Dentin

Detailed description of dentin, its structure and function. Its implications in conservative dentistry and endodontics

1. dentin Guided By - Dr.Vandana Kokane Dr. Pratima Shenoi Dr. Rajesh Kubde Dr. Chetana Makade Dr. Gautam Badole Presented by:- Dr. Himani Thawale

2. Introduction History Properties Structure Types of dentin Deveplopmental defects Clinical consideration CONTENT

3. History

4. Introduction The tooth proper consists of the less mineralized, more resilient and vital hard connective tissue called DENTIN Orban’s oral histology and embryology 13 th edition Provides the bulk and general form of tooth It is characterized as a hard tissue with tubules throughout its thickness

5. It determines the shape of the crown , including the cups and ridges ,and the number and size of the roots. Physically & chemically the dentin closely resembles the bone. Orban’s oral histology and embryology 13 th edition

6. Development of tooth Orban’s oral histology and embryology 13 th edition

7. DEVELPOMENTAL STAGES OF TOOTH

8. Bud stage Low columnar cells Polygonal cells Enamel organ Dental papilla

9. Cap stage Outer enamel epithelium Stellate reticulum Inner enamel epithelium Dental pailla Dental follicle

10. Bell stage

11. Advanced bell Stage Charactrized by start of mineralization and root formation. Formation of DENTINOENAMEL JUNCTION Formation of dentin occurs first along this DEJ. After first layer of dentin is formed , amelobast lay down enamel .

12. DENTINOGENESIS

13. DENTINOGENESIS mainly involes:- FORMATION OF MANTLE DENTIN FORMATION OF CIRCUMPULPAL DENTIN MINERALIZATION FORMATION OF ROOT DENTIN ODONTOBLAST DIFFERENTIATION

14. Odontoblast differentiation

15. Odontoblast differentiation

16. Functional stages of odontoblast Once the odontoblast differentiate , they enter a life cycle related to formation ,maintainance and repair of dentin. The various stages of odontoblast are:- Secretory stage Resting stage Transitional stage

17. Formation of mantle dentin Consist of -Type 1 collagen -Ground substance ORGANIC MATRIX First collagen of dentin appears:- - Extracellularly - Very distinct large diameter fibrils Von Korff’s fibers These large collagen fibers along with the ground substance constitutes the organic matrix of First formed or Mantle dentin .

18. 18 INORGANIC MATRIX

19. Formation of circumpulpul dentin .

20. Mineralization Throughout dentinogenesis, mineralization is acheived by continous deposition of mineral, initially in the matrix vesicle and then at mineralization front

21. Pattern of mineralization Globular Pattern- Deposition of crystals in several discrete areas of matrix, these globular mass continue to enlarge and fuse to form single calcified mass. Linear Pattern- When the rate of formation progress slowly, the mineralisation front becomes more linear and uniform.

22. Formation of root dentin Hertwig’s epithelial root sheath intiate root dentin formation. Less phosphoryn content. Degree of mineralization slightly less .

23. PHYSICAL PROPERTIES It is light yellowish in color. Orban’s oral histology and embryology 13 th edition It is viscoelastic and subject to slight deformation. Harder than bone but softer than enamel. It is more radiolucent than enamel

24. Compressive strength - 266MPa(40,000PSI) Tensile strength- 40MPa (6000 PSI) Modulus of elasticity- 18.5 GPa Oral Anatomy,histology And Embryology : Berkovitz

25. Chemical composition Orban’s oral histology and embryology 13 th edition

26. Orban’s oral histology and embryology 13 th edition

27. Non collagenous matrix proteins Orban’s oral histology and embryology 13 th edition

28. Inorganic matter Calcium hydroxyapatite : CA10(PO4)6(OH)2 Thin plate like crystals , shorter than enamel. Salts – calcium carbonate , sulphate , phosphate. The crystals are poor in calcium but rich in carbon compared to enamel Orban’s oral histology and embryology 13 th edition

29. Types of dentin Primary dentin 1. Mantle dentin 2. circumpulpal dentin Secondary dentin Tertiary dentin 1. Reactionary dentin 2. Reparative dentin Orban’s oral histology and embryology 13 th edition

30. Mantle dentin First formed dentin underlying the DEJ. Orban’s oral histology and embryology 13 th edition It is soft and provides cushioning effect to tooth. The fibrils formed in this zone are Von Korff’s fibers. Undergoes globular mineralization

31. Circumpulpal dentin Remaining bulk of primary dentin. Orban’s oral histology and embryology 13 th edition Collagen fibrils are much smaller in diameter (0.05 µm) The mineralization pattern is globular or linear for circumpulpal dentin.

