Oral Ecology 2 Flashcards
What 2 external factors have a role on whether host population of microorganisms can colonize on tooth surface?
- Saliva
2. Environment
Describe dental plaque interactions between bacteria
- Acquired pellicle on tooth surface made up of components of saliva and bacterial fragments
- Layer of bacteria on top of pellicle made up of streptococcus species
- F. nucleatum bridges early and late colonizers
What are the 2 ways dental plaque can form with regards to species interaction?
- Interaction between bacteria and bacteria
2. Interaction between bacteria and fungi
What is the bacterial composition of the climax community of dental plaque at the fissure site?
Gram positive facultative anaerobes e.g. streptococcus, acitnomyces
What is the bacterial composition of the climax community of dental plaque at the approximal site?
Gram positive and gram negative facultative and obligate anaerobes e.g. neisseria, prevotella, veillonella
What is the bacterial composition of the climax community of dental plaque at the gingival crevice?
Gram positive and gram negative facultative and obligate anaerobes e.g. eubacterium, prevotella, treponema
What 4 things affect oral flora?
- Saliva
- Chewing
- Oral hygiene
- Diet
Describe the ecological stages in establishment of a microbial community
- Transmission
- Acquisition and colonization
- Pioneer species
- Microbial succession
- Increasing species diversity
- Climax community / Environment modification (return to pioneer species)
Give an example of gram positive cocci found in dental plaque
Streptococcus salvaris
Give an example of gram positive rod found in dental plaque
Lactobacillus acidophilus
Where are streptococci spp. found in the oral cavity?
Isolated from all sites in the oral cavity
Give 3 examples of streptococci spp. which are early colonisers of tooth surface
- S. sanguinis
- S. oralis
- S. gordonii
What is the primary pathogen in the aetiology of enamel caries in children and young adults?
S. mutans
Name another gram positive cocci found in dental plaque
Peptostreptococcus spp.
Name 3 types of gram positive rods and filaments found in dental plaque
- Actinomyces spp.
- Lactobacillus spp.
- Propionibacterium spp.
What is most commonly associated with lactobacillus spp.?
Advanced caries
Name 2 gram negative cocci found in dental plaque
- Neisseria spp.
2. Veillonella spp.
Describe neisseria spp. and how they contribute to the formation of dental plaque
- Facultatively anaerobic or aerobic bacteria isolated in fairly low numbers from most sites in oral cavity
- Contribute to plaque by consuming oxygen and creating conditions necessary for obligate anaerobes
Describe veillonella spp. and how they contribute to the formation of dental plaque
- Strictly anaerobic isolated from most sites in oral cavity but in high numbers in dental plaque
- Cannot metabolise carbohydrates so utilise intermediate metabolites e.g. lactic acid
- Reduce potentially harmful effects of lactic acid on dissolution of enamel
Name 4 gram negative rods found in dental plaque
- Aggregatibacter spp.
- Prevotella spp.
- Porphyromonas spp.
- Fusobacterium spp.
Describe aggregatibacter spp.
- Facultative anaerobes
- Implicated in particular aggressive form of periodontal disease in adolescents
Describe prevotella spp.
- Strictly anaerobes
- P. intermedia associated with periodontal disease
- P. nigrescens isolated more often from healthy sites
Describe porphyromonas spp.
- P. gingivalis strictly anaerobic
- Isolated mainly from subgingival sites especially in advanced periodontitis
Describe fusobacterium spp.
- F. nucleatum is obligate anaerobe
- Able to aggregate with most oral bacteria so believed to be important bridging organism between early and late colonisers during plaque formation
What 5 categories can salivary proteins belong to?
- Enzymes
- Proline rich proteins (PRPs)
- Immunoglobulins
- Mucins
- Other proteins
What is saliva’s role in the oral cavity with regard to pH?
Act as a buffer to stabilise pH in the mouth
Name 4 ways in which saliva is adapted for its ability to buffer pH in the oral cavity
- Bicarbonate
- pH
- Calcium and phosphate ions
- Proteins and peptides
What is the function of bicarbonate in saliva in terms of buffering?
- Most important buffering system in stimulated saliva
- Effective buffer system against acid at high salivary flow rates
What is the function of pH in saliva in terms of buffering?
- pH dependent on bicarbonate concentration
- Can range between 5.3 and 7.8
What is the function of calcium and phosphate ions in saliva in terms of buffering?
- Maintain saturation of saliva with respect to tooth mineral
- Important in calculus formation and protection against caries
- Higher salivary flow reduces demineralisation but increases potential of calculus formation
What is the function of proteins and peptides in saliva in terms of buffering?
- Salivary peptide sialin tends to raise salivary pH to neutral
What is a potential problem with saliva buffering capacity in individuals affected by xerostomia?
Low salivary flow which results in low buffering capacity
What is The Stephan Curve?
Describes the change in pH occurring within dental plaque when its subjected to challenge, typically within food stuff
Why is a high starch diet less likely to cause low pH than a high glucose diet?
- Slow metabolism of starch by heterofermentation
- Fast metabolism of glucose by homofermentation
- Lots more of acids including lactic acid are produced by homofermentation
- Lactic acid can damage enamel due to low pH
Below what pH is there demineralisation of enamel?
5.4
Name 4 direct effects of ageing on the oral microflora
- Cell mediated immunity wears
- Change in salivary antibodies
- Hormonal changes
- Altered physiology of oral mucosa
Name 4 indirect effects of ageing on the oral microflora
- Denture wearing
- Medication
- Cancer therapy
- Dietary changes
What type of bacteria tends to cause dental caries?
Acidogenic / aciduric bacteria
What type of bacteria tends to cause periodontal diseases?
Gram negative anaerobes
What 2 things are necessary for caries to develop from a stable plaque community?
- Frequent sugar intake (low pH)
2. Low saliva flow
What 2 things are necessary for periodontal disease to develop from a stable plaque community?
- Inflammation (increased GCF flow)
2. Immune suppression
