Dental caries- etiology clinical features histopathology and caries activity test

Dental Caries-its etiology, clinical features , histopathology and caries activity test.
Presented by: Binaya Subedi

1. DENTAL CARIES

2. Contents Introduction. Classification of dental caries. Etiopathogenesis of dental caries. Clinical features of dental caries Histopathology of Caries Caries Activity Test Conclusion

3. Definition Dental caries is defined as an“irreversible disease of calcified tissues of teeth, characterized by demineralization of the inorganic portion and destruction of the organic substance of the tooth, which often leads to cavitations”. - Shafer, Hine and Levy Dental caries is an infectious microbiologic disease that results in localized dissolution and destruction of the calcified tissues of the teeth. Caries is episodic with alternating phases of demineralization and remineralization .

4. LETS REVIEW OUR CLASSIFICATION OF DENTAL CARIES

5. Gv black classificatio . G.V. Black’s method of the Classification of Dental Caries refers 1.location decay 2.type of preparation needed to restore the tooth 3.name for the final restoration for patient care, 4.insurance reporting, documentation 5.treatment planning and communication with your instructors, peers and future co-workers.

6. Class I LOCATION: PIT & FISSURE AREAS OF: INCISORS- MAXILLARY LINGUAL PREMOLARS- OCCUSAL MOLARS- OCCUSAL FACIAL LINGUALS

7. Class II LOCATION: PROXIMAL SURFACES PREMOLARS: MESIAL DISTAL MOLARS: MESIAL DISTAL

8. Class III LOCATION: Proximal surfaces that DO NOT involve the incisal line angle. INCISORS- Mesial & Distal Canines- Mesial & Distal

9. Class III LOCATION: Proximal surfaces that DO NOT involve the incisal line angle. INCISORS- Mesial & Distal Canines- Mesial & Distal

10. Class IV LOCATION: Proximal Surfaces Involving the incisal line angle. INCISORS: Mesio-incisal, MI Disto-incisal, DI CANINES: Mesio-incisal, MI Disto-Incisal, DI

11. CLASS V LOCATION: CERVICAL 1/3 OF ALL TEETH (Does not include pit & fissure areas)

12. Class VI LOCATION: Incisal Edges of all anterior teeth and cusp tips of all posterior teeth.

13. 1.BASED ON ANATOMICAL SITE OCCLUSAL (PIT AND FISSURE) ROOT CARIES SMOOTH SURFACE CARIES (PROXIMAL AND CERVICAL CARIES ) LINEAR ENAMEL CARIES

14. PIT AND FISSURE CARIES: clinical features

15. Clinical Features: appears brown or black feel slightly soft catch a fine explorer point

16. Clinical Features: lateral spread of caries at DEJ penetration into dentin along dentinal tubules may be extensive without fracturing away overhanging enamel

17. In cross section, the gross appearance of pit and fissure lesion is inverted V with a narrow entrance and a progressively wider area of involvement closer to the DEJ.

18. Smooth surface caries Non cavitated : Intact surfaces:use of explorer to judge the surface Opacity of surface enamel Radiolucency Marginal ridges is not discolored

19. Non-cavitated carious lesion ENAMEL DENTIN

20. Cavitated Surface broken:detected visually and tactilely Opaque area in dentin on transillumination Discolored marginal ridges radiolucency

21. Lesion have a broad area of origin and conical, or pointed extension towards DEJ . V shape with apex directed towards DEJ. After caries penetrate the DEJ softening of dentin spread rapidly and pulpally

22. ROOT SURFACE CARIES also known as cemental caries involves both dentin + cementum in number of people exhibiting gingival recession with clinical exposure of cemental surface

23. Clinical Features: slowly progressing chronic lesion usually found in mandibular molar area + premolar region gingival recession is associate with root surface caries

24. 2.BASED ON PROGRESSION ACUTE CARIES CHRONIC CARIES ARRESTED CARIES

25. ACUTE CARIES Rapid process Involves a large number of teeth. light brown or grey, and their caseous consistency makes the excavation difficult . Pulp exposures and sensitive teeth are often observed As saliva does not easily penetrate the small opening to the carious lesion,shows little opportunity for buffering or neutralizaton

26. CHRONIC CARIES long-standing lesion involvement,affect a fewer number of teeth , Pain is not a common feature because of protection afforded to the pulp by secondary dentin The decalcified dentin is dark brown and leathery . The lesions range in depth and include those that have just penetrated the enamel.

