1 cementum

Periodontium

1. شرف العلم وشرف المكان Dr Sherif Hassan Oral Biology

2. Definition: Periodontium is the attachment system of the tooth to the jaw. Members: Two Hard Tissues: Cementum and Alveolar Bone . Two soft Tissues: G ingiva.and Periodontal ligament. Periodontium

3. Definition: Cementum is a hard calcified tissue covering the anatomical Root. Cementum begin from Cemento-enamel junction ( cervical line ) to the root apex. Cementum forming an attachment media for periodontal ligament fibers binding the tooth to the surrounding alveolar bone. Cementum is a member of the periodontium.

4. Colour: Cementum is a light yellowish in color. Hardness: Cementum is less harder than both enamel & dentin. Permeability: Cementum is permeable from both: 1- Dentin side. 2- Periodontal ligament side. Cellular cementum is more permeable than acellular cementum. Vascularity: Cementum is an avascular tissue ( not contain blood vessels) and so, not perform remodeling. Thickness: Near cervical line 20 – 50 µm. Near root apex 150 – 200 µm. Physical Properties of Cementum

5. Thickness near cervical line Thickness near the apex

6. Chemical Composition of cementum 1- Inorganic materials (45-50 % ): Calcium and phosphorous in the form of Hydroxy-apatite crystals. The unit formula of the crystal is ]3Ca3(PO4)2.Ca(OH)2[ Cementum Contain a Higher Level Of Fluoride Than Any Hard Tissue Allover The Body. 2- Organic materials and water (50-55 %): Collagen Fibers: Type I and small amount of type III. Ground Substance: glycogen, protein, lipid, phospho-protein.

7. Classification of cementum I- Based on cell presentation inside cementum: Cellular cementum: Cementum containing cell (Cementocyte) within it. Acellular cementum: no cells found within it. II- Based on fibers presentation inside cementum: Intrinsic fibers cementum: containing fibers formed from cementoblast cells. Extrinsic fibers cementum: containing fibers formed from fibroblast cells. mixed fibers cementum. Afibrillar cementum.

8. Types of cementum Acellular Cementum. Cellular Cementum. Afibrillar Cementum.

9. Acellular Cementum Definition: It is a type of cementum not contain cells within it. Thickness: 20-50 µm. Site: Covers the coronal half of the root. Lining: Acellular cementum is Covered from outside by a layer of cementoid tissue lined by cementoblast cells. Attachment to PDL: Sharpey’s fibers space can be seen in it . Alternating layers of acellular and cellular cementum could be seen. Dentin Cementum

10. Cellular Cementum Definition: It is a type of cementum that contain cells within it. Thickness: 150-200 µm. Site: Covers the apical half of the root. Lining: Cellular cementum is Covered from outside by a layer of cementoid tissue lined by cementoblast cells. Attachment to PDL: Sharpey’s fibers space can be seen in it. Dentin Cementum

11. Afibrillar cementum Definition Of Afibrillar Cementum: It is a part of cementum found on the enamel at cemento-enamel junction of overlaps type that constitute 60%. Site: Cervical line. How to occur? The crown is covered by reduced enamel epithelium that protect it until eruption of the tooth. Any part of enamel become exposed to connective tissue, it may be resorbed or become covered by cementum. Shrinking or injury of reduced enamel epithelium at cervical line leads to exposure of enamel at that area and formation of cementum on the enamel. This type of cementum not contain fibers and termed afibrillar cementum .

12. Incremental Lines Of Salter Definition: It is a rythmic deposition of cementum into layers. Structure: Incremental line of salters are a hyper-mineralized area within cementum.

13. 30% cementum meets the enamel in a sharp line. 10% cementum and enamel doesn’t meet (area of dentin not covered by cementum). 60% cementum overlaps Enamel (afibrillar cementum ) Cemento-Enamel Junction

14. Cemento-Dentinal Junction Smooth in permanent teeth Scalloped in deciduous teeth

15. Histological Structure of Cementum 1- Cementoid Layer. 2- Cementoblast Cells. 3- Cementocyte Cells. 4- Fiberous Elements.

16. Cementoid layer Definition: it is the last formed layer of cementum facing toward PDL. Site: Facing the periodontal ligament and covering the cementum. Structure: 1. Organic matrix without calcification. When cementoid layer become calcified another cementoid layer will be formed. LM.: Cementoid layer is covered at PDL by cementoblast cells.

17. Cementoblast cells Definition: Cement oblasts are connective tissue cells responsible for formation of cementum originated from dental follicle. Site: Cement oblasts are found within the periodontal ligament covering the cementoid layer. Functions: 1. Formation and secretion of collagen fibers of cementum. 2. Calcification of cementum. LM.: Shape: Branched oval cells. Nucleus: Nucleus is rounded and centrally located. Cytoplasm: Basophilic cytoplasm. EM.: RER., Mitochondria, GC, secretory vesicles. Open faced nucleus. Active cells more seen in younger tissue.

18. Cementocyte cells Definition, Site, and origin: Cement ocytes are connective tissue cells found within the cementum originated as cementoblast enters within cementum matrix during cementogenesis. Function: 1. Maintenance of cementum Calcification. LM.: Shape: Large Branched cells with long cytoplasmic processes. Nucleus: Nucleus is rounded and centrally located. Cytoplasm: Not active cells. Branches: Most of cytoplasmic branches of osteocytes are directed toward PDL ( for nutrition). Lacuna: Osteocytes are found within cementum within lacuna and their branches found within canaliculi.

19. Dentin side PDL side Lacuna Canaliculi Cementocyte Cells Cytoplasmic process

20. Age changes of cementum Decrease permeability. Hypercementosis : It is an abnormal thickening of cementum: May be diffuse or circumscribed. May affect all teeth or a single tooth, or even affect only Parts of one tooth. If the overgrowth occurs in functional teeth and improves the functional qualities of the cementum, it is termed cementum hypertrophy. If the overgrowth occurs in nonfunctional teeth, it is termed cementum hyperplasia .

21. Hypercementosis