Microbiology of Dental caries

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Information about Microbiology of Dental caries

Published on March 21, 2013

Author: nurved

Source: slideshare.net


Describe relationship between plaque and oral diseases
Describe role of plaque in development of caries
Define Dental Caries
Describe the aetiology and the role different factors play in ini4a4on and progression of the disease
Describe the role played by different microorganisms

MicrobiologyDental  Caries Dr. Ali Yaldrum SEGi UC, KD

Learning  OutcomesAt  the  end  of  this  session  students  should  be  !  Describe  rela4onship  between  plaque  and  oral  diseases!  Describe  role  of  plaque  in  development  of  caries!  Define  Dental  Caries!  Describe  the  ae4ology  and  the  role  different  factors   play  in  ini4a4on  and  progression  of  the  disease!   Describe  the  role  played  by  different  microorganisms

Relationship ofPlaque bacteria to Caries

Plaque & CariesHistorically  for  any  microbe  to  be  considered  responsible   for  a  given  condi4on,  Koch s postulate was  applied

Koch s Postulate1.  The  microbes  should  be  found  in  all  cases  of  the  disease  with  a   distribu4on  corresponding  to  the  observed  lesions2.  The  microbes  should  be  grown  on  laboratory  media  for  several   subcultures3.  A  pure  subculture  should  produce  the  disease  in  the  suscep4ble   animal4.  A  high  an4body  4ter  to  the  microbe  should  be  detected  during   infec4on;  this  may  provide  protec4on  on  subsequent  reinfec4on

Koch s Postulate1.  A  microbe  should  be  present  in  sufficient  numbers  to  ini4ate   disease2.  The  microbe  should  generate  high  levels  of  specific  an4bodies3.  The  microbe  should  produce  relevant  virulence  factors4.  The  microbes  should  cause  disease  in  an  appropriate  animal   model5.  Elimina4on  of    the  microbe  should  result  in  clinical  improvement

Role  of  Plaque!   The   Specific  Plaque  Hypothesis (fig.1)!   The   Non-­‐Specific  Plaque  Hypothesis  (fig.2)!   The   Ecological  Plaque  Hypothesis (fig.3)

Specific Plaque Hypothesis Plaque { few species out of diverse resident flora are actively involved in disease X problem ( disease can still occur in absence of these organisms ) Diseasefig.1

Non-Specific Plaque Hypothesis Plaque { out come of the overall activity of the total plaque microflora ( ) plaque mediated diseases are polymicrobial but one problem specific organism predominate Diseasefig.2

Ecological Plaque Hypothesis Plaque { organisms associated with disease are already present on teeth but very low to detectfig.3 Disease ( disease only initiates as a result of shift in the balance of resident microf lora )

Dental Caries

Dental Caries!   It  is  bacterial  disease  of  calcified  4ssue  of  the  teeth  characterized   by   demineraliza4on   of   the   inorganic   and   destruc4on   of   the   organic  substance  of  the  tooth. Dental Caries is known as disease of civilization

Dental CariesThe Early theories!  The legend of Worms!  Endogenous Theory!  Chemical Theory!  Parasitic Theory!  Chemoparasitic Theory

Dental Caries!  Chemoparasitic theoryMiller  in  1890  suggested  that  oral  bacteria  converted  dietary  carbohydrates  into  acid  which  solubilized  the  calcium  phosphate  of  enamel  to  produce  a  caries  lesion

Aetiology of Dental Caries

Saliva Caries Susceptible Surface P laque Saliva Saliva Time Bacteria Sugar Salivafig.4 aetiology of caries

Role of Saliva

Role of SalivaSaliva   plays   a   vital   role   in   the   maintenance   of   oral   health  and  the  integrity  of  oral  4ssuesSaliva  contains: • exfoliated  epithelial  cells • oral  microorganisms • food  residues  (carbohydrates) • an4microbial  factors • minerals

Role of Saliva!   Mechanical   washing   ac4on   of   saliva   is   very   effec4ve   for   cleaning  of  teeth!   high  buffering  capacity  neutralizes  acid!   supersaturated   with   Calcium   and   phosphorus   helps   in   remineraliza4on Salivary  flow  rate:  0.8  mm  /min  on  upper  labial  surface                                              5.0  -­‐  8.0  mm/min  on  lower  lingual  surface

Susceptible Surface

Susceptible SurfaceSome   areas   of   the   tooth   are   more   suscep4ble   to   developing   caries  than  others,  known  as   susceptible areas Suscep4bility  is  related  to  several  factors !   Mineral  &  Fluoride  Content !   Structure  of  that  par4cular  area

Susceptible SurfaceSusceptible tooth surfaces includes !   Pits  &  Fissures  (fig.5) !   Approximal  Enamel  cervical  to  contact  point  (fig.6) !   Exposed  root  surface  (fig.7 & 8) !   Margins  of  Restora4on  (fig.6  &  9) !   Cervical  margins  of  tooth  (fig.10)

pits & fissures cariesfig.5

Caries under restoration Approximal Cariesfig.6

Root surface Cariesfig.7

Root Surface Cariesfig.8

Caries under restoration Amalgam restorationfig.9

white spot lesionsfig.9

From white spot to cavity formationwhite spot lesion Cavitation earliest clinical evidence (reversible) Later clinical stage (irreversible)

