MFD21 Flashcards
Aims • To describe the Mutans Streptococci and their association with dental caries. • To provide an overview of acid and alkali production by oral bacteria Content • An overview of dental caries. • Introduction to the Mutans Streptococci. • Acid production from sugars (acidogenicity). • Acid adaptation and aciduricity
What anatomical sites are there of caries?
Pits and fissures, smooth surfaces (enamel caries or root caries, which starts on exposed cementum/dentin).
What is residual caries?
the decayed material left in a prepared cavity and over which a restoration is placed
What term is used to describe disease caries that occurs on the tooth after the filling has been used for a period of time?
2) What is it the opposite to? What does that term mean?
1) secondary/ residual caries
2) primmary caries
3) the lesion constitutes the initial attack of the tooth surface
what are the opposites of the following:
a) cavitated caries
b) active caries
- Cavitated vs non-cavitated.
* Active vs inactive (arrested)
What is early childhood caries?
the presence of one or more decayed (non-cavitated or cavitated lesions), missing (due to caries) or filled tooth surfaces in any primary tooth in a preschool-age child between birth and 71 months of age
Who is mostly affected by root caries?
2) Why?
1) elderly
2) Gum tissue recedes and cementum isn’t as strong as enamel
Why is caries so prevalent? + a bit of scientific evidence
Probably due to our diet, in the medieval times caries affect surfaces was very low.
What is the most common global disease?
2) What is the 10th most common disease?
1) Untreated caries in permanent teeth is the most common global disease (2.4 bn affected)
2) Untreated caries in deciduous teeth is 10th most common disease (621 m affected)
Caries is the result of microbial sugar fermentation – or is it?
What are the other theory plx list:
- chymical theory
- parasitic or septic theory
- chemico-parasitic theory
- proteolytic theory
- proteolysis-chelation theory
What was the chymical theory?
) Food putrefaction released unidentifed chemical (chymical) agent which dissolved teeth
What was the Parasitic or Septic Theory ?
Erdl (1843) described a filamentous parasite in plaque which he thought responsible
What was the Chemico-parasitic theory ?
2 stages • Stage 1 – decalcification of enamel • Stage 2 – dissolution of the soft residue
What was the Proteolytic Theory ?
Microbes invade enamel lamellae and initiate caries by proteolysis • Pincus (1950) proposes it’s proteolysis of the cuticle (Proteolysis probably plays a role in root caries, but not what starts the disease)
Proteolysis-chelation theory ?
Schatz (1955) - argued that there was too much emphasis on protons and Miller was misunderstood • Microbial proteolytic destruction of the organic matrix • Calcium is removed by chelation (organic acids). By binding out the calcium you force the equilibrium to dissolution.
What are the 2 possible hypothesises of the role of microorganism in caries?
- Ecological plaque hypothesis (disease is an imbalance)
2. Specific plaque hyporthesis (caries aetiology)
What microorganisms are associated with dental caries?
Mutans streptococci • Lactobacillus spp. • Actinomyces spp. • Bifidobacterium spp. and related • Scardovia wiggsiae
What is the basis fo the link between microorganisms associated with dental caries? (2)
1) • Elevated at sites of caries (sometimes)
2) • Virulence factors
Give e.g.s of virulence factors of microorganisms in caries:
- Acid production from sugars (acidogenicity)
- Acid tolerance (aciduricity)
- Adhesions and others: intracellular storage granules, extracellular polysaccharides,
Which of the 7 species of mutans streptococci are found in humans?
S.mutans and S.sobrinus
Mutans Streptococci:
1) gram- or +
2) catalase - 0r +
3) saccharolytic or asaccharolytic
4) aerobe, anaerobe ro something else…
5) What structures do many form?
6) When is it acquired
1) +
2) -
3) saccharolytic
4) facultative anaerobe
5) chains
6) infancy
S.mutans
1) is it acidogenic
2) is it aciduric
3) What does it form from sucrose?
1) yes
2) yes
3) glucans
S.sobrinus and S.mutans
1) Which is carried by more people
2) which is more acidogenic ?
1) S.mutans (around 96%, while S.Sobrinus (6-35%)
2) S.sobrinus
What features does Scardovia has which is characteristic of cariogenic organism?
2) is it gram + or -
3) WHat did it used to be called?
4) describe shape
1) anaerobic, Saccharolytic – produce acetic and lactic acid
2) +
3) bifidobacterium
4) pleymorphic (alters shape and size in response to environmental conditions ) bacilli (rod shaped)
What groups of caries-associated streptococci are there?