27. ARRESTED CARIES :- stationary or static caries No tendency for further progression Both deciduous and permanent affected Arrested caries involving dentin shows a marked brown pigmentation and induration of the lesion [the so called ‘ eburnation of dentin ’]

28. Exclusively seen in caries of occlusal surface with large open cavity in which there is lack of food retention Also on the proximal surfaces of tooth in cases in which the adjacent approximating tooth has been extracted Sclerosis of dentinal tubules and secondary dentin formation commonly occur

29. Etiology: due to nursing bottle containing milk or milk formula, fruit juice or sweetened water sometimes it occurs due to sugar or honey-sweetened pacifier Nursing bottle caries

30. Clinical Feature: prolonged feeding beyond usual time may result in early + rampant caries early carious involvement of maxillary anterior, maxillary + mandibular 1 st , permanent molars, mandibular canines carious process is so severe that only root stumps remain

31. suddenly appearing widespread resulting in early involvement of pulp Rampant caries

32. Etiology: may be due to nutritional deficiency Malnutrition emotional disturbances

33. Clinical Features: occurs in children with poor dietary habits extensive inter-proximal + smooth surface caries

34. Nursing bottle caries Vs Rampant caries Specific form of rampant caries Acute, widespread caries with early pulpal involvement of teeth that are usually immune to decay Primary dentition affected Both dentitions affected C/F: specific pattern- maxillary incisor molars Mandibular incisors not affected Rapid appearance of new lesions Mandibular incisors also affected

35. 4. BASED ON EXTENT OF CARIES INCIPIENT CARIES OCCULT CARIES CAVITATION

36. INCIPIENT CARIES The early caries lesion, best seen on the smooth surface of teeth, is visible as a ‘ white spot ’. Histologically the lesion has an apparently intact surface layer overlying subsurface demineralization . Significantly may such lesion can undergo remineralization and thus the lesion per se is not an indication for restorative treatment

37. These white spot lesion may be confused initially with white developmental defects of enamel formation , which can be differentiated by their 1. position away from the gingival margin 2.shape [unrelated to plaque accumulation ] 3.symmetry [they usually affect the contralateral tooth ]

38. 5.Based on tissue involvement Initial caries Superficial caries Moderate caries Deep caries Deep complicated caries

39. Initial caries : Demineralization without structural defect. This stage can be reversed by fluoridation and enhanced mouth hygiene Superficial caries (Caries superficialis ) : Enamel caries, wedge-shaped structural defect. Caries has affected the enamel layer, but has not yet penetrated the dentin.

40. 3. Moderate caries (Caries media ): Dentin caries. Extensive structural defect. Caries has penetrated up to the dentin and spreads two-dimensionally beneath the enamel defect where the dentin offers little resistance.

41. 4. Deep caries ( Caries profunda ) : Deep structural defect. Caries has penetrated up to the dentin layers of the tooth close to the pulp. 5. Deep complicated caries (Caries profunda complicata ) : Caries has led to the opening of the pulp cavity ( pulpa aperta or open pulp).

42. 6.BASED ON PATHWAY OF CARIES SPREAD 1.FORWARD CARIES 2.BACKWARD CARIES Caries cone in enamel is larger or same sized as present in dentin Spread of caries along DEJ to enamel

43. 7.BASED ON NUMBER OF TOOTH SURFACE INVOLVED Simple Compound Complex A caries involving only one tooth surface A caries involving two surfaces of tooth A caries that involves more than two surfaces of a tooth

44. 8.BASED ON SURFACES TO BE RESTORED Most widespread clinical utilization O for occlusal surfaces M for mesial surfaces D for distal surfaces F for facial surfaces B for buccal surfaces L for lingual surface Various combinations are also possible, such as MOD –for mesio - occluso -distal surfaces.

45. 9.World health organization (WHO) system In this classification the shape and depth of the caries lesion scored on a four point scale D1. clinically detectable enamel lesions with intact (non cavitated ) surfaces D2. Clinically detectable cavities limited to enamel D3. Clinically detectable cavities in dentin D4. Lesions extending into the pulp

46. ETIOLOGY No universally accepted opinion for etiology of dental caries. There are several theories and references, including early theories attemping to explain dental caries. THE EARLY THEORIES ARE: Exogenous theory Endogenous theory The lengends of worm 1.Humoral theory Chemical theory 2.Vital theory Parasitic theory

47. Exogenous theories The Legend of worms : 5000 B.C. By Ancient Sumerian This theory gives an idea that the caries is caused by worms possibly prevalent for long period of time. Fed on the root of jaws

48. Chemical theory : Parmly in 1820s proposed that caries is caused by unidentified “ chymal agents” . And it was supported by Robertson(1835), who proposed that caries was caused due to fermentation of food particles around the teeth.

