Dental Caries Oral Pathology Question And Answers

Dental Caries Question And Answers

Question 1. What is the definition of dental caries?
Answer. Dental caries is defined as a microbial disease of the calcified tissues of tooth, characterized by demineralization of the inorganic portions and destruction of its organic structures.

Question 1a.What is the cause of cavity information (cavitation) in dental caries?
Answer. It occurs due to lateral spread of caries along the dentinoenamel (DE) junction with undermining of overlying enamel.

Read And Learn More: Oral Pathology Short Notes Question And Answers

Question 2. What are the major theories of dental caries?
Answer.

• Acidogenic theory
• Proteolytic theory
• Proteolytic chelation theory
• Sucrose chelation theory
• Autoimmune theory.

Question 2a.Who proposed the acidogenic theory?
Answer. WD Miller.

Question 3. What is other name of acidogenic theory?
Answer.Miller’s chemicoparasitic theory.

Question 4. What is the basic principle of acidogenic theory?
Answer. According to this theory dental caries develops due to acids, which are formed by fermentation of dietary carbohydrates through oral bacteria cause progressive decalcifiation of the tooth structures with subsequent disintegration of the organic matrix.

Question 5. Describe the stages of tooth decay according to acidogenic theory.
Answer.

• Initial stage: Production of organic acids as a result of fermentation of carbohydrates by the plaque bacteria.
• Late stage: The acids produced in the initial stage cause decalcifiation of enamel followed by dentin and thereby cause total destruction of these two structures along with dissolution of their softened residues.

Question 6. Name the factors those contribute in the development of caries according to acidogenic theory.
Answer.

• Dietary carbohydrates
• Microorganisms
• Acids
• Dental plaque.

Question 7. Name the common cariogenic carbohydrates.
Answer. Carbohydrates which are readily fermentable types e.g. glucose, sucrose and fructose,etc. are cariogenic.

Question 8. Which one is the most potent cariogenic carbohydrate?
Answer. Among all types, sucrose is the most potent cariogenic carbohydrate.

Question 9. Does the nature of carbohydrate or frequency of its intake make any difference in cariogenicity?
Answer. Yes, the cariogenicity increases if—

• The dietary carbohydrate contains large amounts of sucrose
• The dietary sugar is sticky in nature
• Sugar is taken repeatedly in between two major meals.

Question 10. Name the different types of carbohydrates and describe their cariogenicity.
Answer.

Question 11. Why glucose, sucrose and fructose, etc are particularly cariogenic?
Answer. These carbohydrates, e.g. glucose, sucrose and fructose, etc. are rapidly diffused into the plaque due to their low molecular weight and therefore make themselves easily available for fermentation by the cariogenic bacteria.

Question 11a.Why starch is a relatively non-cariogenic carbohydrate?
Answer.

• Its fermentation is very slow
• Its large molecular size doesn’t permit its penetration into the plaque.

Question 12. What are xylitol, sorbitol, lactitol and mannitol, etc? Are they cariogenic?
Answer. These are sugar alcohols and are non-cariogenic.

Question 12a.What is aspartame?
Answer. It is a non-caloric sweetener.

Question 13. What are saccharin and aspartame? Are they cariogenic?
Answer. These are non-sugar sweeteners and are non-cariogenic.

Question 14. What are the principal carbohydrates available in human diet?
Answer. The principal carbohydrates available in human diet are sucrose and starches.

Question 15. What are in-between meals?
Answer. These are small meals often taken in between the principal meals.

Question 16. Why are ‘in-between’ meals dangerous for dental caries?
Answer. The in-between meals are often associated with higher caries incidence because of the following:

• These meals often contain higher amounts of sugar
• Proper mouthwash is not often done after consuming these meals
• These high-sugar meals help repeated acid productions in mouth and therefore keep the oral pH critically low.

Question 17. What is Stephen’s curve?
Answer. Stephen’s curve demonstrates the pH curves of plaque in response to repeated intake of sugars.

Question 18. Describe the nature of pH changes with repeated intakes of sugars according to Stephen’s curve.
Answer.

• After the first intake of sugar, the pH of the plaque falls to 4.5 to 5 within 1 to 3 minutes and it takes another 10 to 30 minutes to return to neutrality
• However, if sugar is taken again within 30 minutes, then the pH will fall further and it will take an even longer time to return back to neutrality. (This pH alteration is actually recorded with the help of a graph called Stephen’s curve).

Question 19. What Stephen’s curve indicates in greater sense?
Answer. It indicates the harmful effect of taking in-between meals with regard to the caries prevalence.

Question 20. Why sucrose is considered to be the most cariogenic carbohydrate?
Answer.

• Sucrose produces the maximum amount of acids after fermentation as compared to any other carbohydrate
• It helps in formation of ‘dextran’ with the help of S. mutans bacteria
• Its smaller molecules can diffuse readily into the plaque
• Sucrose also helps in the synthesis of intra cellular polysaccharides by cariogenic bacteria.

Question 20a.Why the enzyme glucosyl transferase is important in caries?
Answer. It helps in establishing S. mutans in dental plaque.

Question 21. What is dextran?
Answer. It is extracellular insoluble polysaccharide produced by cariogenic bacteria, mainly S. mutans.

Question 22. Name the three important factors required for synthesis of dextran.
Answer. There are three factors needed for synthesis of dextran, which are as follow:

• Presence of dietary sucrose.
• Presence of S. mutans bacteria in mouth
• Availability of enzyme glucosyl transferase.

Question 23. How dextran causes increased tooth decay by caries?
Answer. Presence of dextran defiitely increases the amount of tooth decay during caries:

• This extracellular polysaccharide is insoluble and sticky in nature; therefore can bind the plaque bacteria fimly on to the tooth surfaces
• It doesn’t allow the cariogenic bacterias to be removed or washed away easily from tooth surfaces
• It holds the acids produced by plaque bacteria on the tooth wall and make maximum demineralization
• It makes a barrier between the acids and the salivary buffering agents; and doesn’t allow the acids to be neutralized.

Question 23a.Are there any other polysaccharides produced besides dextran during caries?
Answer. Yes, other polysaccharides like levan and glucan are also produced in caries.

Question 23b.Do these polysaccharides levan and glucan increase caries risk as dextran?
Answer. These are weak and soluble polyssacharides and do not help much in bacterial adherence on tooth surface.