- S.Mutans
- S.Sobrinus
- “non mutans low-pH streptococci”( atypical ones within group e.g. some strains of S.sanguinis)
What specific adhesions, a virulence factor of mutans streptococci, have?
oAntigen I/II protein
oGlucosyltransferases (GTFs)
oGlucan binding proteins (allows them to attach to polyglycans in matrix)
What specific way is acid produced, a virulence factor of mutans streptococci, have?
o F-ATPase (kicks protein out the cell)
How is mutans streptococci resistant to acid a virulence factor of mutans streptococci, have? (2)
oDNA repair proteins
oProtective membrane proteins
Name 2 Health-promoting factors ( in the mouth)?
- adhesions of commensal bacteria
2. Alkali production
Adhesions of commensal bacteria :
antigen 1/2 protein
1) How is both glucose and sucrose used by bacteria?
2) How is sucrose only used?
3) what is the significance of ans 2?
4) What is this in spite of?
1) to make acid and intracellular storage polymer
2) to make exopolysaccharides
3) sucrose is more cariogenic than glucose
3) glucose is more easily converted to acid
What do we need to know about sugar uptake in S.mutans?
1, polysaccharides can be digested
- many different mon/disaccharides can be imported
- Xylitol import leads to a “futile” cycle (this results in energy loss, therefore being added to chewing gum to try and reduce caries)
what about S.mutans metabolic reactions are regulated?
2) What is not?
- transporters
2. glucose uptake transporters
What are the effects of transporter (other than glucose) regulation of fermentation in S.mutans have on the products in:
high sugar environments
o lactate is the major product (homofermentation), and glycolysis is accelerated
o Intracellular polysaccharides (IPS) are made
What are the effects of transporter (other than glucose) regulation in S.mutans have on the products in:
low sugar environments
o Mixed acid fermentation (heterofermentation) - lactate dehydrogenase is inhibited
o IPS are degraded
1) when is intracellular polysaccharides made by S.mutans?
2) from what molecule?
3) what is the intracellular polysaccharide called?
3) When is it broken down? what is the name of this series of reactions?
4) How may it be involved in caries?
1) when carbohydrate is in excess
2) Produced via glucose-1- phosphate
3) Glycogen-type glucan
4) Broken down and used for glycolysis during starvation
5) uncertain, but may extend period of time bacteria produce acid after glucose source is removed.
What is the role of S.mutans in the food? what is it’s symbiotic relationship?
- End products of metabolism can be recycled by other bacteria
- Several different bacteria can utilize lactate; in the case of Veillonella spp. it is an essential nutrient
aciduricity is what type of response?
2) How do studies support this?
adaptive
2) Pre-acidification results in greater acid tolerance, particularly in bacteria that are relatively acid sensitive.
What mechanisms of acid adaptation are there?
- Reduced permeability of cell membrane to H+ .
- Induction of H+ -translocating ATPase (expels protons from cells).
- Induction of alkali production systems (arginine deiminase or urease).
- Induction of stress proteins that protect enzymes and nucleic acids from denaturation.
What enzymes do Strep. Gordonii and
Strep. sanguinis have for alkali production? in order of there use in the pathway
B) which steps produce NH3, what is the total no. produced?
A) 1. arginine deiminase
2. Ornithine transcarbamylase
3. carbamate kinase
B) step 1 and 3, total =2 NH3
state the reactions in alkali production in order for Strep. Gordonii and
Strep. sanguinis:
- Arginase = citruilline +NH3
- Citrulline = carbamoyl phosphate
- carbamoyl phosphate +ADP = CO2 + NH3 +ATP
What enzymes do Strep. salivarius and
Actinomyces johnsonii have for alkali production? in order of there use in the pathway
B) which steps produce NH3, what is the total no. produced?
A) 1.arginase
2. Urease
B) step 2 only, total 2
state the reactions in alkali production in order for Strep. salivarius and
Actinomyces johnsonii
- Arginine to Urea
2. Urea +ADP= ATP + CO2 + 2NH3
Does the composition of the oral flora change in relation to the nutrients in the environment?
yes
A) At pH neutral, State a bacteria group present at: 1. low sugar level 2. high sugar level. B) at low pH, and high sugar:
- asaccharolytic bacteria e.g. P.gingivalis
- oral streptococci
B) strep. mutans and lactovacillus spp.
