Dentin /certified fixed orthodontic courses by Indian dental academy


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Dentin /certified fixed orthodontic courses by Indian dental academy

  3. 3. INTRODUCTIONDENTIN PULP COMPLEXEmbryonically and Physiologically,Dentin and Pulp are so intimatelyrelated that Dentin can beconsidered as the peripheralcalcified portion of the dental pulp.Physiologically dentin protects thepulp ; conversely dentin owes itsvitality to the pulp. It also impliespulp would react whenever dentin isinjured in cases like caries, attrition,abrasion, erosion or operativeprocedures.
  4. 4. KNOWING DENTIN►The Dentin provides the bulk and general form of the tooth and is characterized as a hard tissue with tubules throughout its thickness. since it forms slightly before the enamel, it determines the shape of the crown, including the cusps and ridges and the number and size of the roots.
  5. 5. Dentinogenesis... Dentin is formed by cells of theodontoblast that differentiates fromectomesenchymal cells of dental papillafollowing an organizing influence thatemanates from cells of the internal dentalepithelium. Thus dental papilla is the formative organof dentin. Odontoblast produce an organic matrixthat becomes mineralized to form dentin.
  6. 6. It begins at the cusp tips after theodontoblasts have differentiated and begincollagen productionAs the odontoblasts differentiate they changefrom an ovoid to a columnar shape and theirnuclei become basally oriented at this earlystage of development.The length of the odontoblast then increasesto approximately 40 μm although its widthremains constant (7 μm)Proline appears in the rough surfaceendoplasmic reticulum and golgi apparatus.One or several processes arise form the basallamina.
  7. 7. The proline then migrates into the cellprocess in dense granules and isemptied into the extra cellularcollagenous matrix of the predentin.As the cell recedes it leaves behind asingle extension and the several initialprocesses join into one which becomesenclosed in a tubule.As the matrix formation continues theodontoblast process lengthens as doesthe dentinal tubule.
  8. 8. After this time, dentin production slowsto about 1μm / day.After root development is complete dentinformation may decrease further.Although, reparative dentin may form ata rate of 4 μm/day for several monthsafter a tooth is restored.As each increment of predentin is formedalong the pulp border, it remains for a daybefore it is calcified and the nextincrement of predentin forms.
  9. 9. Korff ‘s fibers have beendescribed as the intial dentindeposition along the cusptips. Becauseof the argyrophilic reaction (stainblack with silver) it was long believedthat bundles of collagen formed amongthe odontoblasts.Consequently all predentin is formedin the apical end of the cell and alongthe forming tubule wall.
  10. 10. MINERALIZATION► The earliest crystal deposition is in the form of very fine plates of hydroxyapatite, on the surfaces of the collagen fibrils and in the ground substance. Subsequently crystals are laid down within the fibrils themselves.► The crystal associated with the collagen fibrils are arranged in an orderly fashion with their long axes paralleling the fibril axes and in rows conforming to the 64μm (640 Aº) striation pattern.
  11. 11. ► Within the globular islands of mineralization , crystal deposition appears to take place radially from common centers in a so-called spherulite form.► The general calcification process is gradual but the peritubular region becomes highly mineralized at a very early stage.
  12. 12. ► Although there is obviously some crystal growth as dentin matures the ultimate crystal size remains very small about 3μm (30 Aº) in thickness and 10 μm (100 Aº) length.► The apatite crystals of dentin resemble those found in bone and cementum. They are 300 times smaller than those formed in enamel.
  13. 13.
  14. 14. ODONTOBLASTIC DIFFERENTIATIONThe differentiation of odontoblast fromdental papilla in normal development,requires the presence of epithelial cellsor their products.Before the dentinogenisis begins thecells of internal dental epithelium areshort & columnar, rapidly dividing toaccommodate growth of the tooth germand supported by basement membranethat separates the epithelium fromdental papilla and inbetween those isthe formation of acellular layer.
