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Dentin

This document provides an overview of dentin, including: - Its composition, formation process, and physical properties. - The roles of odontoblasts and other components in dentinogenesis. - The different types and structures of dentin, such as peritubular and intertubular dentin. - Features like dentinal tubules, Von Ebner's lines, and the dentinoenamel junction. - Its clinical significance, including use of the cementodentinal junction as a reference point in root canals. - Potential developmental irregularities below the enamel-dentin junction that could predispose to caries.

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DENTIN Pooja Jayan 1st year PG DEPARTMENT OF CONSERVATIVE DENTISTRY AND ENDODONTICS
Contents • Introduction • History • Composition • Dentinogenesis • Physical Properties • Structure • Types of Dentin • Age & Functional Changes • Innervation of Dentin • Clinical Considerations • Developmental Anomalies • Aesthetic Considerations • Forensic Odontology • Conclusion
Introduction • Dentin is the mineralized hard tissue forming the main bulk of the tooth. • It is classified as the connective tissue that encases the coronal and radicular pulp. • It underlies enamel and cementum and forms the supporting base of enamel. • It forms slightly before the enamel. • It determines the shape of the crown, including the cusps and ridges and also the number and the size of the ridges. • Pashley defined dentin as porous biological composite composed of apatite crystal filler particles in a collagen matrix.
HISTORY 1771 John Hunter - Hard Tissue 1775 Anton Von Leeuwenhoek- Described tubular structures. 1837 Purkinje & Retzius explained about Dentinal Tubules; Cuvien gave the name “Ivory” to Dentin. 1867 Neuman gave the term Neuman’s sheath. 1891 Von Ebner gave the term Ebner’s growth lines or Imbrication lines. 1906 Von Korff gave the term Korff’s fibers.
Composition 35% 65% Organic Matter + Water Inorganic Matter Inorganic Matter Thin plate like crystals, shorter than enamel.3.5 nm thick, 100 nm long • Salts - calcium carbonate, sulphate, phosphate etc. • Trace Elements - Cu, Fe, Zn • Rich in carbon When compared to enamel. Organic Matter + Water • Collagen– 82% , Mainly type I and some amount of Type III & V. • Non Collagenous Matrix Proteins- 18% • Phosphoproteins- DPP, gammacarboxyglutamate • Glycoproteins- Dentin Sialoprotein, Osteonectin, Osteopontin, Osteocalcin (Seen in mineralized matrix) • Proteoglycans- Chondroitin sulphate (seen mainly in Predentin), decorin, biglycan • Enzymes- Acid Phosphatase, Alkaline Phosphatase. • Lipids- phospholipids, glycolipids etc. in traces. • Growth factors-TGF, FGF, BMP, IGF, PLGF, EGF, PDGF
Dentinogenesis  Dentin is the first calcified tissue in tooth embryogenesis  Dentin and pulp develop from the dental papilla, which is mesodermal in origin.  Dentin is formed by odontoblasts that differentiate from the ectomesenchymal cells  Formed in the late bell stage
Stages in Dentin Formation Differentiation of Odontoblasts Matrix Deposition Mineralization
• Differentiation of odontoblasts takes place • Starting at the cuspal or incisal region • Under the control of the cells in the inner dental epithelium. The cells become cylindrical in shape and are sometimes referred to as preodontoblasts. • The number of organelles markedly increases, and the cells become tall and columnar with the nucleus located at the end farthest from the basement membrane of the inner dental epithelium. • These cells are the odontoblasts and they are responsible for predentin formation. • Continued differentiation of new odontoblasts takes place further apically in the dental papilla. • After the crown is fully formed. The rate of dentin deposition slows down markedly (2-3yrs for permanent teeth) until root formation starts. • The root dentin is similar to the cyto- differentiation in the crown; odontoblasts develop from the dental papilla under the influence of the inner dental epithelium.
• The odontoblasts exhibit all the characteristics of matrix- producing orgnanelles i.e., an abundance of rough endoplasmic reticulum, a well developed Golgi apparatus, mitochondria and secretory granules. • Procollagen is synthesized in the rough-surfaced endoplasmic reticulum • Transferred to the Golgi apparatus. • And finally appears in secretary granules.
INITIALLY: • Large diameter fibre. • Type III Collagen - 0.1- 0.2µ • VON KORFF’S FIBRES • Cork Screw Shaped • Perpendicular to DEJ LATER: • Smaller Fibrils • Parallel To DEJ.
As more matrix is formed- the Odontoblast Migrates centripetally, towards the pulp. A Single Prominent Process- Odontoblast Process-- Tubular nature Is established. The rate of matrix production - about- 4-8Âľ/day for Primary Dentin. MINERALIZATION Begins once matrix is about 5Âľ thick.
Matrix vesicles contain Alkaline Phosphatase increases the concentration of phosphates → combine with Calcium → Hydroxyapatite Crystals Crystals- grow rapidly, rupture the matrix vesicles Spread -clusters of crystallites → fuse with adjacent clusters to form a continuous layer of mineralized matrix
DPP ( Dentin Phospho protein) Binds to Ca, Controls Growth of Hydroxyapatite Crystals. OsteonectinInhibits growth of Hydroxyapatite crystals. Osteopontin Promotes mineralization. Gla ( gamma carboxy glutamic acid) proteins Phospholipid Act as nucleators . Proteoglyca ns Inhibit premature mineralization
INTERGLOBULAR PATTERN  With continued crystal growth occurs, globular masses are formed  These globules enlarge and fuse to form a single calcified mass  Areas where the globules do not fuse are hypomineralized and known as interglobular dentin. Clinical significance Presence of interglobular dentin indicates dental anomalies like vitamin D deficiencies or hypophosphatasia. Radial Crystal Growth Interglobular Dentin
LINEAR PATTERN LINEAR : When the rate of Dentin formation occurs Slowly –Mineralization front appears more Uniform – CIRCUMPULPAL DENTIN
 Begins once Enamel & Dentin formation reaches the future CEJ.  Initiated by Cells of HERS- which induce odontoblast differentiation.  Collagen fibers- parallel to CDJ.  Less mineralized, less number of Tubules 18
PROPERTIES Color : light yellowish, becomes darker with age Thickness: 3 – 10mm Hardness: 68 KHN, Carious Dentin: 25KHN, Sclerotic Dentin:80 KHN Modulus of Resiliency: Higher than Enamel Proportional Limit: 148 MPa Radiolucency: more radiolucent than enamel because of lower content of mineral salts Elasticity: Modulus of Elasticity – 15-20 GPA Density: 2.1 gm/ml Tensile Strength: 50 MPa, Compressive Strength: 266 MPa
Histology of Dentin
ODONTOBLASTS • Derived - Dorsal Cranial Neural Crest, Mesenchymal in origin. • Lie along Dental papilla- Adjacent to inner enamel epithelium. • Tall columnar cells- length 25-40 µm, diameter 4-7 µm, cuboidal in the root, ovoid/spindle shaped at apex. • Development- Initiated by epigenetic influence of Ameloblasts. • Gene MAP1B for odontoblastic differentiation.
ODONTOBLAST PROCESS  Cytoplasmic extension of Odontoblast  Integral part Of Dentin.  Originate in the peripheral part of pulp at the pulp-predentin border and extend into the dentinal tubules.  EXTENT- Pulp to 1/2 – 1/3 of Dentin or upto Enamel.  composed of microtubules and intermediate filaments, occasionally mitochondria, dense bodies, lysosomes, few vesicles.  Diameter- 3-4 µm (near pulp), 1 µm (near DEJ)
DENTINAL TUBULES  Shows a gentle ‘S’ shaped curve.  starting at right angle to pulp  End perpendicular to DEJ and DCJ  Occupy 1% superficial and 30% volume of deep dentin.  Size- varies with location.  Smaller branches - canaliculi - more common in root dentin.
