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Cementum in Health and Disease
CONTENTS
INTRODUCTION DEFINITION SIMILARITIES WITH BONE CEMENTOGENESIS PROPERTIES CLASSIFICATION CEMENTOENAMEL JUNCTION CEMENTODENTINAL JUNCTION THICKNESS FUNCTION METABOLISM (TURNOVER) AT THE TISSUE AND
MOLECULAR LEVELS
AGE CHANGES RESORPTION AND REPAIR CEMENTUM IN DISEASE
DEVELOPMENTAL ANOMALIES REGRESSIVE ALTERATIONS OF TEETH ALTERATIONS RESULTING FROM PERIODONTAL
PATHOLOGY NEOPLASMS OF THE CEMENTUM SYSTEMIC DISEASES AND ITS INFLUENCE ON
CEMENTUM APPLICATION IN FORENSIC ODONTOLOGY CONCLUSION REFERENCES
Introduction
Periodontium consists of investing layer and supporting tissues of the tooth: gingiva, periodontal ligament, cementum and alveolar bone.
Divided into 2 parts: Gingiva : protects the underlying tissues Attachment apparatus : composed of PDL, cementum and
alveolar bone Cementum is considered a part of the periodontium because,
with the bone - supports fibres of PDL. It was demonstrated microscopically in 1835 by 2 pupils of
Purkinje (Bhaskar SN, 1991) Hard bone like tissue covering the anatomic roots of the teeth
(Newman et al, 2006) .
Word is derived from Latin word Caementum, “quarried stone”- chips of stone used in making mortar (Nanci A, 2003).
Its a specialized mineralized tissue covering root surfaces and occasionally small portions of crown of teeth
Has many features in common with bone tissue.
Definition Cementum is the calcified, avascular mesenchymal tissue that
forms the outer covering of the anatomic root (Newman et al, 2006).
Cementum is the thin, calcified tissue of ectomesenchymal origin covering the roots of the teeth (glossary of periodontology).
Similarities with bone (Saygin et al, 2000)
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
Differences in physicochemical or biological properties Properties of precementum Increased density of Sharpey’s fibers (particularly in
acellular cementum) Proximity of epithelial cell rests to the root surface
Cementogenesis (Bosshardt and Selvig, 1997) Formation of cementum can be subdivided into
Prefunctional developmental stage : formed during the root development - 3.5 and 7.5 years - prefunctional development is extremely long
Functional developmental stage : commences when the tooth is about to reach the occlusal level associated with attachment of root to bone continues throughout life - adaptive and reparative
processes are carried out by the biological responsiveness of cementum
influences the alterations in the distribution and appearance of the cementum varieties on the root surface with time.
Root formation
Cementoblast origin Precursors of cementoblasts and PDL fibroblasts - dental
follicle Factors within local environment regulate - cementoblasts of
cementum, fibroblasts of PDL or osteoblasts of bone tissue Infiltrating dental follicle cells receive reciprocal inductive
signal from the forming dentin and differentiate into cementoblasts
HERS cells may undergo epithelial-mesenchymal transformation into cementoblasts during development
Extracellular matrix proteins - noncollagenous proteins found in bone – bone sialoprotein - precementoblast chemoattraction, adhesion to root surface and cell differentiation.
Enamel proteins - to be involved in early cementogenesis.
Development of dentinocemental junction Precementoblasts differentiate along external surface of
predentin into cementoblasts Implant initial collagen fibrils (fibrous fringe) of cementum
matrix into predentin by extending numerous tiny cytoplasmic processes
Leads - intimate interdigitation of 2 different fibril populations - forming dentinocemental junction - gets mineralized later
Intermediate cementum - interfacial layer between dentin and cementum - observed particularly between acellular extrinsic fiber cementum and dentin in rodent teeth and not in humans
Development of Primary (acellular) cementum (Berkowitz et al,2002)
PDL fibers oriented more parallel to the root surface and not gained any attachment to fibrous fringe.
Subsequent development of acellular cementum involves Slow increase in thickness Establishment of continuity between collagen fibers of the
periodontal ligament with those of the fibrous fringe at the surface of root dentin
Continued slow mineralization of collagen Establishment of continuity with PDL occurs only after tooth
has erupted into the mouth, when 2/3 of root has formed and acellular cementum may be only about 10 µm thick
Cementum lining tooth before this time - acellular intrinsic fiber cementum
Once PDL fibers become attached, cementum - acellular extrinsic fiber cementum.
Increases slowly and evenly throughout life at a rate of about 2-2.5 µm per year
Mineralization of cementum Does not appear to be controlled by cementoblasts No matrix vesicles observed Likely that presence of hydroxyapatite crystals in the
adjacent dentin initiates mineralization Adjacent PDL fibroblasts, which are rich in alkaline
phosphatase, may also pay a role Proceeds very slowly in a linear fashion, therefore no
evidence of a layer of precementum
Calcospherites not observed As the initial formation of cementum is closely associated
with mineralization of predentin or hyaline layer, when mineralization of initial root dentine is interfered with by administration of drugs known as bisphosphonates, there is inhibition of cementogenesis.
Cementogenesis Occurs rhythmically – periods of activity alternating with
periods of quiescence Structural lines observed indicating the incremental
nature of formation Periods of decreased activity associated with incremental
lines called incremental lines of Salter
These lines contain higher content of ground substance and mineral and lower content of collagen.
