum is composed of both inorganic and organic matter. The inorganic content of cementum (hydroxy apatite)is 45% -50% ,which is less than that of bone,enamel or dentin . The organic matrix is composed 90% type I collagen ,5% typeIII callagen,and non collagenous proteins like enamel protein ,adhesion molecules like tenacin,and fibronectin,glycosaminoglycans like chondroitin sulphate and heparan sulfate. The protein extract of mature cementum promote cell attachment and cell migration and stimulate protein

13. Protein synthesis of gingival fibroblasts and periodontal ligament cells. PERMIABILITY OF CEMENTUM In very young animals acellular cementum and cellular 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.

14. FUNCTION Primary function of cementum is to provide anchorage to the tooth in its alveolus .This is achieved through the collagen fibre bundles of PDL. It also plays an important role in maintaining occlusal relationship,whenever the incisal and occlusal surfaces are abraded due to attrition, the tooth supra erupts in order to compensate for the loss and deposition of new cementum occurs at the apical root area.

15. CEMENTOENAMEL JUNCTION Cementum at and immediately subjacent to the cemento enamel junction is of particular clinical importance in root scaling procedures. Three types of relationship involving the cementum exist at the CEJ . In about 60% -65% of cases cementum overlaps the enamel . In about 30% of cases an edge-to-edge butt joint exists. In 5%-10% of cases the cementum and the enamel fails to meet.In this case gingival recession may result in accentuated sensitivity because of exposed dentin.

17. CEMENTO DENTINAL JUNCTION The terminal apical area of the cementum where it joins the the internal root canal dentin is known as cemento dentinal junction. When the root canal treatment performed ,the obturating material should be at the CDJ . There is no increase or decrease in the width of the CDJ with age. Scanning electron microscopy of the human teeth reveals that CDJ is 2-3micro meter wide. The fibril poor layer contains a significant amount of proteoglycans and fibrils intermingle between the cementum and dentin.

18. THICKNESS OF CEMENTUM Cementum deposition is a continuous process that proceeds at varying rates through out life. Cementum formation is most rapid in the apical region where it compensates for tooth eruption. Thickness of cementum on the coronal half of the root varies from 16 -60micro meter,or about the thickness of a hair. It attains its greatest thickness (upto 150 -200micro meter) in the apical third and in the furcation areas. It is thicker in distal surfaces than in mesial surfaces ,because of functional stimulation from mesial drift over time.

19. CEMENTUM IN DISEASE

20. HYPERCEMENTOSIS Hypercementosis refers to the prominent thickening of cementum,with nodular enlargement of apical third of the root. It appears in the form of spike like excrescences (cemental spikes)created by either the coalescence of the cementicles that adhere to the root or the calcification of the periodontal fibers at the sites of insertion into the cementum . It is largely an age related phenomenon . It may be localised to one tooth or affect entire dentition. Excessive proliferation of cementum may occur in a braod spectrum of neoplastic and non neoplastic conditions.

21. ETIOLOGY Etiology varies and is not completely understood. The spike like type of hypercementosis results from excessive tension from orthodontic appliances or occlusal forcers . The generalised type may be associated with a variety of situations like teeth without antagonists ,in teeth with chronic pulpal and periapical infection. Hypercementosis of the entire dentition may occur in patients with Paget’s disease.

22. RADIOGRAPHIC FEATURE Radiolucent shadow of the periodontal ligament and the radio opaque lamina dura are seen on the outer border of an area of hypercementosis. From a diagnostic point ,peri apical cemental dysplasia,condensing osteitis ,and focal periapical osteopetrosis may be differentiated from hypercementosis because all these entities are located outside the shadow of PDL and lamina dura. TREATMENT Hypercementosis does not require treatment .It could pose problem if an affected tooth requires extraction. In multi rooted tooth sectioning of the tooth may be required before extraction.

23. ANKYLOSIS Ankylosis refers the fusion of cementum and alveolar bone with obliteration of PDL. It occurs in teeth with cemental resorption ,which suggests that it may represent a form of abnormal repair It may also develop after chronic peri apical inflammation,tooth replantation,and occlusaltrauma and embedded tooth. Ankylosis results in resorption of the root and its gradual replacement by bone tissue. Clinically, ankylosed teeth lack the physiological mobility of norrmal teeth,which is one diagnostic sign for ankylotic resorption. Ankylosed teeth usually have a special metallic percussion sound and if the ankylotic process continues they will be in infraocclusion.

24. As the periodontal ligament is replaced with bone in ankylosis, proprioception is lost because pressure receptors in the periodontal ligament donot function properly. Radiographically resortion lacunae are filled with bone and the PDL space is missing. Because no defenitive causes can be found in ankylotic root resorption no predictable treatment can be suggested. Treatment modalities ranges from a conservative approach such as restorative intervention, to surgical extraction of the affected tooth. A true periodontal pocket will not form because apical proliferation of epithelium along the root , a key element of pocket formation ,is not possible because of ankylosis.

25. CEMENTUM RESORPTION & REPAIR Cementumof erupted as well as unerupted teeth is subject to resorptive changes. Approximately 70% all resorption areas were confined to the cementum without involving the dentin. Cementum resorption may be caused by local or systemic factors or may occur without apparent etiology. Local condition causing cementum resorption include trauma from occlusion.pressure from malaligned erupting teeth,cysts and tumours,orthodontic movement,periapical diseases,and periodontal diseases. Systemic condition include calcium deficiency,hypothyroidism,hereditary fibrous osteodystrophy and paget’s disease.

26. Microscopically resorption appear as Bay like concavities in the root surface. Multi nucleated giant cells and large mononuclear macrophages are generally found adjacent to the cementum undergoing active resorption. Resorptive process may extend into the underlying dentin and even into the pulp but it is usually painless. The resorption is not continuous and may alternate with periods of repair and deposition of new cementum. The newly formed cementum is demarcated from the root by a deeply staining irregular line –REVERSAL LINE. Cementum repair requires the presence of vuable connective tissue.

27. If epithelium proliferates in to an area of resorption, repair will not take place. Cementum repair can occur in vital as well as devitalised teeth. The cell rests of Malassez mat be related to cementum repair by activating their potential to secret matrix proteins such as amelogenins, enamelins and sheath proteins. Several growth factors have been shown to be effective in cementum regeneration including bone morphogenic proteins, platelet derived growth factors and enamel matrix derivatives.

28. EXPOSURE OF CEMENTUM TO ORAL ENVIRONMENT Cementum may be exposed to the oral environment in cases of gingival recession and as a result of loss of attachment in pocket formation. In these cases, cementum is permiable to be penetrated by organic substances,inorganic ions and bacteria. Bacterial invasion of the cementum occur frequently in periodontal disease. Cementum caries can also develop.

29. CEMENTUM IN AGING As the cementum deposition continues after tooth eruption ,cemental width may increased by 5-10 times with increaseing age. Increase in width greater apically or lingually. Permiability of cementum diminishes with age. There is no relationship has been established between aging and mineral content of cementum.

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