TUBULE DENSITY PER UNIT AREA  A. - 50,000 to 90,000 / sqmm -pulpal surface  B. - 30,000 to35,000/sqmm - middle dentine  C. -10,000 to 25,000/sqmm - peripheral dentine No. of Tubules / unit area – crown> root
PRIMARY CURVATURES  Tubules exhibit Gentle S (Sigmoid curvatures)  More prominent in crown  Least pronounced at cusp tips, incisal edge first convexity towards apex
SECONDARY CURVATURES At increased magnification- Secondary Curvature minute, relatively regular that are sinusoidal in shape.
LAMINA LIMITANS  Organic sheath or membrane lining the Dentinal tubules  High in GAG and similar to lining of lacunae of cartilage  Seen in EM sections
PERIODONTOBLASTIC SPACE  Potential space between tubule wall and odontoblastic process.  Contents - nerves, collagen fibrils, plasma proteins, glycoproteins and mitochondria.
DENTINAL FLUID ( Dentin Lymph)  Occupies space between dentinal tubule and odontoblastic process.  Ultra filtrate of blood from pulp Capillaries  Plasma proteins, Ca, PO4 CLINICAL SIGNIFICANCE  Exposure of Tubules → Outward movement → sensitivity  Acts as barrier for microbes and toxins.
PREDENTIN/DENTINOID  The predentin is located adjacent to the pulp tissue and is 2 to 6 um wide.  It is the “first formed” dentin and is not mineralized.  As the collagen fibers undergo mineralization at the predentin-dentin junction, the predentin becomes dentin and a new layer of predentin forms circumpulpally  It is composed of collagen fibrils odontoblastic process, nerve fibre, capillary loops and lymphatic channels in ground substance
PERITUBULAR DENTIN  It forms the walls of the Dentinal tubules and surrounds them like a collar  Predominant in the coronal dentin rather in radicular dentin  Thickness varies from 0.75 microns at the dentin surface to about 0.4 microns near the pulp  Thus the dentinal tubules become wider nearer the pulp  Not well differentiated in the young dentin  It is 40 % more mineralized than inter tubular dentin
INTERTUBULAR DENTIN  Main Body Of Dentin.  Located between dentinal tubules or mostly between zones of peritubular dentin.  Its organic matrix is retained after decalicification whereas, peritubular dentin is not.  Less mineralized  Hardness of hydroxyapatite crystals -52KHN
INTERGLOBULAR DENTIN  Unmineralized islands within the Dentin- formed due to failure of fusion of mineral globules  Tubules pass uninterrupted  Vitamin ‘D’ deficiency or Hypophosphatasia
INCREMENTAL LINES :shows periodic deposition of dentin Von Ebner Line  Fine striations - perpendicular to tubules  Shows the daily rhythmic deposition of Dentin  4-8mm apart in crown, closer in root  Indicates growth pattern of dentin  Due to the “Co-incidence of secondary curvatures”  Accentuated incremental line  Disturbance in matrix formation  Shows Hypomineralized areas Contour Line of Owen Neonatal Line  Accentuated Incremental line  Prenatal and postnatal dentin separated by neonatal line  Primary teeth, permanent first molars  Reflects abrupt change in environment that occurs at Birth.
GRANULAR LAYER OF TOMES  Granular zone-under transmitted light- root dentin  Due to looping and coalescing of dentinal tubules.  Hypomineralized areas.  Increases in amount from CEJ to Apex
DENTINOENAMEL JUNCTION  First hard Tissue Interface to Develop  Scalloped- with convexity towards Dentin.  Scalloping greatest in Cuspal area → More Occlusal stress  Branching of Odontoblast Process here → increases sensitivity
CEMENTO-DENTINAL JUNCTION • Firm Attachment • Smooth in Permanent teeth, scalloped in primary dentition. • Intermediate Zone- Hyaline layer Of Hopewell Smith- Cements the cementum to Dentin. • Significance in Endodontics- • Smulson et al estimated that the CDJ is located approximately 1mm from the apical foramen marking the termination of Instrumentation Why is the cementodentinal junction significant? • The area around the cementodentinal junction can become significant in the case of a root canal to remove damaged or dead pulp within the tooth safely and efficiently. • Root canals can be difficult to plan for as the proper junction within the tooth cannot be seen by x-ray. However, a dentist can reliably plan on beginning and terminating the root canal at the point of the CDJ. Using an apex locator, finding the CDJ can be made easier and take less time overall. • Once the CDJ is located, the dentist can use this as an entry and exit point to the pulp chamber inside the tooth to remove the damaged pulp within the tooth and relieve the painful symptoms.
Irregularities below the Enamel-Dentin Junction May Predispose for Fissure Caries J. Kßhnisch*, M. Galler, M. Seitz Š 2012 International & American Associations for Dental Research Abstract This study investigated the structure of the fissure fundus on occlusal surfaces with respect to the detection of possible irregularities below the enamel-dentin junction (EDJ). Occlusal surfaces were examined by micro-computed tomography (¾CT). In total, 203 third molars with clinically sound occlusal fissures or non-cavitated lesions were selected. All specimens were scanned with ¾CT. Subsequently, each tooth was sectioned, and each slice was investigated by stereomicroscopy. In 7 of 203 molars (3.4%), demarcated radiolucencies below the EDJ were detected by ¾CT. These defects were obviously of non- carious origin, because the ¾CT images revealed no gradient of demineralization in the dentin. In all cases, a direct pathway between the oral cavity and the dentin was evident. The comparison of the ¾CT sites with conventional histological images also revealed defects in the dentin. These results demonstrate that demarcated radiolucencies below the EDJ may not necessarily be caries lesions according to ¾CT images and may be classified as possible developmental irregularities. To avoid misinterpreting ¾CT data, dental researchers should carefully consider this condition when analyzing ¾CT images. The clinical significance of this finding is that these defects may predispose molar teeth to early-onset caries in occlusal pits and fissures.
ENAMEL SPINDLES  Odontoblast processes sometimes extend into the Enamel  Length is about 10—40 m  Seen near Incisal edges and cusp tips  Appear dark in ground section  Hypomineralized Areas  Responsible for the Spread of Caries from Enamel to Dentin. Clinical significance They serve as pain receptors thus explains enamel sensitivity experienced by some patients during tooth preparation
Types of Dentin
42
PRIMARY DENTIN  Dentin which is formed before root completion.  Two types : mantle dentin and circumpulpal dentin  Mantle dentin is the first formed dentin in the crown underlying the DEJ  Most outer part and 20um thick  Contain larger diameter collagen fibril  Less mineralized compared to circumpulpal dentin  Pattern of mineralization -globular  Circumpulpal dentin forms remaining primary dentin or bulk of the tooth  6-8 um in thickness  Smaller diameter collagen fibril  Slighty more mineralized than mantle dentin  Pattern of mineralization-linear or globular
SECONDARY DENTIN  Develops after root completion  Narrow band- bordering the pulp  Deposited more slowly - 1µ/day  Fewer tubules  Bending of tubules at the primary & secondary dentin interface  Formed in greater amount.- roof of pulp chamber- protecting the pulp horns
TERTIARY DENTIN  Synonyms: Reactive Dentin, Reparative Dentin, Irritation Dentin, Replacement Dentin, Defense Dentin  Localized formation of Dentin At pulp –Dentin Border in response to noxious stimuli- Caries, Trauma, Attrition , Cavity Preparation Etc.  No continuity with primary or secondary Dentin so there is decrease in Dentin permeability  Quality Depends on :  Intensity of stimulus.  Vitality of pulp.