49. Parasitic theory: Erdl introduced the relation of microorganism as a causative agent of tooth decay . Ficnus attributed dental caries as “ Denticolae ” Laber and Rottenstein said that dental caries initiate as chemical process but living microoraganism continue the disintegration of enamel and dentin.

50. Clark, Tomes, Magitot concurred that bacteria is essential for caries altough they are exogenous sourse of acids. Underwood and Miller presented a septic theory with hypothesis that the bacteria feeding on the organic fibrils of dentin leach out acids which causes decalcification

51. Endogenous theories (1) Humoral Theory Greek physicians, as dental caries was thought to be produced by internal actions of acids and corroding humors . 4 humors of body blood phelgm black bile yellow bile `

52. (2) Vital Theory Greek physicians such as hippocrates , celsus , and Galen proposed the vital theory of tooth decay which postulated that tooth decay is originated like a bone gangrene, from within the tooth itself.

53. Many theories have been proposed but only THREE have stood the test of time 1. Miller’s Chemico – parasitic theory or the acidogenic theory 2. Proteolytic theory 3. Proteolysis - chelation theory

54. I. Miller’s CHEMICO-PARASITIC THEORY W.D.Miller states “Dental decay is a chemico - parasitic process consisting of two stages: decalcification of enamel, which results in its total destruction the decalcification of dentin as a preliminary stage followed by dissolution of the softened residue as a subsequent stage”.

55. The acid causing decay was derived from fermentation of starches and sugars lodged in the retaining centers on teeth. He incubated a mixture of bread, meat and sugar with saliva at body temperature . It produced enough lactic acid within 48 hours to decalcify sound dentin.

56. In his hypothesis, Miller assigned essential roles to 3 factors – 1. Carbohydrate substrate 2. Acid which caused dissolution of tooth minerals 3. Oral micro organisms which produce acid and also cause proteolysis.

57. Factors that causes decay are: ROLE OF CARBOHYDRATES : - fermentable carbohydrates are responsible for increased caries incidence. Cariogenic carbohydrates are dietary in origin Also, whatever is present, is bound to salivary proteins and thus not available for microbial degradation.

58. Cariogenicity of carbohydrate varies with: (1) frequency of ingestion (2) physical form (3) chemical composition (4) route of administration (5) presence of other food constituents

59. (1) Frequency of ingestion: taken repeatedly in between two major meals. provides constant supply of carbohydrate to plaque bacteria for fermentation + production of acids. Meals high in fat, proteins and salts reduces retentiveness of carbohydrates. Refined pure carbohydrates are more cariogenic BACTERIA +SUGAR+ TEETH – ORGANIC ACIDS=CARIES

60. (2) Physical form: sticky, solid carbohydrates, soft retentive foods are cleared slowly. Monosaccharides and polysaccharides are more prone to caries production.

61. (3) Chemical composition: In the form of glucose, sucrose + fructose, sugar alcohol, sorbitol and mannitol . due to low molecular weight rapidly diffuse into plaque make themselves easily available for fermentation by plaque bacteria

62. (4) Route of administration: oral intake of sticky food.

63. (5) Presence of other food constituents: refined pure carbohydrates more caries producing

64. 2. ROLE OF MICROORGANISMS : - Two gram positive coccal bacteria have been implicated in dental caries – L.acidophilus and S.mutans . different types of bacteria causes “initiation” of caries and a completely different species of bacteria causes “progression” of caries. diet – bacterial interaction is involved in producing root and coronal caries.

65. (2) Role of microorganisms Initiation of Dental Caries Progression of Dental Caries Streptococci S. mutans S. milleri S. mitior S. sanguis S. salivaris Streptococcal species: Streptoccal species in deep dentinal caries and root caries Lactobacilli L. acidophillus L. casei Lactobacilli in dentin L. acidophillus L. casei Actinomycoses A. viscosus A. naeslundii Actinomycoses A. Israeli A. odontolyticus

66. Streptococcus mutans First isolated by CLARKE Catalyses gram – ve and gram + ve cocci . Characteristically synthesizes insoluble polysaccharides from sucrose. Homofermentative and more aciduric

67. Infants are more likely to be affected Contains eight serotypes “a” to “h” Specific antigen for each serotypes represents the cell constituents which has been isolated and characterised as polysaccharides.

