Cariology Lecture 1

Dental Caries

A biofilm-mediated, sugar-driven, multifactorial, dynamic disease that results in the physic demineralization and remineralization of dental tissues

What is the most prevalent condition world-wide?

Untreated dental caries in permanent teeth

In 2010, how many people worldwide did untreated caries affect?

2.4 billion

True or false: More individuals suffer from dental disease than any other illness known to humans.

True

What percentage of Americans have some form of dental disease?

98%

What are the goals of treatment of caries?

-Prevent new ones from forming

-Detect lesions early so that they can be treated and arrested by noninvasive means

-Educate pts on the causes of tooth decay and give them preventative tools

How to caries form?

An imbalance of demineralization and remineralization of the teeth

Oral cavity bacteria ferments carbs (sugars) into organic acids, which results in the dissolution of dental hard tissue in the case of lactic acid

What three things interact to form caries?

Teeth

Microorganisms

Saliva

Are caries preventable?

In most cases, yes

What causes demineralization?

Acids that form during the fermentation of sugars by oral bacteria

Lack of protective saliva

Tooth morphology/composition

How can you remineralize teeth?

Remove carcinogenic bacteria through effective oral hygiene

Good salivary flow

Topical fluoride

Sealants

Anticaries/remineralizing agents

Diet modifications

What types of food and drinks cause demineralization?

Acidic ones

4 typical suspects of caries development

Genetics

Bacteria

Diet (sugar)

Saliva

What is the outermost layer of the tooth composed of?

Hydroxyapatite (HAP), a crystalline calcium phosphate mineral

Chemical composition of HAP

Ca5(PO4)3(OH)

What is the hardest substance in the human body, and what does it provide?

Enamel, strength and protection

Percentage of inorganic content in enamel

96% by weight, the remainder is organic material and water

What else is in enamel besides HAP?

It is calcium deficient, so other ions like sodium, magnesium, and carbonate replace calcium and hydroxyl ions

What does carbonate do in the enamel?

Makes the tooth mineral more susceptible to acid dissolution

What does bleaching do to the teeth?

Dehydrates them

Dentin composition

Less mineral content and more organic matter (collagen)

70% inorganic

18% organic

12% water

Does dentin stop forming?

No, it continues to be formed after crown formation is complete

What is dentin?

A vital tissue under the enamel that is softer, but still protective

It is sensitive to hot and cold

Pulp composition

25% organic

75% water

What is the organic content in pulp?

Connective tissue cells (fibroblasts), fibers (collagenous), and ground substances (proteoglycans and fibronectin)

Is the pulp vascular?

Highly; arterioles and venues enter/exit through the apical foramen and accessory root canals

Is the pulp innervated?

Very; nerves follow the course of the blood vessels with extensions into the dentin

When does one need root canal therapy?

When the pulp becomes necrotic

3 pairs of glands that produce saliva

Parotid

Submandibular

Sublingual

How much saliva is secreted per day?

0.7-1.5L

What is saliva composed of?

99% water

Electrolytes and organic components like proteins, glycoproteins, and enzymes

Pellicle

A thin, bacteria-free layer covering the teeth, formed by the absorption of salivary proteins that have a high affinity for surface minerals in the tooth.

Plays an important role in protecting dental hard tissue against mechanical and chemical damage

What does salivary water do?

Rinsing effect of the mouth

Solubilization of food

Facilitation of food clearance

Lubrication of oral soft tissues

Facilitation of mastication, swallowing, and speech

Functions of salivary electrolytes

Maintaining supersaturated calcium and phosphate concentrations and neutralization of acid by buffering actions

Functions of salivary organic components

Enamel pellicle formation

Mucosal coating

Antimicrobial defense

Digestive actions

Saliva’s protective role

Counteracting demineralization

Natural buffer to neutralize acids and raise pH

Supersaturation with calcium and phosphate ions to be redeposited onto the tooth surface

Amylase function

Degradation of starch

Lysozyme function

Antimicrobial activity by destruction of bacterial cell membranes

Lactoferrin function

Antimicrobial activity by high affinity for iron

Peroxidase function

Antimicrobial activity/protection against H2O2

Agglutinin function

Antimicrobial activity by agglutination of bacterial to large aggregates

Statherin function

Inhibits spontaneous precipitation

Function of antibodies

IgA/IgG, IgM inhibition of adhesion, enhancement of phagocytosis

How is biofilm (plaque) formed?

Sticky glycoproteins in saliva from foods high in fermentable carbs (glucose,sucrose,starches) adhere to the tooth surface forming a base for bacteria to attach and multiply

What does S. Mutans do?

Possesses enzyme glucosyltransferase

Forms dextran from glucose polymerized from sucrose

What is dextran?

A highly sticky substance that contributes to the formation of plaque, further trapping bacteria and acids against the tooth

It is a vicious cycle, sticky plaque gets more and more sticky

Bacteria and sugars produce…

Acid

Which bacteria metabolize the sugars through glycolysis?

S. Mutans and Lactobacilli

What is a key byproduct of glycolysis in saliva?

Lactic acid

What is the critical pH level for enamel?

5.5

What happens if the pH falls below that critical level in enamel?

The acidic environment causes the hydroxyapatite crystals to dissolve, which weakens the enamel structure

What happens when the enamel structure is weakened?

Microscopic pores form that can turn into visible lesions (cavities)

What is shown in this photo (broadly)?

Dental plaque

What are the green and magenta bacteria called?

Green- S. Mutans

Magenta- corynebacteria

What chemical reaction occurs when the enamel ph is less than 5.5?

Hydrogen ions react with phosphate and hydroxyl ions in the hydroxyapatite, releasing calcium and phosphate ions into the surrounding solution

Ca10(PO4)6(OH)2+H+→Ca2++HPO4 2- +H2O

What causes pH to drop below 5.5? When?

Lactic acid; when buffering effects of saliva are ineffective

What is this called?

The Stephen Curve

What does The Stephen Curve represent?

The amount of time it takes for pH to fall below the critical level and rise back to normal levels

How long does it take for acid production to cause the pH to fall below 5.5?

5-10 min

How long does the pH typically stay below 5.5?

20-30 min

When should you brush your teeth when correlating with eating and why?

Immediately before you eat: with a fluoride toothpaste, this gives a slight protective layer to the tooth surface

1 hour after you eat: This allows for adequate time to pass to avoid the tooth surface being brushed into after being softened by the acids

What occurs at an oral plaque pH of 5.5?

Tooth enamel demineralization caused by an oral bacteria-induced increase in acidity

What does the green line represent?

A low-risk patient; someone who is caries-resistant

What does the yellow line represent?

A moderate risk patient

What does the red line represent?

A high risk patient, much longer time for return to baseline pH

Prevention measures from erosion caused by sugary and acidic beverages

Drink in moderation

Use a straw

Drink in one sitting or with food

Drink water to rehydrate

Wait an hour to brush after

Use fluoride

Drink milk, it is neutral pH and has a healthy amount of natural sugars