Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

student.ahc.umn.edu

1,140 views

Published on

  • Be the first to comment

  • Be the first to like this

student.ahc.umn.edu

  1. 1. Pathobiology of Caries DENT 5301 Introduction to Oral Biology Dr. Joel Rudney
  2. 2. Major concepts <ul><li>Caries is a process, not a disease </li></ul><ul><ul><li>Driven by biofilm, but initiated by the host </li></ul></ul><ul><ul><li>Closely linked to specific microenvironments </li></ul></ul><ul><li>The process is dynamic and reversible </li></ul><ul><ul><li>Oral ecological shifts are normal and cyclical </li></ul></ul><ul><li>Many factors influence the outcome </li></ul><ul><ul><li>Microbes are necessary, but not sufficient </li></ul></ul>
  3. 3. Understanding the process <ul><li>Enamel is a unique hard tissue </li></ul><ul><li>Enamel is 95% mineralized </li></ul><ul><ul><li>Minimal protein content </li></ul></ul><ul><li>Enamel is acellular and non-vital </li></ul><ul><ul><li>Cannot repair itself </li></ul></ul><ul><li>Enamel is permeable </li></ul><ul><ul><li>Water and small molecules </li></ul></ul><ul><li>Enamel is in dynamic chemical equilibrium with the oral environment </li></ul><ul><li>Enamel caries is primarily a chemical process </li></ul>http://dentistry.uic.edu/CraniofacialGenetics/ResearchTED.htm
  4. 4. Equilibrium at normal pH Saliva is supersaturated with respect to enamel Saliva Enamel Ca 10 (PO 4 ) 6 OH 2 [Ca] [PO 4 ] [Ca] [PO 4 ] Ca+statherin Ca+aPRP
  5. 5. Demineralization Saliva Enamel Ca 10 (PO 4 ) 6 OH 2 [Ca] [PO 4 ] [Ca] [PO 4 ] Ca+statherin Ca+aPRP Dietary CHO + biofilm = lactic acid; diffusion into enamel = local pH drop Enamel solubility increases [Ca] [PO 4 ] exit to saliva CHO CHO CHO [H + ] [H + ] [H + ] [H + ] [H + ]
  6. 6. Remineralization Saliva Enamel Ca 10 (PO 4 ) 6 OH 2 [Ca] [PO 4 ] [Ca] [PO 4 ] statherin Ca+aPRP Saliva flow clears CHO; salivary HCO 3 returns pH to normal Enamel becomes less soluble [Ca] [PO 4 ] move into enamel CHO CHO [HCO 3 ] [HCO 3 ] [HCO 3 ]
  7. 7. Alternating cycles of de/re-min <ul><li>Break even - sound enamel or arrested caries </li></ul><ul><li>Net loss </li></ul><ul><ul><li>Subsurface demineralization </li></ul></ul><ul><ul><li>New caries </li></ul></ul><ul><ul><li>Progression of old lesions </li></ul></ul><ul><li>Net gain - remineralization of existing lesions </li></ul>http://www.uiowa.edu/~ocrdent/crown%20model.htm
  8. 8. Enamel caries <ul><li>Begins as discrete lesions in the enamel of specific sites (reservoirs) </li></ul><ul><li>Occlusal pits and fissures of Interproximal contacts </li></ul><ul><li>molars and premolars between adjacent teeth (usually posterior) </li></ul><ul><li>Caries risk varies greatly between tooth sites </li></ul><ul><li>Micro-environments account for this variation </li></ul>http://www.dentsply.de/products/esthet_x/ http://www.dent.ucla.edu/ce/caries
  9. 9. Enamel caries <ul><li>White spot lesions </li></ul><ul><li>Intact surface </li></ul><ul><li>Subsurface </li></ul><ul><li>demineralization </li></ul><ul><li>Advanced enamel caries </li></ul><ul><li>Intact surface </li></ul><ul><li>“ Sticky” fissures </li></ul><ul><li>Visible in radiographs </li></ul><ul><li>Dentin defensive reaction </li></ul>Enamel caries can be remineralized http://www.dent.ohio-state.edu/radiologycarie http://www.st-andrews.ac.uk/~amc/research/medical.htm http://www.uic.edu/classes/peri/ peri343/WsptPrev02/wspt7.htm
