• Role of diet in dental caries

• Specific, non-specific, etiological plaque hypothesis

• Metabolic activities of dental plaque related to dental caries

Objectives:

DENT 5302 TOPICS IN DENTAL BIOCHEMISTRY

30 March 2007

Outline

Specific vs Non-specific vs Etiological plaque hypothesis

Aciduricity

Production of intra- and extracellular polysaccharides

Alkali production in dental plaque

Acid production by dental plaque bacteria

Methods to modify plaque acidity/cariogenicity

Diet and dental caries

Sugars

Dietary factors

Caries-protecting food

Fermentable carbohydrate: Sugars and starch

sucrosesucroseDowner MC. Comm Dent Health 1999;16:18-21.

Positive correlation between caries experience and sucrose consumption over 50 years

Diet and dental cariesDietaryfactorsDietaryfactors

Woodward M, Walker AR. Br Dent J 1994;176:297-302.

Currently, weaker relationship between sugar and caries?

90 nations: +ve relationship Industrialize nations: No relationship

After ~ 1985, caries decreased more than sugar consumption

The frequent use of fluoride

Change the impact of sugars

Sugars and dental caries. Touger-Decker R, van Loveren C. American J Clin Nutr 2003;78(suppl):881S-92S.

Sugar alcohols

Oligosaccharides

Questions: Myth or Fact

Honey is a natural product, you won’t get caries from it.

Beer makes me drunk, but does not cause caries.

‘Baby bottle caries’ occurs when bedtime habits include

lying with a bottle filed with milk.

I put Splenda in my coffee, so I am safe from both calories

and caries.

Cough syrup can cause tooth decay.

Potatoes are non-cariogenic.

Dietary factors

Amount and type of carbohydrate

Consistency

Degree of retention

‘Caries protective' factors

Eating pattern

Intake frequency

Individual factors

The Vipeholm Study

Institution…..ethic x

Gustafsson BE et al. Acta Odontol Scand 1954; 11:232-264.

Sugar

Frequently

Between meals

Consistency (‘Sticky’)

Stimulate salivary flow.

Antimicrobial action ?

Clinical studies: Xylitol vs Sorbitol

Caries-protecting factors in food

Increase the clearance of sugars and fermentable carbohydrates

Buffering capacity

Interfere glucosyltransfersase activity of MS reduce plaque

Favoring remineralization

Calcium, phosphate, protein: Cheese and dairy products

‘Sialogogue’

Chewing gum stimulates saliva

Polyphenols

Tannins (cocoa, coffee, tea)

Xylitol

Sugar alcohol used in chewing gum

Children and adolescents with low incidence of dental

caries drank more milk.

Eur J Epidemiol 13:659-664, 1997

Com Dent Oral Epidemiol 24:307-311, 1996

Elderly people that eat cheese several times per

week had a lower incidence of root caries.

Am J Clin Nutr 61:417S-422S, 1995

Remineralization of enamel was observed when cheese

and milk were used as between meal snacks.

Dairy products, except sweetened yogurt, generally

reduced the amount of dentin demineralization.

J Contemp Dent Prac 1:1-12, 2000

Is dental caries a transmittable, infectious disease?

Yes, because……………….

No, because………………..

Paradigm changeCariogenic aspects

of dental plaqueCariogenic aspects

of dental plaque

Discussion: (group of 6-8)

Dental caries is a multifactorial disease resulting from

an ecological shift in the tooth surface biofilm (dental

plaque), leading to mineral imbalance between plaque

fluid and tooth, hence net loss of tooth mineral.

Fejerskov, 2004

1950

Preventive & treatment: eliminate specific infection

Antibiotics and immunization

Bacteria & number of caries lesions

Specific Plaque Hypothesis

animal + S. mutans Caries

Other animals

Cariogenic bacteria:

mutans streptococci (MS)

lactobacilli

71% of carious fissures: > 10% MS

70% of ‘caries-free’ fissures: no detectable MS

Rampant caries: MS & lactobacilli

NonspecificPlaque Hypothesis

plaque = pathogenic

Should be eliminated

?some plaque

no caries?

more plaque

more disease

2000

? Current ?

2000

? Current ?

Contribution from other bacteria:

S. mutans: final pH 3.95-4.1.

S. mitis, S. salivarius, S. anginosus: final pH 4.05-4.5.

High proportion of MS no caries / Caries developed without MS

Ecologic Plaque Hypothesis

• MS & other microorganisms = endogenous bacteria (resident of oral cavity)

• No caries: lower level & stability in plaque composition (microbial

homeostasis)

• Change in local environment Shift the balance of plaque microfloraFrequent sugar intake Repeated low pH

Favors growth of cariogenic species

Dental caries

Marsh PD, 1994

1. Produce acid rapidly from fermentable carbohydrate

(Acidogenicity)

2. Survive and continue to produce acid at acidic pH

(Aciduricity)

3. Produce extracellular polysaccharides from dietary

sucrose to facilitate adherence to tooth surfaces and

build-up of large bacterial deposits

4. Produce intracellular polysaccharides as storage

components to prolong acid formation & acidic pH

Role of cariogenic microorganisms

Plaque AcidsPlaque Acids

AceticPropionic

SuccinicFormicLactic

Ability of bacteria to produce organic acids from fermentable carbohydrates

Glycolysis (fermentation):

