role of diet in dental caries specific, non-specific, etiological plaque hypothesis metabolic...
TRANSCRIPT
• 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.