  10. 10. Dentinal caries <ul><li>Cavitation </li></ul><ul><li>Demineralization + proteolysis </li></ul><ul><li>Bacteria move down tubules </li></ul><ul><li>Pulpal involvement </li></ul><ul><li>Major damage if unchecked </li></ul>Can be arrested, but generally must be restored http://www.st-andrews.ac.uk/~amc/research/medical.htm http://www.dent.umich.edu/research/loeschelabs Love et al. Infect. Immun. 68:1359
  11. 11. Risk factors http://wwwsam.brooks.af.mil/af/files/fsguide/HTML/Graphics/fig_12-06.gif The initiation and progression of caries is the outcome of interaction between: <ul><li>Microbial factors </li></ul><ul><li>Host factors </li></ul><ul><li>Behavioral/dietary/environmental factors </li></ul><ul><li>Institutional factors </li></ul>
  12. 12. Cariogenicity of microbes <ul><li>Streptococcus mutans/sobrinus </li></ul><ul><ul><li>Major source of demineralization </li></ul></ul><ul><ul><li>Cariogenic properties </li></ul></ul><ul><ul><ul><li>Highly acidogenic </li></ul></ul></ul><ul><ul><ul><li>Highly aciduric </li></ul></ul></ul><ul><ul><ul><li>Extracellular polysaccharide </li></ul></ul></ul><ul><ul><ul><li>from sucrose - insoluble </li></ul></ul></ul><ul><ul><ul><li>Adheres to pellicle </li></ul></ul></ul><ul><ul><ul><ul><li>So do most oral strep </li></ul></ul></ul></ul><ul><ul><ul><li>Transmisible - mother/caregiver to child </li></ul></ul></ul><ul><ul><ul><ul><li>So are all oral bacteria </li></ul></ul></ul></ul><ul><ul><li>Microcolonies - localized zones of high acidity in protected sites </li></ul></ul><ul><ul><ul><li>Occlusal pits and fissures; interproximal contacts </li></ul></ul></ul>http://www.dokidoki.ne.jp/home2/saishika/caries01.htm
  13. 13. Microbes as risk factors <ul><li>Necessary, but not sufficient </li></ul><ul><li>High S. mutans levels in saliva/plaque increase risk </li></ul><ul><ul><li>Longitudinal studies </li></ul></ul><ul><ul><ul><li>Most people who get new lesions will have “high” levels BUT </li></ul></ul></ul><ul><ul><ul><li>Many people with “high” levels won’t get new lesions </li></ul></ul></ul><ul><li>The majority of oral streptococci belong to non-mutans species </li></ul><ul><ul><li>S. mutans is a minority streptococcus - not a good competitor </li></ul></ul><ul><ul><li>High % of acidogenic/aciduric non-mutans = increased risk? </li></ul></ul><ul><ul><li>Low % of acidogenic/aciduric non-mutans = decreased risk? </li></ul></ul><ul><li>Other species may moderate risk </li></ul><ul><ul><li>Are high levels of Veillonella related to lower lactate levels? </li></ul></ul>
  14. 14. Antimicrobial strategies <ul><li>Targeted attacks on mutans streptococci </li></ul><ul><ul><li>Fundamental concept - S. mutans is the main demineralizer </li></ul></ul><ul><ul><li>Caries vaccines - results not impressive </li></ul></ul><ul><ul><ul><li>Secretory immune system (S-IgA) is tolerant of oral microbes </li></ul></ul></ul><ul><ul><li>Topical antibodies - results not impressive </li></ul></ul><ul><ul><li>NEW Antimicrobial peptides combines w/ S. mutans pheromones </li></ul></ul><ul><li>Broad-spectrum attempts to eliminate/limit biofilm </li></ul><ul><ul><li>Allows for the possibility of other acidogenic species </li></ul></ul><ul><ul><li>Systemic antibiotics (fungal overgrowth) </li></ul></ul><ul><ul><li>Chlorhexidine rinses or varnishes (recolonization from reservoirs) </li></ul></ul><ul><ul><li>NEW Antimicrobial peptides (a “natural” defense system) </li></ul></ul><ul><ul><li>NEW Quorum sensing inhibitors </li></ul></ul><ul><li>Replacement with “probiotics”, natural or genetically engineered </li></ul><ul><li>All approaches have limitations, possible risks </li></ul>