  15. 15. The ectomesenchymal cells adjusting theacellular zone rapidly enlarge to becomepreodentoblast and then odontoblasts , astheir cytoplasm increases in volume tocontain increasing amount of RER & golgiapparatus,the highly polarised nucleimoves away form internal dentalepithelium .The acellular zone between dental papillaand IDE is gradually eliminated as theodontoblast differentiates and increases insize and occupy this zone.
  16. 16. During the final division ofectomesenchymal cells, adjacent todental epithelium their mitoticspindles are perpendicular tobasement membrane supporting theIDE. therefore it is only those cellsnext to the basement membrane thatdifferentiate into odontoblast.
  17. 17. As a result two layers can bedistinguished such as odontobalasticlayer and the sub odontobalastic layer.Because they are away from the sphereof influence of internal dentalepithelium during last cell division,experimental evidence indicates that,what the basal lamina provides is asurface containing fibronectin thatpermits the preodontoblast to alignthemselves along the membrane andbecome odontoblast.
  18. 18. PATTERN OF DENTIN FORMATION CROWN DENTIN► Dentin formation begins at the late bell stage of development in the papillary tissue adjacent to the tip of the folded internal dental epithelium.► Though actually this is not the site where the future cusp will reside, the cuspal development begins from here. The dentin formation spreads down the cuspal slopes .
  19. 19. ►In multicusped teeth, dentin formation begins independently at the sites of each future cusptip►coronal dentin deposition is approx 4μm per day.
  20. 20. ROOT DENTIN► Forms slightly at a later stage of development and requires the proliferation of epithelial cells from cervical loop of dental organ around the growing dental papilla to intiate the differentiation of root odontoblasts.► The tooth reaches the functional position when about 2/3 rd of root dentin has formed.
  21. 21. ROOT COMPLETION► Deciduous teeth  18 months after eruption► Permanent teeth  2-3 years after eruption
  23. 23. SECRETORY ODONTOBLASTThe secretary odontoblast is seen with alarge plump cell with a open faced nucleussituated basally and basophillic cytoplasmcontaining a negative golgi image.The apical basophillic cytoplasm is foundto contain a full complement of organellesrequired for synthesis and secretion of extracellular material.
  24. 24. TRANSITIONAL ODONTOBLASTUnder electron microscope it becomes Narrower. nucleus is displaced from the basal extremity. exhibits chromatin condensation. amount of endoplasmatic reticulum is reduced and confirmed to the area around the nucleus. Autophagic vacuoles are present.
  25. 25. RESTING ODONTOBLASTSSmall flattened cell with a closednucleus,less cytoplasm and no golgi body. In image by electron microscopy,thenucleus is found to be situated sufficientlyapical to create a prominent infranuclearregion where a reduced amount ofcytoplastic organelle are clustered. Thesupra nuclear region is devoid oforganelles except for a large lipid filledvacuoles in cytoplasm containing tubules& filamentous structures. secretarygranules are absent.
  27. 27. MICROSCOPIC STRUCTURESMANTLE DENTIN OR PRIMARY DENTIN► It is the name of the first formed dentin in the crown underlying the dentinoenamel junction.► It is 20microns thick.► It is the area of initial dental matrix formation.
  28. 28. CIRCUMPULAPAL DENTIN► It forms the remaining primary dentin or bulk of the tooth.► It is the circumpupal dentin that represents all of the dentin formed prior to root completion.► The collagen fibrils in circumpulpal dentin is much smaller in diameter (0.05 μm) and are more closely packed together.► The Circumpulpal dentin may contain slightly more mineral than mantle dentin.
  29. 29. SECONDRY DENTINIt is narrow band of dentinbroadening at the pulp andrepresenting that dentinthat is formed after rootcompletion.This dentin contains fewertubules than primarydentin there is usually abend in the tubules whenthe primary and secondarydentin interface.
  30. 30. REPARATIVE DENTIN•If by extensive abrasion,erosion, caries, pooroperative procedures theodontoblast processes areexposed or cut, Theodontoblasts die or if theylive deposit reparativedentin. The majority ofodontoblast in thissituation degenerate but afew may continue to formdentin.
