Microbiology of Dental Caries: Unit 21

Classification of Dental Caries

• Dental caries can be classified based on the location of the lesion as pit and fissure caries, smooth surface caries, and root caries.

Theories of Dental Caries

• The theory of dental caries that dates back to the VII century BC suggests that cavities are due to the acids produced by microorganisms from sugars.
• The Chelation theory proposes that bacterial proteolytic enzymes degrade organic matter, releasing chelating agents that dissolve tooth minerals.

Prevalence of Dental Caries

• In Spain, approximately 80% of the population is affected by dental caries.

Consequences of Dental Caries

• Consequences of dental caries include tooth tissue destruction, pain, and potentially, systemic infections.

Types of Caries

• Recurrent caries is associated with an existing restoration.
• Rampant caries is a type of decay that is described as the most frequent in the initial lesion of caries affecting the enamel.
• Secondary caries occurs in the dentin.

Tooth Tissue Destruction

• The main cause of tooth tissue destruction in dental caries is the acid produced by microorganisms from sugars.

Keyes Scheme

• The Keyes Scheme involves three factors in dental caries: tooth, oral microbiota, and diet.

Bacteria and Dental Caries

• Streptococcus mutans is known for producing insoluble extracellular polysaccharides from sucrose, helping them adhere to tooth surfaces and bind more bacteria.
• Lactobacilli become predominant when pH drops below a certain range.
• Actinomyces bacteria predominate in tissues such as root and dentine.
• Streptococcus sanguis is isolated from the oral cavity of people without caries.

Factors Contributing to Dental Caries

• Factors that can contribute to breaking the balance between demineralization and remineralization, leading to the appearance of caries, include diet, oral microbiota, and tooth characteristics.
• A diet high in sugars and acids can favor aciduric bacteria, such as S.mutans and lactobacilli, becoming predominant.

pH and Demineralization

• The pH range below which demineralization of enamel starts is 5.5.

Prevention of Dental Caries

• Fluoride utilizes the mechanism of inhibition of acid production and inhibition of enzymatic activity to prevent dental caries.
• Noncaloric sweeteners, such as xylitol, can prevent dental caries by reducing the amount of sugars available for fermentation by bacteria.
• The primary effect of polyols, such as xylitol, in preventing dental caries is to reduce the production of acid by bacteria.
• Systemic fluoride intake is primarily from community water fluoridation.

Control of Dental Caries

• The primary method for controlling bacterial plaque is good oral hygiene practices, including regular brushing and flossing.
• Patients at high risk of dental caries can be identified through a combination of clinical examination, radiographs, and evaluation of diet and oral hygiene habits.
• The main purpose of identifying patients at high risk of caries is to provide targeted prevention and early intervention.

Bacteriocins

• Bacteriocins can inhibit the growth of Streptococcus mutans.

Excessive Fluoride Intake

• A potential consequence of excessive fluoride intake is dental fluorosis, which can cause white spots on the teeth.