68. S. mutans polymerises the glucose and fructose moieties of DIASACCHARIDES sucrose. Glucosyl transferase fructosyltransferases Glucose moieties Fructose moieties Glucans Fructans

69. Glucans Homopolymers Dextran Mutans Mutans is an important contituents for fibrillar plaque matrix and are more resilient to enzymatic attacks . Also acts as an diffusion barrier which affects the diffusion of acids out of plaque and transport of metabollites and salivary buffer into the plaque.

70. Fructans Soluble polymer of sucrose which can be degraded by plaque bacteria Thus, serves as fermentable sugar for oral bacteria

71. S. Mutans strains stored glycogen amylopectin that acts as reservior of substrate and increses metabollic activity Both extracellular and intracellular polysaccharides acts as substrate reserviors which the organisms utilises for enerygy productions. Hence, causes the survival of organisms and incresed potential lactic acid productions by glycolysis well beyond meal time

72. Sucrose adapted S. mutans posseses invertase activity Invertase is activated by inorganic phosphate which is coupled by acid production Hydrolyses sucrose intracellularly into free fructose and glucose and regulates the sucrose degradations.

73. Lactobacilli : Gram + ve non spore forming rods Acidogenic and aciduric Produces lactic acids

74. Other actinomyces Gram + ve , filamentous organisms Facultative anaerobes: 1. A. naeslundii 2. A. viscosus Strict anaerobes: 1. A. israelii 2. A. odontolyticus Actinomyces and Rothia species are predominantly found in human dental plaque.

75. Early studies implies that gram + ve cocci and gram + ve pleomorphic rods causes dental caries predominently Along with the significant variations in microbial flora associated with pit and fissures caries, smmoth surface caries, root caries, deep dentinal caries. Human dental caries as well as several microbial factors influences the formation,composition and metabolism of dental plaque. In past, total plaque was pathological structure which had to be eliminated after prevention of caries

76. Recent studies indicates that the qualitative nature of the flora in plaque determines the metabolism and potential of dental caries The above view is termed as SPEFCIFIC PLAQUE HYPOTHESIS given by LOESCHE,1982 Which states that most of the carious lesion are due t specific bactrial species Suggests that cariogenesis is a specific bacterial infection and methods implemented for its elimination are more than just reduction of total plaque

77. 3. ROLE OF ACIDS : - Acids are produced by enzymatic breakdown of sugars by cariogenic bacteria. Acids are – Lactic acid mainly and butyric acid to some extent. production of acid must be localized and retained on the tooth surface for it to cause the caries. Its accepted that dental plaque does this.

78. 4. ROLE OF DENTAL PLAQUE :- Plaque defined as a soft, unmineralized , bacterial deposit or biofilm which forms on teeth and dental prostheses that are not adequately cleaned. Resists cleansing by physiological oral forces like salivary washing and tongue movements but is removable by tooth brushing.

79. Considered as a contributing factor for at least initiation of caries. However mere presence of dental plaque doesn’t necessarily mean caries will occur.

80. COMPOSITION OF DENTAL PLAQUE : Water – 80% Solids – 20% Dry weight of plaque composed of Bacterial & Salivary proteins - 50% Carbohydrates & Lipids - 25% Inorganic ions, mainly Ca ++ & Po4 --- - 10%

81. CLASSIFICATION OF DENTAL PLAQUE : Plaque classified as – SUPRAGINGIVAL & SUBGINGIVAL. Supragingival plaque – essential role in causing caries, while subgingival plaque – role in periodontal diseases.

82. MECHANISM OF FORMATION : Plaque formation proceeds through following stages Deposition of a cell free layer, ACQUIRED PELLICLE which is derived from salivary glycoproteins . This layer acts as nutrient for plaque bacteria.

83. 2. Colonization of pellicle by Gram positive bacteria like S.sanguis and S.mutans within 24 hours. 3. Maturation of plaque by further colonization with filamentous and other bacteria. Also there is build up of plaque substance by polysaccharides produced by plaque bacteria.

84. In contrast to acidogenic theory, this theory postulated by Gottleib , Diamond and Applebaum states that caries is essentially a proteolytic process the organic or protein elements like enamel lamellae, rod sheath etc are the initial pathway of invasion by microorganisms.

85. OBJECTIONS TO THE HYPOTHESIS : - 1. Unable to explain predilection of specific sites on tooth to caries. 2.Initiation of smooth surface caries not explained. 3.Unable to explain why some populations are caries free and some are caries prone. Note : accepted by majority in unchanged form. bulk of evidence DOES implicate carbohydrates, acids and Microorganisms.