Question 23c.Why levan and glucan are weak polysaccharides?
Answer. They are not sticky like the dextran, can be easily washed away from the tooth surface.

Question 23d.What was the objective of the famous Vipeholm study on dental caries?
Answer.To find out the role of sticky and non-sticky form of carbohydrates of dental caries.

Question 24.What is the role of intracellular polysaccharides in caries?
Answer. The intracellular glucan like polysaccharides are produced by plaque bacteria with the help of sucrose; these polysaccharides are stored by the cariogenic organisms within their cells. These are metabolized into acids at the time of dietary restrictions of sucrose in future, so that caries can continue.

Question 25. Name the Streptococcal group of organisms which can cause caries.
Answer.

• Streptococcus mutans
• Streptococcus sanguis
• Streptococcus mitior
• Streptococcus salivarius
• Streptococcus milleri
• Peptostreptococcus.

Question 26.In the entire Streptococci group, which one is the most cariogenic?
Answer. Streptococcus mutans is the most potent among all cariogenic organisms.

Question 27. Why Streptococcus mutans is considered to be the most cariogenic bacteria?
Answer.

• S. mutans organisms are present in large numbers in normal saliva, always ready to attack the tooth as soon as suitable carbohydrates are available
• S. mutans produce acids from fermentation of sucrose, glucose and lactose, etc.
• It can survive at a pH as low as 4.2
• S. mutans can synthesize extracellular insoluble polysaccharide dextran; which helps in adhering plaque bacteria to the tooth surface to enable more tooth decay
• S. mutans can produce caries in a tooth even in laboratory environment
• It can adhere to acquired pellicle and thus facilitates in plaque formation
• Streptococcus mutans also has the ability to adhere and grow even on hard and smooth surfaces of tooth
• It helps in the synthesis of intracellular polysaccharides by the plaque bacteria.

Question 28. Name the lactobacillus organism which is cariogenic.
Answer. Lactobacillus acidophilus.

Question 29. Why these organisms are called acidophilus?
Answer. Because they exist comfortably in acidic environments.

Question 30. Name the actinomycotic group of organisms which are cariogenic.
Answer.

• Actinomyces israelii
• Actinomyces viscosus
• Actinomyces naeslundii.

Question 31. What is the signifiance of actinomycotic group of organisms in caries?
Answer. These organisms produce caries in the root portions of the teeth.

Question 32. Name the important acids, which are produced to cause tooth decay in caries.
Answer.

• Lactic acid
• Aspartic acid
• Butyric acid
• Acetic acid
• Propionic acid
• Glutamic acid.

Question 32a.Among these acids, which one is produced in maximum amounts in caries?
Answer. Lactic acid.

Question 33. How these acids are produced during caries?
Answer. During the process of caries formation, large varieties of these acids are produced in the oral cavity due to the bacterial fermentation of dietary carbohydrates.

Question 33a.How quickly the cariogenic bacterias can produce acid after ingestion of sucrose?
Answer. Within 3 to 5 minutes.

Question 34. What is so called the critical pH with reference to dental caries?
Answer. The pH of 5.5 at the tooth surface is called the critical pH; as any further drop in local pH below this level causes demineralization of tooth surfaces.

Question 35. At what pH subsurface demineralization of tooth starts?
Answer. When the local pH falls to about 5.0, subsurface demineralization is inevitable in the tooth enamel.

Question 36. What is subsurface demineralization?
Answer. When the enamel of tooth starts to demineralize deep to and below the surface layer, it is called subsurface demineralization.

Question 37.What type of caries clinically occurs due to subsurface demineralization?
Answer.The caries which occurs due to subsurface demineralization is called incipient caries,where the tooth surface appears intact but caries has already started in the deeper layers.

Question 38. During caries, what happens if the pH falls to as low as 3.0 to 4.0?
Answer. If the pH goes down to the level of 3.0 to 4.0, the surface enamel of tooth begins to demineralize directly and leads to cavity formation.

Question 39. When the pH of saliva can fall to as low as 3.0-4.0?
Answer.

• Consumption of high sucrose-containing sticky carbohydrate
• Repeated intake of in-between meals.

Question 40. Name the factors which determine the rate of acid demineralization of tooth in caries.
Answer.

Question 41. What is dental plaque?
Answer. Plaque is a thin, transparent fim produced on the tooth surfaces and it consists predominantly of microorganisms suspended in salivary mucins and extracellular bacterial polysaccharides (glucans).

Question 42. What is acquired pellicle?
Answer. Acquired pellicle is a component of the dental plaque, which is made by the salivary glycoprotein and is formed just prior to the bacterial colonization.

Question 43. Describe the stages of plaque formation.
Answer.

• On a clean tooth surface, fist there is deposition of cell-free structureless acquired pellicle
• Thickening of acquired pellicle due to further deposition salivary glycoproteins following bacterial stimulation
• Colonization of S. mutans and S. sanguis within 24 hours
• Progressive build-up of plaque substance by bacterial polysaccharides
• Colonization of fiamentus and other organisms as the plaque matures.

Question 44. What are the pioneering organisms of dental plaque?
Answer. There are some organisms such as S. sanguis, A. viscous, A. naeslundii, and Peptostreptococcus, etc. which are the fist to colonize the dental plaque (as early as one hour after the formation of acquired pellicle). Hence these organisms are called ‘pioneering organisms’.

Question 45. What is the caries producing ability of the so called pioneering organisms of dental plaque?
Answer. These organisms lack in caries-producing potential, since they are mostly aerobic in nature and produce very little amount of acid by fermentation of the carbohydrates.

Question 46. Describe the role of dental plaque in the initiation of dental caries.
Answer.

• It harbours the cariogenic bacteria on the tooth surface
  It supplies the carbohydrate needed for bacterial fermentation during caries formation
• Thick layer of plaque helps to hold the acids on to the tooth surface for a long duration
• Increased thickness of plaque also does not allow the acids to escape from the tooth surface
• Plaque even does not allow the acids to become neutralized as it does not allow the buffering agents from saliva to enter into it
• Continued sugar production from bacterial intracellular polysaccharides helps to maintain a low pH.

Question 47. What are the limitations of acidogenic theory of dental caries?
Answer.