TERTIARY DENTIN REACTIONARY DENTIN REPARATIVE DENTIN STIMULUS FOR FORMATION MILD AGGRESSIVE FORMATIVE CELLS SURVIVING POST MITOTIC ODONTOBLASTS NEW ODONTOBLAST- LIKE CELLS FROM PROGENITORS STRUCTURE PHYSIOLOGIC DENTIN CHANGE IN DIRECTION OF NEW DENTINAL TUBULES HETEROGENOUS: -TUBULAR (ORGANISED) OSTEODENTIN FIBRODENTIN (DISORGANISED)
REPARATIVE DENTIN REACTIONARY DENTIN The average daily rate of reparative dentin formation is about 2.8-3 Âľ/day- acc to Stanley in 1996.
Pulp Stem Cells: Implication in Reparative Dentin Formation Sasha Dimitrova-Nakov, DDS, PhD, Anne Baudry, PhD, Yassine Harichane, DDS, PhD, Odile Kellermann, Dr es Sciences Naturelles, and Michel Goldberg, DDS, PhD, Dr es Sciences Naturelles • Abstract Many dental pulp stem cells are neural crest derivatives essential for lifelong maintenance of tooth functions and homeostasis as well as tooth repair. These cells may be implicated in the healing process or indirectly involved in cell-to-cell diffusion of paracrine messages to resident (pulpoblasts) or nonresident cells (migrating mesenchymal cells). The identity of the pulp progenitors and the mechanisms sustaining their regenerative capacity remain largely unknown. Taking advantage of the A4 cell line, a multipotent stem cell derived from the molar pulp of mouse embryo, we investigated the capacity of these pulp-derived precursors to induce in vivo the formation of a reparative dentin-like structure upon implantation within the pulp of a rodent incisor or a first maxillary molar after surgical exposure. One month after the pulp injury alone, a nonmineralized fibrous matrix filled the mesial part of the coronal pulp chamber. Upon A4 cell implantation, a mineralized osteodentin was formed in the implantation site without affecting the structure and vitality of the residual pulp in the central and distal parts of the pulp chamber. These results show that dental pulp stem cells can induce the formation of reparative dentin and therefore constitute a useful tool for pulp therapies. Finally, reparative dentin was also built up when A4 progenitors were performed by alginate beads, suggesting that alginate is a suitable carrier for cell implantation in teeth. • Conclusions and Perspectives The stem cells appear as tools to get a better understanding of the cellular mechanisms of pulp repair. They display innovating potential in dental therapies. The present results indicate that the direct implantation of mouse progenitor cells in the dental pulp of a rat molar leads to the formation of reparative osteodentin. It is important to determine whether precursor cells reintroduced in a pulpal ‘‘natural’’ environment differentiate into osteoodontogenic cells or whether the implanted cells recruit resident pulp stem cells toward osteoodontogenic differentiation and indirectly promote the formation of the dentinal bridge. Future prospects will determine whether the implanted progenitor cells are directly involved in the formation of the reparative dentin or whether they induce the recruitment and differentiation of host progenitor cells. In conclusion, our preclinical experimental approach paves the way for the development of cellular therapies after pulp injury. The long-term goal should provide new clinical strategies to restore the functionality of an injured tooth by using pulp stem cells. (J Endod 2014;40:S13–S18)
AGE AND FUNCTIONAL CHANGES  DEAD TRACTS  DENTIN SCLEROSIS  REPARATIVE DENTIN
DEAD TRACTS  Represent Empty Tubules Filled with air.  Due to Degeneration of odontoblastic process (caries, erosion, attrition etc.)  In dried Ground Sections  Seen in older Teeth and has decrease sensitivity. BLACK IN TRANSMITTED LIGHT, WHITE IN REFLECTED LIGHT.
SCLEROTIC DENTIN  Presence of irritating stimuli -Caries, Attrition, Erosion, Cavity Preparation causes Deposition of Apatite Crystals & Collagen in Dentinal Tubules.  Blocking of tubules- Defensive reaction.  Elderly people – Mostly in Roots
 Also seen- slowly progressing Caries.  Reduced Permeability  Prolonged pulp vitality  Resistant to Caries  Forensic Odontology One of the criteria for age determination using Gustafson’s method. SCLEROTIC DENTIN
Resin bonding to cervical sclerotic dentin: A review Franklin R. Taya,*, David H. Pashley Journal of Dentistry (2004) 32, 173–196 Several reports have indicated that resin bond strengths to noncarious sclerotic cervical dentin are lower than bonds made to normal dentine. This is thought to be due to tubule occlusion by mineral salts, preventing resin tag formation. The purpose of this review was to critically examine what is known about the structure of this type of dentine. Recent transmission electron microscopy revealed that in addition to occlusion of the tubules by mineral crystals, many parts of wedge-shaped cervical lesions contain a hypermineralised surface that resists the etching action of both self-etching primers and phosphoric acid. This layer prevents hybridisation of the underlying sclerotic dentine. In addition, bacteria are often detected on top of the hypermineralised layer. Sometimes the bacteria were embedded in a partially mineralised matrix. Acidic conditioners and resins penetrate variable distances into these multilayered structures. Examination of both sides of the failed bonds revealed a wide variation in fracture patterns that involved all of these structures. Microtensile bond strengths to the occlusal, gingival and deepest portions of these wedge-shaped lesions were significantly lower than similar areas artificially prepared in normal teeth. When resin bonds to sclerotic dentine are extended to include peripheral sound dentine, their bond strengths are probably high enough to permit retention of class V restorations by adhesion, without additional retention
EBURNATED DENTIN  Exposed portion of reactive sclerotic dentin  Slow caries has destroyed overlying tooth structure  Hard, darkened, cleanable surface  Resistant to further caries attack
INNERVATION OF DENTIN  Numerous Nerve Endings in Predentin and Inner Dentin.  100-150µm from pulp.  increased Near Pulp Horns –40% , decreased near CEJ- 10%  Closely Associated with Odontoblast Process.  Arise from myelinated nerve fibers of Dental Pulp- (Aδ fibres) Reach Brain via Trigeminal N.
PAIN TRANSMISSION THROUGH DENTIN  Direct Neural Stimulation  Transduction Theory  Hydrodynamic Theory
Direct Neural Stimulation  It was proposed by Scott Stella in 1963  Nerve endings in Tubules are directly activated by External Stimuli  This view rests on the assumption that Nerve fibers extend to DEJ  Not accepted
Transduction Theory  Odontoblastic processes are primary structures excited by stimulus  Transit impulse to nerve endings  Supported by evidence that odontoblasts -> Neural Crest Origin  Discarded – No synaptic contacts or vesicles between odontoblasts and axons
Hydrodynamic theory/ Brannstrom’s Theory  Most popular Theory  Gysi (1900), Brannstrom  Various stimuli such as Heat, Cold, Air, Mechanical Pressure →Movement of Fluid Within Tubule ↓  Activating the Free Nerve Endings Associated with Odontoblast and its Process  Act as Mechanoreceptors- Sensation is felt as pain.
