Aetiology of Dental Caries

Aetiology of Dental Caries

• Dental caries is a localized, chemical dissolution of a tooth surface, caused by metabolic activity in plaque biofilm.
• Dental caries is a progressive disease of the hard tissues (enamel, dentine, and cementum) and is reversible in the early stages.
• Key factors contributing to dental caries are: susceptible tooth surface, fermentable carbohydrates, and plaque bacteria.

Learning Outcomes

• Understand the aetiology (cause) and pathogenesis (development) of oral diseases.
• Recognize psychological and sociological factors impacting poor oral health and treatment success.
• Explain the significance of each stage in the patient assessment process.
• Explain the role of a dental therapist in tooth restoration.
• Define what dental caries is.
• Explain the aetiology of dental caries.
• List and describe 4 aetiological factors leading to dental caries.
• List the evidence supporting identified aetiologies.

Reasons for Tooth Loss

• Periodontal disease
• Trauma
• Elective procedures
• Caries

Burden of Dental Caries

• Average cost of a tooth extraction in hospital for a child under 5 is £836.
• £50.5 million was spent on tooth extractions for those under 19 in 2015-2016.
• £7.8 million was spent on tooth extractions for those under 5 in the same period.

Preventing Dental Caries and Treating It

• Preventative and treatment strategies for reducing caries are dependent on understanding the process.

What is the Caries Process?

• A localized, chemical dissolution of a tooth surface brought about by metabolic activity within a microbial deposit (a biofilm) covering the affected surface area.
• Dental caries are described in terms of their signs and symptoms, and a localized chemical dissolution of tooth surfaces by metabolic events happening within the biofilm (dental plaque).
• The process is caused by the actions of bacteria on fermentable carbohydrates.

Main Points

• Involves chemicals.
• Involves microbes and their metabolites.
• Involves dissolution.
• Affects all hard tissue.
• Often localized.
• Can be reversible.
• Involves fermentable carbohydrates.

Etiological Agents for Caries

• Susceptible tooth surface
• Plaque bacteria
• Fermentable carbohydrate
• Time

All Encompassing Definition

• A localized, chemical dissolution of a susceptible tooth surface over time brought about by metabolic activity on fermentable carbohydrates in a microbial deposit (a dental biofilm) covering the tooth surface.

True Extent

• Factors influencing caries development include social class (saliva flow rate), education, diet (composition and frequency), microbial species, behavior and attitudes.
• Saliva flow rate and its effect on the acid environment and mineral dissolution and remineralisation are important in the caries development process.

Susceptible Tooth Surface

• All dental hard tissues are susceptible to some degree of caries.
• Some areas are more susceptible than others, including pits and fissures, smooth surfaces, and proximal surfaces.
• Susceptible areas often have factors that increase their ability to accumulate plaque biofilm.

Fermentable Carbohydrate

• Bacteria need food to survive, and sugars present in the diet provide a substrate for oral commensal bacteria to metabolize and produce lactic acid.
• Simple sugars (glucose, fructose, sucrose) are rapidly metabolized and produce acid, they are considered cariogenic.
• Complex carbohydrates are not completely digested in the mouth and are less cariogenic.
• Intrinsic sugars are naturally occurring sugars found in whole foods, like fruit and vegetables
• Extrinsic sugars are not bound within a cellular structure, some are glucose, sucrose, lactose, fructose.

Bacteria + Simple Sugars = Acid

• Bacteria metabolizing simple sugars produce acid.
• Critical pH is the point below which tooth tissue starts losing mineral to saliva or plaque.

Critical pH

• Critical pH of enamel is 5.5.
• Critical pH of dentine is 6.5.

Time

• Time is a significant factor in caries development.
• Frequent exposure to fermentable carbohydrates leads to more time below the critical pH, increasing demineralization risk.
• Infrequent intake allows for remineralization to happen, lowering caries risk.

Evidence for the Caries Process

• Experiments with germ-free animals and those fed a sugar-free diet demonstrated the necessity of bacteria and fermentable carbohydrates for caries to develop.
• The Vipeholm study (1945–1952) showed a correlation between cariogenic food frequency, quantity, and the development of caries.
• Further studies on populations with limited access to cariogenic foods and beverages have also confirmed the role of the other factors in developing caries.