86. ii. The proteolytic theory In contrast to acidogenic theory, this theory postulated by Gottleib , Diamond and Applebaum states that caries is essentially a proteolytic process. the organic or protein elements like enamel lamellae, rod sheath etc are the initial pathway of invasion by microorganisms. As a proof of principle, it has been established that enamel contains approximately 0.56% by weight of organic matrix.

87. OBJECTIONS TO THE THEORY : - Out of 0.56% of organic matrix, 0.18% is Keratin. However, no enzyme systems capable of attacking keratins have been isolated so far. Studies in germ free rats have shown that caries can occur in the absence of proteolytic organisms. However, even though proteolysis may not play any role in initiation of caries, their role in progression of more advanced carious lesions cannot be ruled out.

88. III. PROTEOLYSIS – CHELATION THEORY Schatz et al in 1955 proposed that caries occurred as a result of simultaneous degradation of organic substances (Proteolysis) and dissolution of tooth minerals by a process called Chelation .

89. Chelation is a process of complexing of a metallic ion to a complex substance through a co-ordinate covalent bond resulting in a highly stable, poorly dissociated ionized compound. Examples are – Chlorophyll molecule in green plants where 4 pyrrole nuclei are linked to magnesium and Hemoglobin where 4 pyrrole nuclei are linked to iron.

90. According to this theory, the initial attack on the tooth is on the organic components of enamel. Breakdown products of the proteolysis have chelating properties which form chelates with mineralized components of enamel and thereby decalcify the enamel even in neutral or even alkaline pH.

91. OBJECTIONS TO THIS THEORY : - Direct evidence for proteolysis – chelation as a mechanism for causing caries is lacking. Recent studies have shown that saliva as well as plaque do not contain substances in sufficient concentrations to chelate calcium from enamel. However, although chelation may not be actually responsible for initiating caries, it may still have some role to play in advanced carious lesion where the pH levels return to neutral.

92. Current etiology of dental caries saliva caries Time

93. The caries environment: etiological factors Saliva Diet Hard tissue ultrastructure Role of plaque in etiology of d ental caries

94. Saliva Bathes the tooth surface. Vehicle for solubilizing and transporting media for various substances Cleansing property Clear the acids produced by microorganism Buffering property Maintenance of pH

95. Mandel and colleagues & mandel and bennick Could not observe differences between caries active & caries resistant individuals when analysing salivary proteins and acidic PRPs, respectively. Vitorino & colleagues Used spectrometer Strong correlation between presence of phosphorprotein and absence of caries Phosphoprotein could contribute to more effective remin . Process.

96. Recently , Rundney and collegues They identified statherin and cystatin as predictors of occlusal caries. Increased level is associated with high rates of remineralisation. More research is needed to verify

97. Diet Dental caries and fermentable carbohydrate From etiology basis, it is still remain the main driver of caries process. Consideration on Retentiveness of food Presence of protective factors Type of carbohydrate Complex Simple

98. Cariogenic properties of carbohydrates

99. In previous study it has been shown that enhanced demineralization is associated with s.mutans . This was attributed to alteration of diffusion properties of plaque owing to presence of water insoluble extracellular matrix material synthesized from sucrose.

100. Tooth Host factor involved in caries process are location, morphology, composition, and posteruptive maturation . Enamel is composed of mainly hydroxyapatite crystals, but should not be considered as pure hydroxyapatite. Chemically it is Ca10(PO4)2(OH)2 More resistant to caries challenges Less stable, susceptible to demineralisation

101. Dental caries is a consequence of an imbalance in resident microflora due to enrichment within microbial community of potentially more cariogenic bacteria due to frequent conditions of low pH in plaque biofilms.

102. Chemistry of dental caries: reminerlaization & demineralization events Dental decay: demineralization of tooth surface goes beyond the mineral exchange Mineral exchange-? It occur regularly between tooth surface and surrounding environment From mechanistic aspect: From clinical point of view:

103. Dynamic changes in Tooth surface “not all mineral loss from tooth structure” is part of pathologic process. Tooth surface is a dynamic: Periods of remineralisation (mineral gain) and demineralization (mineral loss) Particularly in surfaces covered by stagnant biofilms.

104. Post-eruptive maturation: Enamel-porous, Carbonate, water, Mg etc Remin and demin less porous, decreased content

105. Undersaturaiton :

106. Change in pH and its role in dental caries Acidogenic bacteria in dental plaque rapidly metabolize fermentable carbohydrates producing acidic end products. In the mouth, these changes over time in response to a challenge (usually a cariogenic food) are known as Stephan responses or Stephan curves.