CLINICAL CONSIDERATIONS
DENTINAL CARIES  Tubular Nature of Dentin → Rapid spread of Caries Through Dentin.  Lateral spread along DEJ → Undermined Enamel.  ZONE 1 – Normal dentin  ZONE 2 – Sub transparent  ZONE 3 – Transparent dentin  ZONE 4 – Turbid dentin  ZONE 5 – Infected dentin
AFFECTED AND INFECTED DENTIN INFECTED DENTIN AFFECTED DENTIN Softened and contaminated with bacteria Hard , demineralized but not yet invaded by bacteria Contains irreversibly denatured collagen – stained by caries detecting dye (1% acid red in propylene glycol). Contains reversibly denatured collagen Requires removal Does not require removal No capacity to undergo mineralisation Can undergo mineralisation
OPERATIVE INSTRUMENTATION Undue trauma from operative instruments can damage pulp. Air driven cutting instruments cause dislodgement of odontoblasts and aspiration with in dentinal tubules, this could be an important factor in survival of inflamed pulp • AVOID- • Excessive Cutting • Heat Generation • Continuous Drying – dislodgement - aspiration into tubules. • USE : • Air- Water Coolant. • Sharp hand Instruments- most suitable
During tooth preparation, Dentin & Enamel can be distinguished from Enamel by: • Dentin is normally yellow-white and slightly darker than enamel, in older patients dentin is darker and become brown or black in cases if dentin exposed to oral fluids, old restorative materials or slowly advancing caries. Color • Dentin surfaces are more opaque and dull, being less reflective to light than enamel surfaces, which appear shiny. Reflectance •Dentin is softer than enamel, sharp explorer tends to catch and hold in dentin. Hardness • When moving an explorer tip over the tooth, enamel surfaces provide a sharper, higher pitched sound than dentin surfaces Sound
VITAL PULP THERAPY DIRECT AND INDIRECT PULP CAPPING The Reparative Dentin Formation can be stimulated by cavity lining materials such as Calcium Hydroxide. • Indirect pulp capping- partial removal of carious dentin and insertion of sedative dressing. • Direct pulp capping- done to stimulate reparative dentin in young, non-inflamed pulp. • THE DENTINAL BRIDGE repair tissue forms across the pulpal wound.
EXPOSURE OF DENTINAL TUBULES  1 mm of Exposed Dentin → Damage to 30,000 living odontoblasts.  Leads to hypersensitivity  Sharp Pain – easily localized  Best explained by Hydrodynamic Theory  Management – Block the dentinal tubules  Desensitising toothpastes-AgNo3, SrCl2, fluorides, Bonding Agents, lasers etc.
DENTIN ADHESION  The classic concepts of operative dentistry were challenged by the introduction of new adhesive techniques to dentin  Dentin adhesion primarily relies on the penetration of adhesive monomers into collagen fibers left exposed by acid etching.
CHALLENGES IN DENTIN BONDING  Dentinal tubule connects pulp with the DEJ. The constant pressure from the pulp causes the fluid to move towards the DEJ.  Tubular nature of dentin that permit fluid flow under a slight but constant outward pressure from the pulp.  Cut dentinal surface form a unique structure called as the ‘smear layer’. It is composed of debris of hydroxyapatite crystals and denatured collagen.
SMEAR LAYER Tooth structure is prepared with bur residual organic and inorganic components “smear layer” The smear layer fills the orifices of dentin tubules, “Smear plugs” decreases dentin permeability
SMEAR LAYER  ‘Smear plugs’ decreases dentin permeability by 85%.  The removal of smear layer and smear plugs will result in an increase of fluid flow onto the exposed dentin.  This fluid can interfere with adhesion due to the hydrophobic nature of resins even if the resin tags are created.
CAVITY PREPARATION  Cavity Floor → Dentin  Dentin is RESILIENT → Absorbs and Resists Forces of Mastication and Deformation – Grips the restorative material.  Mainly for amalgam, cast and pre gold restorations  Grooves, coves, pins etc -completely in Dentin.  Blushing of Dentin :Coronal Dentin → a pinkish hue when cut- seen during cavity preparation & crown cutting – attributed to frictional heat.
PULP PROTECTION • Irritants from Restorative Materials- Pulpal Damage • Thermal Protection- Bases below Restoration • Chemical Protection- Cavity liners and varnish Remaining Dentin Thicknesss (RDT) is the remaining part of dentin present after cavity preparation or caries removal  ≥1.5 – 2 mm : No need for pulpal protection  For Amalgam - varnish  Composite – Bonding Agent  < 0.5mm : Calicium Hydroxide, Base, Sealer/ Varnish
SIGNIFICANCE IN ENDODONTICS OBLITERATION OF PULP CHAMBER & ROOT CANALS • Secondary & Tertiary Dentin deposition • Endodontic treatment → Difficult APICAL DENTIN CHIP PLUG • Dentinal Chips compacted at apex during Obturation- provides a “biologic seal”
DEVELOPMENTAL DISTURBANCES IN DENTIN
DENTINOGENESIS IMPERFECTA
DENS INVAGINATUS
DENTIN DYSPLASIA
REGIONAL ODONTO DYSPLASIA
HYPOPHOSPHATASIA Rare familial disorder characterized by a deficiency of alkaline phosphatase. Decreased no of odontoblasts. Abnormally wide predentin zone. Abundance of interglobular dentin.
CONGENITAL PORPHYRIA  Congenital erythropoietic porphyria is a rare autosomal recessive disorder with progressive photomutilation and hemolysis due to excessive porphyrin production.  Porphyrins are deposited in both enamel and dentin of deciduous and permanent teeth.  Localization of uroporphyrin in discrete bands in dentin.
VITAMIN DEFICIENCIES • Vitamin A • Interferes with histodifferentiation. • Enamel epithelium-prerequisite for odontoblastic differentiation. • Interferes with normal dentin matrix elaboration. • Excess vitamin A-prevents tooth morphogenesis and odontoblastic differentiation. • Vitamin C • Important for elaboration of collagen. • Alters the development of dentin. • Vitamin D • Affects mineralization process. • Dentin formation is disturbed. • Increased dentinal striations and interglobular dentin.
THALASSEMIA Dentin changes similar to Dentinogenesis imperfecta have been reported to occur in the teeth of patients afflicted with beta thalassemia major.
ESTHETIC CONSIDERATION Shade Selection Dentin materials- are shades used to substitute and mimic the dentin layers - inner and outer dentin of natural teeth. Example- beautiful ii - dentin shades A1-A4, B2 B3, C2 C3.
FORENSIC ODONTOLOGY  Chronological Age can be estimated by racemization of aspartic acid from human dentin.  Digital approach for measuring dentin translucency can also be used in forensic age estimation.
CONCLUSION  Dentin forms an integral part of the tooth structure.  It has a regenerative potential and is a vital tissue that provides support to the overlying enamel and protection to the underlying pulp.  Thus we as clinicians, should consider its importance in each and every aspect of treatment without doing any harm intentionally or unintentionally.
REFERENCES  Orbans’ Oral Histology and Embryology-G.S Kumar – Twelfth Edition  Ten Cate’s Oral Histology- Development, structure and Function- Antonio Nanci- Sixth Edition.  Dentin and Dentinogenesis- Vol I and II –linde  Pathways of the pulp- Cohen. Hargreaves- Ninth Edition.  Shafer’s Textbook of Oral Pathology- Shafer, Hine, Levy-5th Edition.  Oral and Maxillofacial Pathology- Neville-3rd Edition.  The art and science of Operative dentistry- Sturdevant 4th edition

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Dentin

  • 1.
    DENTIN Pooja Jayan 1st yearPG DEPARTMENT OF CONSERVATIVE DENTISTRY AND ENDODONTICS
  • 2.
    Contents • Introduction • History •Composition • Dentinogenesis • Physical Properties • Structure • Types of Dentin • Age & Functional Changes • Innervation of Dentin • Clinical Considerations • Developmental Anomalies • Aesthetic Considerations • Forensic Odontology • Conclusion
  • 3.
    Introduction • Dentin isthe mineralized hard tissue forming the main bulk of the tooth. • It is classified as the connective tissue that encases the coronal and radicular pulp. • It underlies enamel and cementum and forms the supporting base of enamel. • It forms slightly before the enamel. • It determines the shape of the crown, including the cusps and ridges and also the number and the size of the ridges. • Pashley defined dentin as porous biological composite composed of apatite crystal filler particles in a collagen matrix.