As acellular cementum is formed slowly, the incremental lines are closer together than that of cellular cementum which is deposited more rapidly.
Development of acellular afibrillar cementum Deposited as a thin layer overlying enamel at the cervical
margin of the tooth Presumably, the protection of the reduced enamel epithelium
overlying this enamel in an unerupted tooth is damaged or lost
Adjacent connective tissue cells of the dental follicle then come into contact with the enamel surface and are induced to form cementoblasts
These secrete an afibrillar matrix that calcifies
Development of Secondary (cellular) cementum Secondary cementum appears in the apical region of the root at
time tooth erupts. Also in furcation area of multirooted teeth. Associated with increase in the rate of formation of the tissue Following loss of continuity of the HERS, large basophilic cells
are seen to differentiate from adjacent cells of the dental follicle against the surface of the root dentine – form a distinct layer of cementoblasts
These cementoblasts possess more cytoplasm and cytoplasmic processes than the cells associated with acellular cementum
Basophilia is due to roughened endoplasmic reticulum – their presence suggests that cementoblasts secrete the collagen (together with ground substance) that forms the intrinsic fibers of secondary, cellular cementum
These fibers are oriented parallel to root surface Due to increased rate of formation, thin unmineralized
precementum layer (about 5 µm thick) will be present on the surface of cellular cementum
Precementum is less mineralized than primary cementum Multipolar mode of matrix secretion by the cementoblasts
will result in cells becoming incorporated into the forming matrix – thus called cementocytes
Incremental lines are more widely spaced due to increased rate of formation
Properties Physical properties: (Berkowitz et al, 2002)
Pale yellow with a dull surface Softer than dentine Permeability
cellular variety more permeable as the canaliculi in some areas are contiguous with the dentinal tubuli
more permeable than dentine decreases with age
Soft and thin cervically – readily removed by abrasion when gingival recession exposes the root surface to the oral environment
Chemical properties: (Berkowitz et al, 2002) and Bosshardt and Selvig,1997)
On a wet weight basis: Inorganic – 65% Organic – 23% Water – 12%
By volume: Inorganic – 45% Organic -33% Water -22%
Inorganic Acellular cementum is more mineralized than cellular
cementum - presence of uncalcified lacunae and core of Sharpey’s fibers in cellular cementum and slow formation of acellular cementum which allows longer direct contact of tissue fluids
CDJ shows a zone of high mineral content and low organic content delineated by zones of low mineral content on the dentin and sometimes on cementum side
Principle inorganic component- hydroxyapatite (Ca10(PO4)6(OH)2) with small amounts of amorphous calcium phosphates present These crystals are thin and plate like and similar to those in
bone and arranged parallel to the long axis of collagen fibril
Avg- 55nm wide and 8nm thick Length varies Minute size of mineral crystals allows for greater
capacity for adsorption of fluoride and other elements and more readily decalcifies in the presence of acidic conditions
Concentration of fluoride tends to be higher at the external surface, conc. of 0.9% ash weight – increases with age and varies with the nutritional fluoride supply to the individual
Contains 0.5-0.9% Mg – occupies the place of an equal no. of Ca ions in hydroxyapatite crystal lattice Similar to that of bone but half of that of dentine Mg conc. appears to be lower at the surface than in deeper layers
of cementum Contains 0.1-0.3% sulfur as a constituent of the organic
matrix Trace elements – Cu, Zn and Na
Organic Collagen :
Primarily collagen type I and III, like in bone and PDL
90% of organic matrix – type I collagen and approximately 5% - type III
Wang et al suggested that type I fibrils are coated by type III collagen whereas some other authors suggest that both the collagens are co – localized in the same fibril
Non – collagenous proteins : Glycolipids, glycoproteins or proteoglycans Non-collagenous proteins are similar to that of bone - bone
sialoprotein and osteopontin – both are phosphorylated and sulfated glycoproteins
Bind tightly to collagenous matrices and hydroxyapatite
Participate in mineralization process Reveal cell attachment properties through tripeptide
sequence Arg-Gly-Asp that binds to integrins Acellular cementum contains much more of these
than cellular cementum
Osteonectin – another glycosylated protein Found in extracellular matrix of mineralized
tissue Close relation between osteonectin and
collagen seems to exist in mineralization process
Enzyme alkaline phosphatase believed to participate in cementum mineralization (Beertsen and Everts, 1990) Supersaturation of phosphate ions, released from
organic phosphate esters, would result in the precipitation of calcium phosphate salts
Although it exists in a plasma membrane bound form, part of the enzyme may also be bound to extracellular matrix
Enzyme activity adjacent to cellular intrinsic fiber cementum is higher than that to acellular extrinsic fiber cementum and thickness of the latter correlates positively with the enzyme activity (Groeneveld et al, 1995)
Glycoproteins – fibronectin and tenascin – more widely distributed High molecular weight and multifunctional proteins
of the extracellular matrix Fibronectin binds cells to components of
extracellular matrix During tooth development, both are present in the
basement membrane of HERS at the time of odontoblast differentiation
Later, they are also found at the attachment site of PDL to cementum but not in the cementum layer itself (Lukinmaa et al 1991)
Enamel related proteins – have been detected Proteoglycans – core protein to which sulfated
polysaccharides are covalently linked – chondroitin sulfate, dermatan sulfate and hyaluronic acid
Classification (Berkowitz et al, 2002)
Based on presence or absence of cells Cellular cementum:
Contains cells (cementocytes) Found in the apical and interradicular areas and
overlying the acellular cementum Formed after acellular - secondary cementum Fast rate of matrix formation – incremental lines farther Presence of precementum Spaces that the cementocytes occupy are called lacunae
and the channels that their processes extend along are the canaliculi
