CEMENTUMCEMENTUM

NORMAL MICROSCOPIC FEATURES

- It is the calcified mesenchymal tissue that forms the outer covering of the anatomical root

Two main forms of root Two main forms of root cementumcementum

Acellular or Primary Cementum- is the first to be formed and covers

approximately the cervical two-thirds of the root and doesn’t contain cells

- formed before the tooth reaches the occlusal plane

- contains other collagen fibers that are calcified and irregularly arranged or parallel to the surface

Cellular or Secondary Cementum

- formed after the tooth reaches the occlusal plane- more irregular and usually contains cells in individual spaces (lacunae) that - communicate with each other through a system of anatomizing canaliculi- less calcified and Sharpey’s fibers occupy a smaller portion of cellular cementum

Both acellular and cellular cementum are arranged in lamellae separated by incremental lines parallel to the long axis of the rootThese lines represent rest periods in cementum formation and are more mineralized than the adjacent cementumSharpey’s fibers make up most of the structures of acellular cementum, which has a principal role in supporting the tooth

CEMENTO-ENAMEL JUNCTIONCEMENTO-ENAMEL JUNCTION

THICKNESS OF CEMENTUMTHICKNESS OF CEMENTUM

The thickness of cementum on the coronal half of the root varies from 16 to 60 microns, or the thickness of a hairIt attains its greatest thickness (up to 150 to 200 microns) in the apical third and also in furcations areas

DEVELOPMENT AND ACQUIRED DEVELOPMENT AND ACQUIRED ANOMALIES ASSOCIATED WITH ANOMALIES ASSOCIATED WITH

CEMENTOGENESISCEMENTOGENESIS

Enamel Projection continuous enamel formation over root surface normally covered by cementum from odontogenic epithelium destined to form Hertwig’s root sheath and frequent in furcations in mandibular molars

Enamel pearlsEnamel pearls Globules of enamel on root surface in cervical region and resemble small pearls, up to several millimeters in diameterIts clinical relevance is that is promotes periodontal lesions by acting as plaque – retentive structuresIt may mimic calculus clinically and radiographically and can be scaled off or can be removed by grindingLarge pearls may contain pulpal extensions

CementiclesCementicles

Globular masses of acellular Globular masses of acellular cementum generally less than 0.5 cementum generally less than 0.5 mm in diameter, which form within mm in diameter, which form within the periodontal ligamentthe periodontal ligament

Cementicles are not of clinical Cementicles are not of clinical significance unless they become significance unless they become exposed to the oral environment exposed to the oral environment where they may act as sites for where they may act as sites for plaque retentionplaque retention

Types:

Free cementicles – lie free in periodontal ligamentAttached / Sessile cementicles – fused or attached to radicular cemental surfaceInterstitial cementicles – totally incorporated or embedded in cementum

HypercementosisHypercementosis Hyperplastic cementumHyperplastic cementum

Formation of abnormally thick radicular Formation of abnormally thick radicular cementumcementumMay take the form of multiple, localized, May take the form of multiple, localized, knoblike or spike shaped projections, which knoblike or spike shaped projections, which give the root an irregular contourgive the root an irregular contourMay occur as a thickening of the cementum May occur as a thickening of the cementum layer, generally more marked in the apical layer, generally more marked in the apical third of the rootthird of the rootGeneralized hypercementosis may be Generalized hypercementosis may be hereditary or may be associated with hereditary or may be associated with Paget’s Paget’s diseasediseaseLocalized hypercementosis may be observed in Localized hypercementosis may be observed in impacted teeth and teeth without antagonistsimpacted teeth and teeth without antagonists

CementomaCementoma

Masses of cementum generally Masses of cementum generally located apical to the teeth, to which located apical to the teeth, to which may or may not be attached may or may not be attached Considered either odontogenic Considered either odontogenic neoplasm or developmental neoplasm or developmental malformationmalformationOccur more frequently in females and Occur more frequently in females and more often found in the mandible than more often found in the mandible than in the maxillain the maxillaHarmlessHarmless

AnkylosisAnkylosis

It is the fusion of the mineralized root It is the fusion of the mineralized root surface with alveolar bone with surface with alveolar bone with obliteration of the periodontal ligament obliteration of the periodontal ligament

Generalized injury or removal of the Generalized injury or removal of the periodontal ligament may lead to the periodontal ligament may lead to the condition condition

Results in resorption of the root and its Results in resorption of the root and its gradual replacement by bone tissuegradual replacement by bone tissue

