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Questions and Answers
Which type of bacteria is primarily responsible for acid production in dental caries?
What is the role of fluoride in the prevention of dental caries?
Which classification of dental caries refers to decay occurring on smooth surfaces of teeth?
What characteristic defines aciduric bacteria in dental plaque?
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Which factor regarding carbohydrates contributes to the risk of dental caries?
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Which component of dental plaque is predominantly responsible for its protective function?
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What is the main characteristic of recurrent caries?
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What effect does the presence of dental plaque have on the teeth?
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What characterizes the phase of bacterial invasion in enamel?
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Which phase describes the complete destruction of enamel due to proteolytic bacteria?
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What is NOT true about the infected lesion that occurs after enamel cavitations?
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Which zone is characterized by the presence of decalcified infected material?
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In the clinical picture of dentine caries, what shape is the lesion described as?
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What does the term 'liquefaction foci' refer to in infected lesions?
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What is the primary action of acidogenic bacteria during the first wave of infection in dentine?
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Which zone is responsible for the formation of secondary or reactionary dentine?
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What is one of the primary roles of the plaque matrix in dental health?
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Which factor does NOT directly influence plaque formation?
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In the pathology of enamel caries, which phase truly signifies the destruction of dental tissue?
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Which zone of the carious lesion lies at the advancing front and is due to initial demineralization?
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Which of the following theories best explains the process of caries developing under restorations?
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Which of the following elements in saliva contributes to its buffering effect?
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What is the composition of the 'dark zone' in the carious lesion?
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What is a characteristic of the surface zone in enamel caries?
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Study Notes
Dental Caries
- A disease characterized by demineralization of tooth's inorganic part followed by the dissolution of its organic part due to bacteria.
- The most common dental disease worldwide.
Classification
- Pit & fissure caries
- Smooth surface caries
- Cemental (root) caries
- Recurrent caries
- Acute (rampant) caries
- Arrested caries
Contributing Factors
- Susceptible tooth surface
- Tooth position
- Tooth morphology
- Tooth structure
- Genetic factors
- Fluorides
Mechanisms of cariostatic effect of fluoride
- Reduction of apatite solubility by converting hydroxy-apatite to fluoro-apatite crystals.
- Enhancement of re-mineralization of the carious lesion.
- Anti-bacterial activity
Anti-bacterial activity of fluoride
- Decreased lactic acid production, making organisms less cariogenic.
- Decreased glucose uptake by organisms, leading to a decrease in energy reserve and metabolic activity.
- Decreased bacterial adhesion.
Carbohydrates
- Type: mono, di & polysaccharides
- Total amount of carbohydrate intake
- Frequency of carbohydrate intake
- Consistency of carbohydrates
Micro-organisms
- Acidogenic bacteria: Lactobacilli & Streptococci (Strept.Mutans)
- Proteolytic bacteria: Actinomyces, Clostridia & Pseudomonas
- Chromogenic bacteria: Asprigillus
Essential features of cariogenic bacteria
- Acidogenic
- Production of low pH (lower than 5.5)
- Aciduric
- Attachment mechanisms for firm adhesion to the tooth surface
- Production of abundant polysaccharides for plaque matrix formation
Dental Plaque
- An adherent bacterial structure on tooth surfaces.
- Contains a large number of closely packed micro-organisms surrounded by an extracellular material of bacterial and salivary origin.
- Two major interfaces:
- Internal one (pellicle)
- External one (plaque saliva interface)
Types of Dental Plaque
- Sub-gingival
- Supra-gingival
Composition of Dental Plaque
- Micro-organisms
- Matrix: protein, lipids, carbohydrates, inorganic component, and water
Role of plaque matrix
- Acts as a diffusion limiting membrane retaining acid in high concentration to initiate caries.
- Slows down the entry of buffers from saliva, delaying their neutralizing action.