32. Secondary dentin formed after root completion. A narrow band of dentin bordering the pulp It is formed in response to external stimuli Clinical significance:- Protect the pulp from exposure in older teeth. Orban’s oral histology and embryology 13 th edition

33. Tertiary dentin Also called as reparative , response, or reactive dentin. It is formed in response to stimuli - Attrition -Abrasion - Erosion - Cavity preparation Clinical significance:- It is deposited at specific site in response to injury Orban’s oral histology and embryology 13 th edition

34. Types of tertiary dentin

35. STRUCTURE

36. Structure The bodies of the odontoblasts are arranged in a layer on the pulpal surface of the dentin, and only their cytoplasmic processes are included in the tubules in the mineralized matrix . Orban’s oral histology and embryology 13 th edition

37. Each cell gives rise to one process, which traverses the predentin & calcified dentin within one tubule

38. Dentinal tubules The course follows a gentle curve in the crown, less so in the root, where it resembles S in shape. Orban’s oral histology and embryology 13 th edition

39. Canaliculi:- The dentinal tubules have lateral branches throughout dentin, which are termed canaliculi or microtubules. Orban’s oral histology and embryology 13 th edition Enamel spindle:- A few dentinal tubules extend through the dentinoenamel junction into the enamel. These are termed enamel spindles.

40. Clinical significance Dentin permeability depends upon total surface area of exposed dentin. Bacterial and their toxin products are the most significant to travel down the tubules. Heat or air desiccation eliminates fluid from tubules and thus increases the dentin permeability. The tubular structure of dentin also provides for rapid spread of dental caries.

41. Intratubular dentin (Peritubular) Orban’s oral histology and embryology 13 th edition Originally, the peritubular dentin is dentin immediately surrounds the dentinal tubules. It is 44nm wide near the pulp and 750nm wide near the dentinoenamel junction Rich in glycosaminoglycans termed Lamina limitans.

42. Intertubular dentin Main body of dentin. Location:- between the zones of peritubular dentin. Its organic matrix is retained after decalcification. About one-half of its volume is organic matrix, specifically collagen fibers 0.2 to 0.5um diameter Orban’s oral histology and embryology 13 th edition

43. Predentin Location:- adjacent to the pulp tissue. Is 2 to 6 um wide. First formed dentin and is not mineralized. Orban’s oral histology and embryology 13 th edition

44. Odontoblast process Orban’s oral histology and embryology 13 th edition

45. Interglobular dentin Small globular areas that fail to fuse into a homogeneous mass called interglobular dentin. The dentinal tubules pass uninterruptedly, demonstrating a defect of mineralization & not of matrix formation. Occurs more in cervical and middle third of crown Orban’s oral histology and embryology 13 th edition

46. Tomes granular layer In dry ground section of root dentin, a zone adjacent to the cementum appears granular in transmitted light. Orban’s oral histology and embryology 13 th edition

47. It increases in amount from the CEJ to the root apex Caused due to coalescing and looping of terminal portions of dentinal tubules. High amount of calcium and phosphorus. Recent studies relate it as a special arrangement of collagen and non collagenous matrix proteins at the interface between dentin and cementum. Orban’s oral histology and embryology 13 th edition

48. Incremental lines The incremental lines of von ebner , or imbrication lines, appear as fine lines or striations in dentin. Accentuated incremental lines because of disturbances in matrix and mineralization process are termed as Contour Lines of Owen. Orban’s oral histology and embryology 13 th edition

49. Neonatal line :- In decidous teeth and first permanent molars the prenatal and postnatal dentin are seperated by accentuated incremental line termed as ‘Neonatal line’. Orban’s oral histology and embryology 13 th edition

50. Dentinoenamel junction Scalloped line. The convexities of scallops are directed towards dentin. More pronounced in occlusal area where masticatory stresses are greater.

51. Dentinocemental junction Smooth in outline . In deciduous teeth it may be scalloped. The DCJ is a wide zone containing large quantities of collagen along with chondroitin sulphate and dermatan sulphate.