  31. 31. Some of the odontoblast that are killed arereplaced by the migration of undifferentiatedcells arising in deeper regions of the pulp to thedentin interface it is believed that the origin ofthe new odontoblast is from undifferentiatedneurovascular cells.Both the damaged and the newly differentiatedodontoblasts then begin deposition of reparativedentin. This action to seal off the zone of injury,occurs as a healing process initiated by the pulpresulting in resolution of the inflammatoryprocess and removal of dead cells.
  32. 32. Steps in Reparative dentin formation► Injury to odontoblasts► Inflammatory response to subjacent pulpal connective tissue.► Differentiation of new odontoblasts a) synthesis of cytoplasmic granules b) sulfation► Secretion of ground substance matrix and soluble collagen pecursors, tropocollagen .
  33. 33. ► Formation of collagen fibrils which serve as matrix for calcification.► Alteration of mineral salts, calcium phosphate is absorbed to form initial predentin which acts as a nidus for hydroxy apatite crystal formation.
  34. 34. ► Sclerotic, Reactive and Eburnated dentin.► Sclerotic dentin results from aging or mild irritation and causes a change in the composition of the primary dentin.► Sclerosis resulting from aging is physiologic dentin sclerosis; sclerosis resulting from mild irritation is reactive dentin sclerosis.► Eburnated dentin refers to outward portion of reactive sclerotic dentin ,where slow caries has destroyed formally overlying tooth structure, leaving a hard, darkened, cleanable surface.
  35. 35. DEAD TRACTS► In dried ground sections of normal dentin the odontoblast processes disintegrate and the empty tubules are filled with air. They appear black in transmitted and white in reflected light.► loss of odontoblast processes may also occur in teeth containing vital pulp as a result of caries ,attrition ,abrasion, cavity preparation or erosion.
  36. 36. ► Their degeneration is often observed in the area of narrow pulpal horns because of crowding of odontoblasts.► Again, where ever reparative dentin seals dentinal tubules, at their pulpal ends. dentinal tubules are filled with fluid or gaseous substances.► These areas demonstrated decreased sensitivity and appear to a greater extent in older teeth.
  37. 37. DEAD
  38. 38. GRANULAR LAYER OF TOMES► When dry ground sections of the root dentin are visualized in transmitted light there is a zone adjacent to the cementum that appears granular. This is known as (Tomes) granular layer.► This zone increases slightly in amount from the cementoenamel junction to the root apex and is believed to be caused by a coalescing and looping of the terminal portions of the dentinal tubules.
  39. 39. ► The cause of development of this zone is probably similar to the branching and beveling of the tubules at the dentinoenamel junction.► In any case the differentiating odontoblast initially interacts with ameloblasts or the root sheath cells through the basal lamina.► In the crown, extensive branching of the odontoblast process occurs and in the root there is branching and coalescing of adjacent processes.
  40. 40. INCREMENTAL LINES OF VON EBNER•The incremental lines (VonEbner ) or imbrication linesappear as fine lines orstriations in dentin.•They run at right angles to thedentinal tubules andcorrespond to the incrementallines in enamel or bone.•These lines reflect the dailyrhythmic recurrent depositionof dentin matrix as well as thedaily formative process.
  41. 41. ► The distance between lines varies form 4 to 8 μm in the crown to much less in the root .► The daily increment decreases after a tooth reaches functional occlusion. The course of the lines indicates the growth pattern of the dentin.► Occasionally some of the incremental lines are accentuated because of distrubacnes in the matrix and mineralization process. Such lines are readily demonstrated in ground sections and are know as contour lines (Owen).
  42. 42. INTERGLOBULAR DENTIN► Sometimes mineralization of dentin begins in small globular areas that fail to fuse into a homogenous mass. This results in zones of hypomineralization between the globules. These zones are known as interglobular dentin.► Interglobular dentin formed in the crowns of teeth is the circumpulpal dentin that lies just below the mantle dentin and it follows the incremental pattern.