  • 4.
    HISTORY 1771 John Hunter - HardTissue 1775 Anton Von Leeuwenhoek- Described tubular structures. 1837 Purkinje & Retzius explained about Dentinal Tubules; Cuvien gave the name “Ivory” to Dentin. 1867 Neuman gave the term Neuman’s sheath. 1891 Von Ebner gave the term Ebner’s growth lines or Imbrication lines. 1906 Von Korff gave the term Korff’s fibers.
  • 6.
    Composition 35% 65% Organic Matter +Water Inorganic Matter Inorganic Matter Thin plate like crystals, shorter than enamel.3.5 nm thick, 100 nm long • Salts - calcium carbonate, sulphate, phosphate etc. • Trace Elements - Cu, Fe, Zn • Rich in carbon When compared to enamel. Organic Matter + Water • Collagen– 82% , Mainly type I and some amount of Type III & V. • Non Collagenous Matrix Proteins- 18% • Phosphoproteins- DPP, gammacarboxyglutamate • Glycoproteins- Dentin Sialoprotein, Osteonectin, Osteopontin, Osteocalcin (Seen in mineralized matrix) • Proteoglycans- Chondroitin sulphate (seen mainly in Predentin), decorin, biglycan • Enzymes- Acid Phosphatase, Alkaline Phosphatase. • Lipids- phospholipids, glycolipids etc. in traces. • Growth factors-TGF, FGF, BMP, IGF, PLGF, EGF, PDGF
  • 7.
    Dentinogenesis  Dentin isthe first calcified tissue in tooth embryogenesis  Dentin and pulp develop from the dental papilla, which is mesodermal in origin.  Dentin is formed by odontoblasts that differentiate from the ectomesenchymal cells  Formed in the late bell stage
  • 8.
    Stages in DentinFormation Differentiation of Odontoblasts Matrix Deposition Mineralization
  • 9.
    • Differentiation ofodontoblasts takes place • Starting at the cuspal or incisal region • Under the control of the cells in the inner dental epithelium. The cells become cylindrical in shape and are sometimes referred to as preodontoblasts. • The number of organelles markedly increases, and the cells become tall and columnar with the nucleus located at the end farthest from the basement membrane of the inner dental epithelium. • These cells are the odontoblasts and they are responsible for predentin formation. • Continued differentiation of new odontoblasts takes place further apically in the dental papilla. • After the crown is fully formed. The rate of dentin deposition slows down markedly (2-3yrs for permanent teeth) until root formation starts. • The root dentin is similar to the cyto- differentiation in the crown; odontoblasts develop from the dental papilla under the influence of the inner dental epithelium.
  • 11.
    • The odontoblastsexhibit all the characteristics of matrix- producing orgnanelles i.e., an abundance of rough endoplasmic reticulum, a well developed Golgi apparatus, mitochondria and secretory granules. • Procollagen is synthesized in the rough-surfaced endoplasmic reticulum • Transferred to the Golgi apparatus. • And finally appears in secretary granules.
  • 12.
    INITIALLY: • Large diameterfibre. • Type III Collagen - 0.1- 0.2µ • VON KORFF’S FIBRES • Cork Screw Shaped • Perpendicular to DEJ LATER: • Smaller Fibrils • Parallel To DEJ.
  • 13.
    As more matrixis formed- the Odontoblast Migrates centripetally, towards the pulp. A Single Prominent Process- Odontoblast Process-- Tubular nature Is established. The rate of matrix production - about- 4-8Âľ/day for Primary Dentin. MINERALIZATION Begins once matrix is about 5Âľ thick.
  • 14.
    Matrix vesicles containAlkaline Phosphatase increases the concentration of phosphates → combine with Calcium → Hydroxyapatite Crystals Crystals- grow rapidly, rupture the matrix vesicles Spread -clusters of crystallites → fuse with adjacent clusters to form a continuous layer of mineralized matrix
  • 15.
    DPP ( Dentin Phospho protein) Bindsto Ca, Controls Growth of Hydroxyapatite Crystals. OsteonectinInhibits growth of Hydroxyapatite crystals. Osteopontin Promotes mineralization. Gla ( gamma carboxy glutamic acid) proteins Phospholipid Act as nucleators . Proteoglyca ns Inhibit premature mineralization
  • 16.
    INTERGLOBULAR PATTERN  Withcontinued crystal growth occurs, globular masses are formed  These globules enlarge and fuse to form a single calcified mass  Areas where the globules do not fuse are hypomineralized and known as interglobular dentin. Clinical significance Presence of interglobular dentin indicates dental anomalies like vitamin D deficiencies or hypophosphatasia. Radial Crystal Growth Interglobular Dentin
  • 17.
    LINEAR PATTERN LINEAR :When the rate of Dentin formation occurs Slowly –Mineralization front appears more Uniform – CIRCUMPULPAL DENTIN
  • 18.
     Begins onceEnamel & Dentin formation reaches the future CEJ.  Initiated by Cells of HERS- which induce odontoblast differentiation.  Collagen fibers- parallel to CDJ.  Less mineralized, less number of Tubules 18
  • 19.
    PROPERTIES Color : lightyellowish, becomes darker with age Thickness: 3 – 10mm Hardness: 68 KHN, Carious Dentin: 25KHN, Sclerotic Dentin:80 KHN Modulus of Resiliency: Higher than Enamel Proportional Limit: 148 MPa Radiolucency: more radiolucent than enamel because of lower content of mineral salts Elasticity: Modulus of Elasticity – 15-20 GPA Density: 2.1 gm/ml Tensile Strength: 50 MPa, Compressive Strength: 266 MPa
  • 20.
  • 21.
    ODONTOBLASTS • Derived -Dorsal Cranial Neural Crest, Mesenchymal in origin. • Lie along Dental papilla- Adjacent to inner enamel epithelium. • Tall columnar cells- length 25-40 µm, diameter 4-7 µm, cuboidal in the root, ovoid/spindle shaped at apex. • Development- Initiated by epigenetic influence of Ameloblasts. • Gene MAP1B for odontoblastic differentiation.
  • 22.
    ODONTOBLAST PROCESS  Cytoplasmic extensionof Odontoblast  Integral part Of Dentin.  Originate in the peripheral part of pulp at the pulp-predentin border and extend into the dentinal tubules.  EXTENT- Pulp to 1/2 – 1/3 of Dentin or upto Enamel.  composed of microtubules and intermediate filaments, occasionally mitochondria, dense bodies, lysosomes, few vesicles.  Diameter- 3-4 µm (near pulp), 1 µm (near DEJ)
  • 23.
    DENTINAL TUBULES  Showsa gentle ‘S’ shaped curve.  starting at right angle to pulp  End perpendicular to DEJ and DCJ  Occupy 1% superficial and 30% volume of deep dentin.  Size- varies with location.  Smaller branches - canaliculi - more common in root dentin.
  • 24.
    TUBULE DENSITY PERUNIT AREA  A. - 50,000 to 90,000 / sqmm -pulpal surface  B. - 30,000 to35,000/sqmm - middle dentine  C. -10,000 to 25,000/sqmm - peripheral dentine No. of Tubules / unit area – crown> root
  • 25.
    PRIMARY CURVATURES  Tubulesexhibit Gentle S (Sigmoid curvatures)  More prominent in crown  Least pronounced at cusp tips, incisal edge first convexity towards apex
  • 26.
    SECONDARY CURVATURES At increasedmagnification- Secondary Curvature minute, relatively regular that are sinusoidal in shape.
  • 27.
    LAMINA LIMITANS  Organicsheath or membrane lining the Dentinal tubules  High in GAG and similar to lining of lacunae of cartilage  Seen in EM sections
  • 28.
