Dental Cariology Quiz

Dental Cariology

• Dental caries is a disease that results from the demineralization and remineralization of tooth structures.
• Cavitated tooth surfaces provide more space for biofilm, leading to accelerated destruction.
• Enamel caries rapidly spreads to the dentin-enamel junction (DEJ) as dentin is less resistant to acid demineralization.
• This creates a sheltered, highly acidic, and anaerobic environment ideal for cariogenic bacteria.

Clinical Sites for Caries Initiation

• There are three primary sites of caries initiation: pits and fissures, smooth surfaces, and root surfaces.
• Pits and fissures of enamel are the most susceptible, due to their morphology restricting biofilm removal, causing rapid colonization by bacteria like S. sanguis.
• Smooth enamel surfaces are less prone to caries but caries can occur near the gingival or proximal contacts.
• Root surfaces are also susceptible, primarily due to the thin cementum layer offering little protection against caries attack in comparison to enamel.

Progression of Enamel Caries

• Non-cavitated enamel caries (white spot lesions) to cavitated caries takes approximately 18 months on smooth surfaces.
• Softened, chalky enamel that chips away with an explorer indicates active caries.
• Remineralization (arresting caries) can occur and results in discolored, usually brown or black spots.

Progression of Enamel Caries (Continued)

• Remineralized areas can be left unrestored unless severely impacting aesthetics.
• Saliva with calcium and phosphate ions, along with trace amounts of fluoride, fuels the remineralization process.

Classification of Dental Caries (Table 2-5)

• Dental caries stages can be determined using criteria such as hydration level, desiccating, surface texture, and surface hardness.

1- Enamel Caries

• White spots (chalky, opaque) are the initial indicators on smooth surfaces.
• These lesions form on facial and lingual enamel surfaces.
• They become visible when the surface is dry.
• Enamel loses translucency due to extensive subsurface porosity.

Microscopic Features of Non-cavitated Enamel

• Four zones exist before cavitation: translucent zone (advancing edge), dark zone (always present), body zone (greatest demineralization area), and surface zone (least affected).

2- Dentin Caries

• Dentin, owing to its lower mineral content and tubules, is more susceptible to caries than enamel, leading to faster lateral expansion.
• Dentin caries is V-shaped in cross-section, with a wide base at the DEJ and apex toward the pulp.
• Tubules within dentin provide an easy path for bacteria ingress and demineralization.
• Caries advances quickly in dentin due to less resistance to acid attack.

Microscopic Features of Non-cavitated Dentin

• Three zones are key: normal dentin (deepest area with smooth tubules and no bacteria), affected dentin (demineralization of intertubular dentin), and infected dentin (outermost layer exhibiting widening and distortion of tubules and bacterial invasion). Affected dentin can be divided into subtransparent, transparent, and turbid subzones.

Characteristics of Affected and Infected Dentin

• Affected dentin: vital, remineralizable, hard and sensitive, minimally invaded by microorganisms; leave it to remineralize.
• Infected dentin: non-vital, unmineralizable, soft with little sensation, significantly more deeply invaded by microorganisms; excavate and treat.

How to Discriminate Between Different Dentine Layers

• Visual inspection: Infected: dark brown; Affected: paler light brown; Sound: yellowish-white.
• Tissue consistency: Infected: wet/soft; Affected: sticky/scratchy; Sound: hard.
• Caries disclosing dyes: Infected: dark red; Affected: pale red; Sound: pink.

2- Dentin Caries (Continued)

• Pulp-dentin react to caries by attempting remineralization and blocking open tubules.
• Three levels of pulp reaction exist:
  • Reaction to prolonged, low-acid demineralization in slowly advancing lesions.
  • Reaction to moderate-intensity attacks.
  • Reaction to severe, rapidly advancing attacks with high acid levels.

Slowly Advancing Caries

• Dentin can repair/remineralize intertubular dentin and create appositions of peritubular dentin if the pulp is vital.
• Sclerotic dentin (more mineral) forms as a defense mechanism. It appears shiny and dark, feels hard, and contains reduced tubule diameter, blocking lesion spread.

More Intense Caries Activity

• High acid, enzymes, bacteria, debris from the infection can irritate the pulp, causing inflammation.
• This can trigger secondary odontoblasts from undifferentiated mesenchymal cells, creating reparative dentin.
• This reparative dentin, acts as a barrier against materials and promotes dentin repair.

2- Dentin Caries (Final)

• The severe level of advancing caries overwhelms the defences, resulting in pulp infection, abscess, and death.