  43. 43. ► The dentinal tubules pass uninterruptedly through interglobular dentin thus demonstrating a defect of mineralization and not of matrix formation.► In dry ground sections some of the interglobular dentin may be lost and a space results that appears black in transmitted light.► However spaces in interglobular dentin are not believed to occur naturally.
  44. 44. DENTINAL TUBLES► The course of dentinal tubules follows a gentle curve in the crown, less so in the root where it resembles `S` in shape.► Starting right angle form pulpal surface, first concavity of this doubly curved course is directed toward the apex of tooth.► Perpendicular to DEJ and DCJ
  45. 45. ► Near the root tip and along the incisal edges and cusps the tubules are almost straight.► Over the entire lengths, the tubules exhibit minute ,relatively regular secondary curvatures ,that are sinusoidal in shape.
  46. 46. ► The ratio between the outer and inner dentin surface is about 5:1► Accordingly, the tubules are farther apart in the peripheral layers and more closely packed near the pulp.► Larger in diameter near pulp cavity (3- 4μm) and smaller at their outer ends (1μm).
  47. 47. ► The ratio between number of tubules per unit area on the pulpal and the outer surface of dentin is about 4:1► Near the pulpal surface of the dentin ,the number per sq mm varies from 50,000 and 90,000.► More tubules per unit area are in crown than in roots.
  48. 48.
  50. 50. Dentin that immediately surrounds thetubules.Twice thicker in outer dentin (0.75 μm) thanin inner dentin (0.4 μm) .More highly mineralized (about 9%) thanintertubular dentin.
  51. 51. By its growth it constricts thedentinal tubules to a diameter of1μm near the DE junction. Indecalcified dentin, visualized witha light microscope, tubule diameterwill therefore appear similar ininner and outer dentin because ofthe loss of peritubular dentin.
  52. 52. INTERTUBULAR DENTINMain body of dentin is composed ofintertubular dentin.Located between the dentinal tubules ormore specifically between the zones ofperitubular dentin.Although it is highly mineralized thismatrix like bone and cementum is retainedafter decalcification whereas peritubulardentin is not.
  53. 53. About half of its volume is organicmatrix specifically collagen fiberswhich are randomly oriented aroundthe dentinal tubules.Fibrils range from (0.5 to 0.2μm)diameter and exhibit cross banding at64nm (640 A°) interval which is typicalfor collagen.Hydroxyapatite crystals which average0.1μm in length are formed along thefibers with their long axes orientedparallel to collagen fibers.
  54. 54. PROPERTIES OF DENTINPHYSIOLOGICAL PROPERTIES Dentin is softer than enamel but harder than bone. It becomes harder with age, due to its mineral content. It is some what flexible despite being hard, its modulus elasticity being 1.67 X 10^6 PSI. The Tenstile strength is apprx.40 Mpa. The compressive strength of dentin is 266 Mpa.
  55. 55. CHEMICAL PROPERTIESInorganic material - 70%Organic material - 20%Water - 10%Inorganic component mainly consist ofhydroxyapatite crystals.Unit formula - 3ca3 (po4)2 , ca(OH)2Crystals are plate shaped slightly smallerthan the hydroxyapatite crystals ofenamel.
  56. 56. Organic substance consists ofcollagenous fibrils and a groundsubstance of mucopolysaccrides(proteoglycans &glysosaminoglycans).organic & inorganic substances canbe separated by decalcification orincineration.
  58. 58. Dentinal tubules contain numerous nerveendings in the predentin and inner dentin nofarther than 100 to 150μm from the pulp.Most of these small vesiculated endings arelocated in tubules in the coronal zonespecifically in the pulp horns.The nerves and their terminals are found inclose association with the odontoblastprocess within the tubule.The primary afferent somatosensory nerves ofthe dentin and pulp project to the mainsensory nucleus of midbrain.
  59. 59. THEORIES OF PAIN TRANSMISSION THROUGH DENTIN Direct neural stimulation theory. Fluid or Hydrodynamic theory. Transduction theory.