• It cannot explain subsurface demineralization
• It fails to justify the rampant caries
• It cannot explain the caries in impacted tooth.

Question 48. What is the proteolytic theory of dental caries?
Answer. The proteolytic theory of dental caries states that the proteolytic enzymes liberated by cariogenic bacteria cause destruction of the organic matrix of enamel, following which the inorganic crystal structures of tooth easily disintegrate.

Question 49. Who fist proposed the proteolytic theory of dental caries?
Answer. The proteolytic theory of dental caries was fist proposed by Gotte lieb in 1944.

Question 50. How the theory was further extended by Pincus?
Answer. The concept of proteolytic theory was further extended by Pincus in 1949 and he proposed that the sulfatase enzyme liberated by gram negative bacilli hydrolyze the sulfated mucosubstances of enamel matrix and thereby liberate sulfuric acid, glutamic acid and aspartic acid, etc. which dissolve the mineral portion of the enamel.

Question 50a.According to proteolytic theory, how the bacterias take entry inside enamel?
Answer. Bacterias enter into enamel via the enamel lamella.

Question 51. Does the concept of proteolytic theory sound realistic?
Answer. The scope of the proteolytic mechanism in initiating the enamel caries is very limited;fist of all, not only the organic (protein) content of enamel matrix is very scanty but also the proteolytic organisms in the mouth are very uncommon. However, this mechanism can be a more appropriate one in cases of dentinal and cemental caries or root caries.

Question 52. How dental caries occurs according to proteolysis Chelation theory?
Answer. According to the proteolytic-chelation theory, dental caries occurs in three stages:

• Stage I—Proteolytic breakdown of the organic portion of the enamel matrix occurs by bacterial enzymes
• Stage II—A chelating agent is formed by the combination of proteolytic breakdown products, acquired pellicle and food debris, etc
• Stage III—Negatively charged chelating agent (mostly due to its protein content) releases the positively charged calcium ions (Ca++) from enamel or dentin via a process called “chelation”, and it eventually results in tooth decay.

Question 53. What is the process of chelation?
Answer. Chelation can be defied as a process that involves complexing of a metallic ion into a complex substance by a coordinate covalent bond; which results in a highly stable,poorly dissociated and weakly ionized compound called chelate.

Question 54. What is the basic conceptual difference between proteolytic-chelation theory,acidogenic theory and proteolytic theory?
Answer.

• Acidogenic theory states that destruction of inorganic portions of tooth occurs fist
• Proteolytic theory states that destruction of organic portions of tooth occurs fist
• Proteolytic chelation theory explains that the destruction of organic matrix of enamel as well as its mineral parts both occurs simultaneously and interdependently.

Question 55. What is sucrose chelation theory?
Answer. According to the sucrose chelation theory, if there is a very high concentration of sucrose present in the mouth of a caries active individual, it may result in the formation of complex substances like calcium saccharates and calcium complexing intermediaries, etc. by the action of phosphorylating enzymes. These complexes cause release of the calcium and phosphorus ions from the enamel and thereby result in tooth decay.

Question 56. Why the sucrose chelation theory doesn’t sound very realistic?
Answer. This theory is unlikely to be a realistic one; fist of all, once there is large amount of sucrose in the mouth, it readily gets metabolized to form acids and there is hardly any scope for formation of calcium saccharates, etc. Moreover, for the formation of calcium saccharates, a very high level of pH is required, the range which is never achievable in the oral cavity.

Question 57. What is autoimmune theory of dental caries?
Answer. According to autoimmune theory, dental caries occurs in areas of tooth which are weakened due to autoimmune damage of the odontoblast cells. Damage of these cells reduces the defence capacity and integrity of the overlying enamel or dentin.

Question 58. What are called the contributing factors in dental caries?
Answer. A large number of factors inflence the caries process directly or indirectly and are known as contributing factors.

Question 59. Name the contributing factors in dental caries.
Answer. There are two major factors: Intrinsic factors (tooth factor) and extrinsic factors.

Question 60. Name the extrinsic factors which contribute to dental caries.
Answer.

• Saliva factor
• Diet factor
• Systemic factors
• Immunity.

Question 61. Describe how the tooth factor matters in dental caries.
Answer.

• Composition of tooth—low solubility of enamel resists caries while high enamel solubility or hypomineralized enamel increases the risk of caries
• Effective pulp-dentin complex—helps in formation of reparative dentin and resist against the caries attack
• Morphology of tooth—presence of deep, narrow, retentive pits and fisures on the tooth surface increases the risk of caries
• Positions of tooth—misaligned, rotated or out of position teeth in the dental arch are more vulnerable to be attacked by caries as these teeth are diffiult to keep clean.

Question 62. Describe the role of saliva in dental caries.
Answer. There are some salivary factors which decrease the risk dental caries:

• High flow rate
• Proper salivation
• Normal viscosity
• Buffering capacity
• Salivary enzymes
• Fluoride action
• Salivary immunoglobulins
• Remineralization
• Direct antibacterial action.

Question 62a.How the salivary buffering capacity and caries susceptibility are interrelated?
Answer. Caries susceptibility is inversely proportional to the salivary buffering capacity; i.e. caries
will be more if salivary buffering capacity is reduced and vice-versa.

Question 63. Name the salivary factors which increase the risk of dental caries.
Answer.

• Low salivary flow rate
• De-salivation (xerostomia)
• Too high or too low viscosity
• Lack of salivary buffering action
• Salivary components may contribute to plaque formation
• Sucrose in saliva may be used up by the plaque bacteria to produce caries.

Question 64. Describe the role of floride in dental caries.
Answer.

• During the development of tooth, systemic florides cause conversion of the hydroxyapatite crystals of enamel into floroapatite crystals and thereby reduce the solubility of enamel; the floroapatite crystals are highly resistant to the cariogenic bacteria-induced acid demineralization
• Fluorides help in remineralization of incipient carious lesions by redepositing or by reprecipitating the mineral ions lost from tooth surface during acid–demineralization by caries
• Fluorides prevent the activity of the enzyme glucosyl transferase which is essential for the formation of extracellular polysaccharides (dextran, levan, etc.) and thereby reduce the bacterial (cariogenic) adhesion on to the tooth surface
• The floride ions can limit the rate of carbohydrate metabolism by the cariogenic bacteria and thereby reduce the acid attacks on the tooth.
• Fluorides prevent carbohydrate metabolism and subsequent acid production by inhibiting the enzyme enolase
• In high concentrations, the floride ions can be directly toxic to the Streptococcus mutans.