    PERIODONTOBLASTIC SPACE  Potential spacebetween tubule wall and odontoblastic process.  Contents - nerves, collagen fibrils, plasma proteins, glycoproteins and mitochondria.
  • 29.
    DENTINAL FLUID ( DentinLymph)  Occupies space between dentinal tubule and odontoblastic process.  Ultra filtrate of blood from pulp Capillaries  Plasma proteins, Ca, PO4 CLINICAL SIGNIFICANCE  Exposure of Tubules → Outward movement → sensitivity  Acts as barrier for microbes and toxins.
  • 30.
    PREDENTIN/DENTINOID  The predentinis located adjacent to the pulp tissue and is 2 to 6 um wide.  It is the “first formed” dentin and is not mineralized.  As the collagen fibers undergo mineralization at the predentin-dentin junction, the predentin becomes dentin and a new layer of predentin forms circumpulpally  It is composed of collagen fibrils odontoblastic process, nerve fibre, capillary loops and lymphatic channels in ground substance
  • 31.
    PERITUBULAR DENTIN  Itforms the walls of the Dentinal tubules and surrounds them like a collar  Predominant in the coronal dentin rather in radicular dentin  Thickness varies from 0.75 microns at the dentin surface to about 0.4 microns near the pulp  Thus the dentinal tubules become wider nearer the pulp  Not well differentiated in the young dentin  It is 40 % more mineralized than inter tubular dentin
  • 32.
    INTERTUBULAR DENTIN  MainBody Of Dentin.  Located between dentinal tubules or mostly between zones of peritubular dentin.  Its organic matrix is retained after decalicification whereas, peritubular dentin is not.  Less mineralized  Hardness of hydroxyapatite crystals -52KHN
  • 33.
    INTERGLOBULAR DENTIN  Unmineralized islandswithin the Dentin- formed due to failure of fusion of mineral globules  Tubules pass uninterrupted  Vitamin ‘D’ deficiency or Hypophosphatasia
  • 34.
    INCREMENTAL LINES :showsperiodic deposition of dentin Von Ebner Line  Fine striations - perpendicular to tubules  Shows the daily rhythmic deposition of Dentin  4-8mm apart in crown, closer in root  Indicates growth pattern of dentin  Due to the “Co-incidence of secondary curvatures”  Accentuated incremental line  Disturbance in matrix formation  Shows Hypomineralized areas Contour Line of Owen Neonatal Line  Accentuated Incremental line  Prenatal and postnatal dentin separated by neonatal line  Primary teeth, permanent first molars  Reflects abrupt change in environment that occurs at Birth.
  • 35.
    GRANULAR LAYER OFTOMES  Granular zone-under transmitted light- root dentin  Due to looping and coalescing of dentinal tubules.  Hypomineralized areas.  Increases in amount from CEJ to Apex
  • 36.
    DENTINOENAMEL JUNCTION  First hardTissue Interface to Develop  Scalloped- with convexity towards Dentin.  Scalloping greatest in Cuspal area → More Occlusal stress  Branching of Odontoblast Process here → increases sensitivity
  • 38.
    CEMENTO-DENTINAL JUNCTION • Firm Attachment •Smooth in Permanent teeth, scalloped in primary dentition. • Intermediate Zone- Hyaline layer Of Hopewell Smith- Cements the cementum to Dentin. • Significance in Endodontics- • Smulson et al estimated that the CDJ is located approximately 1mm from the apical foramen marking the termination of Instrumentation Why is the cementodentinal junction significant? • The area around the cementodentinal junction can become significant in the case of a root canal to remove damaged or dead pulp within the tooth safely and efficiently. • Root canals can be difficult to plan for as the proper junction within the tooth cannot be seen by x-ray. However, a dentist can reliably plan on beginning and terminating the root canal at the point of the CDJ. Using an apex locator, finding the CDJ can be made easier and take less time overall. • Once the CDJ is located, the dentist can use this as an entry and exit point to the pulp chamber inside the tooth to remove the damaged pulp within the tooth and relieve the painful symptoms.
  • 39.
    Irregularities below theEnamel-Dentin Junction May Predispose for Fissure Caries J. Kßhnisch*, M. Galler, M. Seitz Š 2012 International & American Associations for Dental Research Abstract This study investigated the structure of the fissure fundus on occlusal surfaces with respect to the detection of possible irregularities below the enamel-dentin junction (EDJ). Occlusal surfaces were examined by micro-computed tomography (¾CT). In total, 203 third molars with clinically sound occlusal fissures or non-cavitated lesions were selected. All specimens were scanned with ¾CT. Subsequently, each tooth was sectioned, and each slice was investigated by stereomicroscopy. In 7 of 203 molars (3.4%), demarcated radiolucencies below the EDJ were detected by ¾CT. These defects were obviously of non- carious origin, because the ¾CT images revealed no gradient of demineralization in the dentin. In all cases, a direct pathway between the oral cavity and the dentin was evident. The comparison of the ¾CT sites with conventional histological images also revealed defects in the dentin. These results demonstrate that demarcated radiolucencies below the EDJ may not necessarily be caries lesions according to ¾CT images and may be classified as possible developmental irregularities. To avoid misinterpreting ¾CT data, dental researchers should carefully consider this condition when analyzing ¾CT images. The clinical significance of this finding is that these defects may predispose molar teeth to early-onset caries in occlusal pits and fissures.
  • 40.
    ENAMEL SPINDLES  Odontoblastprocesses sometimes extend into the Enamel  Length is about 10—40 m  Seen near Incisal edges and cusp tips  Appear dark in ground section  Hypomineralized Areas  Responsible for the Spread of Caries from Enamel to Dentin. Clinical significance They serve as pain receptors thus explains enamel sensitivity experienced by some patients during tooth preparation
  • 41.
  • 42.
  • 43.
    PRIMARY DENTIN  Dentinwhich is formed before root completion.  Two types : mantle dentin and circumpulpal dentin  Mantle dentin is the first formed dentin in the crown underlying the DEJ  Most outer part and 20um thick  Contain larger diameter collagen fibril  Less mineralized compared to circumpulpal dentin  Pattern of mineralization -globular  Circumpulpal dentin forms remaining primary dentin or bulk of the tooth  6-8 um in thickness  Smaller diameter collagen fibril  Slighty more mineralized than mantle dentin  Pattern of mineralization-linear or globular
  • 44.
    SECONDARY DENTIN  Developsafter root completion  Narrow band- bordering the pulp  Deposited more slowly - 1µ/day  Fewer tubules  Bending of tubules at the primary & secondary dentin interface  Formed in greater amount.- roof of pulp chamber- protecting the pulp horns
  • 45.
    TERTIARY DENTIN  Synonyms:Reactive Dentin, Reparative Dentin, Irritation Dentin, Replacement Dentin, Defense Dentin  Localized formation of Dentin At pulp –Dentin Border in response to noxious stimuli- Caries, Trauma, Attrition , Cavity Preparation Etc.  No continuity with primary or secondary Dentin so there is decrease in Dentin permeability  Quality Depends on :  Intensity of stimulus.  Vitality of pulp.
  • 46.
    TERTIARY DENTIN REACTIONARY DENTINREPARATIVE DENTIN STIMULUS FOR FORMATION MILD AGGRESSIVE FORMATIVE CELLS SURVIVING POST MITOTIC ODONTOBLASTS NEW ODONTOBLAST- LIKE CELLS FROM PROGENITORS STRUCTURE PHYSIOLOGIC DENTIN CHANGE IN DIRECTION OF NEW DENTINAL TUBULES HETEROGENOUS: -TUBULAR (ORGANISED) OSTEODENTIN FIBRODENTIN (DISORGANISED)
  • 47.