  60. 60. DIRECT NEURAL STIMULATION THEORYThe first is that of direct neuralstimulation meaning that stimuli insome manner as yet unknown reach thenerve endings in the inner dentin. Thereis little scientific support of this theory.
  61. 61. FLUID or HYDRODYNAMIC THEORYThe second most popular theory is the fluid orhydrodynamic theory.Various stimuli such asheat, cold, air blast desiccation, or mechanicalpressure affect fluid movement in the dentinaltubules. This fluid movement either inward oroutward stimulates the pain mechanism in thetubules by mechanical disturbance of the nervesclosely associated with the odontoblast and itsprocess. Thus these endings may act asmechanoreceptors as they are affected bymechanical displacement of the tubular fluid.
  62. 62. TRANSDUCTION THEORYThe Third theory is the transductiontheory, which presumes that theodontoblast process is the primarystructure excited by the stimulus andthat the impulse is transmitted to thenerve endings in the inner dentin.
  63. 63. AGE AND FUNCTIONAL CHANGESSince the odontoblast and its process arean integral part of the dentin there is nodoubt that dentin is a vital tissue ,again,if vitality is understood to be thecapacity of the tissue to react tophysiologic and pathologic stimuli dentinmust be considered a vital tissue.
  64. 64. ► Dentin is laid down throughout life. although, after the teeth have erupted and have been functioning for a short time. Dentinogenesis slows and further dentin formation is at a much slower rate.► Pathologic effects of dental caries, abrasion, attrition or the cutting of dentin or operative procedures cause changes in dentin. The formation of reparative dentin pulpally underlying an area of injured odontoblast processes can be explained on the basis of increased dentinogenic activity of the odontoblast.
  65. 65.
  66. 66. CLINICAL CONSIDERATIONSOne should bear in mind that when 1 mmof dentin is exposed about 30,000 livingcells are damaged.It is advisable to seal the exposed dentinsurface with a nonirritating insulatingsubstance.The rapid penetration and spread of cariesin the dentin is the result of the tubulesystem in the dentin.
  67. 67. The dentinal tubules form a passage forinvading bacteria that may thus reach thepulp through a thick dentinal layer.Electron micrographs of carious dentin showregions of massive bacterial invasion ofdentinal tubules. The tubules are enlarged bythe destructive action of the microorganisms.Dentin sensitivity of pain unfortunately maynot be a symptom of caries until the pulp isinfected and responds by the process ofinflammation leading to toothache.
  68. 68. Undue trauma from operative instrumentsalso may damage the pulp air-drivencutting instruments,cause dislodgement ofthe odontoblast form the periphery of thepulp and their “aspiration” within thedentinal tubule.The sensitivity of the dentin has beenexplained by the concept that alterationof the fluid and cellular contents of thedentinal tubules causes stimulation of thenerve endings in contact with these cells.
  69. 69. This theory explains pain throughoutdentin since fluid movement will occurat the dentinoenamel junctions well asnear the pulp.Because we know that reparative dentinstimulates cavity lining materials andthat dentin forms throughout the life of atooth it is now possible to save teeththat previously were lost by extractionor treated by endodontic therapy.
  70. 70. Again teeth with deep penetrating cariouslesions can be treated by only partial removalof carious dentin and insertion of a “dressing”containing calcium hydroxide for eg , for aperiod of a few weeks or monthsDuring this period the odontoblasts form newdentin along the pulpal surface underlying thecarious lesion and the dentist can then reopenthe cavity and remove the remaining bacteria-laden decay without endangering the pulp.This treatment is termed indirect pulp capping.
  71. 71. DENTIN PERMEABILITYThe chemical irritation of the P-D Organresults from the diffusion of irritatingagents through the dentin.Dentin permeability differs from oneperson to another from one tooth toanother and from one area of a tooth toanother area of the same tooth.
  72. 72. Factors governing Dentin Permeability► Type of dentin from lowest to highest permeability are Calcific barrier dentin, Sclerosed dentin, Primary dentin, Secondary dentin, Tertiary dentin, Globular dentin, Granular dentin & Deadtract dentin.► Types and nature of penetrants- Plaque acids & highly dissociable acids penetrate quickly. Salivary ions penetrate dentin dependent upon their molecular cells. Calcium & Fluoride can penetrate dentin but reaction product will decrease dentin permeability.
