Dental Caries Overview

Dental Caries

• Dental caries is a progressive, irreversible microbial disease of calcified dental tissues.
• It's characterized by demineralization of inorganic tissue and destruction of organic tissue.
• It's the most prevalent chronic disease affecting humans.
• Its effects persist throughout life, even after treatment.
• It affects both sexes and all races, social-economic backgrounds, and age groups.

Requirements for Dental Caries Development

• Development requires specific conditions occurring simultaneously.
• A susceptible tooth is necessary.
• A diet rich in fermentable carbohydrates is essential.
• Specific types of bacteria are required.
• Dental plaque is involved.
• Time is a factor in the process.

Contributing Factors in Dental Caries

Tooth

• Tooth composition (fluoride content) influences resistance to caries.
• Tooth morphology (deep pits) predisposes to caries development.
• Tooth malalignment can increase caries risk.

Saliva

• Saliva composition with higher ammonia content can offer caries resistance.
• Low saliva pH promotes caries development.
• Xerostomia (decreased saliva flow) increases caries risk.
• Thick saliva can increase caries risk.
• Antibacterial factors in saliva play a role in caries prevention.

Diet

• Refined foods tend to promote caries.
• High carbohydrate content promotes caries.
• Vitamins D, K, and B6 can reduce caries risk.
• Fluoride content in the diet influences caries development.

Etiology of Dental Caries

• No single, universally accepted theory explains etiology.
• Several theories have been proposed.
  • Acidogenic theory (Miller's chemico-parasitic theory)
  • Proteolytic theory
  • Proteolysis-Chelation theory

Acidogenic Theory (Miller's Chemico-Parasitic Theory)

• Dental caries is a two-stage process.
  • Decalcification of calcified parts.
  • Dissolution of residue.
• Acid is formed from sugar fermentation in retained areas of the teeth.

Acidogenic Theory (Mechanisms)

• Acidogenic bacteria and carbohydrates produce acid.
• Acid demineralizes tooth enamel and dentin.
• Proteolytic bacteria digest organic materials.

Role of Carbohydrates

• Tooth incubated with saliva and sugar leads to caries.
• Tooth incubated with saliva and meat does not develop caries.
• Dietary carbohydrates are the primary source because saliva contains insignificant amounts.
• Monosaccharides promote more caries due to ease of breakdown and quick diffusion into plaque.
• Increased carbohydrate intake correlates with increased caries activity.
• Frequent carbohydrate intake between meals increases caries activity.
• Sticky carbohydrates remain attached to teeth, increasing caries risk.

Role of Microorganisms

• Microorganisms are necessary for caries development.
• Saliva with carbohydrates and no microorganisms prevent caries.

Cariogenic Bacteria

• Acidogenic bacteria produce acid.
• Aciduric bacteria can thrive in acidic environments.
• Extra-cellular polysaccharide production leads to plaque formation.

Streptococcus Mutans

• A key acidogenic bacterium in early stages of dental caries.
• Strongly acidogenic and produces acid at low pH levels
• Can mutate from round to rod shape in varying pH.
• Dextran production enables bacterial adhesion to teeth.

Lactobacilli

• Isolated from late-stage dental caries.
• Some bacteria are involved in initiating caries, and others in its progression.
• Other streptococci, such as Streptococcus sanguinis and Actinomyces, play roles in root surface caries (but not enamel caries).

Role of Acid

• Formed by enzymatic breakdown of carbohydrates by bacteria.
• Lactic acid is a common type of acid formed.
• Butyric acid can also potentially form.
• Enamel dissolves when the pH drops below 5.5.
• Acids need to be retained on tooth surfaces for extended periods, which plaque aids.

Role of Dental Plaque

• A tenacious, bacterial structure.
• Soft and unmineralized.
• Forms on inadequately cleaned teeth.
• Removable with tooth brushing.

Mechanism of Plaque Formation

• Initial deposition of a cell-free layer (acquired pellicle) consisting of salivary glycoproteins.
• Colonization of the pellicle by bacteria.
• Plaque maturation through further colonization.

Composition of Dental Plaque

• Contains water (80%), proteins (from saliva), carbohydrates (like dextran), lipids (bacterial origin), and inorganic components (calcium, phosphate, potassium, magnesium, fluoride).
• Specific types of bacteria, such as Streptococcus, filamentous bacteria, and lactobacilli are part of dental plaque.

Role of Plaque Matrix

• Acts as a diffusion barrier, retaining acid in high concentrations.
• Slows down buffer entry from saliva.
• Contributes to plaque adhesiveness.

Role of Saliva in Dental Caries

• Saliva forms the pellicle (initial layer).
• Saliva provides a rinsing effect (xerostomia increases incidence).
• Saliva has buffering capacity (bicarbonates, phosphates).
• Saliva contains antibodies that kill microorganisms.
• An antibacterial substance like lysozyme, peroxidase, and lactoferrin are also present.

Proteolytic Theory

• Microorganisms invade the organic areas in enamel as well as destroying inorganic part and producing acids.
• This acid demineralizes the inorganic areas of the enamel.

Proteolysis-Chelation Theory

• Chelation is the complexing of metal ions.
• Metal ions complexing promotes stability. (chlorophyll and hemoglobin are examples).
• This theory involves bacterial attack on the organic parts of the enamel, complexing the organic, and producing acids from the calcium ions.
• This theory suggests enamel caries can start from organic or inorganic materials.

High-Risk Patients for Caries

• Patients undergoing chemotherapy
• Patients who frequently consume fermentable carbohydrates
• Individuals with autoimmune diseases.
• Pregnant people
• Those taking medications impacting saliva flow