Periodontal disease- microbiology Flashcards
what is a plaque biofilm?
complex microbial community found on the tooth surface
how is plaque part of the host defence?
it aims to exclude exogenous pathogenic bacteria through process called colonisation resistance
what is the first stage of plaque formation?
within seconds a pellicle forms on the tooth surface
bacteria do not directly adhere to enamel - they adhere to pellicle
what is the pellicle derived from?
- salivary glycoproteins
- proteins
- enzymes
- lipids
- GCF fluid
- minerals
what are the functions of the pellicle?
- lubrications
- protection against acids
- attatchment
what happens after the pellicle forms on the tooth?
within minutes pioneer species begin attaching to the pellicle via adhesins
what are the early plaque pioneer species known as?
streptococcus species- gram positive facultative anaerobes- cocci
give examples of early streptococcus species
oralis
sanguis
mites
what are other early colonisers?
as micro colonies form and the diversity and complexity of the biofilm increases- other species including actinomycete, haemophillus and neisseria species attach
what are the properties of:
actinomyces
haemophillus
neisseria
- gram + filamentous facultative anaerobes
- gram - facultative anaerobes cocci
- gram - aerobic bacteria cocci
what species dominates within 24 hrs?
gram + streptococci
what happens as plaque matures?
within one week- as plaque matures within an aerobic environment - aerobic bacteria consume 02 which reduces the redox potential which causes a shift to favour an anaerobic environment favouring the growth of GNABs- actinomycete and GNABS increase
what GNABs begin to colonise the biofilm?
prevotella intermedia
fusobacterium nucleatum
porphoramonas gingivalis
what does it mean when plaque matures and becomes more organised?
within 7-28 days
supra gingival plaque- streptococci dominate surface of tooth and as plaque thickens and matures- GNABs dominate the outer surface of plaque
sub gingival plaque- organised structure with GNAB motile spirochetes found at base of pocket, GNAB found within pocket and anaerobic bacteria attached to surfaces within pockets.
what are the differences between surpagingival and sub gingival plaque ?
supra- variable env, 02 env, influenced by diet, streptococcus dominate, GNAB increase as plaque increases
subgingival- constant env, influenced by GCF, anaerobic env, streptococcus dominates, GNAB more abundant