Factors affecting plaque formation
- Anatomy & position of tooth
- Presence of appliance
- Structure of tooth surface
- Friction from diet
- Oral hygiene procedures
- Composition of the diet
Mechanism of action of dental plaque
- Allows adhesion of bacteria & acids on the surfaces of teeth
- Prevents escape of acids and entry of salivary buffers
Saliva & Caries
- Washing effect of saliva
- Buffering effect of saliva by phosphate and bicarbonate content
- Salivary antibodies (IgA)
- Antibacterial substances: lysozymes, Peroxidases & lactoferrin
Theories of dental caries
- Acidogenic theory (Miller's chemico-parasitic theory): most accepted.
- Proteolytic theory: Explains penetrating caries under restorations & caries of impacted teeth.
- Proteolosis- chelation theory
Pathology of Enamel Caries
- Clinical picture
- White chalky area
- Rough to the probe with staining
- Cavitations
- Cone-shaped carious lesion
- Pits & fissure caries: Base toward DEJ, apex toward surface
- Smooth surface caries: Base toward surface, apex towards DEJ
- Microscopic picture (With polarized light microscope):
- 4 phases:
- Initiation phase
- Bacterial invasion phase
- Destruction phase
- Phase of secondary enamel caries
- 4 phases:
Initiation phase (4 zones)
- Translucent zone
- Lies at the advancing front of the carious lesion
- Due to initial demineralization
- Contains pores accounting for 1-2% of enamel volume
- Dark zone
- Lies superficial to the translucent zone
- Due to further enamel demineralization
- Contains micro-pores accounting for 2-4% of enamel volume
- Body of the lesions
- Lies under the surface zone and constitutes the largest area of the carious lesion.
- Due to advanced demineralization
- Contains pores accounting for 5% at the periphery and 25% at the center of the zone
- Appears translucent
- Surface zone
- Although not intact, it appears more radio-opaque and harder than deeper zones.
- Continuous re-mineralization from saliva
- Contains much fluoride
- Contains much insoluble proteins
- Prism-less enamel may delay diffusion of acids.
Phase of bacterial invasion
- Bacteria begin to invade enamel when sufficient spaces are created by the action of acids.
Phase of destruction
- Proteolytic bacteria begin to act on the organic matrix of the enamel leading to complete destruction of enamel.
Phase of secondary enamel caries
- Acid and bacteria reach DEJ, spread laterally along it and begin to invade enamel from beneath leading to its undermining.
Pathology of Dentin caries
- Clinical picture
- Appears brownish & soft to the probe
- Cone-shaped with the base toward DEJ & the apex toward the pulp
- Microscopic picture
- Initial uninfected lesions (occur before enamel cavitations)
- Zone 1: Zone of reactionary or reparative dentine formation (secondary dentine)
- Zone 2: Zone of sclerotic or translucent dentine formation (Ca.ion deposition)
- Zone 3: Zone of the body of the lesion (dead tract)
- Initial uninfected lesions (occur before enamel cavitations)
Infected lesion (occurs after enamel cavitations)
- Dentinal tubules provide a pathway of bacterial invasion in 2 waves:
- 1st wave: Pioneer bacteria consists of acidogenic bacteria that decalcify dentine leaving organic matrix intact.
- 2nd wave: Consists of mixed infection containing proteolytic bacteria that distort the organic matrix.
- Consists of 4 zones :
- Zone 1: Mild pulp inflammation
- Zone 2: Reparative or reactionary dentine
- Zone 3: Sclerotic dentine
- Zone 4: Body of the lesion
- Decalcified uninfected zone
- Decalcified infected zone
- Destruction zone
Decalcified infected zone
- Beading: lateral distension of dentinal tubules by the action of bacteria.
- Liquefaction foci: Coalescence of neighboring beads and lie at the long axis of dentinal tubules.
- Transverse clefts: Liquefaction foci lie at right angles to dentinal tubules due to their existence on a lateral branch of dentinal tubules.
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Description
This quiz explores the intricacies of dental caries, including its classification, contributing factors, and the mechanisms by which fluoride combats this common disease. Test your knowledge on how dental health professionals address and prevent the progression of carious lesions.