Adjacent canaliculi are often connected and the processes within them exhibit gap junctions
Cementocytes are more widely dispersed and more randomly arranged
Canaliculi preferentially oriented towards PDL - chief source of nutrition
Once embedded cementocytes become relatively inactive Their cytoplasmic/nuclear ratio is low Sparse organelles responsible for energy
production and for synthesis Some unmineralized matrix may be seen in the
perilacunar space Border with dentine clearly demarcated
Acellular cementum: Appears relatively structureless – no cells. First formed – primary cementum Covers the root adjacent to the dentine more in the
cervical 2/3 Slower rate of matrix formation Incremental line closer Precementum virtually absent
Border with dentin not clearly demarcated
Based on the nature and origin of the organic matrix Cementum derives its organic matrix from 2 sources
Extrinsic fibers: from the inserting Sharpey’s fibers of the periodontal ligament – perpendicular or oblique to root surface
Intrinsic fibers: from cementoblasts – run parallel to root surface and approximately at right angles to extrinsic fibers
Mixed fiber cementum: both the above fibers are present
Based on presence or absence of cells and the nature and origin of the organic matrix – Schroeder’s classification (Newman et al, 2006) Acellular afibrillar cementum (AAC):
Contains neither cells nor extrinsic or intrinsic collagen fibers
Only mineralized ground substance Product of cementoblasts Found as coronal cementum Thickness – 1-15µm
Acellular extrinsic fiber cementum (AEFC): Composed almost entirely of densely packed bundles of
Sharpey’s fibers Product of fibroblasts and cementoblasts Cervical third of roots but may extend farther apically Thickness – 30-230µm
Cellular mixed stratified cementum (CMSC): Composed of extrinsic (Sharpey’s) and intrinsic fibers May contain cells Co-product of fibroblasts and cementoblasts Primarily in the apical third, apices and in furcation areas Thickness – 100-1000µm
Cellular intrinsic fiber cementum (CIFC): Contains cells, but no extrinsic collagen fibers Formed by cementoblasts Fills resorption lacunae
Intermediate cementum: Poorly defined zone near cementodentinal junction of
certain teeth that appears to contain cellular remnants of Hertwig’s sheath embedded in calcified ground substance
Cementoenamel junction (Newman et al, 2006)
Cementum overlaps enamel – 60-65% Edge-to-edge butt joint – 30% Cementum and enamel fail to meet – 5-10%
In this case, gingival recession may result in accentuated sensitivity because of exposed dentin
Cementodentinal junction Terminal apical area of cementum where it joins the internal
root canal dentin Obturating material in RCT should be at the CDJ No increase or decrease of width of the CDJ with age –
remains relatively stable CDJ – 2-3 µm wide Here the fibrils intermingle between cementum and dentin
Thickness (Berkowitz et al, 2002)
Varies at different levels of the root Thickest at the root apex and interradicular areas of
multirooted teeth – 50-200µm (may exceed to 600µm) Thinnest cervically – 10-15µm Thickest in distal side than mesial due to mesial drift Between ages 11 and 70 – thickness increases 3 fold – 95µm
at 20yrs and 215µm at 60yrs (Zander and Hurzler, 1958) Impacted teeth have thin cementum
Function Its contiguous with the periodontal ligament on its outer
surface and is firmly adherent to dentine on its deep surface – gives attachment to collagen fibers of the periodontal ligament
Maintains the tooth in functional position in the mouth Maintains the integrity of the root
Metabolism (turnover) at the tissue and molecular levels (Bosshardt and Selvig, 1997)
Cementum is excluded from metabolic processes of the body Variety of noncollagenous proteins are stored in the mineralized
matrix of the cementum, among which those specific for cementum are Cementum derived attachment protein – mediates attachment
of connective tissue cells Cementum derived growth factor – during root resorption and
surgical instrumentation, proteins exposed to root surface could possibly influence the initiation of repair process by cell migration, division, attachment and differentiation
Fluoride accumulates in the surface layer which is exposed to the circulating tissue fluids in the periodontal ligament
Age changes (Bosshardt and Selvig, 1997)
Continuous deposition: Cementum formation continues throughout life unless
disturbed by periapical or periodontal pathology Deposited at a linear rate (Azaz et al, 1974) More cementum is formed apically than cervically Cementum thickness shows variations among tooth
groups and surfaces Thick layers may form in root surface grooves and
furcations of multirooted teeth Great variations in incremental lines indicate that rate of
cementum formation may vary
Changes in tooth position may exert temporal and spatial variations in pressure and tension on root and bone surfaces – biological responsiveness of cementoblasts to these stimuli may influence the rate as well as pattern of cementum deposition – maintaining the tooth in proper position and relation to adjacent teeth
Nonfunctioning, impacted teeth appear to have thicker cementum and structural architecture is different
Impacted teeth – Sharpey’s fibers may be nearly completely absent in the cementum and it is built up mainly by intrinsic fibers arranged parallel to root surface
Physiological activity of cementocytes: No. of cells that become incorporated into cementum matrix
while its formation is proportional to the rate of cementum deposition
Cementocytes close to cementum surface may resemble cementoblasts but the amount of cytoplasm is reduced and they contain less endoplasmic reticulum and fewer mitochondria
Most well developed cell processes point towards root surface – indicate that exchange of metabolites through cellular intrinsic fiber cementum is limited
In deeper layers of CIFC, more advanced nuclear and cytoplasmic changes may occur or lacunae may appear empty – could be due to starvation or consequence of age
Cementum reactions to physiological tooth movement and occlusal forces: Presence of cementum on impacted teeth indicates that
occlusal forces are not necessary to stimulate cementum deposition
In posterior teeth, cementum is markedly thicker on the distal than on the mesial root surface – indicating relationship to mesial drift
Cementum like bone is dynamically responsive and its growth may be stimulated by tensional forces
Cementum thicker in areas exposed to tensional forces