  73. 73. The other factors governing Dentin Permeability…► Degree of mineralization of dentin► Dentin exposed during tooth preparation► Effective depth► Induced stresses► Hydraulic pressure► Deficient resistance and retention form► Microleakage► Cracks & Microcracks in the dentin► Type of intermediary base or restorative material► Desiccation of dentin
  74. 74. REACTION OF BASES ON DENTINAfter removing the diseased tissues andcompleting the tooth preparation it isnecessary to prevent irritation of the pulpdentin organ this is accomplished byintermediary basing.Zinc oxide & Eugenol, Calcium hydroxide,Zinc phosphate cement & Polycarboxylatecement are the bases used.
  75. 75. Reaction of Zinc Oxide & Eugenol On DentinZOE is the least irritating to the pulp dental organof all intermediary base materials. Whenever thereis any effective depth between the unmodified ZOEand the pulp tissues the pulpal reaction will be ahealthy reparative reaction provided the pulp ishealthy. The underlying pulp dentin organ willhave odontoblastic activity stimulated, increasingthe dimensions of the peritubular dentinperipherally (sclerosed dentin) and depositingsecondary dentin.
  76. 76. Reaction of Calcium Hydroxide on DentinIt can be an irritant to the P-D organ, if it comesin contact with it. Whenever there is a effective depth of100micrometers, a healthy reparative reactionhappens. With less than 100 microns effectivedepth, unhealthy reparative reaction takes place.When calcium hydroxide comes in contact withthe pulp directly it will undergo chemical necrosis.
  77. 77. Reaction of Zinc Phosphate Cement on DentinZinc phosphate cement is the most irritating ofthe all the intermediary base materials.At an effective depth of 2.5mm and above zincphosphate cement will create a healthyreparative reaction.At effective depth of 1.5-2.5mm unhealthyreparative reaction occurs.At effective depth less than 1.5mm there willalways be a destruction in the pulpal tissue.
  78. 78. Reaction ofPolycarboxylate Cement on DentinIt is a minimally irritating base to the P-DOrgan.With effective depth of 1mm and abovehealthy reparative action occurs.Whenever effective depth is less than 1mmunhealthy reparative reaction takes place.When the material comes in contact withthe pulp destruction occurs.
  79. 79. DENTIN HYPERSENSITIVITYDentin hypersensitivity is a common conditionof transient tooth pain associated with avariety of exogenous stimuli.There is substantial variation in the response tosuch stimuli from one person to another. Except for sensitivity associated with toothbleaching or other tooth pathology, the clinicalcause of dentin hypersensitivity is exposeddentinal tubules as a result of gingival recessionand subsequent loss of cementum on rootsurfaces.
  80. 80. The most widely accepted theory of howthe pain occurs is Brännströmshydrodynamic theory of dentinhypersensitivity.Dentinal hypersensitivity must bedifferentiated from other conditions thatmay cause sensitive teeth prior totreatment.
  81. 81. Three principal treatment strategies are used. Dentinal tubules can be covered by gingival grafts or dental restorations.  The tubules can be plugged using compounds that can precipitate together into a large enough mass to occlude the tubules. The third strategy is to desensitize the nerve tissue within the tubules using POTASSIUM NITRATE. Several over-the-counter products are available to patients to treat this condition.
  82. 82. BONDING OF DENTIN► Dentin bonding is comparatively difficult because of the fact that dentin is a complex tissue and contains plenty of fluids.► Along with chemical issue of adhesion, biologic concern on pH, pulpal compatibility becomes exceedingly important when dentin is concerned.► The successful bonding of a resin composite to dentin includes micromechanical attachment between resin and demineralized, primed surface layer of intertubular dentin (Hybrid Layer).