Question 64a.What is the effect of proline-rich protein on caries?
Answer. It helps in supersaturation of saliva and thus increases caries resistance in the tooth.

Question 64b.What is the ideal floride concentration of water for good caries control?
Answer.1 PPM.

Question 64c.What does 1 PPM of floride mean?
Answer. It means 1mg of floride in 1 liter of water.

Question 64d.What is the recommended average daily dose of floride from all sources combined in adults?
Answer.2 to 2.2 mg.

Question 64e.What is the recommended average daily dose of floride from all sources combined in children?
Answer.1.2 mg.

Question 64f.Name one common daily drink which contains good amount of floride.
Answer.Tea.

Question 64g.How floride is transported in the blood?
Answer.Via the plasma and RBC.

Question 64h.At which dose floride can cause acute toxicity?
Answer.At 7 mg of floride.

Question 65. What is the importance of dietary factor in dental caries?
Answer.

• Diet containing sufficient amount of firous foods help not only to keep the teeth clean but also it stimulates the salivary flw and thus prevent caries
• More intakes of soft and sticky foods increase the possibility of caries development
• Presence of phosphates in the diet (either organically bound or inorganic) can reduce the incidence of caries
• Diets containing traces of molybdenum and vanadium may reduce the incidence of caries
  The diet that contains adequate amounts of vegetables, vitamin (A, D, K and B-complex) and minerals, etc. is often associated with a low caries incidence
  Increase in the proportion of fat in the diet may cause reduction in the cariogenic effect of sugar.

Question 66. How hereditary factor plays its role in dental caries?
Answer. Some people hereditarily have increased tendency to develop caries while other people show just the reverse tendency.

Question 67. Which salivary antibody is most likely to prevent S. mutans from adhering to the tooth surface?
Answer. The salivary immune mechanism probably acts through secretary IgA, which prevents S. mutans from adhering to the tooth surface.

Question 68. Name the immunoglobulins and other immunologic elements present gingival crevicular flid.
Answer. Immunoglobulins (IgG, IgM and IgA), complements, neutrophil leukocytes, sensitized lymphocytes and macrophages, etc.

Question 69. How the immunoglobulin IgG helps in inhibiting dental caries?
Answer. The IgG immunoglobulin acts as opsonin and facilitate phagocytosis by neutrophil leukocytes and macrophages to cause death of the S. mutAnswer.

Question 70. Among the maxillary and the mandibular teeth, which group develops more caries?
Answer. Maxillary teeth.

Question 70a.Which tooth is most frequently affected by caries, among all the teeth in mouth?
Answer. Mandibular fist permanent molar.

Question 70b.Which teeth are considered to be least susceptible to dental caries?
Answer. Mandibular incisors.

Question 70c.Caries can affect any surface of tooth but which is the most commonly affected surface?
Answer. Occlusal surface.

Question 70d.What is the earliest visible change in enamel of tooth as the caries initiates?
Answer. Localized area of loss of translucency of enamel at the site of attack.

Question 70e.Name the different types of caries seen clinically.
Answer.

• Incipient caries
• Pit and fisure caries
• Smooth surface caries
• Rampant caries
• Nursing bottle caries
• Arrested caries
• Recurrent caries
• Root caries
• Radiation caries.

Question 71. What is incipient caries?
Answer. The initial carious lesion limited to the enamel is called incipient caries and it is characterized by virtually intact surface with subsurface demineralization.

Question 72. How incipient caries clinically appears?
Answer. The affected tooth in incipient caries presents an intact enamel surface, which appears chalky-white when the surface of the tooth is dry; however, the typical chalky-white
condition disappears if the surface of the tooth becomes wet.

Question 73. Why the affected tooth surface in incipient caries appears chalky-white?
Answer. It occurs due to subsurface demineralization of enamel.

Question 74.What is pit and fisure caries?
Answer. This is a type of lesion which occurs in the developmental pits and fisures of teeth.

Question 75. Under which circumstances the risk of development of pit and fisure caries increase?
Answer. If the developmental pits and fisures in the teeth are deep, narrow and retentive in nature; then the risk of development of pit and fisure caries becomes more.

Question 76. Name the teeth and their surfaces where pit and fisure caries often develops.
Answer.

• Occlusal surfaces of molars and premolars
• Buccal and lingual surfaces of molars
• Lingual surfaces of maxillary incisors.

Question 77. What is the clinical appearance of pit and fisure caries?
Answer. The lesion usually appears brown or black with little softening and opaqueness of the surface. When the lesion is examined by a fie explorer tip a catch point is often felt.

Question 78. Describe the shape of a pit and fisure caries lesion.
Answer. Pit and fisure caries lesion is often triangular in shape, with its base toward the dentinoenamel junction and the tip toward the surface of tooth.

Question 79. Why the pit and fisure caries lesions appear triangular?
Answer. Because initially the lesions are small at the surface of the tooth, but as the lesions progress into the deeper layer and reach dentin, they become wider due to the typical
orientation of the enamel rods.

Question 80. How undermining of enamel occurs in pit and fisure caries?
Answer. After the pit and fisure caries reaches the dentino-enamel junction (DEJ), it spreads laterally along the soft DEJ, and thus a large amount of dentin is lost deep inside the
tooth while the overlying enamel is intact. This situation is called undermining of enamel.

Question 80a.What actually causes the cavity formation in caries?
Answer. Lateral spread of caries along the DEJ causes undermining of enamel which breaks eventually due to lack of support, resulting in a cavity formation on the tooth.

Question 81. What is smooth surface caries?
Answer. When caries occurs in relation to the smooth surfaces of teeth, it is called smooth surface caries; the lesion often begins as a well-demarcated, chalky-white opacity on enamel with no loss of surface continuity.

Question 82. Name the areas of teeth where smooth surface caries often occurs.
Answer. Smooth surface caries most commonly occurs in the proximal surface of the teeth just below the contact point; besides this, gingival areas of the buccal and lingual aspect of tooth are also affected occasionally.