Resorption and repair (Bosshardt and Selvig, 1997)
Types of resorption: Physiological root resorption : normal phenomenon of
deciduous teeth during tooth shedding Causes for resorption of permanent teeth
pathological like infectious, systemic diseases like calcium deficiency, hypothyroidism, hereditary fibrous osteodystrophy and Paget’s disease or tumors
nonpathological like trauma (mechanical, chemical or thermal) or sustained overcompression of the PDL
idiopathic Root resorption classified according to location as
Internal External
According to degree of persistence Transient Progressive
Root surface more resistant to resorption than bone No. of teeth resorbed and severity of resorption are markedly
increased by orthodontic treatment Appears microscopically as bay like concavities in the root
surface Multinucleated giant cells and large mononuclear macrophages
are generally found adjacent to cementum May extend into underlying dentin Not necessarily continuous, may alternate with periods of repair
and deposition of new cementum, new cementum is demarcated from the root by a deeply staining irregular line - reversal line
Repair: Following detachment of odontoclasts from the root
surface, cementogenic cells repopulate the Howship’s lacunae and attach the initial repair matrix to a thin decalcified layer of residual and exposed collagen fibrils
Basophilic and electron dense reversal line forms at the fibrillar junction
Deposited repair matrix resembles cellular intrinsic fiber cementum
Cementum repair requirea viable connective tissue Can occur in devitalized and in vital teeth
CEMENTUM IN DISEASE
Developmental anomalies
Concrescence (Shafer et al, 2006) Form of fusion which occurs after root formation Teeth are united by cementum Thought to arise as a result of traumatic injury or
crowding of teeth with resorption of interdental bone, so that 2 roots are in approximate contact and become fused by deposition of cementum
May occur before or after tooth eruption Diagnosed radiographically Extraction of 1 may result in the extraction of the other
Ectopic enamel (Neville et al, 2002) Presence of enamel in unusual locations, mainly tooth rooth Enamel pearl :
Hemispheric structures consisting entirely of enamel or contain underlying dentin and pulp tissue
Project from surface of root, more in maxillary molars Thought to arise from localized bulging of odontoblastic
layer – bulge may provide prolonged contact between HERS and developing dentin, triggering induction of enamel formation
Majority occur in furcation area or CEJ Precludes normal periodontal attachment with connective
tissue and a hemidesmosomal junction probably exists – less resistant to breakdown, once separation exists – rapid loss of attachment
Conducive to plaque retention and inadequate cleansing
Cervical enamel projections : Represent dipping of enamel from CEJ toward the
bifurcation More in mandibular molars – buccal surface Correlated positively to localized loss of periodontal
attachment with furcation involvement Have been associated with development of inflammatory
cysts – histopathologically identical to periapical cysts – develop along buccal surface over the bifurcation – called buccal bifurcation cysts
Both cases meticulous oral hygiene to prevent localized loss of periodontal support
Sometimes removal of the enamel is advised to achieve a more durable periodontal attachment
Hypercementosis (Neville et al, 2002) Nonneoplastic deposition of excessive cementum that is
continuous with the normal radicular cementum Radiographically – thickening or blunting of the root, surrounded
by radiolucent PDL space and adjacent intact lamina dura Also appears in form of spike-like excrescences called cemental
spikes created by either coalescence of cementicles to the root or calcification of PDL fibers
May be isolated, may involve multiple teeth or may appear as a generalized process
Premolar teeth involved most frequently Occurs predominantly in adulthood and frequency increases with
age
Factors associated Local factors
Abnormal occlusal trauma Adjacent inflammation Unopposed teeth (eg. Impacted, embedded, without
antagonist) Systemic factors
Acromegaly and pituitary gigantism Arthritis Calcinosis Paget’s disease of bone Rheumatic fever Thyroid goiter
Histopathologically Periphery of root demonstrates deposition of an excessive
amount of cementum over the original layer of primary cementum
Excessive cementum may be hypocellular or exhibit areas of cellular cementum that resemble bone(osteocementum)
Often arranged in concentric layers May be applied over the entire root or be limited to the
apical portion Use of polarized light clearly separates dentin and cementum
Treatment – require no treatment, certain cases extraction has been difficult where sectioning of the tooth may be required
Ankylosis (Shafer et al, 2006) Cessation of continued eruption Anatomic fusion of tooth cementum or dentin with alveolar bone Other terms – infraocclusion, secondary retention, submergence,
reimpaction and reinclusion Pathogenesis is unknown and may be secondary to disturbances
from Changes in local metabolism Trauma Injury Chemical or thermal irritation Local failure of bone growth Abnormal pressure from the tongue
Periodontal ligament might act as a barrier that prevents osteoblasts from applying bone directly onto cementum, ankylosis could arise from a variety of factors that result in a deficiency of this barrier – could be due to trauma or genetically decreased periodontal ligament gap
Other theories point to a disturbance between normal root resorption and hard tissue repair
Several investigators believe genetic predisposition has a significant influence and point to monozygotic twins who demonstrate strikingly similar patterns of ankylosis
Clinical and radiographic features May occur at any age, mainly 7-18 years Most commonly involved tooth – mandibular primary 1st
molar
Occlusal plane is below that of adjacent dentition Sharp solid sound on percussion when more than 20% of
the root is fused to bone Radiographically – absence of periodontal ligament space,
but the area of fusion is often in the bifurcation and interradicular root surface making radiographic detection difficult
Ankylosed teeth that are allowed to remain in position – adjacent teeth incline towards it leading to occlusal and periodontal problems
Opposing tooth exhibits overeruption It also leads to impaction of the underlying permanent tooth