52. Innervation of nerves Nerve fibers accompany 30 to 70% of odontoblastic processes -intratubular nerves. They are terminal processes of the myelinated nerve fibers of the dental pulp. Synapse like relation between the process and nerve fibers were demonstrated Orban’s oral histology and embryology 13 th edition

53. Difference between deciduous and permanent dentin Orban’s oral histology and embryology 13 th edition

54. Age and functional changes Various age and functional changes are:- 1 ) Reparative dentin 2) Dead tracts 3) Sclerotic dentin

55. Reparative dentin Also known as tertiary or response dentin . Has fewer & more twisted tubules than normal dentin. Sometimes, a combination of osteodentin & tubular dentin is seen Odontoblasts lay down at a rate of 4 um/day Orban’s oral histology and embryology 13 th edition

56. Dead tracts In dry ground section, the odontoblast process disintegrate and the empty tubules get filled with air. Orban’s oral histology and embryology 13 th edition

57. Sclerotic dentin Found specially in roots. Transparent or light in transmitted and dark in reflected light. Orban’s oral histology and embryology 13 th edition

58. Orban’s oral histology and embryology 13 th edition

59. Developmental defects in dentin Dentinogenisis imperfecta Dentin dysplasia Regional odontodysplasia Dentin hypocalcification

60. Dentinogenesis imperfecta Autosomal dominant condition. Teeth appears Gray to yellowish brown. Broad crowns with constriction of cervical area results in TULIP shape. Enamel is easily broken and leads to exposure of dentin.

61. Dentinogenesis Imperfecta type I :- Opalescent dentin,Capdepont teeth,Shields type II. Due to mutation in DSPP gene mapping to chromosome 4 . Blue, gray or amber brown and opalescent teeth.

62. Dentinogenesis Imperfecta type II Shield’s type III, Brandywine type DI . Dentin is amber coloured and smooth. Classic SHELL teeth are seen.

63. Radiographic features Bulbous crown, roots narrower ,pulp chambers and canal smaller or completely obliterated. Presence of ‘shell teeth’.

64. Histologic features Dentin is composed of irregular tubules often with large areas of uncalcified dentin. Tubules are large in diameter in some areas & may also be absent. Pulp chamber is obliterated due to dentin deposition.

65. Directed primarily towards prevention of loss of enamel and dentin by attrition. Cast metal crowns on posteriors, Jacket crowns on anterior teeth. Restorations are not usually permanent because of softness of dentin. Treatment

66. Dentin dysplasia (rootless tooth) Normal enamel but atypical dentin formation and abnormal pulpal morphology. Radiographically, extremely short roots and obliteration of pulp chambers and root canals

67. Type I radicular dentin Radiographically:- In deciduous teeth pulp chamber and canals are obliteratedwhile,crescent shaped pulpal remnant seen in permanent dentition. Histologically:- New dentin forms is Lava flowing around the boulders .

68. Type II (coronal type):- Radiographically, deciduous dentition shows obliteration of pulp chambers while, permanent teeth shows ‘Thistle tube’ appearance. Histologically , atubular dentin in deciduous teeth and numerous pulp stones are seen in permanent teeth.

69. Regional odontodysplasia Maxillary teeth involved more frequently. Teeth are irregular in appearance and shape is altered markedly. Evidence of defective mineralization.

70. Radiographic features It shows marked reduction in radiodensity of teeth. This is called as ‘Ghost’ appearance. Enamel and dentin appear very thin and pulp chamber is exceedingly large.

71. Histologic features There is marked reduction in amount of dentin. Widening of predentin layer Presence of large areas of interglobular dentin and irregular tubular pattern of dentin Treatment : involves extraction and prosthetic replacement.

72. Dentin hypocalcification Normal dentin is calcified by deposition of calcium salts in the organic matrix in the form of globules. In dentinal Hypocalcification there is failure of union in these globules.

73. Clinical considerations

74. Dentinal caries Caries in dentin begins with natural spread of disease process along DEJ and rapid involvement of large number of dentinal tubules. Which acts as pathway for micro-organisms leading to dental pulp. Dentinal caries advances more rapidly in dentin than in enamel.

75. Events in dentinal caries:-

76. Zones of dentinal caries

77. Infected and affected dentin

78. Infected dentin Affected dentin Outer carious dentin soft and leathery in consistency Inner carious dentin hard in consistency dark brown in color. light brown in color. high concentration of bacteria does not contain bacteria collagen is irreversibly denatured Collagen is reversibly denatured not remineralised and must be removed. Can be remineralised and therefore should preserved Infected and affected dentin

79. Dentin hypersensitivity DEFINATION:- It is defined as short , sharp pain arising from exposed dentin in response to stimuli typically thermal, chemical, tactile or osmotic and which cannot be ascribed to any form of dental defect or pathology.

