Cementum: Definition, Structure, and Clinical Relevance PDF

CEMENTUM Prepared by:Dr Azizah Ahmad Fauzi  CEMENTUM Prepared by:Dr Azizah Ahmad Fauzi  Physical characteristics Definition cementum-chemical properties Is the thin layer of calcified tissue Covering the root dentine...

CEMENTUM Prepared by:Dr Azizah Ahmad Fauzi  CEMENTUM Prepared by:Dr Azizah Ahmad Fauzi  Physical characteristics Definition cementum-chemical properties Is the thin layer of calcified tissue Covering the root dentine · soft tissue:Pulp · others, hard tissue Identine cementum · surround enamel the rOOt dentine  Physical characteristics Colour: Pale yellow  Physical characteristics Vascularity / Innervation: Avascular & No innervation (No marrow spaces) ↓ no blood vessel  Physical characteristics Thickness: variable o Thinnest cervically (10-15µm) 6 o Thickest at the surround rot dentine MOLAV - root apex (50 – 200µm) & I premolar - interradicular areas (multirooted teeth) ~ - nicker especially at  Physical characteristics Hardness: Softer than dentine -tend to Worn 0 If (makes cementum readily removed by abrasion in the present of * gingival recession). excessive force - of toothbrushing  Physical characteristics Permeability: o Cementum > permeable than dentine o Cementum < permeable with age o Cellular Cementum > permeable than AC  Physical characteristics Resorption pattern: o Less readily resorbed in comparison to bone ~ probably dt few reasons. ie: properties of precementum / increased Sharpey’s fibres esp in AC. Clinical importance: Orthodontic tx. ~ Cementum is less readily resorbed in comparison to bone ~ imp. feature to allow ortho. tooth m/ments without jeapordising tooth str.  Physical characteristics Continuity in formation: Slowly formed throughout life. ~ allows continual reattachment of PDL fibres.  Chemical properties On wet-weight basis, cementum contains… 65% inorganic 23% organic 12 % water mineralearier · compact to Water Principle component: Primary component: hydroxyapatite collagen (mainly Type 1) I · cementum matrix protein Crystal Functions: ~ accommodates mineral deposition! ~ anchor tooth to bone through its integration with collagen fibers within PDL region. Fluoride -Sialoprotein (in cementum matrix), - …[ ] higher -Osteopontin (in incremental lines), - at external surf & -CAP: Cementum derived attachment protein (in - in AC than CC. cementum matrix & cementoblast) -GAG; mainly chondroitin SO4  Further reading for the importance (function) of the E organic content….Ten Cate page 244- 245.  Classification Based on : ⑧ ② presence / absence of cells (acellular /cellular cementum) COMPAR AL BC) by Nature and origin of organix matrix (extrinsic / intrinsic / mixed fibre cementum) ACCIIUl9r SOURC · external Cellulat · source internat Acellular vs Cellular cementum  Formation Acellular cementum (AC) - a.k.a primary cementum : being formed first, subsequently formed CC.  cementocyte Location - : Covers the root adjacent to dentine · glass like appearing : Usually overlies AC, (mainly in apical area & interradicular areas.)  Microscopic appearance (1) : relatively structureless (- No cementocytes, - cementoblast identifiable for a short time) to formation ~due orcementor - Contains cementocytes - Cementoblast identifiable for longer period Cementocytes? = cementoblast embedded in cementum matrix located within lacuna of · ciue rementocyte Presence  Microscopic appearance (2): In comparison to AC, CC has more widely spaced, thicker & more irregular incremental lines. ( dt more rapidly formed CC). ↳ developmental line oindMat development Of cementum thicker in appearance · cellyal · incremental im tataway from elo · widely space thicker  Microscopic appearance (3) : o cementoblast from AC.. ~ fibroblast-like morphology, o cementoblast from CC.. ~ osteoblast-like morphology,  Derivation of cementoblast : o cementoblast from AC.. derived from HERS. o cementoblast from CC.. derived from mesenchyme of dental follicle.  