Question 83. What is rampant caries?
Answer. The term rampant means something violent or unrestrained; and rampant caries means an acute fulminating type of carious process, which is characterized by simultaneous involvement of multiple number of teeth (may be all teeth) in multiple surfaces.

Question 84. Describe the characteristics of rampant caries.
Answer.

• Rapid coronal destruction in multiple teeth within a short-span of time
• Early involvement of the pulp
• Rampant caries can occur in persons with no previous history of the disease
• Can occur in persons who maintain a good level of oral hygiene
• Rampant caries may attack those surfaces of teeth, which are otherwise immune to the disease.

Question 85. What is the common age of occurrence of rampant caries?
Answer. The common age of occurrence of rampant caries is about 4 to 8 years for the deciduous teeth and 11 to 19 years for the permanent teeth.

Question 86. What is nursing bottle caries?
Answer. This is also another type of acute carious lesion which occurs among those children who take milk or fruit juices by the nursing bottle for a considerably longer duration of time, preferably during sleep.

Question 87. How does nursing bottle occur?
Answer. As the child takes large amounts of easily fermentable sugars with milk, the sugar facilitates the cariogenic bacteria to produce caries at a rapid pace by fermenting those sugars.

Question 88.In case of nursing bottle caries, which teeth are often affected?
Answer. Nursing bottle caries commonly occurs in the upper anterior teeth (as these are constantly come in contact with the sweetened milk).

Question 88a.Why the mandibular incisors are not affected in nursing bottle caries?
Answer. The lower incisor teeth are not affected as they remain protected under the cover of tongue (the sweetened milk doesn’t touch these teeth as the baby sleeps).

Question 89. Why the nursing bottle caries and rampant caries are called acute carious lesions?
Answer. Because both the nursing bottle caries and rampant caries spread at a very rapid pace to cause early pulp involvement of the affected teeth and there is hardly any time for the pulp to protect itself by forming tertiary or reparative dentin.

Question 89a.Why acute caries often develop in young children?
Answer. Their tooth enamel unlike adults is relatively less mineralized and the dentinal tubules are wide and open; all these contribute to rapid spread of caries in the tooth and early
pulp exposure.

Question 90. What is chronic caries?
Answer. This type of caries progresses very slowly and rarely causes pulp involvement (unless the tooth is left untreated for many years); because the pulp gets sufficient time to produce tertiary dentin or reparative dentin to protect itself.

Question 90a.What is the color of dentin in chronic type of caries?
Answer. Dentin looks deep brown in color.

Question 90b.How the size of cavity opening varies in acute and chronic caries?
Answer. In acute caries, the cavity opening is often narrower while in chronic caries it is much wider.

Question 91. What is arrested caries?
Answer. Arrested caries is a lesion whose progression has been ceased after the initial development. It can occur both in enamel and in dentin.

Question 92. What is arrested caries in enamel?
Answer. Arrested caries in enamel may occur when the carious process stops before cavity formation. It occurs if the adjacent carious tooth (from which the disease has actually spread to this new tooth) is lost or extracted, so that the carious lesion in the new tooth becomes easily accessible for cleaning and plaque control measures.

Question 93. In case of arrested caries in enamel, what happens to the affected part of enamel?
Answer. It repairs itself by remineralization.

Question 93a.What is the criterion for remineralization of carious enamel?
Answer. It can only take place in a tooth where caries has started but cavity has not developed (non-cavitated caries).

Question 94. What is arrested caries in dentin?
Answer. The arrested caries of dentin usually occurs when a carious cavity becomes wide open;so that it gets exposed to the cleaning measures like tooth brushing, salivary secretions and mastication, etc.

Question 95. What is eburnated dentin?
Answer. The arrested caries presents a hard, black or brown colored dentinal surface at its base,which is known as eburnated dentin.

Question 95a.In which type of caries, eburnated dentin is often present?
Answer. Arrested caries.

Question 95b.In which surface of tooth-arrested caries is mostly found?
Answer. Occlusal surface.

Question 96.What is recurrent caries?
Answer. Recurrent caries refers to a carious lesion that begins around the margins or at the base of a pre-existing defective restoration.

Question 97. What is forward caries?
Answer. When a carious lesion progresses unidirectionally from enamel into the dentin and then pulp, it is called a forward caries.

Question 98. What is backward caries?
Answer. This caries initially progresses from enamel into dentin where it spreads laterally along the DEJ and involves a wide area of dentin undermining the enamel.

Later on, the lesion proceeds in a backward direction from dentin back into enamel and creates cavity in the enamel once again at a different location.

Question 99. What is root caries?
Answer. These are carious lesions which involve the cemental wall of the exposed root surfaces of teeth.

Question 99a.What is the essential precondition in the development of root caries?
Answer. Exposure of roots of the affected teeth in the oral environment either due to ageing or due to gingival recession.

Question 100. How root caries starts?
Answer. Development of root caries is often preceded by exposure of roots of the affected teeth in the oral environment either due to ageing or due to gingival recession.

Thereafter caries begins on the exposed root surfaces due to accumulation of plaque facilitated by roughness of the cementum.

At first, the cementum is invaded along the direction of Sharpey’s fiers, and microorganisms spread along the incremental lines.

Question 101. Describe the characteristics of root caries.
Answer. Clinically these lesions are extensive, shallow and saucer-shaped with ill-defied margins.

Question 101a.Why root caries spreads so rapidly as compared to enamel caries? 
Answer. Root caries spreads rapidly due to relative softness of the cementum and dentin.

Question 101b.In case of root caries, which teeth are more frequently affected?
Answer.Mandibular molars.

Question 102. Which organisms produce root caries?
Answer. The actinomycotic groups of organisms (A. viscosus) are mostly responsible for the causation of root caries.

Question 103. What is radiation caries?
Answer. A specific type of large caries–like lesions often develop in the cervical areas of teeth in patients receiving large doses of radiation and are called radiation caries.

Question 103a.At which portion of teeth does radiation caries often starts?
Answer.In the cervical area of teeth.

Question 104. When radiation caries begins? How radiation caries clinically appear?
Answer. These lesions begin a few weeks to few months after radiotherapy, and they often surround the entire crowns of the affected teeth, gradually weaken them, and even sometimes can cause their amputations.