Time &Sugar Substrate

Sugar Substrate!   Direct   rela4onship   between   intake   of   Carbohydrates   (sugar)  &  Caries!   Glucose,  Fructose  &  Sucrose  are  cariogenic  ! Sucrose  is  the  most  cariogenic  sugar •   fermentable • easily  penetrates  plaque

Time & Sugar SubstrateThere  is  a  direct  rela4onship  between  caries  and: !  Frequency  of  sucrose  consump4on !  s4ckiness  of  the  sucroseBoth   affects   the   amount   of   4me   sugar   stays   into   contact  with  the  teeth  surface

Plaque Bacteria

Plaque BacteriaDental  Caries  does  not  occur   in vivo   if  microorganisms  in  the  form  of  dental  plaque  are  absent;  making  it  clear  that  dental  caries  is  a  plaque  mediated  disease

Plaque Bacteria!   Streptococcus  mutans!   Lactobacillus  species!   Ac4nomyces  Species!   Veillonella  species

Streptococcus speciesThe  term  mutans  streptococci  refers  to  a  group  of  7  different  species,  but  two  species  are  most  commonly  found  in  humans!   S.  mutans  (serotypes  c/e/f)!   S.  sobrinus  (serotypes  d/g)

Streptococcus speciesFactors related to Cariogenicity of S. mutans! S.mutans  counts  in  saliva  and  at  site  of  lesion!   Isolated  from  site  before  the  development  of  caries!   Efficient  sugar  metabolism  &  transport  capability! Acidogenic  &  acidouric!   Liele  effect  of  pH  on  growth  and  metabolism!   Produc4on  of  EPS  &  IPS

Streptococcus speciesS.  mutans  been  implicated  in  !   Pits  &  fissure  caries  (strong  evidence)!   Root  surface  caries!   All  forms  of  caries!   Some  strains  are  more  pathogenic  than  others

Streptococcus species!   S.  Sobrinus  role  is  uncertain!   Frequently  isolated  from  plaque  but  in  lesser  numbers!   Shares  the  same  cariogenic  proper4es  as  S.mutans

Lactobacillus speciesLactobacilli  can  be  divided  into  two  groups !   Homofermenta4ve  species !   Heterofermenta4ve  species

Lactobacillus speciesHomofermentative species!   L.  acidophilus  &  L.  casei!   Mainly  produce  lac4c  acid  from  glucose  fermenta4onHeterofermentative species!   L.  fermentum!   Produce  lac4c  acid  and  significant  amounts  of  acetate

Lactobacillus speciesMost  commonly  isolated  species  from  oral  cavity  are!   L.  casei!   L.  fermentum!   L.  acidophilus

Lactobacillus speciesFactors related to Cariogenicity of Lactobacillusspecies!   Increased  number  in  carious  cavi4es  affec4ng  enamel  &   root  surface!   Number  in  saliva  reflect  caries  ac4vity! Acidogenic  and  acidouric!   Few  strains  can  produce  EPS

Lactobacillus species!   Have  a  low  affinity  for  tooth  surface!   Low  in  numbers  at  healthy  site!   Implicated  in  progression  of  caries  deeper  into  den4ne   rather  than  ini4a4on!   Implicated  in  ae4ology  of  root  surface  caries

Actinomyces speciesAc8nomyces  spp.  form  a  major  and  complex  part  of  theoral  microflora,  par4cularly  at  the  approximal  site  andgingival  crevice

Actinomyces species! Ac8nomyces  odontoly8cus  been  associated  with    very   early  stages  of  tooth  demineraliza4on! Ac8nomyces  naeslundii  been  associated  with   development  of  root  surface  caries


Caries VaccinationIn  rats  ,  experimental  dental  caries  have  been  reduced  by  immunizing   with   cell-­‐wall   associated   an4gens   or  glucosyltransferase  from  S.mutans

Caries VaccinationThe  following  mechanism  have  been  suggested! Inhib4on  by  secretory  IgA  of  bacterial  coloniza4on  of   teeth!   Interference  with  bacterial  metabolism!   Enhancement  of  phagocy4c  ac4vity  in  gingival  crevices

Summary!   Dental  Caries  is  a  mul4factorial  disease,  strongly   associated  with  the  dental  plaque!   Ecological  Plaque  Hypothesis  caries  forms  as  a  result  of   disturbance  in  the  normal  balance  of  Oral  Biota!   The  main  factors  involved  are  suscep4ble  tooth  surfaces,   4me,  sugar  substrate  and  plaque  bacteria!   Pits  &  fissure  are  the  most  suscep4ble  areas!   Frequency  of  sugar  intake  is  more  decisive  than  total   consump4on

Summary!   Sucrose  is  the  most  cariogenic  sugar! Mutans  streptococci  are  implicated  in  ini4a4on  of  pits  &   fissure  and  root  caries!   Lactobacillus  spp  are  associated  with  progression  of   caries

References!   Philip   D.   Marsh,   Michael   V   Mar4n,   Plaque   mediated   diseases-­‐  Dental  Caries  and  Periodontal  diseases  in  Oral   Microbiology,  5th  Edi4on,  Churchil  Livingstone,  2009,  pp   104-­‐117!   J.   Bagg,   T.   W.   Macfarlane,   I.   R.   Poxton   and   A.   J.   Smith,   Dental   Caries   in   Essen4als   of   Microbiology   for   Dental   Students,   2nd   Edi4on,   Oxford   University   Press,   2006   pp238-­‐248

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