Presentation on theme: "Role of diet in dental caries Specific, non-specific, etiological plaque hypothesis Metabolic activities of dental plaque related to dental caries Objectives:"— Presentation 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 sucrose Downer MC. Comm Dent Health 1999;16:18-21. Positive correlation between caries experience and sucrose consumption over 50 years Diet and dental caries Dietary factors Dietary factors
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 MSreduce 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 change Cariogenic aspects of dental plaque Cariogenic 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. mutansCaries 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 Nonspecific Plaque 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 microflora Frequent 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 Acids AceticPropionic Succinic Formic Lactic Ability of bacteria to produce organic acids from fermentable carbohydrates Glycolysis (fermentation): - Anaerobic catabolism of carbohydrates - Energy production Glucose2 lactic acids + 2 ATPs Heterofermentative bacteria Produce a mixture of metabolites: Homofermentative bacteria Produce > 90% lactic acid Cariogenic bacteria Acidogenicity Role of cariogenic bacteria Role of cariogenic 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 of cariogenic bacteria Role of cariogenic 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 of cariogenic bacteria Role of cariogenic 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 IPSEnergy for ATPase Contribute to aciduricity
Extracellular polysaccharides (EPS) glucanfructan 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 bondenergy Plaque accumulation S. mutans glucose sucrose (S. mutans surface ) Glucan-binding ligands adherence & accumulation + glucan Glucosyltransferase: Virulent factor of S.mutans
glucose sucrose 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 CO 2 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 pH Role of cariogenic bacteria Role of cariogenic bacteria
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.
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