Question 104a.What is the other name of radiation caries?
Answer. It is also known as amputation caries; because the affected teeth often break down at the neck portion due to severe weakening.

Question 105. Why radiation caries develops?
Answer. The exact cause of radiation caries is not known, but it may occur due to reduced salivary secretions, secondary to the radiotherapy.

Question 106. Name the common radiographs used for detection of caries.
Answer. Intraoral periapical (IOPA), panoramic and bitewing radiographs are usually advised.

Question 107. What is the indication of a bitewing radiograph?
Answer. The bitewing radiograph is especially indicated for detection of proximal caries in teeth.

Question 107a.Which other X-ray can also help in easy detection of proximal caries?
Answer. Intraoral periapical (IOPA) X-ray.

Question 108. How pit and fisure caries radiographically appears?
Answer. Pit and fisure caries radiographically appears as a triangular-shaped radiolucent area in tooth with its base located towards the dentino-enamel junction (it is narrow at the surface and wider at the DEJ).

Question 109.How smooth surface caries radiographically appears?
Answer. The smooth surface caries also produces a triangular-shaped radiolucent area in tooth but its base is located toward the surface of the tooth (it is wider at the surface and gradually becomes narrower as it moves toward the DEJ).

Question 110.What does a radiograph indicate if it shows enamel radiolucency extending up to the DEJ?
Answer. It indicates that the tooth has a cavity which has defiitely involved the underlying dentine.

Question 111. What does a radiograph indicate if it shows enamel radiolucency not extending up to the DEJ?
Answer. If the enamel radiolucency does not extend to the DEJ, there should be no clinically detectable cavity in the tooth although caries has started.

Question 111a. Which part of the normal tooth may be mistaken for caries in a radiograph?
Answer. Cervical area (cement-enamel junction).

Question 112. How root caries radiographically appears?
Answer. Root caries radiographically produces a U-shaped radiolucent area in root portion of tooth with irregular margin.

Question 112a. What is fieroptic-transillumination method of caries detection?
Answer. Fiberoptics is the method of transmission of an image along flxible bundles of glass or plastic fiers; an image of tooth decay in caries can be detected by this method, as carious enamel and healthy enamel have different index of light transmission.

Question 113. What is the earliest histologic change in enamel due to caries?
Answer. Loss of interprismatic or inter-rod substances.

Question 113a. Describe the histological appearance of early enamel caries.
Answer. The affected enamel will exhibit the following changes:

• Loss of inter prismatic or inter-rod substances with increase in the prominence of enamel rods
• Appearance of transverse striations of the enamel rods due to segmental demineralization
• Accentuation of the incremental striae of retzius often occurs.

Question 114. In the histologic picture of advanced enamel caries how many zones are seen?
Answer. There are four zones seen, starting from deeper layer of enamel up to the surface layer;which are as follow:

• Zone I: Translucent zone
• Zone II: Dark zone
• Zone III: Body of the lesion
• Zone IV: Surface zone.

Question 114a.What is the earliest histologic change in enamel in caries?
Answer. Loss of interprismatic or inter-rod substance.

Question 115. Describe the features seen in zone I or translucent Zone of advanced enamel caries.
Answer. It is the deepest zone in the carious enamel and is the fist recognizable histological change at the advancing front of the lesion. Here the enamel shows increased porosity due to dissolution of minerals at the junction of prismitic and interprismitic enamel.

Question 116. Describe the features seen in zone II or dark zone of advanced enamel caries.
Answer. The dark zone is located just superfiial to the translucent zone. This zone is narrower in rapidly advancing caries and wider in slowly advancing lesions. This zone also reveals some degrees of remineralization in the carious enamel.

Question 116a.Why this zone appears dark?
Answer. The dark appearance is because of excessive demineralization of the enamel due to caries.

Question 117. Describe zone III or body of the lesion in advanced enamel caries.
Answer. This zone is situated between the dark zone and the surface layer of enamel; acid attacks on enamel cause dissolution of minerals both from the periphery of the apatite crystal and their cores and the lost minerals are often replaced by unbound H2O and organic matters.

Question 117a.What is the signifiance of zone III or body of the lesion?
Answer. It represents the area of greatest demineralization.

Question 117b.Among the different zones in enamel caries, which zone represents the area of greatest demineralization?
Answer. Zone III or body of the lesion.

Question 118. Describe zone IV or surface zone of the lesion in advanced enamel caries.
Answer. Initially, the surface zone of carious enamel remains comparatively unaffected despite subsurface demineralization and it may be due to the surface remineralization by the salivary mineral ions. However, in untreated cases, the surface enamel often gets destroyed and a cavity is formed.

Question 118a.Which is the single most important factor favoring lateral spread of caries with undermining of enamel?
Answer. Dentinoenamel junction.

Question 119. From which sources the minerals may come when remineralization occurs in caries affected enamel?
Answer. The mineral ions often come from three sources:

• Mineral ions present in saliva
• Mineral ions present in dental plaque
• Mineral ions produced by demineralization of deeper layers of enamel.

Question 120.How many zones are seen histologically in dentinal caries (caries in dentin)?
Answer. Dentinal caries histologically presents fie zones in the tissue, which are as follows:

• Zone I: Normal dentin
• Zone II: Sub-transparent dentin
• Zone III: Transparent dentin
• Zone IV: Turbid dentin
• Zone V: Infected dentin.

Question 121. Describe the zone I (normal dentin) in histology of dentinal caries.
Answer. This zone represents the innermost layer of the carious dentin; here the dentinal tubules appear normal,although there is evidence of fatty degeneration of the Tome’s processes.

Question 121a.What is the earliest microscopic change in dentinal caries?
Answer. Fatty degeneration of the Tome’s processes.

Question 122. Describe the zone II (sub-transparent dentin) in histology of dentinal caries.
Answer. This is the zone of dentinal sclerosis and it is characterized by the deposition of very fie crystal structures within the dentinal tubules at the advancing front. No bacteria are seen in the tubules and this dentin is capable of remineralization.

Question 122a.Can sclerotic dentin be destroyed by caries?
Answer.No, it is resistant to caries.

Question 123. Describe the zone III (transparent dentin) in histology of dentinal caries.
Answer. This zone appears transparent because of demineralization of dentin due to caries. It is softer than normal dentin with further loss of mineral ions from intertubular dentin. No bacteria are seen in tubules and this zone also capable of self-repair and remineralization.

