-CODSJournal voi-s Issue-1, March 2013

Dr. Selvamani M,Assistant Professor *,

E-mail:selvamani.mds@gmail.comContact no: 09900978281

Dr. Madhushankari GS,Professor *,

Dr. Praveen S Basandi,Asst. Professor *,

Department of Oral Pathology and Microbiology,College of Dental Sciences, Davangere.

ABSTRACT:

Sclerosis of dentinal tubules may be a response to pathological or physiological insult in the crown & rootthat starts in the root and gradually extend to the crown of the tooth in case of physiological sclerotic dentin.The exact mechanism of the formation of sclerotic dentin is not known, however various authors haveproposed different possible mechanisms, which are not universally accepted but, it is generally agreed thatsclerotic areas of root dentin increases in size with age.

Keywords: Sclerotic dentin, Dentinal tubules.

INTRODUCTION

Dentin is a mineralized connective tissue. Similar toall other mineralized tissues, it is laid down as anorganic matrix which subsequently mineralizes. Theorganic matrix of dentin is formed by odontoblasts.The initial and foremost mineralization occursduring dentinogenesis while a gradualmineralization continues with agel. Odontoblastsform and maintain dentin and are located in thepulp, sending a long, cellular extension into thedentin, called the odontoblastic process.

The dentinal tubules contain either the odontoblasticprocesses or their remnants and tissue fluid (alsocalled "dentin liquor"). The odontoblast layer is anintegral part of the dental pulp. This intimaterelationship between the cells of the dentin and thepulp represents as one functional entity'.

On the basis of histologic characteristics and time ofdevelopment, dentin has been termed into primary,secondary and tertiary dentin. Primary dentin is themajor component of the crown and root, which isformed before root completion, the dentin formedafter the root completion is the secondary dentin andresponsive dentin formed to protect pulp is termed astertiary dentin/

Sclerotic dentin is one of the form of dentin whichmay be a response to pathological or physiologicalinsult in the crown & root that starts in the root andgradually extend to the crown of the tooth in case ofphysiological sclerotic dentin.

SCLEROTIC DENTIN

Aging manifest as cumulative changes in various

tissues including dental hard tissue. One such agerelated change is the formation of physiologictranslucent dentin (sclerotic dentin).

Sclerotic dentin, which forms gradually with aging,begins at the apical end of the root and in theperiphery of the dentin, later extending into thecoronal dentin. Physiologic sclerotic root dentin, asdistinguished from pathologic sclerosis subjacent tocaries, appears to form without trauma or cariesattack as a natural part of aging.

MECHANISM OF SCLEROTICFORMATION

Sclerotic dentin is formed either as a reactiveprocess or aging and is seen in the occlusal andapical part, latter being more common.

Stimuli may not only induce additional formation ofreparative dentin but also lead to protective changesin the existing dentin. In situation of caries, attrition,abrasion, and cavity preparation, sufficient stimuliare created to cause collagen fibers and apatitecrystals to begin appearing in the dentinal tubules.Apatite crystals are initially only irregular in adentinal tubule but gradually the tubule becomesfilled with a fme meshwork of crystals. Thereby thedifference in refractive indices between intratubularorganic and extratubular inorganic materials will beequalized resulting in increasing translucency of thedentin so affected'.

Sclerotic dentin may be related to aging, whenassociated with the dentinal tubules close to rootapex. The root dentin usually appears to becometransparent during the third decade that starts at the

CODSJournal Vol-S Issue-l, March 2013

tip of the root and advances coronally with age". Thealteration is believed to be caused by a reduction ofthe diameter of the dentinal tubules caused byintratubular calcification.

The exact reason for intratubular calcification is notknown but suggested that translucent dentin hasbeen regarded to be caused by changes in the organicsubstances of the dentin, possibly a fattydegenerations. However the theory was questionedsince permeability of dentin was found to be notaffected by the removal of fat by solvents-".

Sclerotic dentin was considered to be due tosecondary dentin formation on the sides of the pulpchamber leaving no room for the odontoblasts,which gradually die off, allowing calcification of thetubules". However this theory can also be probedsince secondary dentin is found at the incisal end ofthe pulp chamber, but transparency starts with themost apical tubules.

Another explanation put forward by Jenkins was thatthe tubules become narrower by deposition ofcalcium salts upon the peri tubular dentine of thewalls. This leads eventually to the total occlusion ofindividual tubules'.

Other explanation was based on "Dissolution &Reprecipitation" where a smaller mean intertubularcrystal size could be the result of dissolution ofmineral from the intertubular matrix, which is thendeposited into the tubules. The similar chemicalcomposition of the inter and intra tubular mineral intransparent dentin supports such a "Dissolution -Reprecipitation." It is also possible that I thedissolved mineral is re-deposited within theintertubular matrix instead of within the dentintubules lumens. With age, the intertubular crystaldissolve uniformly, thereby decrease in size, and themineral is reprecipitated within the tubules as aresult of an increased saturation of calcium andphosphate ions within the dentinal tubules",

Chemical analysis suggests that the materialoccluding the lumina of the dentinal tubules of thesclerotic areas of root dentin is mineralized to aboutthe same extent as cementum". Microradiographyshows that the degree of mineralization is more likethat of peri tubular dentin".