  83. 83. Chemical conditioning – (15 secs)  37% phosphoric acid used usually  Other acids which can be used -Maleic acid, citric acid, nitric acid, oxalic acid, pyruvic acid, HCl. Objective :- • To remove smear layer • Simultaneously demineralizing superficial dentin of 3 - 7µ ms to expose a microporous collagen in which resin will penetrate.
  84. 84. DYNAMICS OF DENTIN BONDINGROLE OF PRIMER: The dentin being a hydrophilic, thecomposite a hydrophobic,intermediate betweenboth groups a Primer is essential. The primerHEMA(hydroxy ethamethyl acrylate)has bothhydrobphoic and hydrofillic group to achievebonding. The next is Adhesive Resin which is appliedafter the application of primer.
  85. 85. Factors affecting the interaction of dentinal permeability & monomer diffusionCollagen Fibril Network The resin monomers penetrate acid- etched collagen fibrils via spaces that can swell or shrink depending on bonding conditions. This nearly molecular level of enlargement of resin polymer with biologic polymer (i.e, Collagen Molecules) may be responsible for resin bonds collagen
  86. 86. Noncollagenous Proteins They are distributed along the collagen fibrils (constituting about 10% of protein content of the dentinal matrix) which are highly charged molecules that bind large amounts of water in dematerialized dentin. The combination of collagen and noncollagenous proteins with large amounts of water, may create a matrix that is a hydrogel, these hydrogels may serve to maintain the hydration of wet substrate.
  87. 87. Primer Solubility Some hydrophilic monomers, such as HEMA, are extremely soluble in either water or acetone. On the substrate side of the applied solution, the uptake of monomer by demineralized dentin depends on the size of the spaces between the collagen fibrils and on the depth that it must diffuse from the surface. In a air-dried dentin the permeability of that dentin to monomer would be very low but wet demineralized dentin exhibits high permeability.
  88. 88. Fluid Flow After priming, the dental surfaces should be uniformly shiny, but there are regions of high permeability that are in direct communications with pulp may appear dull due to its high tubule density and high water content. Such regions may be difficult to dehydrate. With multiple applications of primers these tubules may become sufficiently occluded with resin monomers to block further diffusion of water from the pulp.
  89. 89. Tubular Branching Most tubules contain multiple lateral branches that radiate 2-6mm from the lumen. These small branches provide another root for monomer filtration of hybrid layers this would be classified as a form of inter tubular dentinal permeability.
  90. 90. The Smear layer: being an obstacle !► When the tooth surface is altered by rotary and manual instrumentation during cavity preparation, the cut debris is smeared over enamel and dentin surfaces called the smear layer, it reduces the dentinal permeability by 86%, it is important to remove the layer.► Total etch or unietch is the commonly used etchent.
  91. 91. Mechanism of bonding the dentinAcid etching of the dentinIncrease of transdentinal permeabilityMineral content removed in intertubulardentin (aprox. 2-7 microns)Formation of resin tags and hybrid layer. The resin tags and hybrid layer form themajor contributors for a good dentinbonding.
  92. 92. Under ideal conditions, hybrid layerformation would be the major bondingmechanism in superficial dentin as thepresence of dentinal tubules in this area isless and gives a less significant credit toresin tags but in deep dentin, the resin tagswould contribute most of the bond strengthas the tubules become larger and closer.The diffusivity of the monomers also play amajor role in bond strength. The substrate(dentin) with high permeability and the resinwith high diffusivity make up an idealcombination.
  93. 93. DENTINAL CARIES► One of the basic steps in restorative operative procedure is the removal of carious dentin.► Carious dentin consist of two layers such as outer & inner layer.► Outer layer is the infected dentin which has bacteria and it cannot be remineralized.► Inner layer is the affected dentin which has no bacteria and can be remineralized.