Question 124. Describe the zone IV (turbid dentin) in histology of dentinal caries.
Answer. This zone is called the turbid dentin and is marked by the widening and distortion of the dentinal tubules which are packed with microorganisms. There is very little amount of mineral present in this dentin which also shows degeneration of collagen fiers. This zone cannot undergo remineralization.

Question 125. Which zone in the histology of dentinal caries is called turbid dentin?
Answer. Zone IV is called turbid dentin.

Question 126. Describe the zone V (infected dentin) in histology of dentinal caries.
Answer. This is the outermost zone of the carious dentin and is characterized by complete destruction of the dentinal tubules (as a result of their severe expansion due to accumulation of large number of microorganisms and their by-products).The expanded tubules cause compression and bending of the adjacent tubules and eventually destroy them.

Question 127. What are liquefaction foci of Miller in dentinal caries?
Answer. In zone V or infected dentin, if the areas of decomposition of dentin occur along the direction of the dentinal tubules, such defects are called liquefaction foci of Miller.

Question 128. What are transverse clefts in dentinal caries?
Answer. Within zone V or infected dentin, there are some areas where the cariogenic microorganisms spread laterally by destroying the dentin and thus large bacteria-filed clefts-like areas develop at right angles to the direction of the tubules which are called transverse clefts.

Question 129. Describe the possible mechanisms by which transverse clefts develop in infected dentin.
Answer.

• Decomposition of dentin with spread of microorganisms along the course of incremental lines of Von Ebner, which run at right angles to the dentinal tubules
• Transverse clefts may also result from the coalescence of liquefaction foci of Miller of adjacent tubules
• Transverse clefts may also arise by extensive proteolytic activity along the interconnecting lateral branches of odontoblastic processes.

Question 130.How the zone IV and zone V of dentinal caries differ, although bacteria are present in both?
Answer. In zone IV, bacteria are present mainly within the dentinal tubules, while in zone V bacteria destroy the dentinal tubules and move out in intertubular dentin and cause complete destruction of the dentinal structure.

Question 131. Which is the outermost layer in carious dentin?
Answer. Zone V or infected dentin.

Question 132. Which is the innermost layer in carious dentin?
Answer. Zone I or normal dentin is the innermost layer.

Question 133. What is tubular sclerosis in dentinal caries?
Answer. When the caries attack reaches dentin, individual dentinal tubules become obliterated by the deposition of peritubular dentin to prevent the bacterial penetration; this protective mechanism is called tubular sclerosis.

Question 134. What is reactionary dentin?
Answer. This is a type of dentin which is formed to protect pulp tissue from mechanical, thermal or bacterial injuries; however, this dentin tends to develop mostly during caries.

Question 135.What is the basic difference between reactionary dentin and primary dentin?
Answer. Reactionary dentin is always hypomineralized than the primary dentin.

Question 136. What are the types of reactionary dentin?
Answer. These are of two types:

• Regular reactionary dentin
• Irregular reactionary dentin.

Question 137. How regular reactionary dentin differs from irregular reactionary dentin?
Answer. Regular reactionary dentin forms in response to mild irritation to the odontoblast cells; and contains regular tubular structures. Whereas irregular reactionary forms in response to moderate to severe irritation to the odontoblast cells; and it contains only few irregularly shaped and tortuous tubules.

Question 138. What are dead tracts?
Answer. The dead tracts form when the odontoblast cells die or retract; and the respective tubules become sealed off. They often prevent the further progression of caries in dentin toward the pulp.

Question 139. What are caries activity tests?
Answer. Caries activity tests have been evolved to access the cariogenic potential of oral cavity;they evaluate oral conditions associated with high-risk of caries and these can also predict the need for preventive measures to be taken before the caries has actually started in mouth.

Question 140. Name the common caries activity tests.
Answer.

• Snyder test
• Swab test
• Salivary reductase test
• Salivary buffering capacity test
• Microbiological test
• S. mutans dip-slide method
• Fosdick calcium dissolution test or enamel solubility test.

Question 141. What is Snyder’s test?
Answer. Snyder’s test is the qualitative determination of acidogenic organisms in mouth, which measures the ability of salivary microorganisms to produce acids from a carbohydrate medium.

Question 141a.What Snyder’s test actually detects?
Answer. It detects the ability of acid formation in saliva by cariogenic bacteria due to fermentation of sugar during caries.

Question 141b.What is the importance of Snyder’s test?
Answer. It provides a quantitative determination of cariogenic microorganisms in the oral cavity.

Question 142. Describe the procedure of Snyder’s test?
Answer. Glucose agar medium containing an indicator dye (bromocresol green) is used for this test. The indicator dye changes from green to yellow in the range of pH from 5.4 up to 3.8 at 37° C temperature for a period of 72 hours.

Paraffi-stimulated saliva (0.2 mL) is added into the medium, change of the medium from green to yellow is indicative of the degrees of caries activity.

Question 143. Describe the results in Snyder’s test.
Answer.

• If the color of the medium changes from green to yellow within 24 hours, caries susceptibility of the patient should be considered very high
• If the similar color change occurs within 48 hours, then the patient is considered to have defiite caries susceptibility
• If the color change occurs in 72 hours, limited caries susceptibility is indicated
• Finally, if the color change does not occur at all in 72 hours, the patient should be considered caries immune.

Question 144. What is swab test?
Answer. Swab test is done to measure the aciduric and acidogenic elements in oral flra.

Question 145. How the swab test is done?
Answer. Sample of oral flra is collected by swabbing the buccal surfaces of teeth with applicator, which is then incubated in Snyder media for 48 hours. The pH change after incubation is read on a pH meter or the color change is read by use of a color comparator.

Question 146.Describe the observations in swab test.
Answer.

Question 147.What is salivary reductase test?
Answer. Salivary reductase test measures the activity of reductase enzyme liberated by cariogenic bacteria present in patients saliva.

Question 148. Describe how salivary reductase test is done?
Answer. Paraffi-stimulated saliva is collected in a plastic container and an indicator dye diazoresorcinol is added to it, which colors the saliva blue. The Reductase enzyme causes color changes in the medium from blue to other colors which indicates the caries conduciveness of the patient.