    REPARATIVE DENTIN REACTIONARYDENTIN The average daily rate of reparative dentin formation is about 2.8-3 Âľ/day- acc to Stanley in 1996.
  • 48.
    Pulp Stem Cells:Implication in Reparative Dentin Formation Sasha Dimitrova-Nakov, DDS, PhD, Anne Baudry, PhD, Yassine Harichane, DDS, PhD, Odile Kellermann, Dr es Sciences Naturelles, and Michel Goldberg, DDS, PhD, Dr es Sciences Naturelles • Abstract Many dental pulp stem cells are neural crest derivatives essential for lifelong maintenance of tooth functions and homeostasis as well as tooth repair. These cells may be implicated in the healing process or indirectly involved in cell-to-cell diffusion of paracrine messages to resident (pulpoblasts) or nonresident cells (migrating mesenchymal cells). The identity of the pulp progenitors and the mechanisms sustaining their regenerative capacity remain largely unknown. Taking advantage of the A4 cell line, a multipotent stem cell derived from the molar pulp of mouse embryo, we investigated the capacity of these pulp-derived precursors to induce in vivo the formation of a reparative dentin-like structure upon implantation within the pulp of a rodent incisor or a first maxillary molar after surgical exposure. One month after the pulp injury alone, a nonmineralized fibrous matrix filled the mesial part of the coronal pulp chamber. Upon A4 cell implantation, a mineralized osteodentin was formed in the implantation site without affecting the structure and vitality of the residual pulp in the central and distal parts of the pulp chamber. These results show that dental pulp stem cells can induce the formation of reparative dentin and therefore constitute a useful tool for pulp therapies. Finally, reparative dentin was also built up when A4 progenitors were performed by alginate beads, suggesting that alginate is a suitable carrier for cell implantation in teeth. • Conclusions and Perspectives The stem cells appear as tools to get a better understanding of the cellular mechanisms of pulp repair. They display innovating potential in dental therapies. The present results indicate that the direct implantation of mouse progenitor cells in the dental pulp of a rat molar leads to the formation of reparative osteodentin. It is important to determine whether precursor cells reintroduced in a pulpal ‘‘natural’’ environment differentiate into osteoodontogenic cells or whether the implanted cells recruit resident pulp stem cells toward osteoodontogenic differentiation and indirectly promote the formation of the dentinal bridge. Future prospects will determine whether the implanted progenitor cells are directly involved in the formation of the reparative dentin or whether they induce the recruitment and differentiation of host progenitor cells. In conclusion, our preclinical experimental approach paves the way for the development of cellular therapies after pulp injury. The long-term goal should provide new clinical strategies to restore the functionality of an injured tooth by using pulp stem cells. (J Endod 2014;40:S13–S18)
  • 49.
    AGE AND FUNCTIONAL CHANGES  DEADTRACTS  DENTIN SCLEROSIS  REPARATIVE DENTIN
  • 50.
    DEAD TRACTS  RepresentEmpty Tubules Filled with air.  Due to Degeneration of odontoblastic process (caries, erosion, attrition etc.)  In dried Ground Sections  Seen in older Teeth and has decrease sensitivity. BLACK IN TRANSMITTED LIGHT, WHITE IN REFLECTED LIGHT.
  • 51.
    SCLEROTIC DENTIN  Presenceof irritating stimuli -Caries, Attrition, Erosion, Cavity Preparation causes Deposition of Apatite Crystals & Collagen in Dentinal Tubules.  Blocking of tubules- Defensive reaction.  Elderly people – Mostly in Roots
  • 52.
     Also seen-slowly progressing Caries.  Reduced Permeability  Prolonged pulp vitality  Resistant to Caries  Forensic Odontology One of the criteria for age determination using Gustafson’s method. SCLEROTIC DENTIN
  • 53.
    Resin bonding tocervical sclerotic dentin: A review Franklin R. Taya,*, David H. Pashley Journal of Dentistry (2004) 32, 173–196 Several reports have indicated that resin bond strengths to noncarious sclerotic cervical dentin are lower than bonds made to normal dentine. This is thought to be due to tubule occlusion by mineral salts, preventing resin tag formation. The purpose of this review was to critically examine what is known about the structure of this type of dentine. Recent transmission electron microscopy revealed that in addition to occlusion of the tubules by mineral crystals, many parts of wedge-shaped cervical lesions contain a hypermineralised surface that resists the etching action of both self-etching primers and phosphoric acid. This layer prevents hybridisation of the underlying sclerotic dentine. In addition, bacteria are often detected on top of the hypermineralised layer. Sometimes the bacteria were embedded in a partially mineralised matrix. Acidic conditioners and resins penetrate variable distances into these multilayered structures. Examination of both sides of the failed bonds revealed a wide variation in fracture patterns that involved all of these structures. Microtensile bond strengths to the occlusal, gingival and deepest portions of these wedge-shaped lesions were significantly lower than similar areas artificially prepared in normal teeth. When resin bonds to sclerotic dentine are extended to include peripheral sound dentine, their bond strengths are probably high enough to permit retention of class V restorations by adhesion, without additional retention
  • 54.
    EBURNATED DENTIN  Exposedportion of reactive sclerotic dentin  Slow caries has destroyed overlying tooth structure  Hard, darkened, cleanable surface  Resistant to further caries attack
  • 55.
    INNERVATION OF DENTIN Numerous Nerve Endings in Predentin and Inner Dentin.  100-150µm from pulp.  increased Near Pulp Horns –40% , decreased near CEJ- 10%  Closely Associated with Odontoblast Process.  Arise from myelinated nerve fibers of Dental Pulp- (Aδ fibres) Reach Brain via Trigeminal N.
  • 56.
    PAIN TRANSMISSION THROUGH DENTIN Direct Neural Stimulation  Transduction Theory  Hydrodynamic Theory
  • 57.
    Direct Neural Stimulation It was proposed by Scott Stella in 1963  Nerve endings in Tubules are directly activated by External Stimuli  This view rests on the assumption that Nerve fibers extend to DEJ  Not accepted
  • 58.
    Transduction Theory  Odontoblasticprocesses are primary structures excited by stimulus  Transit impulse to nerve endings  Supported by evidence that odontoblasts -> Neural Crest Origin  Discarded – No synaptic contacts or vesicles between odontoblasts and axons
  • 59.
    Hydrodynamic theory/ Brannstrom’sTheory  Most popular Theory  Gysi (1900), Brannstrom  Various stimuli such as Heat, Cold, Air, Mechanical Pressure →Movement of Fluid Within Tubule ↓  Activating the Free Nerve Endings Associated with Odontoblast and its Process  Act as Mechanoreceptors- Sensation is felt as pain.
  • 60.
  • 61.
    DENTINAL CARIES  TubularNature of Dentin → Rapid spread of Caries Through Dentin.  Lateral spread along DEJ → Undermined Enamel.  ZONE 1 – Normal dentin  ZONE 2 – Sub transparent  ZONE 3 – Transparent dentin  ZONE 4 – Turbid dentin  ZONE 5 – Infected dentin
  • 62.
    AFFECTED AND INFECTEDDENTIN INFECTED DENTIN AFFECTED DENTIN Softened and contaminated with bacteria Hard , demineralized but not yet invaded by bacteria Contains irreversibly denatured collagen – stained by caries detecting dye (1% acid red in propylene glycol). Contains reversibly denatured collagen Requires removal Does not require removal No capacity to undergo mineralisation Can undergo mineralisation
  • 63.
    OPERATIVE INSTRUMENTATION Undue trauma fromoperative instruments can damage pulp. Air driven cutting instruments cause dislodgement of odontoblasts and aspiration with in dentinal tubules, this could be an important factor in survival of inflamed pulp • AVOID- • Excessive Cutting • Heat Generation • Continuous Drying – dislodgement - aspiration into tubules. • USE : • Air- Water Coolant. • Sharp hand Instruments- most suitable
  • 64.