- Anaerobic catabolism of carbohydrates

- Energy production

Glucose 2 lactic acids + 2 ATPs

Heterofermentative bacteria

Produce a mixture of metabolites:

Homofermentative bacteria

Produce > 90% lactic acid

Cariogenic bacteria

AcidogenicityRole ofcariogenic bacteria

Role ofcariogenic bacteria

Organic acids - acetic, propionic, succinic, formic

Ethanol

Aciduricity = Ability of bacteria to live in a low pH environment

“Dental caries is a consequence of successful adaptation by oral

bacteria to survive and continue to produce acid at acidic pH”

Role ofcariogenic bacteria

Role ofcariogenic bacteria Aciduricity

Ecologic plaque hypothesis:

Beginning: - Low level of MS or lactobacilli

- Other bacteria produce acid

Frequent consumption of fermentable carbohydrate

Best acid adaptation bacteria survive (MS & Lactobacilli)

Increase level of MS & lactobacilli

Proton-translocating membrane ATPase

Increase energy demand

increased glycolysis

more acid production

Zero DT. Adaptation in Dental Plaque.

Cariology for the Nineties. p 333-349.

Maintaining intracellular pH at optimum

1. Low proton permeability of the cell membrane: cell wall thickening

2. Production of bases

3. Buffering capacity of the cytoplasm

4. Active transport of proton out of cell

1

2

3

Intra & extracellular polysaccharides formation

Role ofcariogenic bacteria

Role ofcariogenic bacteria

Pathways of sucrose metabolism

Intracellular polysaccharides (IPS)

Storage form of carbohydrate: glycogen-amylopectin

Energy production and acids (by-product) when dietary CHO is depleted

Excess nutrient: Up to 20% of sucrose converted to IPS

Produced by most plaque bacteria

IPS as a virulence factor:

Contribute to acidogenicity

Caries-prone plaque has prolong production of acid (e.g., after meal) from IPS storage

Drive protons out of cell

Adapt to low pH environment

IPS Energy for ATPase

Contribute to aciduricity

Extracellular polysaccharides (EPS)

glucan fructan

EPS may serve as carbohydrate storage:

Fructans – degrade rapidly within a few hours,

Glucans – longer period

Major component of interbacterial matrix

Barrier to the outward diffusion of acids from plaque

Glucans

Before sucrose enters the cells, <10% of sucrose glucans & fructans

Remain associated with cell

Diffuse into surrounding plaque

Sucrose (not other CHO)

Fructosyltransferase Glucosyltransferase

Fructans Glucans

disaccharide bond energy

Plaque accumulation

S. mutans

glucoseglucose sucrosesucrose

(S. mutans surface )

Glucan-binding ligands

adherence & accumulation

+ glucan

Glucosyltransferase:

Virulent factor of S.mutans

glucoseglucose sucrosesucrose

Question (group of 3-4)Scanning electron micrograph of S. mutans grown in glucose broth (left), and

sucrose (right). The amorphous material covering the colonies is

extracellular polysaccharides.

From your knowledge in the synthesis of EPS, what are the main points told by

these micrographs?

Sucrose, not glucose, is necessary for the synthesis of EPS.

EPS permit the bacteria to accumulate on the surface.

Alkalinization phase Acid diffusion

Buffering capacity

Alkali from bacterial metabolism

Alkali generation: End products are ammonia and/or CO2

Ureolysis

Arginine deiminase system (Major source of ammonia)

Strickland reaction

S. salivarius, A. naeslundii, haemophili use

enzyme urease to hydrolyze urea in saliva.

Peptostreptococci oxidize proline in amino

acids and reduce protons in plaque.

S. gordonii, S. rattus, S. sanguis, lactobacilli, spirochetes use

enzyme arginine deiminase to catabolize arginine in diet.

Fluctuation of plaque pHRole ofcariogenic bacteria

Role ofcariogenic bacteria

plant extracts

1. Stimulate salivary flow chewing gum

3. Disrupt plaque mechanical

enzyme

2. Increasing plaque pH bicarbonate (‘baking soda’)

ammonium salts

4. Antimicrobial agent chlorhexidine xylitol fluoride, stannous

6. Modify microflora reduce lactate producer

increase lactate user (Veillonella)

increase base producer

Methods to modify plaque acidity/cariogenicity

5. Caries vaccine

Recommended references

1. Touger-Decker R, van Loveren C. Sugars and dental caries. Am J Clin Nutr 2003;78(suppl):881S-892S.

2. Zero DT. Sugars – The arch criminal? Caries Res 2004;38:277-285.

3. Marsh PD. Microbiologic Aspects of Dental Plaque and Dental Caries. Dent Clin North Am 1999;43(4):599-614.

4. Gordon Nikiforuk. Understanding Dental Caries 1. Etiology and Mechanisms, Basic and Clinical Aspects. Basel; New York: Karger 1985. Chapters 5 & 6.

5. Burne RA, Marquis RE. Alkali production by oral bacteria and protection against dental caries. FEMS Microbiology Letters 2000;193:1-6.

6. Fejerskov O. Changing paradigms in concepts of dental caries: Consequences for oral health care. Caries Res 2004;38:182-191.

7. Twetman S. Antimicrobials in future caries control? Caries Res 2004;38:223-229.