ALVEOLAR BONEALVEOLAR BONE

ALVEOLAR PROCESSALVEOLAR PROCESS –– It is the part of the It is the part of the maxilla or mandible that forms and supports maxilla or mandible that forms and supports the teeththe teethALVEOLAR BONE PROPERALVEOLAR BONE PROPER – It consists of – It consists of a thin lamella of bone (cortical bone) a thin lamella of bone (cortical bone) surrounding the root. Fibers of the surrounding the root. Fibers of the periodontal ligament are embedded in this periodontal ligament are embedded in this boneboneSUPPORTING BONESUPPORTING BONE – It consists of – It consists of cancellous trabeculae and surrounds the cancellous trabeculae and surrounds the alveolar bone proper and provides alveolar bone proper and provides additional supportadditional support

In radiographs the alveolar bone proper (inner wall of In radiographs the alveolar bone proper (inner wall of the socket or inner cortical plate) appears as an the socket or inner cortical plate) appears as an opaque line called the opaque line called the lamina duralamina duraThe alveolar bone proper is perforated by many The alveolar bone proper is perforated by many openings through which the blood vessels, lymphatics, openings through which the blood vessels, lymphatics, and nerves of the periodontal ligament pass and also and nerves of the periodontal ligament pass and also called the called the cribriform platecribriform plate because of these because of these perforationsperforationsThe outer cortical plate is covered by a fibrous and The outer cortical plate is covered by a fibrous and cellular cellular periosteumperiosteumThe The interdental septainterdental septa (singular, septum) are bony (singular, septum) are bony partitions that separate adjacent alveolipartitions that separate adjacent alveoliAlveolar bone proper is formed for the express Alveolar bone proper is formed for the express purpose of purpose of supportingsupporting and and attachingattaching the teeth. The the teeth. The alveolar process depends on the presence of teeth for alveolar process depends on the presence of teeth for its existenceits existence

Alveolar dehiscence is a dipping of the crestal bone margin exposing the root surface

Alveolar fenestration is a circumscribed hole in the cortical plate over the root and does not communicate with the crestal margin

PERIOSTEUM

It is a lining at the outer surface of the alveolar processIt contains the neural, vascular, as well as the cellular elements necessary for the maintenance of normal bone function and repairOn the alveolar surface, the periodontal ligament serves in the same capacity as the periosteumThe endosteum is the corresponding cellular layer found within marrow spaces

PHYSIOLOGIC TOOTH PHYSIOLOGIC TOOTH MIGRATIONMIGRATION

Under physiologic conditions teeth migrate continuously in a mesial direction towards the midline. This is called physiologic mesial driftThe migration leads to a resorption of the inner wall of the alveolus on the mesial side of the tooth and the formation of new bone on the distal surfacePhysiologic tooth migration continues throughout life but slows or halts in old ageThe alveolar bone adapts and reconstructs itself continuouslyPathologic changes occur when this process of adaptation is disturbed

BLOODBLOOD SUPPLYSUPPLY

Branches of the alveolar artery

Periodontal Structure in Aging Periodontal Structure in Aging HumansHumans

Age changes affect the following periodontal tissues:1. Vasculature2. Periodontal ligament3. Cementum4. Alveolar bone5. Gingiva and alveolar mucosa

VASCULATUREVASCULATURE

In advancing age, there is a reduction in blood flowa decrease in connective tissue cellularity and an increase in the number of coarseness of collagenous fibersprincipal fibers of the periodontal ligament are thicker in ageing humans than in younger individualsfewer fibroblasts, osteoblasts, and cementoblastsdegenerative hyaline changescalcified bodies are common in the periodontal ligament of elderly humans

CEMENTUMCEMENTUM

Cemental deposition slows in old ageThe attachment of cementum to dentin may be weakenedSpurring of cementum is sometimes the result of the fusion of calcospheroid bodies near cementum or of the calcification of epithelial rest aggregates

ALVEOLARALVEOLAR BONEBONE

Physiologic tooth migration may be slow or halt in old ageThe vascularity of bone appears to be diminishedOsteoporosis may be observed in aging, particularly in the alveolar bone of postmenopausal womenThere is slowing and even a halt in bone remodelingThus the replacement of extracted teeth with prostheses in order to prevent overeruption, malpositioning, and tilting of neighboring teeth may not be necessaryFunction and esthetics will be the principal reasons for tooth replacement

GINGIVA AND ALVEOLAR GINGIVA AND ALVEOLAR MUCOSAMUCOSA

The gingiva becomes fibrotic in old ageThe gingiva becomes fibrotic in old age