  15. 15. Host factors - teeth <ul><li>Genetics (twin studies) </li></ul><ul><ul><li>Occlusal morphology </li></ul></ul><ul><ul><ul><li>Predisposing </li></ul></ul></ul><ul><ul><ul><ul><li>Complexity (e.g. buccal pits) </li></ul></ul></ul></ul><ul><ul><ul><li>Simplicity may be protective </li></ul></ul></ul><ul><li>Environment (diet, prevention) </li></ul><ul><ul><li>Resistance to demineralization </li></ul></ul><ul><ul><li>Replacement ions in hydroxyapatite </li></ul></ul><ul><ul><ul><li>Fluoride, strontium - protective </li></ul></ul></ul><ul><ul><ul><li>Selenium - predisposing </li></ul></ul></ul>http://www.zahntechnik-online.de
  16. 16. Host factors - no saliva <ul><li>Saliva is an important regulator of the caries process </li></ul><ul><ul><li>Xerostomia due to radiation therapy or Sjogren’s syndrome </li></ul></ul><ul><ul><ul><li>Very high S. mutans levels + rampant caries </li></ul></ul></ul><ul><ul><ul><li>Decay in unusual sites in multiple teeth </li></ul></ul></ul>http://www.eastman.ucl.ac.uk/climages/ © Eastman Dental Institute
  17. 17. Host factors - normal saliva <ul><li>What is the effect of individual variation in saliva? </li></ul><ul><li>Variation in flow rate </li></ul><ul><ul><li>High flow rate - protective; low (normal) flow rate - predisposing </li></ul></ul><ul><ul><li>Not considered a major risk factor by itself </li></ul></ul><ul><li>Variation in salivary buffering capacity (HCO 3 ) </li></ul><ul><ul><li>High HCO 3 - protective; Low HCO 3 - predisposing </li></ul></ul><ul><ul><li>Not considered a major risk factor by itself </li></ul></ul><ul><li>Variation in antimicrobial protein concentrations </li></ul><ul><ul><li>S-IgA , peroxidase , lysozyme , lactoferrin and others </li></ul></ul><ul><ul><li>Expectation: High [ ] - protective; Low [ ] - predisposing </li></ul></ul><ul><ul><li>Studies results are inconsistent, sometimes contradictory </li></ul></ul>
  18. 18. Diet and behavior <ul><li>Sucrose and refined CHO - predisposing </li></ul><ul><ul><li>Archeological and historical evidence define major changes </li></ul></ul><ul><ul><li>Effect of smaller fluctuations more difficult to measure </li></ul></ul><ul><li>Intraoral plaque pH studies of cariogenicity </li></ul><ul><ul><li>Hard cheeses - protective BUT NOT HEART-HEALTHY </li></ul></ul><ul><ul><li>Artificial sweeteners (xylitol) - protective </li></ul></ul><ul><ul><li>The Happy Tooth logo in Europe - plaque pH ≥ 5.7 </li></ul></ul><ul><li>“ Stickiness” - resistance to clearance - how long does pH stay low? </li></ul><ul><li>Frequency of intake - how many demineraliztion episodes/day </li></ul><ul><ul><li>The extremes of Vipeholm </li></ul></ul><ul><ul><li>The reality of shifting dietary patterns </li></ul></ul><ul><li>Oral hygiene (F - products), dental visits, parental oversight </li></ul>
  19. 19. “ Social demineralization” <ul><li>Affecting caries prevalence at the population level </li></ul><ul><li>Institutional “remineralizing” factors </li></ul><ul><ul><li>Public health programs - water fluoridation and sealants </li></ul></ul><ul><ul><li>Research on prevention - NIDCR, IADR, and ADA </li></ul></ul><ul><ul><li>Dental education and outreach - dental insurance </li></ul></ul><ul><ul><li>Corporate introduction of fluoride oral health products </li></ul></ul><ul><ul><li>Dramatic declines in caries prevalence during the ‘80s </li></ul></ul><ul><li>Institutional “demineralizing” factors </li></ul><ul><ul><li>Lifestyle change - high frequency use of high CHO foods </li></ul></ul><ul><ul><li>Mass-marketing of junk foods - the school budget dilemma </li></ul></ul><ul><ul><li>Budget cuts - decreases in prevention, access to care </li></ul></ul><ul><ul><li>Will this be a decade of demineralization? </li></ul></ul>$

×