107. Supersaturation Although pH is strongest determinant for saturation level leading to demineralisation / remineralisation remain under clinical conditions

108. Several factor affect this process: Saliva flow Intrinsic buffering capacity Urea- prevent fall in pH Urea converted to ammonia by urease Arginine- deaminase system Gorden at al found significantly higer level of urease activity in plaque in caries free subjects compared with caries active.

109. Carious lesion formation

110. Subsurface lesion Consequences

111. At some point , that three dimensional structure of a lesion is not able to withstand the stress created by external forces coming from mastication , bruising etc. , and surface collapses , crating an irreversible cavitation.

112. DENTAL CARIES Simply,carious process is basically demineralization of inorganic portion and destruction of organic substance of teeth. There are different methods to study dental caries:- .Ground section .Microradiography . Histochemistry and radioisotopes For the study of enamel caries in microscopic examination,ground section is used that are usually between 60-100   μ m .

113. For ease understanding histopathology of caries is describe under the general heading of caries of enamel,dentin and of cementum .

114. Enamel Caries Caries of Enamel progress through following stages: Early submicroscopic lesion. Phase of nonbacterial enamel crystal destruction. Cavity Formation. Bacterial invasion.

115. Earliest macroscopic evidence of smooth surface caries; Areas of decalcification beneath dentalplaque,resemble smoothy ‘chalky white’ surface. It is best observed in extracted tooth.

116. It forms a triangular or cone shape with apex at junction and base toward smooth surface.

117. In early pits and fissure caries,on both side of fissure wall the visual changes occurs like yellow or brown discoloration. Also enamel begin thin in base of pits and fissures,dentin involvement occurs much earlier.

118. Pits and fissure caries does not differ in nature from smooth surface caries except it have variation in anatomical and histologic structure .

119. FEATURES OF ENAMEL CARIES: -In electron microscope of enamel caries,there is loss of interrod or interprismatic substance which result in increase prominence of enamel rods. -And due to roughening of rod,more suspectible to acid attack. - Enamel rod organic substance is made up by mucopolysaccharide which undergoes degradation in early caries process.

120. -Changes occur as appearance of transverse striation of enamel rod because of segmental demineralization occur. - Another changes in early carious lesion is accentuation of incremental line of Retzius .

121. -This appearance of calcification lines,which occur due to loss of mineral due to carious process and organic structure are more prominent. - There may also be accenutation of perikymata .

122. HISTOPATHOLOGY OF ENAMEL CARIES Before the complete disintregration of enamel several zones can be appericated starting from the advancing end of lesion. Under lightmicroscope,four zone are clearly distinguished; These zones are: 1 )A translucent zone 2 ) Dark zone 3)The body of carious lesion 4 )Surface layer

123. ZONE 1: THE TRANSLUCENT ZONE Is present in advancing front or end of enamel lesion. Occurs due to formation of submicroscopic pores at enamel rod boundaries and striae of Retzius . Seen in longitudinal ground section with transmitted light after imbibition with quinolone(RI=1.62)

124. This zone is slightly more porous than sound enamel having a pore volume of 1% than 0.1% of normal enamel. No evidence of organic matter,no evidence of protein loss seen.And is structureless .

125. ZONE 2:THE DARK ZONE Lies adjacent and superficial to translucent zone. Appears dark brown in ground section under transmitted light due to demineralization. P ositive birefringence in contrast to sound enamel ,with polarized microscope after imbibition with quinolone. Positive zone,it is always present.

126. Relatively small pores.(get fills with air & become dark,may penetrate water .) Pore volume is 2-4%. Increased porosity in this zone is due to greater degree of demineralization in this zone . Micropore system.

127. ZONE 3:BODY OF LESION Between unaffected surface and dark zone. Area of greatest demineralization, having a pore volume of 5% near the periphery to about 25% in the center of intact lesion . Imbibition with quinolone and under transmitted light,body appears translucent compared with sound enamel.

128. Section examined with polarized light after water imbition :-show positive birefringence compared to sound enamel. 24 % of mineral is loss and have increased unbound water and organic content due to ingress of bacteria and saliva.

129. ZONE 4:THE SURFACE ZONE This zone not only remains intact during the early stages of attack by caries, but also remains more heavily mineralized. This zone is demineralized by the time caries penetrates dentin. Quantitative studies of this zone shows—partial demineralization about 1-10% loss of mineral salt has taken.

130. Pore volume is less than 5% of spaces . Positive birefriengence pourous subsurface zone . Negative birefriengence when examined with water.