Treatment Fail to respond to orthodontic treatment When an underlying permanent successor is present, extraction
should not be performed until it is obvious that exfoliation is not proceeding normally or adverse occlusal changes are developing
In permanent teeth or primary teeth without underlying successors – prosthetic buildup can be placed to augment the occlusal height
Luxation of affected permanent teeth may be attempted with extraction forceps to break the ankylosis – subsequent inflammatory reaction may result in the formation of a new fibrous ligament in the area of previous fusion – reevaluation in 6 months is mandatory
Regressive alterations of teeth (Shafer et al, 2006)
Abrasion : Pathologic wearing away of tooth substance through some
abnormal mechanical process Usually occurs on exposed root surfaces Robinson stated that the most common cause of abrasion is the
use of an abrasive dentifrice Modern dentifrices are not sufficiently abrasive and can cause
remarkable wear of cementum and dentin if toothbrush carrying it is injudiciously used, particularly in horizontal direction
V-shaped or wedge shaped ditch on root side of CEJ in teeth with some gingival recession – angle formed in lesion - sharp and dentin appears highly polished
Improper use of dental floss and toothpicks may produce lesions on proximal exposed root surface
Cementicles : Small foci of calcified tissue, not necessarily true cementum,
which lie free in the PDL of lateral and apical root areas Exact cause is unknown Mostly represent areas of dystrophic calcification and thus are an
eg. of regressive or degenerative change Develop by
Calcification of epithelial cells – enlarge by further deposition of calcium salts in the adjacent surrounding connective tissue – continued peripheral calcification may result in eventual union or even inclusion of the cementicle in the root cementum or alveolar bone – pattern of calcification is of a circular lamellated structure. Only when embedded in the cementum, it may impart a roughened globular outline to the root surface
Focal calcification of connective tissue between Sharpey’s bundles with no apparent central nidus – occurs as small round or ovoid globules of calcium salts
Small spicules of cementum torn from the root surface – cemental tears – or fragments of bone detached from the alveolar plate, if lying free in the PDL may resemble cementicles, particularly after they have undergone some remodeling through resorption and repair
Calcification of thrombosed capillaries in PDL, as Mikola and Bauer pointed are analogous to phleboliths – too small to be seen on radiographs – 0.2-0.3mm in diameter
Clusters of cementum may form and the apices these have been regarded as a cementoma particularly as they unite through interstitial deposition of bone or cementum
No clinical significance
Root caries Defined by Hazen et al as soft progressive lesion that is found anywhere
on the root surface that has lost connective tissue attachment and is exposed to the oral environment
Dentitions of older age group with significant gingival recession and exposed root surfaces
Was earlier referred to as caries of cementum Initiates on mineralized cementum and dentin surfaces which have
greater organic component than enamel Frequently on buccal and lingual surfaces of roots Dental plaque and microbial invasion are an essential part of the cause
and progression of the lesion Organisms – filamentous Microorganisms appear to invade the cementum either along Sharpey’s
fibers or between bundles of fibers
Since cementum is formed in concentric layers and presents a lamellated appearance, microorganisms tend to spread laterally between various layers
After decalcification of cementum, softening and destruction of the remaining matrix takes place
Later invasion of microorganisms into dentinal tubules – matrix destruction – pulpal involvement
Westbrook et al – as there are less dentinal tubules per unit area in root than in crown, there is difference in rate of caries progression and amount of dentinal sclerosis present
According to Katz et al – most frequently affected teeth are mandibular molars, next the mandibular premolars and then the maxillary cuspids, interproximal areas were mostly affected in the maxillary arch and the buccal surface in mandibular arch
Attachment of calculus Zander in 1953 investigated calculus attachment and observed
four types of attachment (Shafer et al, 2006) Attachment to the secondary cuticle Attachment to microscopic irregularities in the surface of
cementum corresponding to previous location of Sharpeys fibers
Penetration of microorganisms of calculus matrix into cementum
Attachment into areas of cementum resorption Calculocementum: Calculus embedded deeply in cementum may
appear morphologically similar to cementum (Newman et al)
Alterations resulting from periodontal pathology (Bosshardt and Selvig, 1997)
Effect of gingival inflammation Subsurface alteration :
Alterations in structure and composition of its organic and inorganic components consequential to pathological changes
Longstanding presence of inflammatory process in gingival connective tissue results in net loss of collagen and in breakdown of dentogingival fibers - enzymatic breakdown of collagen fiber is obvious in the gingival soft tissue and extension of this process into the hard tissue of the root, with loss of collagen cross-banding and dissolution of mineral crystals has also been described – surface limited with diffuse transition to subjacent unaffected tissue
Cervical root resorption : Development of large root resorption defect in cervical region
is, most likely, triggered by inflammatory processes in adjacent connective tissue
Such resorption generally has an undermining character Tooth is resorbed after the alveolar bone – immunity to
resorption has been linked to presence of an uncalcified, vital layer of precementum on root surface Another explanation could be because cementum is
avascular Odontoclasts take their origin from bone marrow and
cannot attack the root surface as fast as the osteoclasts reach the bone surface
Exposure to oral environment Bacterial contamination:
Obvious alterations may occur following exposure of cementum to the environment of periodontal pocket or oral cavity
Root surface wall of periodontal pockets is significant as they may perpetuate periodontal infection, cause pain and complicate periodontal treatment
The root cementum suffers structural, chemical and cytotoxic changes.
