Dental Cariology Overview

Dental Cariology

• Dental caries is a disequilibrium between demineralization and remineralization.
• Cavitated tooth surfaces provide a more retentive environment for biofilm, leading to rapid tooth structure destruction.
• Enamel caries penetrating the DEJ expands laterally due to dentin's lower resistance to acid. This creates a sheltered, acidic, anaerobic environment ideal for cariogenic bacteria.

Clinical Sites for Caries Initiation

• Caries initiates in distinct areas: pits and fissures, smooth enamel surfaces, and root surfaces.
• Enamel pits and fissures are highly susceptible due to their shape, preventing biofilm removal.
• Smooth enamel surfaces, near gingiva or proximal contacts, are less favorable but still susceptible.
• Root surfaces are rougher, readily allowing biofilm formation, and cementum is thinner, offering less resistance to decay.

Pits and Fissures of Enamel

• Bacteria rapidly colonize newly erupted teeth's pits and fissures.
• S. sanguis is common in pits and fissures of newly erupted but Mutanus Streptococci are more prevalent in carious pits and fissures.
• The shape of pits and fissures contributes to susceptibility, impeding biofilm removal due to the long, narrow fissures.
• Pit-and-fissure caries expands as it penetrates the enamel.
• The entry site might appear smaller than the actual lesion, making diagnosis difficult.
• In cross-section, a pit-and-fissure lesion typically appears as an inverted V-shape, widening towards the DEJ.

Smooth Enamel Surfaces

• Cariogenic biofilm usually develops only on smooth surfaces near gingiva or under proximal contacts, which are less susceptible.
• A smooth-surface lesion shows a V-shape in cross-section, widening towards the DEJ.

Root Surface Caries

• Root surfaces are typically rougher than enamel, allowing biofilm formation readily.
• Thin cementum covering root surfaces offers minimal resistance to decay.
• Root caries lesions have less defined margins and are often U-shaped in cross-section, decaying more rapidly.

Progression of Enamel Caries

• Progression of smooth-surface enamel caries (non-cavitated to cavitation) takes about 18 months on average.
• Softened, chalky enamel that crumbles away with an explorer indicates active caries.
• Remineralization (arrested caries) appears as intact, discolored (brown or black) spots on teeth and is more resistant to future decay.
• These should not be restored unless they are esthetically objectionable.
• The microscopic features of non-cavitated enamel show 4 zones leading to decay, the translucent, dark, body and surface.

Classification of Dental Caries

• The classification table displays different stages of enamel, showing characteristics of hydrated, desiccated, surface texture, and hardness.

1- Enamel Caries

• Early caries on clean, dry smooth surfaces looks like a white spot (chalky, white, opaque).
• These marks appear on facial or lingual tooth surfaces and show up only after drying.
• Non-cavitated enamel caries lose translucency due to extensive subsurface porosity caused by demineralization.

Microscopic Features of Non-Cavitated Enamel

• Four zones are recognized pre-cavitation: translucent zone (usually present in 50% of lesions), dark zone (essential, present in 95% of lesions), body of the lesion (most demineralized), surface zone (almost unaffected, highly mineralized due to calcium, phosphorus, and fluoride).

2- Dentin Caries

• Dentin contains less mineral, with microscopic tubules facilitating bacteria passage.
• Caries spreads laterally along the DEJ, affecting wide areas of dentin.
• Dentinal caries has a V-shape in cross-section, wide at the DEJ and apex toward the pulp.
• Caries advances faster in dentin owing to its lower mineral content.
• Lesions advance further by having tubules in dentin providing a path for bacteria.
• The microscopic images show stages of dentin affected by caries.

Affected Dentin

• The affected zone is the inner region of carious dentin.
• It shows demineralization of intertubular dentin, but is remineralizable.
• Subzones of affected dentin include subtransparent, transparent, turbid dentin .

Infected Dentin

• The infected dentin is the outermost carious layer, the first part of the carious lesion.
• Bacterial invasion and widening of tubules that contain bacteria characterize this zone

Additional Information

• Affected dentin is vital, remineralizable, and sensitive.
• Infected dentin is non-vital, unmineralizable, and without sensation (dead).
• Different dentin layers have different characteristics for identification clinically.
• The pulp-dentin complex tries to remineralize, blocking off open tubules during caries attacks.
• Rapidly advancing caries overpowers these mechanisms, inducing infection, abscess and pulp death.
• Slow advancing caries are repaired through pulp remineralization of dentin by intertubular remineralization and apposition of peritubular dentin.
• Sclerotic dentin forms during slow advancing caries, it has more mineral and is darker, appearing hard to the explorer.