According to Nalbandian et al, occlusion of thedentinal tubules in the translucent zones of rootdentin is the result of the centripetal growth of theperitubular dentin". These results conflict withfindings of Vasiliadis L et al, who found that theannular space between the peri tubular dentin & theoccluding material might be the result of differencein structure. The shape of the exposed parts of the

occluding rods indicated that they were not part ofthe peritubular dentin which had been accidentallyfractured at this level, but was a material of differentstructure"

In physiological sclerosis the occluding materialpresents a relatively smooth surface 'and there ischaracteristically a plane of separation or cleftbetween it and the surrounding dentin, which maybe either intertubular or peri tubular dentin.Transmission electron microscopy of sclerotic rootdentin found to have same electron density asperi tubular dentin in its final stages of formation andconcluded that the developmental process of theoccluding material is different from that ofperitubular dentin".

According to present knowledge, the formation ofperitubular dentin is governed by the odontoblastand its process. Ithas been shown that the process ofdevelopment and formation of peritubular dentinproceeds in an appositional fashion maintaining aclear forming front, whereas the occlusive changesoccurs diffusely, with the packing of the occludingminerals increasing with time!'.

Absolute increase in the amount of mineral in the.sclerotic dentin indicates that the occluding mineralis not derived from the adjacent intertubular dentinbut originates from another source like the pulpbecause, if it arose from an external source andpassed through the cementum, the process ofsclerosis would be self-limiting".

Study focused on differences in the structure andmechanical properties of normal versus transparentdentin, stated that the mineral concentration, asmeasured by X - ray computed microtomography,was significantly higher in transparent dentin, theelevated concentration being consistent with theclosure of the lumens. Crystallite size, as measuredby small angle X - ray scattering, was slightlysmaller in transparent dentin, unlike normal dentin,exhibiting almost no yielding before failure. Inaddition, the fracture toughness was lowered byroughly 20% while the fatigue lifetime wasdeleteriously affected at high stress levels".

When the effect of aging on the mineral phase ofdentin, was studied by high resolution TEM andrevealed that the intertubular mineral crystalliteswere smaller in transparent dentin, and that theintratubular mineral (larger crystals depositedwithin the tubules) was chemically similar to thesurrounding intertubular mineral",

The increase in size of apical zone of sclerotic dentinin human teeth has been used in forensic science asa method of age estimation, as one of several

COOSJournal Vol-S Issue-l, March 2013

regressive changes related to age 4 or, morecommonly, as the sole variable since the finding thatthe increase in apical translucency was the factormost commonly linked to ageI5,16,

CONCLUSION:

Knowledge of the development and distribution ofsclerotic dentin which produces translucency in rootdentin is still incomplete. The theories proposed toexplain the cause and mechanism of sclerotic dentinformation are not universally accepted but, it isgenerally agreed that sclerotic areas of root dentinincreases in size with age.

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2. Avery JK. Oral Development and Histology. 3rd ed.Germany: Library of Congress Cataloging - in -Publication Data; 2002. p. 90-91.

3. Dentin. In: Kumar GS, editor. Orban's oral histologyand embryology. 12th ed. New Delhi: Reed ElsevierIndia Private Ltd; 2008. p. 84.

4. Gustafson G. Age determination on teeth. J Am DentAssoc 1950;41 45-54

5. Solheim T. Dental root translucency as an indicator ofage. Scand J Dent Res 1989;97: 189-97

6. Jenkins NG. The Physiology of the Mouth. BlackwellScientific Publications (third edition). Oxford. 1966

7. Rushton MA. Observations on Fish's 'dead tracts' indentine. British Dental Journal 1940; 68:11.

Sclerotic or Translucent Dentin: A Review

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9. Manly and Brooks. Transparent and light scattering ofperitubular dentinal and hard tissue. J Dent Res1947;26:427-34.

10. Nalbandian. J, Gonzales F & Sognaes R.F Scleroticage changes in root dentin of human teeth as observedby optical electron and X-ray microscopy J Dent Res1960;39:598-607

11. Vasiliadis L, Darling AI and Levers BGH. Histologyof Scerotic Human Root Dentin. Archs Oral Bioi1983;28(8):693-700

12. Lester & Boyde. Some preliminary observations incaries ("remineralization")crystals in enamel anddentin by surface electron microscopy. Virchows ArchAbtA Path Anat 1968;344: 196-212

13. akuma S & Eda S Structure and development of theperitubular matrix in dentin. J Dent Res 1966;45:683-92

14. Kinney JH, Nalla RK Pople JA Berunig TM, RitchieRO. Age-related transparent root dentin: mineralconcentration, crystallite size and mechanical proper,ties. Biomaterials 2005;26:3363-76

15. Johansson, G. Age Determinations from HumanTeeth. Odontologisk Revy 1971; 22(21): 40-126.

16. Maples WR. An improved technique using dentalhistology for estimation of adult age. J forensic Sci1978;23:764-70.