  94. 94. ZONES OF DENTINAL CARIESAFFECTED DENTIN: Zone 1- Normal dentin Zone 2- Sub-transparent dentin Zone 3- Transparent dentinINFECTED DENTIN: Zone 4- Turbid dentin Zone 5- Infected dentin
  95. 95. Zone 1-Normal dentin►Smooth tubule with odontoblastic process►No crystals in lumen►Stimulation produces sharp pain
  96. 96. Zone 2- Sub-Transparent dentin►Zone of demineralization►Damage to odontoblastic process is evident►No bacteria found►Capable of remineralization►Stimulation produces pain
  97. 97. Zone 3- Transparent dentin► Softer then normal dentin► Loss of mineral is more► Many large crystals are present in the dentinal tubules► Stimulation produces pain► No bacteria present► Organic acid attack both mineral and organic content of dentin the collagen cross linking remain intact. This intact collagen serves as a template for remineralization.► This region is capable of self repair provided pulp remain vital (kantor et al, 1989)
  98. 98. Zone 4- Turbid dentin► Zone of bacterial invasion , marked by Widening and distortion of dentinal tubule which are filled with bacteria .► very little mineral present .► Collagen irreversibly denatured .► Not capable of self repair.► Must be removed prior to restoration.
  99. 99. Zone 5- Infective dentin► This is outer most zone.► Decomposed dentin.► Many bacteria present.► Absence of collagen and mineral.► Removal is essential to sound successful restoration procedure as well as prevention of spreading the infection.
  100. 100. DEVELOPMENTAL DISTURBANCES OF DENTINDentinogenesis imperfecta (Hereditaryopalescent dentin).Dentin dysplasia (Root less teeth).Regional Odontodysplasia (Odontogenicimperfecta, odontogenic dysplasia, ghostteeth).
  101. 101. Dentin Hypocalcification .Dens in dente(Dens invaginatus,dilalated composite odontome).Dens evaginatus (Occlusal enamel pearlevaginated odontome) , leong’spremolar, occlusal tuberculatedpremolar.
  102. 102. DENTINOGENESIS IMPERFECTACLASSIFICATION► TYPE 1-Dentinogenesis imperfecta(DI) that always occurs in families with osteogenesis imperfecta (OI) although the latter may occur without dentinogenesis imperfecta.► TYPE II-Dentinogenesis imperfecta that never occurs in association with (OI) unless by chance. This type is the one most frequently referred to as hereditary opalescent dentin.
  103. 103. ► TYPE- III-Dentinogenesis imperfecta of the “Brandywine type”. This is a racial isolate in Maryaland with this unusual form of DI characterized by the same clinical appearance of the teeth as types I and II but also by multiple pulp exposures in deciduous teeth, a characteristic not seen in types I or II.
  104. 104. DENTIN DYSPLASIAClassification (witkop)► Type I - Radicular dentin dysplasia  Normal Morphologic appearance and color (clinically). Roots are short blunt conical or similarly malformed.  Pulp chamber and root canal completely obliterated .► Type II - coronal dentin dysplasia  Thistle tube appearance (Radiagraphically )- Exhibit an abnormally large pulp chamber in the coronal portion of the tooth.
  105. 105. REGIONAL ODONTODYSPLASIA► Delay or total failure in eruption► Shape markedly altered - irregular► X Ray- Ghost appearance► Pulp chamber - Extensively large Dentin hypo calcification •This is due to failure in union of dentinal globules leaving interglobular areas of uncalcified matrix
  106. 106. ► Dens in dente ►Result of an invagination in the surface of a tooth crown before calcification has occurred ►Most affected - Permanent maxillary lateral incisor► Dens evaginatus - Appears clinically as an accessory globule of enamel on the occlusal surface between the buccal and lingual cusps of premolar.► Proliferation and evagination of an area of inner enamel epithelium and subjacent odontogenic mesenchyme into the dental organ during early tooth development.
  107. 107. CONCLUSION Dentin can remove 99.8% of a bacterial suspensionof streptococci that are approx. 0.5 microns, whichtend to prevent infection of the pulp even whenpatients masticate on infected carious dentin. Thisphenomenon is why there are no bacteria in thetubules at the extreme front of the carious attack. The structure and function of the dentin pulp organalways sees that the tooth remains sound andfunctional.
  109. 109. Thank You!