    During tooth preparation,Dentin & Enamel can be distinguished from Enamel by: • Dentin is normally yellow-white and slightly darker than enamel, in older patients dentin is darker and become brown or black in cases if dentin exposed to oral fluids, old restorative materials or slowly advancing caries. Color • Dentin surfaces are more opaque and dull, being less reflective to light than enamel surfaces, which appear shiny. Reflectance •Dentin is softer than enamel, sharp explorer tends to catch and hold in dentin. Hardness • When moving an explorer tip over the tooth, enamel surfaces provide a sharper, higher pitched sound than dentin surfaces Sound
  • 65.
    VITAL PULP THERAPY DIRECT ANDINDIRECT PULP CAPPING The Reparative Dentin Formation can be stimulated by cavity lining materials such as Calcium Hydroxide. • Indirect pulp capping- partial removal of carious dentin and insertion of sedative dressing. • Direct pulp capping- done to stimulate reparative dentin in young, non-inflamed pulp. • THE DENTINAL BRIDGE repair tissue forms across the pulpal wound.
  • 66.
    EXPOSURE OF DENTINALTUBULES  1 mm of Exposed Dentin → Damage to 30,000 living odontoblasts.  Leads to hypersensitivity  Sharp Pain – easily localized  Best explained by Hydrodynamic Theory  Management – Block the dentinal tubules  Desensitising toothpastes-AgNo3, SrCl2, fluorides, Bonding Agents, lasers etc.
  • 67.
    DENTIN ADHESION  Theclassic concepts of operative dentistry were challenged by the introduction of new adhesive techniques to dentin  Dentin adhesion primarily relies on the penetration of adhesive monomers into collagen fibers left exposed by acid etching.
  • 68.
    CHALLENGES IN DENTIN BONDING  Dentinaltubule connects pulp with the DEJ. The constant pressure from the pulp causes the fluid to move towards the DEJ.  Tubular nature of dentin that permit fluid flow under a slight but constant outward pressure from the pulp.  Cut dentinal surface form a unique structure called as the ‘smear layer’. It is composed of debris of hydroxyapatite crystals and denatured collagen.
  • 69.
    SMEAR LAYER Tooth structureis prepared with bur residual organic and inorganic components “smear layer” The smear layer fills the orifices of dentin tubules, “Smear plugs” decreases dentin permeability
  • 70.
    SMEAR LAYER  ‘Smearplugs’ decreases dentin permeability by 85%.  The removal of smear layer and smear plugs will result in an increase of fluid flow onto the exposed dentin.  This fluid can interfere with adhesion due to the hydrophobic nature of resins even if the resin tags are created.
  • 71.
    CAVITY PREPARATION  CavityFloor → Dentin  Dentin is RESILIENT → Absorbs and Resists Forces of Mastication and Deformation – Grips the restorative material.  Mainly for amalgam, cast and pre gold restorations  Grooves, coves, pins etc -completely in Dentin.  Blushing of Dentin :Coronal Dentin → a pinkish hue when cut- seen during cavity preparation & crown cutting – attributed to frictional heat.
  • 72.
    PULP PROTECTION • Irritants fromRestorative Materials- Pulpal Damage • Thermal Protection- Bases below Restoration • Chemical Protection- Cavity liners and varnish Remaining Dentin Thicknesss (RDT) is the remaining part of dentin present after cavity preparation or caries removal  ≥1.5 – 2 mm : No need for pulpal protection  For Amalgam - varnish  Composite – Bonding Agent  < 0.5mm : Calicium Hydroxide, Base, Sealer/ Varnish
  • 73.
    SIGNIFICANCE IN ENDODONTICS OBLITERATIONOF PULP CHAMBER & ROOT CANALS • Secondary & Tertiary Dentin deposition • Endodontic treatment → Difficult APICAL DENTIN CHIP PLUG • Dentinal Chips compacted at apex during Obturation- provides a “biologic seal”
  • 74.
  • 76.
  • 77.
  • 78.
  • 79.
  • 80.
    HYPOPHOSPHATASIA Rare familial disorder characterized by adeficiency of alkaline phosphatase. Decreased no of odontoblasts. Abnormally wide predentin zone. Abundance of interglobular dentin.
  • 81.
    CONGENITAL PORPHYRIA  Congenital erythropoieticporphyria is a rare autosomal recessive disorder with progressive photomutilation and hemolysis due to excessive porphyrin production.  Porphyrins are deposited in both enamel and dentin of deciduous and permanent teeth.  Localization of uroporphyrin in discrete bands in dentin.
  • 82.
    VITAMIN DEFICIENCIES • VitaminA • Interferes with histodifferentiation. • Enamel epithelium-prerequisite for odontoblastic differentiation. • Interferes with normal dentin matrix elaboration. • Excess vitamin A-prevents tooth morphogenesis and odontoblastic differentiation. • Vitamin C • Important for elaboration of collagen. • Alters the development of dentin. • Vitamin D • Affects mineralization process. • Dentin formation is disturbed. • Increased dentinal striations and interglobular dentin.
  • 83.
    THALASSEMIA Dentin changes similarto Dentinogenesis imperfecta have been reported to occur in the teeth of patients afflicted with beta thalassemia major.
  • 85.
    ESTHETIC CONSIDERATION Shade Selection Dentin materials-are shades used to substitute and mimic the dentin layers - inner and outer dentin of natural teeth. Example- beautiful ii - dentin shades A1-A4, B2 B3, C2 C3.
  • 86.
    FORENSIC ODONTOLOGY  Chronological Agecan be estimated by racemization of aspartic acid from human dentin.  Digital approach for measuring dentin translucency can also be used in forensic age estimation.
  • 87.
    CONCLUSION  Dentin formsan integral part of the tooth structure.  It has a regenerative potential and is a vital tissue that provides support to the overlying enamel and protection to the underlying pulp.  Thus we as clinicians, should consider its importance in each and every aspect of treatment without doing any harm intentionally or unintentionally.
  • 88.
    REFERENCES  Orbans’ OralHistology and Embryology-G.S Kumar – Twelfth Edition  Ten Cate’s Oral Histology- Development, structure and Function- Antonio Nanci- Sixth Edition.  Dentin and Dentinogenesis- Vol I and II –linde  Pathways of the pulp- Cohen. Hargreaves- Ninth Edition.  Shafer’s Textbook of Oral Pathology- Shafer, Hine, Levy-5th Edition.  Oral and Maxillofacial Pathology- Neville-3rd Edition.  The art and science of Operative dentistry- Sturdevant 4th edition

Editor's Notes

  • #10 This process is carried out by specialised cells known as odontoblasts. orban-IN odontoblast diff.fibronectin, decorin, laminin, and chondroitin sulfate may be involved.recent studies showed that laminin alfa 2 a subunit of laminin is essential for diff. ten cate- signaling molecule and growth factor in the cell of iee cause diff.
  • #12 This process is carried out by specialised cells known as odontoblasts. orban-IN odontoblast diff.fibronectin, decorin, laminin, and chondroitin sulfate may be involved.recent studies showed that laminin alfa 2 a subunit of laminin is essential for diff. ten cate- signaling molecule and growth factor in the cell of iee cause diff.
  • #19 The formation of root dentin is initiated by the cells of he HERS once the enamel and dentin formation have reached the future CEJ. The HERS consists of IEE and OEE. It induces the dental paplila cells to lay down dentin.
  • #23 Odontoblast cell bodies -- approx. length-40um, diameter-7um
  • #24 Because of the presence of tubules, dentin has higher permeability which can increase the sensitivity of pain and tooth decay