131. HISTOPATHOLOGY OF DENTINAL CARIES

132. Early dentinal changes Initial penetration of dentin by carious lesion causes,dentinal sclerosis or transparent dentin . Formation of sclerotic dentin is minimal in rapidly advancing caries and is most prominent in slow chronic caries.

133. It appear dark in reflected light and transparent in transmitted light. In early dentinal caries,carious lesion appear as triangular shape ; with base at dentino -enamel junction , and apex toward pulp.

134. HISTHOPATHOLOGY OF DENTINAL CARIES

135. In early cases of dentinal caries, Zone 1 : FATTY DEGENERATION OF TOMES FIBERS - Apperance of fatty degeneration in odontoblastic process,with depostion of fat globules which precedes early sclerotic changes. - Demonstarated by special stain-Sudan Red which selectively stain fats. -Significance Fat contribute to impermeability of dentinal tubules. Predisposing factors favouring dentinal sclerosis.

136. ZONE 2 SCLEROTIC DENTIN: -There is a reaction of the vital dentinal tubules & vital pulp which lay down a calcific barrier(dentinal / transparent dentin) -This barrier protect from further invasion of microorganisms . -This zone is minimal in rapidly advancing lesion and prominent in slow progressive lesion .

137. -Sclerotic dentin appear white in transmitted light and dark in reflected light.

138. ZONE 3: DECALCIFICATION OF DENTINAL TUBULES -Appears above of dentinal sclerosis. -Initial decalcificaton only in wall of Dentinal tubules . - Even before carious process become evident clinically,few bacteria are found penetrating the dentinal tubules,termed as ‘Pioneer bacteria ’. -Study reveals that inidivual tubules show pure form of bacteria.

139. ZONE OF MICROBIAL INVASION: -Closer examination reveals dentinal tubules packed with microorganisms. Acidogenic Organism in early caries causes decalcification of tubules. Proteolytic organism prominent in deeper layer. - Supporting the hypothesis that initiation and progression are two distinct processes and must be differentiated.

140. ADVANCED DENTINAL CARIES: -Further decalcification of individual wall of dentinal tubules lead to their confluence. -Increase in diameter of dentinal tubules due to packing of microorganism. -Tiny ‘liquefaction foci’ or ‘Miller foci of liquefication ’form due to breakdown of dentinal tubules.

141. This foci is ovoid area of destruction ,parallel to course of tubules and filled with necrotic derbis .

142. -Initial decalcification by acidogenic organism. - Martix destruction by proteolytic organism . -Dentin become ‘Leathery’ consistensy .

143. -The caries extend to right angles to dentinal tubules and parallel to contour lines of dentin,thus resulting the clefts.

144. SECONDARY DENTINAL INVOLVEMENT: -The carious process is same as in primary dentin but the process is slower because; dentinal tubules are fewer in number. and more irregular course,thus delaying the penetration of invading organisms.

145. -But sooner or later,the involvement of pulp results with ensuing inflammation and necrosis. - Occasionally caries will spread laterally at junction of primary and secondary dentin and produce separation between two layer.

146. CARIES ACTIVITY TEST : Caries activity refers to the increment of active lesions(new or recurrent lesion) over a slated period of time. Caries susceptibility refers to the inherent tendency of the host and target tissue,the tooth to be afflicted by the caries process.

147. Caries activity measures the degrees to which the local environment challenge (e.g. dietary effect on microbial growth and metabolism) favors the probability of carious teeth.

148. Caries activity test helps to: Identify high-risk groups and individuals. Determine the need for personalized preventive measures and motivate the individual. Monitor effectiveness of oral health programs by establishing an initial baseline level of cariogenic pathogens as a basis for future evaluation. Ensure low level of caries activity before starting any extensive restoration procedure.

149. Lactobacillus (LB) Colony Test -Oldest and most widely used method. -First proposed by Hadley, Principle involved :- -Measures the aciduric bacteria in a patient’s saliva by counting the number of colonies. -Patient saliva was inoculated with selective media (Tomato peptone agar plates) with pH 5.0 was used and incubated.

150. - Rogosa’s Medium is an improved selective media that is highly selective growth for Lacto bacillus. -It is the medium with an acidic pH having high amount of acetate,salts and lower surface tension and which is inoculated with patient saliva and incubated.

151. - -The colonies grown on media upon incubation reflect the number of aciduria flora in patient saliva. -The number of lactobacillus/ml saliva of is calculated by multiplying the number of colonies.(CFU/ml)

152. Colorimetric Synder Test -Developed by Synder in 1951. Principle:- -Measures the ability of salivary microorganisms to form organic acids from carbohydrate medium. -Based on rate of acid produced when stimulated patient saliva is inoculated in a glucose and agar containing medium with pH 4.7-5.0.