80. Theories of dentinal hypersensitivity Direct Innervation theory - Neural theory -according to this theory , direct mechanical stimulation of exposed nerve endings at DEJ is responsible for dentin hypersensitivity . Odontoblast Receptor theory - tranduction theory - it proposes that odontoblast itself act as neural receptors and relay the signal to the nerve terminal

81. Hydrodynamic theory

82. ATTRITION ABRASION ABFRACTION DENUDATION OF CEMENTUM GINGIVAL RECESSION EROSION Causes

83. CLINICAL FEATURES PAIN is the most common clinical feature Most commonly involved teeth are i) buccal surface of premolars ii) facial surface of insciors External stimuli which elict the expression of this condition include: i)thermal stimuli ii)osmotic stimuli - hot/ cold beverages - sweet food iii) acidic stimuli iv) mechanical stimuli - citrus fruits - toothbrush

84. Managment Removal of Etiological factors Patient education Treatmant strategies include:- i) Desensitizing the nerve - Potassium nitrate ii) Occluding the dentinal tubules - 0.4% stannous flouride - 2% sodium flouride - potassium oxalate - CPP-ACP complex

85. iii) Dental adhesives - D Fluoride varnishes - Oxalic acid and resin -Dentin bonding agents - Glass ionomer cements - Composite resins iv) Crown placement v) Periodontal grafting

86. vi) Lasers - CO2 lasers - Nd : YAG, Er: YAG lasers Use of anti-inflammatory agents which induce mineralization leading tubule occlusion Symptom still persist- Root canal treatment / extraction .

87. DENTIN ADHESION

88. Introduction The concept of dentistry with the introduction of adhesives has changed from - Extension for Prevention to PREVENTION OF EXTENSION !!! Adhesion of restorative materials to enamel has become a routine and reliable aspect of modern restorative dentistry But adhesion to dentin has proved to be more difficult and less predictable. Much of the difficulty in bonding to dentin is the result of the complex microstructure and variable composition of dentin in different areas of the tooth.

89. The presence of water and organic components lower the surface energy of dentin and make bonding with hydrophobic resins essentially impossible Dentin is an intrinsically hydrated tissue, penetrated by a maze of 1- to 0.25- μ m-diameter fluid-filled dentin tubules. Dentin close to the pulp shows a higher tubule density than in dentin remote from the pulp. The higher the tubule density, the lower the bond strength values of the dentin adhesives

90. Dentin bonding agents Bonding agents can be defined as material of low viscosity, when applied on the tooth surface forms thin film after setting. This thin film strongly bonded to tooth surface, on which the viscous composite restorative resin is applied. This sets forming an integrated resin restoration.

91. FIRST GENERATIONS NPG-GMA, was the of first commercially available dentin bonding agent. ADHESION TO SMEAR LAYER SECOND GENERATION:- Introduced in 1970s and bonded chemically to either inorganic or organic components of dentin But they produced only limited bond strength (5-6 mpa) Examples:- Clear fill bonds system F scotch bond bond lite.

92. THIRD GENERATION Third generation attempted to deal with smear layer and dentinal fluid They employed two approaches:- Modification of smear layer to improve its property Or Removal of smear layer without disturbing smear plugs that occlude the dentinal tubules. The idea was to avoid aggressive etching of dentin because it cause pulpitis Eg:- Tenure, Scotch bond2

93. Role of water in bonding process Water acts as plasticizer for collagen and keeps it in a soft state If dentin is excessively dried it will lead to collapse of collagen network Critical amount of water is essential for bonding, that prevents the collapse of collagen network and allow expansion of dried dentin An over wet dentin decreases the bond strength and formation of blister like structure at the interface.

94. Most new adhesives utilize the ‘ wet bonding technique’. The ‘wet bonding’ has repeatedly shown enhanced bond strengths as water preserves the porosity of collagen network available for monomer interdiffusion.