Question 149. Describe the results of salivary reductase test.
Answer.

Question 150. What is salivary buffering capacity test?
Answer. Salivary buffering capacity test is a chairside test done to evaluate the quantity of acid required to lower the pH of saliva. It helps to measure the buffering capacity of saliva and caries activity.

Question 151. How Salivary buffering capacity test is done?
Answer. A special kit called dento buff is used for this test, which contains a small vial of weak HCl and a color indicator chart. If 1 milliliter of saliva is put into the acid solution, its pH will rise gradually depending upon the buffering capacity of the saliva and this change of pH is measured by the accompanying color chart.

Question 152. Describe the results of salivary buffering capacity test.
Answer.

• If the buffering capacity of saliva is normal, the fial pH of the solution will rise up to 5 to 7
• If the buffering capacity is low, the pH will rise up to 4 only (However, it is understood that more is the buffering capacity of saliva, less will be the acid demineralization of the tooth due to caries).

Question 153. What is microbiological test?
Answer.Microbiological test is an important caries activity test, which helps to measure the number of Streptococcus mutans and Lactobacillus acidophilus per microliter of saliva.

Question 154. Describe how Microbiological test is done?
Answer. Two samples of paraffin-stimulated saliva (1 mL each) are collected from patient’s mouth, these are diluted 10 times and each is cultivated in two different special media: (1) Rogosa’s SL agar medium for Lactobacillus, and (2) Mitis salivarius agar medium for Streptococcus mutAnswer.

Question 155. Describe the results of microbiological test.
Answer. After incubation, the number of colonies that develop in two separate media are counted and then are multiplied by 10 (dilution factor) to estimate the number of bacteria in 1 mL of saliva.

• If the count is more than 10,00,000 S. mutans and more than 1,00,000 L. acidophilus,then the caries susceptibility of the individual should be considered very high
• If the count is less than 1,00,000 S. mutans and less than 1,000 L. acidophilus, the individual is considered less susceptible to caries.

Question 156. What is S. mutans dip-slide method in caries activity test?
Answer. This caries activity test measures the Streptococcus mutans levels in saliva by counting the number of S mutans colonies in modifid MSA (Mitis salivarius agar).

Question 157. How the S. mutans dip-slide method is carried out?
Answer. The saliva is collected for 5 minutes from patient’s mouth and is poured over the agar coated slide. Slides are then dried and bacitracin discs are placed in the middle of the inoculated agar about 1 cm from each other.

The slide is then incubated in a tube containing CO2 for 48 hours. A zone of inhibition of 10 to 20 mm in diameter is formed around each bacitracin disc and S. mutans presents small blue colonies within the zone of inhibition.

Question 158. Describe the result in S. mutans dip-slide method.
Answer. The colony density is compared with a model chart and classified as 0 (negligible),1 (less than 100,000), 2 (100,000–1000,000), and 3 (more than 1000,000) S. mutans colony forming units/mL of saliva.

More the number of S mutans in saliva more is the risk of caries in the patient.

Question 159. What is Fosdick’s calcium dissolution test or enamel solubility test?
Answer. Fosdick’s calcium dissolution test measures the capacity of the acids produced by cariogenic bacteria to dissolve the tooth enamel.

Question 160. How this Fosdick’s calcium dissolution test or enamel solubility test is done?
Answer. In this test, patient’s saliva is mixed with glucose and thereafter measured amount of (in milligram) powdered enamel is mixed with it and kept for 4 hours.

Acid produced due to fermentation of glucose by the cariogenic bacteria present in the saliva cause dissolution of powdered enamel.

The test measures the amount of enamel powder dissolved during the 4 hours period.

Question. 161. Name the methods of caries prevention.
Answer.

• By limiting substrate (sugar)
• By modifying oral microflra
• By plaque disruption
• By modifying tooth
• By stimulating salivary flow
• By restoring tooth surface.

Question. 162. How substrate (sugar) can be limited from diet to prevent caries?
Answer.

• Eliminate sucrose from the diet or reduce its amount
• Eliminate sucrose from the in–between meals and snacks.

Question 163. How oral microflras can be modifid to prevent caries?
Answer. It can be done by the following methods:

• Bactericidal mouth-rinse by chlorhexidine
• Topical floride treatments
• Antibiotic treatment by vancomycin and tetracyclines.

Question 164. How plaque disruption can be done to prevent caries?
Answer. It is mainly done by proper brushing and flssing of teeth.

Question 165. How modifiation is done in tooth to prevent caries?
Answer.

• Systemic florides
• Topical florides
• Maintain a smooth surface of the tooth.

Question 165a.What is the best method of caries prevention for the general population?
Answer. Use of systemic florides.

Question 166. How salivary flw can be stimulated in order to prevent caries?
Answer.

• Eating non-cariogenic firous foods that require lots of chewing
• Use sugarless chewing gums
• By administering sialogogues.

Question 167.What are the different types of prophylactic restorations done in the teeth?
Answer.

• Restoration of all cavities
• Sealing of all deep, narrow and retentive, pits and fisures in teeth
• Correction of all defects, e.g. marginal crevice, proximal overhangs, etc.

Question 168. What is caries vaccine?
Answer. These vaccines are given to induce active (predominantly) or passive immunity in individuals against S. mutAnswer.

Question 169. Describe the criteria of a good caries vaccine.
Answer.

• It should prevent the cariogenic microorganisms to colonize on the tooth surface
• Should alter the pattern of polysaccharide metabolism by cariogenic bacteria
• Should be able to reduce the adhering capacity of bacteria on the tooth surface
• It should reduce ability of microorganisms to produce acids
• Should help in the process of killing the cariogenic microorganisms if possible.

Question 170.Generally at what age caries vaccines are given?
Answer. The caries vaccines are usually given at the age of about 6 months, before the eruption of the deciduous teeth.

Question 171. What are the routes of administration of caries vaccine?
Answer. Oral administration or subcutaneous injection of killed Streptococcus mutans are given; to induce formation of specific IgA, IgG, and IgM against S. mutans in the blood.

Question 172. What is the major drawback in caries vaccination?
Answer. Although the caries vaccine is theoretically very convincing, it has failed to gain a wide range of acceptance because these vaccines often produce cardiotoxicity in humans by cross-reacting with the heart tissue.