153. -The medium has colour indicator such as bromocresol green,which changes from blue green at pH4.7-5.0 to yellow at pH4.0 - It indirectly detect the presence of acidogenic and aciduric microorganisms .

154. -The acid produced by oral acidogenic flora is detected by change in pH indicator,and compared to un-inoculated control tube after 24,48 and 72 hours of incubation.

155. Tube 1:  Un-inoculated Synder tube Tube 2:  No color change indicates little or no susceptibility to forming dental caries Tube 3:  Sight color change indicates mild susceptibility to forming dental caries. Tube 4:  Significant color change indicates moderate susceptibility to forming dental caries. Tube 5:  Complete color change indicates high susceptibility to forming dental caries.

156. -Observation in Synder test:-

157. Swab Test -Principle is same as Synder test. -Both aciduric and acidogenic elements of oral flora are measured by recording the pH directly on a pH meter after appropiate incubation periods by employing a colour indicator in the test medium

158. -Test involves sampling the oral flora by swabbing buccal surfaces of teeth with cotton applicator and incubated in medium for 48 hours. -48 hours incubation is read on pH meter or colour change is read.

159. pH Caries activity pH 4.1 Marked pH 4.2 – 4.4 Active pH 4.5 – 4.6 Slighty active pH 4.6 and over Inactive

160. Salivary S.mutans Level test: S.Mutans constitute less than 1% of the total oral flora of plaques and these concentration may be extremely variable even from the same site. S.Mutans also ascertain its location on teeth or assess its degree of infection at a given site. It is also difficult to distinguish a carrier state from a cariogenic infection based on S.mutans .

161. Principle: The number of S.mutans forming units per unit volume of saliva is the fundamental basis of this test. Sites : Plaque is collected.For the plaque sample collection Pits & Fissure or from Proximal surface are more appropriate for detecting and quantitating S.mutans that have colonized on teeth. Sample is collected using tongue blades or wooden spatula

162. Media used : Mitis Salivarius Agar (MSA) a selective streptococcal medium with:- - increased concentration of sucrose (20%) and 0.2U bacitracin/ml - Bacitracin suppresses the growth of non S.mutans colonies. Then,Agar plates are incubated at 37 C for 48 hours 95% N 2- 5% CO 2.

163. Levels of S.mutans greater than 10^5 (100,000)are indicative of acceptable cariogenic challenge. -Because colonization does not occur until the level of S.mutans reaches 4.5x10^4/ml (45,000) for smooth surface and 10^3 (1000) of occlusal fissures. There is thus evidence for associating high S.mutans counts with caries activity.

164. S.mutans Dip Slide test This test classifies salivary samples according to estimates of S.mutans colonies growing on modified MSA. Media used: Modified Mitis Salivarius Agar(MSA) Stimulated saliva is collected for 5 minutes and is poured over the agar coated slide.

165. After slides are dry,bacitarian disk are placed in middle of inoculated agar of about 1cm diameter Slide is incubated in tube containing CO 2 tablet for 48 hours If present, S.mutans appears as small blue colonies growing with zone of inhibition .

166. Colonies density is compared with model chart and classified as 0 (negligible) 1(less than 100,000) 2 ( 100,000-1,000,000) 3(more than 1,000,000)

167. Salivary Reductase Test The activity of Salivary reductase enzyme present in salivary bacteria is measure in this test. Salivary reductase test measure the rate which the indicator molecule diazoresorcinol changes from blue to red to colourless or whitish on reduction by mixed with salivary flora.

168. No incubation period is required and caries conduciveness reading is taken in 15 minutes. Some investigator have concluded that this test does not give accurate results and may not be of diagnostic value.

169. The interpretation of these laboratory test are more reliable with good clinical assessment. None of these caries activity test are comprehensive or reliable of expected dental caries activity. The combined use of several selected test is best predictor of expected caries. Thus Caries activity test provides indirect evidence that an aciduric and acidogenic flora is associated with the development of dental caries.

170. -References: Shafrer’s Textbook of Oral Pathology. Operative dentistry Wikipedia

171. Conclusion The caries process can be understood in very simple terms as being the result of acids generated by dental biofilm from dietary fermentable carbohydrates causing demineralization of tooth mineral and ultimately leading to a caries lesion. However , the complex and dynamic environment created by various contributing factors must be taken into account to fully understand the caries disease process.

172. References : Shafer ‘Textbook of Oral Pathology ’ Sturdevant ‘Art and Science of Operative Dentistry ’