Extrinsic fibre cementum Derives its fibrous matrix (collageneous fibres) from the Sharpey fibres of PDL. Extrinsic fibres run perpendicular / oblique to the root surface. For human teeth, it usually associated with AC >> AEFC  Intrinsic fibre cementum Derived its fibrous matrix from cementoblast.. Intrinsic fibres run parallel to the root surface & approximately perpendicular to the extrinsic fibres. For human teeth, it usually associated with CC >> CIFC Does not act in supportive role since no Sharpey’s fibres from PDL inserted into it  Cementogenesis form first: CrOWD ↓ WOf ~acellular A. Formation of AEFC ⑭trinsin C tibte cement um SOUrCe from external o Fenestration of HERS >> o HERS undergo epithelial- mesenchymal transformation >> finger shape appearance giving fibroblast-like cells of adjacent dental follicle · come into contact with hyaline layer of HS represent cementoblast oterlayer ofdentine secrete non-collagenous protein (ie: bone sialoprotein, osteopontin, CAP) will &D ire grat Or gant -collagen tibles IORGI A v not Close to Al o Subsequently, continuity between principal collagen fibres of PDL with · cell from fibrous fringe of dentine is established. dental follicle come closer to Al and C become cuboid shape Cementogenesis ~from dentine - mineralization of hyaline layer of HS (by hydroxyapatite crystals in dentine)from main source of inorganic source - - >> spreads into fibrous fringe of AC cement am In this way, 0- AC firmly attached to dentine. - Dentine ↓0 crystal Fibrom  Cementogenesis B. Formation of CIFC ·faster o Disintegration of HERS >> o Basophilic cells from dental follicle (adjacent to AC) >> become cuboidal layer of cementoblast forms cementum matrix (collagen fibrils & ground substance) Increased rate of cementoblast formation in CIFC causing cementoblast become embedded in the cementum matrix forms cementocytes. I +hal why can see lOB in CC Cementogenesis C C Overall, CIFC less mineralized than AEFC. Functions Give attachment to collagen fibres of PDL. >> Help to support tooth in the jaw. A AC:action of external fibrous Cementum Dentine Maintain root integrity. Being involved in tooth repair & regeneration. S CC: tend to develop much faster rule Reparative cementum  AC ‘vs’ CC AC CC Location Covers all root surface Mainly at apical 1/3 & interradicular area of multirooted tooth. apex of root Rate of formation Formed at slow rate Formed at faster rate Histology -Does not contain cementocytes. - Contains cementocytes -Incremental lines⑧ closer together, - Incremental lines more O widely thinner & more even. spaced, thicker & more irregular.  AC ‘vs’ CC AC CC -collagen; ground substance Organic - AC Usually present as - CC usually present as content extrinsic fibre type. intrinsic fibre type. - Protein content: - Protein content: bone sialoprotein, dentine sialoprotein, osteopontin, CAP fibronectin, tenascin. Mineralization Sharpey’s fibres are Fibres generally mineralized @ fully mineralized. partially mineralized at their periphery.  AC ‘vs’ CC AC CC Function Tooth support Has minor involvement in tooth attachment, has reparative role.  CEJ 3 patterns: Pattern 1 Pattern 2 Pattern 3 C overlaps E C&E C&E for a short distance meet at a butt joint fail to meet (in bet dentine is exposed) - Most common - 30% - 10% (60% of sections)  Clinical correlations remove and Root canal treatment (RCT). ~clean pulp region - All root can al ~ cementum is deposited over root apex & for a short distance (≈ 0.5-1.5mm) from anatomical apex clean until >> creates apical constriction: junction of pulp & perio tissue >> important in RCT to establish position of the final root canal filling.  Clinical correlations Hypercementosis (difficulty extraction) in ~ hx of chronic pa inflammation (untreated) >> may cause excessive cementum formation >> Lhypercementosis7 >> difficulty Xn. Concrescence One oftooth · ~ loss of interdental bone anomabz cementum >> continued cementum formation merge N each >> cementum of adjacent teeth fused other >> concrescence >> difficulty Xn.  Age changes in cementum Width (esp at apical & furcation areas). Permeability. The end….