95. Smear layer whenever tooth structure is prepared with a bur or other instrument, residual organic and inorganic components form a layer of debris on the surface of the substrate Smear layer fills the orifices of dentin tubules and form smear plugs and decreases dentin permeability by nearly 90%

96. Thickness of smear layer : 0.5-2 μ m Thickness of smear plug : 1-10 μ m COMPOSITION:- Iatrogenically produced smear layer is predominantly made of hydroxyapatite and altered denatured collagen. Altered collagen acquire gelatinised consistency due to friction and heat

97. CLINICAL CONSIDERATIONS The presence of intact smear layer is detrimental for bonding OPTIMAL DENTIN BONDING can take place by: a) Complete removal of smear layer prior to the bonding procedure by using etch and rinse adhesive b) Incorporation of smear layer into bonding layer by using self etch adhesives.

98. Smear layer in restorative dentistry Composite resin restorations Early bonding agents were hydrophobic and were bonded directly to dentin smear layer- Bond strength unsatisfactory. Newer bonding system leads to:- a) Complete removal of smear layer prior to the bonding procedure by using etch and rinse adhesive b) Incorporation of smear layer into bonding layer by using self etch adhesives .

99. Amalgam restorations Dentin smear layer are left in place for unbonded amlagam restorations It produces some degree of dentinal tubule sealing , although it is 25 % to 30% porous Halving the diameter of the opening produces a sixteen fold reduction in flow. Therefore the smear layer is very effective barrier.

100. smear layer in endodontics ADVANTAGES :- Reduction of dentin permability to toxins and oral fluids Reduction of diffusion of fluid and prevents wetness of cut dentin surface Bacterial penetration of dentinal fluid is prevented.

101. DISADVANTAGES It may harbour bacteria, either from original carious lesion or saliva, which may multiply taking nourishmaent from smear layer or dentinal fluid. Smear layer is permeable to bacterial toxins Smear layer itself is infected(Presence of bacteria) It blocks antimicrobial effect of intracanal medications and increases disinfecting tissue.

102. Presence of smear layer would necessitate use of higher concentration and/ or amount of anti bacterial agents. Act as a intermediate physical barrier, interfere with adhesive penetration of sealers(obturating material) with dentinal tubules Studies have shown better adhesion of obturation materials to the canal walls after removal of smear layer.

103. Effect of restorative materials CALCIUM HYDROXIDE Herman (1930) – Ca(OH)2 pulp capping The greatest benefit of Ca(OH)2 is the stimulation of reparative dentin bridge formation. Ex:- Pulpdent paste & Dycal

104. biodentin Biodentine is a new generation material based on calcium silicate synthesized by bioactive technology Biodentine stimulates release of TGF- β from pulpal cells, stimulating reparative dentin formation in a very short period of time.

105. COMPOSITE COMPOSITE Shrinkage during polymerization may induce internal stresses on dentin and create voids that may lead to cuspal fracture and microleakage

106. Effect of remaining dentin thickness

107. Type of restoration Shallow RDT >2mm Moderately deep RDT(>0.5-2mm) Deep RDT <0.5mm Silver amalgam varnish Base –e.g. zinc phosphate , zinc polycarboxylate Calcium hydroxide (sub base) with base Glass ionomer cement Not required Not required Calcium hydroxide as liner Composite resin Dentin bonding agent Dentin bonding agent Calcium hydroxide as liner followed by GIC as base Cast restoration Base Calcium hydroxide as liner with base over it

108. Effect of operative procedures on dentin It is known that if 1mm.sq. of dentin is exposed 30,000 living cells are damaged. So, it is advisable to seal exposed dentin surface with non-irritating and insulating materials. Preparation with rotary instruments is likely to injure the odontoblastic layer. Owing to dehydration of the tubular content, odontoblasts may even be sucked into the dentinal tubules.

109. Heat produced during deep cavity preparation causes loss of odontoblasts or their aspiration into the dentinal tubules. Thus, a coolant should be used while cutting dentin. Dessication during cavity preparation has long been known to cause aspiration of odontoblastic nuclei into dentinal tubules.

110. Effect of Periodontal disease Periodontal diseases cause attachment loss exposing the root surface to the oral cavity which may lead to dentinal hypersensitivity.

111. If tetracycline is given in the period of pregnancy or during the development of tooth, Then stains are likely to be developed in the line related to the dentinal curvature.

112. Refrences Ten cate oral histology (development structure and function)- 5 th edition. Orban’s oral histology and embryology- 13 th edition. Oral anatomy,histology and embryology : berkovitz. Shafer’s textbook of oral pathology- 7 th edition. Sturdevent’s art & science of operative dentistry- 5 th edition. Grossman – 13 th edition Cohen pathology of the pulp 10 th edition.

113. THANK YOU