Cariology Lecture 5

What causes dental caries?

An imbalance between demineralization and remineralization, primarily driven by acid production from plaque bacteria such as Streptococcus mutans and Lactobacillus.

What are the key factors in caries etiology?

Host (tooth, saliva), microflora (biofilm composition), substrate (dietary sugars), and time.

What is the main cause of acid production in plaque?

Bacterial fermentation of dietary carbohydrates, especially sucrose, resulting in lactic acid formation.

What is the critical pH for enamel demineralization?

Approximately 5.4 (below this, hydroxyapatite dissolves).

What is demineralization?

The loss of calcium, phosphate, and carbonate ions from enamel or dentin due to acid attack.

What is remineralization?

The natural repair process in which calcium and phosphate ions re-enter enamel crystals, often enhanced by fluoride.

What determines whether demineralization or remineralization dominates?

The balance between acid challenges (frequency and duration) and the protective actions of saliva and fluoride.

What is the Demin/Remin equilibrium?

A dynamic process where mineral loss and gain occur constantly — caries develops when demineralization outweighs remineralization.

What is the importance of saliva in caries dynamics?

Saliva buffers acids, provides calcium and phosphate for remineralization, and helps clear food and bacteria.

What role does fluoride play in remineralization?

Fluoride enhances mineral reuptake, forms fluorapatite (more acid-resistant), and inhibits bacterial metabolism.

What happens when plaque pH is above the critical level?

Remineralization occurs because plaque fluid remains saturated with calcium and phosphate.

What happens when plaque pH falls below the critical level?

Demineralization occurs as hydroxyapatite dissolves and minerals diffuse out of the tooth.

What are the zones of enamel caries under microscopy?

Surface zone, body of lesion, dark zone, and translucent zone.

Where does enamel caries usually begin?

In subsurface enamel beneath the intact surface, due to acid diffusion through microchannels.

What happens in dentinal caries?

Acid and bacterial products penetrate dentinal tubules, causing demineralization followed by bacterial invasion and collagen breakdown.

What is affected dentin?

Demineralized but not infected — can be remineralized if the lesion is arrested.

What is infected dentin?

Soft, necrotic, and heavily colonized by bacteria — cannot be remineralized.

What are root caries?

Lesions that occur on exposed cementum or dentin when the root surface is uncovered by gingival recession.

Why are root caries more common in older adults?

Increased gingival recession, xerostomia, and longer tooth retention expose roots to plaque and acid attack.

What are the main types of caries by location?

1. Pit and fissure caries 2. Smooth surface caries 3. Root surface caries 4. Secondary (recurrent) caries.

Where do pit and fissure caries occur?

On occlusal surfaces of molars and premolars, and on lingual pits of maxillary incisors.

Where do smooth surface caries occur?

On proximal surfaces (mesial/distal), and along cervical areas (Class V).

Where do root caries occur?

On exposed cementum and dentin below the CEJ.

What are secondary caries?

Lesions that form adjacent to existing restorations due to plaque accumulation and microleakage.

What does "active caries" mean?

A lesion that is currently progressing — appears matte, soft, and chalky.

What does "arrested caries" mean?

A lesion that has stopped progressing — hard, shiny, and darkly discolored.

Why is prevention important in dental caries?

Because caries is a reversible process in its early stages, and prevention addresses the disease cause rather than symptoms.

How does fluoride prevent caries?

By promoting remineralization, inhibiting demineralization, and reducing bacterial acid production.

what is the treatment for early, incipient (non-cavitated lesions)

prevention

what is the treatment for moderate to severe cavitated lesions

pervention and restorative treatment

why do caries progress quicker in the dentin

the dentin is less mineralized

what is included in saturation

maintained by saliva

Ca, phosphate, pH (most variable)

what is calculus

mineral deposits on the tooth surface when the tooth is supersaturated with saliva

demineralization

loss of minerals (Ca, phosphate, carbonate) from the tooth due to the addition of sugars

Remineralization

Gain of minerals (Ca, phosphate, carbonate) from the tooth due to application of fluoride and removal of sugars

dentin can be demineralized at a (higher/lower) pH than enamel

higher

Enamel begins demineralization under pH of 5.5, and dentin under 6.2

lesion formation requirements

• thermodynamic undersaturation (of saliva and plaque)

• diffusion of hard tissue at significant rates

• insufficient remineralization

What are the two zones of dentinal decay

1. outer carious layer/ intected dentin

2. inner carious later/affected dentin

what are the 3 zones within the inner carious layer of dentin decay

1. The Turbid Zone

2. Transparent Zone

3. Subtransparent Zone

Turbid Zone

loss of peritubular dentin and intertubular dentin is mostly demineralized

Transparent Zone

retain peritubular dentin and tubule lumen is partly filled with minerals

Subtransparent zone

presents granular shaped crystals and normal dentin is found underneath

Lesion formation requirements

undersaturation of saliva

diffusion out of hard tissue at significant rates

insufficient remineralization