Structural changes: (Carranza and Newman, 1996) Presence of Pathologic Granules:
First reported by Bass,1951 Represent areas of collagen degeneration or areas where
collagen fibrils have not been mineralized initially These granules extend 3-12 µm into the surface of
cementum from overlying plaque Granules appeared in 4 basic morphologic patterns:
Grape like structure Long chain aggregate Small isolated vacuoles Very long fissure like area (Garrett, 1975)
Areas of increased mineralization: Probably a result of an exchange, on exposure to oral cavity,
of minerals and organic components at cementum-saliva interface
Microhardness remains unchanged Development of highly mineralized superficial layer may
increase the tooth resistance to decay Hypermineralized zones are detectable by electron microscopy
and are associated with increased perfection of the crystal structure and organic changes suggestive of a subsurface cuticle – seen in microradiographic studies as a layer 10-20µm thick with areas as thick as 50µm
Lack of preferred crystal orientation
Crystals are more densely packed and appeared as distinct, tablet shaped, polygonal structures (Selvig, 1969)
No decrease in mineralization found in deeper areas, therefore indicating that increased mineralization does not come from adjacent areas
Increase in calcium, magnesium, phosphorus and fluoride (Wirthlin et al, 1979)
Loss of, or reduction in, the cross-banding of collagen near the cementum surface and subsurface condensation of organic material of exogenous origin have also been reported
Areas of demineralization Commonly related to root caries Exposure to oral fluid and bacterial plaque results in
proteolysis of the embedded remnants of Sharpey’s fibers Cementum may be softened and may undergo
fragmentation and cavitation Progress around teeth and appear as well defined yellowish
or light brown areas, covered by plaque and have a soft or leathery consistency on probing
Dominant microorganism - actinomycosis viscosus Root caries may be the cause of toothache in patients with
periodontal disease and no evidence of coronal decay
Areas of cellular resorption of cementum and dentin Common in roots unexposed by periodontal disease Symptom free As long as root is covered by PDL, they are likely to
undergo repair If root is exposed before repair occurs, these areas appear
as isolated cavitations that penetrate into dentin
Chemical changes: Mineral content is increased Following minerals are increased in diseased root surfaces
Calcium Magnesium Phosphate Fluoride
Exposed cementum may absorb calcium, phosphorus and fluoride from its local environment forming a highly calcified layer that is resistant to decay
This ability of cementum to absorb substances may be harmful if the absorbed materials are toxic
Cytotoxic Changes: Bacterial penetration into the cementum can be found as deep
as the cemento dentinal junction - facilitated by the occurrence of minifracture and cracks of cemetum or a common sequence to chronic periodontal disease
Bacterial lypopolysaccharide have been detected in the 40-70µm deep surface of periodontally diseased roots
Bacterial endotoxins have also been detected in the cemental wall of periodontal pockets, whether the toxin is actually absorbed to or trapped in the tissue has not been established
Reduced opacity, cavitation and partial decalcification extending as deep as 300µm without any loss of surface contour can exist
These imperfections can harbour endotoxin on a submicroscopic basis and serve as a substrate for inflammatory exudate.
Components of this exudate can include substance such as histamine, bradykinin, high molecular weight immunoglobulins IgG, IgA, IgM and complement
Endotoxin which has been found in the cementum also may act to produce direct labializations of the lysozomal enzyme found within the cells of the tissue which then spill out into the tissues to effect their resorptive activities
Cementum may act to perpetuate the destructive effects of periodontal disease by acting as a reservoir for potentially destructive material.
