Dental Caries and Its Etiology

Dental Caries

• Defined as a progressive, irreversible microbial disease affecting tooth enamel, leading to cavity formation.
• Modern dentistry focuses on recognizing caries as an infectious disease, considering factors like causative agents, symptoms, prevention, and treatment.
• A multifactorial disease with a complex interaction of cariogenic oral flora and fermentable dietary carbohydrates on tooth surfaces.
• A dynamic process that disrupts the balance between tooth structure and plaque, resulting in mineral loss.

Etiology of Dental Caries

Ecology

• The study of interactions between organisms and their environment.

Ecosystem

• A defined area containing a biological community.

Ecological Niche

• Combination of food and shelter for microorganisms.

Contributing Factors of Dental Caries

• Three primary factors: host, microflora, substrate
• Host factors include teeth, saliva
• Microflora involves bacteria like streptococci and lactobacilli.
• Substrate refers to dietary carbohydrates, specifically sugars.
• Time is also considered a crucial contributor in the development of caries.

Dental Plaque (Pellicle and Bacteria)

• An adherent deposit of bacteria and their products on tooth surfaces.
• Consists of an amorphous organic film (acquired pellicle) mainly glycoproteins precipitated from saliva.
• Attracts bacteria, especially streptococci.

Role of Bacteria

• Acidogenic (produce acid)
• Aciduric (tolerant to acid)
• Adhere to tooth surfaces
• Produce sticky extracellular polysaccharides (primarily glucose polymers) from sugars.
• These polysaccharides create a matrix and aid bacterial adhesion.

Role of Dietary Carbohydrates

• Not all carbohydrates have the same cariogenicity.
• Complex carbohydrates like starch are relatively harmless.
• Low-molecular weight carbohydrates (sugars) are rapidly metabolized by bacteria, leading to a rapid drop in plaque pH.
• This drop in pH (below 5.5) initiates demineralization of tooth enamel.
• Sucrose causes more rapid production of extracellular polysaccharides than glucose, fructose, and lactose.

Oral Carbohydrate Clearance

• Factors affecting clearance time include: saliva rinsing effect, masticatory muscle activity, and tongue/lip/cheek movement.
• Factors that potentially prolong clearance time: dental cavities, low salivary flow, and viscous saliva.
• The Stephan curve demonstrates the sudden drop in pH following a glucose rinse, returning to normal within 30-60 minutes.

The Host (Tooth Surface)

• Enamel pits and fissures, cervical areas, and areas adjacent to restorations are sites prone to plaque retention and subsequent caries.
• Exposed root surfaces due to gingival recession and surfaces adjacent to dentures/bridges are also at risk.

Environment of the Tooth (Saliva and Fluoride)

• Saliva functions in maintaining normal oral flora through bacterial clearance, direct antibacterial activity, and buffering.
• Saliva helps to maintain pH balance, enabling remineralization of enamel.
• Fluoride in saliva enhances the remineralization process.
• Reduced salivary flow impacts the buffering action of saliva, leading to increased food retention.

Time

• Caries progression involves periods of destruction and repair.
• Mechanical removal of plaque exposing the tooth to saliva allows for remineralization.
• Mineral re-precipitation occurs due to an external supply from the oral cavity and internal supply from the pulp.

Epidemiology of Dental Caries

• DMF index: crucial method to assess prevalence and treatment needs in populations.
• It does not provide a full measure given its reliance on visual inspection without X-rays.

Classification of Dental Caries

• Classifications based on chronology, affected tissue, anatomical site, restoration surface, new/recurrent lesions, activity, speed, and pathway.

Severity

• WHO system classifies based on the shape and depth of the lesion (D1-D4).
• D1: Clinically detectable enamel lesions with intact surfaces
• D2: Clinically detectable cavities limited to enamel.
• D3: Clinically detectable cavities extending into dentin.
• D4: Lesions extending into the pulp.

Other Factors

• Radiation caries can lead to three types of defects.
• Dental caries in various age groups (nursing, rampant, adolescent, and adult).