DENT 5302 TOPICS IN DENTAL BIOCHEMISTRY
30 March 2007
Objectives:
• Role of diet in dental caries
• Specific, non-specific, etiological plaque hypothesis
• Metabolic activities of dental plaque related to dental caries
Outline
Diet and dental caries
Sugars
Dietary factors
Caries-protecting food
Specific vs Non-specific vs Etiological plaque hypothesis
Acid production by dental plaque bacteria
Aciduricity
Production of intra- and extracellular polysaccharides
Alkali production in dental plaque
Methods to modify plaque acidity/cariogenicity
Dietary
factors
Diet and dental caries
Fermentable carbohydrate: Sugars and starch
Downer MC. Comm Dent Health 1999;16:18-21.
sucrose
Positive correlation between caries experience
and sucrose consumption over 50 years
Currently, weaker relationship between sugar and caries?
90 nations: +ve relationship
Industrialize nations:
No relationship
Woodward M, Walker AR. Br Dent J 1994;176:297-302.
After ~ 1985, caries decreased
more than sugar consumption
The frequent use of fluoride
Change the impact of sugars
Oligosaccharides
Sugar
alcohols
Sugars and dental caries. Touger-Decker R, van Loveren C. American J Clin Nutr 2003;78(suppl):881S-92S.
Questions: Myth or Fact
Honey is a natural product, you won’t get caries from it.
Potatoes are non-cariogenic.
Beer makes me drunk, but does not cause caries.
I put Splenda in my coffee, so I am safe from both calories
and caries.
Cough syrup can cause tooth decay.
‘Baby bottle caries’ occurs when bedtime habits include
lying with a bottle filed with milk.
Dietary factors
Individual factors
Amount and type of carbohydrate
Eating pattern
Consistency
Intake frequency
Degree of retention
‘Caries protective' factors
The Vipeholm Study
Institution…..ethic x
Sugar
Frequently
Between meals
Consistency (‘Sticky’)
Gustafsson BE et al.
Acta Odontol Scand 1954; 11:232-264.
Caries-protecting factors in food
‘Sialogogue’
Chewing gum stimulates saliva
Increase the clearance of sugars and fermentable carbohydrates
Buffering capacity
Polyphenols
Tannins (cocoa, coffee, tea)
Interfere glucosyltransfersase activity of MS
reduce plaque
Xylitol
Sugar alcohol used in chewing gum
Stimulate salivary flow.
Antimicrobial action ?
Clinical studies: Xylitol vs Sorbitol
Favoring remineralization
Calcium, phosphate, protein: Cheese and dairy products
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
Cariogenic aspects
of dental plaque
Paradigm change
Discussion: (group of 6-8)
Is dental caries a transmittable, infectious disease?
Yes, because……………….
No, because………………..
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
Nonspecific
Plaque Hypothesis
Specific Plaque Hypothesis
? Current ?
1950
plaque = pathogenic
Should be eliminated
2000
animal + S. mutans
Caries
Other animals
more plaque
more disease
?some plaque
no caries?
Cariogenic bacteria:
mutans streptococci (MS)
lactobacilli
71% of carious fissures: > 10% MS
70% of ‘caries-free’ fissures: no detectable MS
Rampant caries: MS & lactobacilli
Preventive & treatment: eliminate specific infection
Antibiotics and immunization
Bacteria & number of caries lesions
? Current ?
2000
High proportion of MS
no caries / Caries developed without MS
Contribution from other bacteria:
S. mutans: final pH 3.95-4.1.
S. mitis, S. salivarius, S. anginosus: final pH 4.05-4.5.
Ecologic Plaque Hypothesis
Marsh PD, 1994
• MS & other microorganisms = endogenous bacteria (resident of oral cavity)
• No caries: lower level & stability in plaque composition (microbial homeostasis)
• Change in local environment
Frequent sugar intake
Shift the balance of plaque microflora
Repeated low pH
Favors growth of cariogenic species
Dental caries
Role of cariogenic microorganisms
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 bacteria
Acidogenicity
Ability of bacteria to produce organic acids from fermentable carbohydrates
Glycolysis (fermentation):
Propionic
- Anaerobic catabolism of carbohydrates
Plaque Acids
- Energy production
Formic
Glucose
Acetic
2 lactic acids + 2 ATPs
Homofermentative bacteria
Produce > 90% lactic acid
Lactic
Succinic
Cariogenic
bacteria
Heterofermentative bacteria
Produce a mixture of metabolites:
Organic acids - acetic, propionic, succinic, formic
Ethanol
Role of
cariogenic bacteria
Aciduricity
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”
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
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
Proton-translocating membrane ATPase
more acid production
Increase energy demand
increased glycolysis
Zero DT. Adaptation in Dental Plaque.
Cariology for the Nineties. p 333-349.
Intra & extracellular
polysaccharides formation
Role of
cariogenic bacteria
Pathways of sucrose metabolism
1
3
2
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
Contribute to aciduricity
IPS
Energy for ATPase
Drive protons out of cell
Adapt to low pH environment
Extracellular polysaccharides (EPS)
Before sucrose enters the cells, <10% of sucrose
glucans & fructans
Diffuse into surrounding plaque
Remain associated with cell
glucan
Glucans
fructan
Major component of interbacterial matrix
Barrier to the outward diffusion of acids from plaque
EPS may serve as carbohydrate storage:
Fructans – degrade rapidly within a few hours,
Glucans – longer period
S. mutans
Sucrose
(not other CHO)
disaccharide bond
Fructosyltransferase
Fructans
energy
Glucosyltransferase
Glucans
Glucan-binding ligands
Plaque accumulation
glucose
sucrose
(S. mutans surface )
+ glucan
adherence & accumulation
Glucosyltransferase:
Virulent factor of S.mutans
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?
glucose
sucrose
Sucrose, not glucose, is necessary for the synthesis of EPS.
EPS permit the bacteria to accumulate on the surface.
Role of
cariogenic bacteria
Alkalinization phase
Fluctuation of plaque pH
Acid diffusion
Buffering capacity
Alkali from bacterial metabolism
Alkali generation: End products are ammonia and/or CO2
Ureolysis
S. salivarius, A. naeslundii, haemophili use
enzyme urease to hydrolyze urea in saliva.
Strickland reaction
Peptostreptococci oxidize proline in amino
acids and reduce protons in plaque.
Arginine deiminase system (Major source of ammonia)
S. gordonii, S. rattus, S. sanguis, lactobacilli, spirochetes use
enzyme arginine deiminase to catabolize arginine in diet.
Methods to modify plaque acidity/cariogenicity
 chewing gum
1. Stimulate salivary flow
2. Increasing plaque pH
 bicarbonate (‘baking soda’)
ammonium salts
3. Disrupt plaque  mechanical
enzyme

plant extracts
4. Antimicrobial agent  chlorhexidine
 xylitol
 fluoride, stannous
5. Caries vaccine
6. Modify microflora
reduce lactate producer
increase lactate user (Veillonella)
increase base producer
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.