Aleo et al observed that endotoxin was found to be present in the cementum of untreated periodontally involved teeth having 30% or more loss of supporting bone. The biologic effects of this cementum - bound endotoxin, studied in vitro concentration as low as 0-30 mg/ml of culture medium, were effective in depressing cell proliferation and viability
When compared to endotoxin form E-coli the cementum – bound endotoxin was found to be more toxic. Either biologic activities of endotoxins studied are not present to an equal degree, or the cementum bound material contain heat resistant toxic substances (Aleo et al, 1974)
Surface changes (SEM descriptions) (Garrett, 1975) 3-D view of the ultrastructural level Landay et al 1971 showed numerous surface projections
above cemental plane in normal cementum Landay 1972 – areas exposed to periodontal disease
At base of pocket – most recently exposed cementum showed partial filling in spaces between projections
Cementum which has undergone longer exposure showed complete covering of normal projections with what appeared to be flat sheet of calculus
No holes or spaces where Sharpey’s fibers had been once
Surface morphology of the tooth wall of periodontal pockets: (Newman et al,2006)
The following zones can be found Cementum covered by calculus Attached plaque, which covers calculus and extends apically
from it to a variable degree, probably 100 to 500 µm Zone of unattached plaque that surrounds attached plaque &
extends apically to it Zone of attachment of junctional epithelium to tooth - The
extension of this zone, which in normal sulci is more than 500 µm, is usually reduced in periodontal pockets to less than 100 µm
Zone of semidestroyed connective tissue fibers – apical to junctional epithelium
Zones 3,4 & 5 compose - plaque free zones seen in extracted teeth.
The total width of the plaque free zone varies according to type of tooth (It is wider in molars than incisors) and the depth of the pocket (It is narrower in deeper pockets).
Term plaque-free zone refers only to attached plaque because unattached plaque contains a variety of gram-positive coli and various gram negative morphotypes including cocci, rods, filaments, fusiforms and spirochetes. Most apical zone contains predominantly gram-negative rods and cocci.
Neoplasms of the cementum (Shafer et al, 1997)
Benign cementoblastoma (True Cementoma): Probably a true neoplasm of functional cementoblasts
which form a large mass of cementum or cementum like tissue on the tooth root.
Clinical features: Frequently, under age of 25 years No significant sex predilections Mandibular first permanent molar - most frequently
affected tooth Other teeth involved - mandibular second and third
molars, bicuspids, maxillary bicuspids and first, second and third molars
Associated tooth is vital unless coincidentally involved Lesion is slow growing and may cause expansion of
cortical plates of bone, but is usually otherwise asymptomatic
Radiographic features: Tumor mass is attached to tooth root Appears as a well circumscribed dense radioopaque mass
often surrounded by a thin, uniform radiolucent line Outline of the affected root is generally obliterated
because of resorption of root and fusion of the mass to the tooth.
Histologic features: Main bulk of tumor mass is composed of sheets of
cementum – like tissue, sometimes resembling secondary cellular cementum, but, other times being deposited in a globular pattern resembling giant cementicles
Reversal lines scattered throughout this calcified tissue are quite prevalent
Variable soft-tissue component consisting of fibrillar, vascular & cellular elements
Many cemental trabeculae in areas of activity are bordered by layers of cementoblast
Away from these trabecular surfaces, cementoclasts may be evident
Frequently microscopically indistinguishable from the benign osteoblastoma or giant osteoid osteoma - discussed by Larsson et al
Some areas are so cellularly active that they bear strong resemblance to osteosarcoma
Periphery of tumour generally shows a soft tissue cellular layer resembling capsule - here cemental trabeculae are almost arranged at right angles
Treatment and prognosis : Because of tendency for expansion of the jaw, it is believed that
extraction of the tooth is justified despite the fact, that the pulp is vital – recurrence rare
Distinguish from severe hypercementosis or chronic focal sclerosing osteomyelitis (i.e., condensing osteitis) both of which may superficially resemble
Periapical cemental dysplasia Other names
Cementoma Periapical Osteofibroma Osteofibrosis Cementifying fibroma Localized fibro-osteoma Cementoblastoma Periapical fibrous Dysplasia.
Etiology Unknown Suggested to occur as a result of mild chronic trauma or
traumatogenic occlusion
Clinical feature : Age - 20 years – common More common in females and more often in mandible Lesion occurs in PDL around the apex of the tooth usually
mandibular incisor Almost asymptomatic, when localized near the mental
foramen appear to impinge mental nerve and produce pain, paresthesia and even anaesthesia
Histologic and radiographic features: The lesion progress through three distinct stages:
Osteolytic phase: Periapical bone is replaced by a fibrous connective tissue, there is fibroblastic proliferation that may contain small foci of osteoid formation – Radiographically a radiolucent area
Cementoblastic phase: Islands and spicules of cementum like matrix form within the connective tissue – Radiographically calcification in radiolucent area
Mature stage: The lesion is predominantly composed of irregular cementum like material, which is densely mineralized. Roentenogram has a well defined radioopacity that is usually bordered by a thin radiolucent line or band
Treatment and Prognosis : Periodic observation, since its harmless, under no
circumstances should one extract the tooth or institute endodontic procedures or otherwise disturb the tooth unless, for reasons not related to the condition
Central cementifying fibroma Neoplasm of the bone Close histogenetic relationship between central
cementifying fibroma and central ossifying fibroma Clinical features:
Common in young and middle aged adults, avg-35 yrs Females : males = 2:1 Marked predilection for mandible Generally asymptomatic until growth produces
noticeable swelling and mild deformity Displacement of teeth may be an early feature Relatively slow growing tumour, the cortical plates of
bone and overlying mucosa or skin are intact
Radiographic features: Variable depending upon stage of development Well circumscribed, demarcated from surrounding bone Early stages – appears radiolucent As tumor matures – increasing calcification – radiolucent
areas becomes flecked with opacities until it appears as an extremely radioopaque mass
Displacement of adjacent teeth is common Have a centrifugal growth pattern – grow by expansion in all
directions When it reaches the inferior border of mandible, produces an
expansion thats in continuity with outline of tumor mass
Histologic features: Composed of many delicate interlacing collagen fibers
interspersed by large numbers of active, proliferating fibroblasts or cementoblasts
Many small foci of basophilic masses of cementum-like tissue – irregularly round, ovoid or slightly elongated
As lesion matures, islands increase in no. enlarge and coalesce
Treatment and prognosis: Should be excised conservatively Recurrence is rare
Gigantiform cementum (Familial Multiple Cementoma) Very rare condition which may or may not prove to be
distinct entity Clinical features:
Onset at young age Develops slowly and involves all four jaw quadrants
Radiographic features: Diffuse radioopaque masses scattered throughout the
jaw, sometimes expanding the jaw Described as consisting of dense, highly calcified, almost
totally acellular cementum which is poorly vascularized and frequently becomes infected with ensuing suppuration and sequestration
Focal cementoosseous dysplasia Benign lesion, occupies a portion of the spectrum between
periapical and florid cemento osseous dysplasia Posterior mandible is predominant site Asymptomatic and detected only on radiographic examination Smaller than 1.5 cm in diameter May occur on dentulous and edentulous areas Histologic feature:
Tissue consists of fragments of cellular mesenchymal tissue composed of spindle shaped fibroblasts and collagen fibers with numerous small blood vessels
Trabeculae of woven bone and cementum like material are interspersed throughout the fibrous framework
Systemic diseases and its influence on cementum (Shafer et al,
2006)
Cleidocranial dysplasia
Characterized by abnormalities of the skull, teeth jaws and shoulder girdle and occasionally stunting of the long bones
Oral findings - prolonged retention of deciduous teeth and subsequently delay in eruption of the succedaneous teeth Roots of the teeth are often short and thinner than usual
and may be deformed Surprising and unexplained feature was the absence of
cellular cementum on the erupted teeth in both dentition, with no increased thickening of primary acellular cementum
Hypophasphatasia
Hereditary disease due to deficiency of enzyme alkaline phosphatase in serum or tissues and excretion of phosphoethanolamine in urine
Earliest manifestation - may be loosening and premature loss of deciduous teeth, chiefly incisors
Teeth present a unique appearance characterized by the absence of cementum, presumably, as a result of cementogenesis, so that there is no sound functional attachment of the tooth to bone by PDL – accounts for spontaneous exfoliation of deciduous teeth. Occasionally a foci of poorly formed cementum may be found on some teeth.
Hyperpituitarism
Increase in no. of granules in acidophilic cells or an adenoma of anterior lobe of the pituitary gland – gigantism or acromegaly
Enlargement of jaws- mainly mandible, macroglossia, anterior openbite
Root of posterior teeth enlarge as result of hypercementosis - may be the result of functional and structural demands on teeth, instead of a secondary hormonal effect
Supraeruption of the posterior teeth may occur in an attempt to compensate for the growth of the mandible
Hypothyroidism (Neville et al, 2002)
Cretinism in infants or myxedema in adults Decreased levels of thyroid hormone Clinical features – lethargy, dry coarse skin, swelling of face
and extremities, husky voice, constipation, weakness and fatigue, bradycardia, hypothermia
Oral findings – enlarged tongue, teeth my fail to erupt if developed during childhood, in adults external resorption of roots may occur
Hyperparathyroidism Excess production of PTH, usually occurs in response to low
levels of serum calcium Clinical features
Stones – renal calculi, metastatic calcifications involving other soft tissues
Bones – subperiosteal resorption of phalanges of index and middle fingers, loss of lamina dura around teeth and root resorption, brown tumor which is dark reddish brown color of tissue specimen because of abundant hemorrhage and hemosiderin deposition in th tumor – ground glass appearance radiographically
Abdominal groans – due to duodenal ulcers
Paget’s disease of bone (Neville, 2002)
Multicentric benign tumor of osteoclasts has been suggested Characteristic deformities of skull, jaw, back, pelvis and legs Facial appearance – leontiasis ossea Ground glass change in alveolar bones Loss of lamina dura and root resorption Generalized hypercementosis sometimes
Application in forensic odontology
Age estimation from incremental lines of cementum Kagerer and Grupe suggested the possibility of age
estimation from acellular cementum Used mineralized unstained cross sections of teeth, preferably
mandibular central incisors and third molars Authors claimed an accuracy of within 2 or 3 yrs of
chronologic age Pathologic state of periodontium may compromise the
precision of ageing Hypermineralized bands gave an indication of events such as
pregnancies, skeletal trauma, and renal disorders
CONCLUSION (Bosshardt and Selvig, 1997)
The periodontal tissues form a functional unit designed to maintain tooth support and protection. In particular, cementum by virtue of its structural and dynamic qualities, provides tooth attachment and maintenance of occlusal relationship. These multiple functions are fulfilled by the biological activity and reactivity of cementoblast, which deposit two collagen – containing varieties of cementum with
completely different properties.
The discovery of variety of non collagenous proteins in cementum has opened a new research area of great therapeutic potential, cementum specific matrix proteins - cementum derived growth and/or attachment factors may result in accelerated wound healing and in controlled neocementogenesis following periodontal regenerative surgery.
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