Download Lecture 13-14 Dental plaque and caries

What is a dental plaque?
•A microbial deposit on the hard-tissue surface of the mouth
comprising living and dying bacteria, their products and host
compounds derived from saliva
•Its role is to exclude exogenous often pathogenic microbes
•However shift in the balance of the endogenous microflora of the
plaque predisposes to dental and parodontal disease
Maturation of dental plaque
clean enamel
early colonizer cocci – bacterial polysaccharides
late colonizers – climax community with corn-cob fromation
Tooth surfaces
•non shedding surface (enamel)
•pellicle (biofilm) formation form saliva and bacterial
products
salivary pellicle onto clean enamel
Successive development of dental plaque I
•Salivary pellicle comprises salivary glycoproteins and minerals
•Saliva flow transports bacteria to the site
•Oral streptococci and commensal Neisseriae can attach to the pellicle
and not directly to the enamel (n.b. they have enhanced binding ability
and increased resistance to oral defense mechansims)
Successive development of dental plaque II
•Long-range (distant) interactions of bacterial attachment –van der
Waals’ forces – reversible (can washed off with water flush)
•Short-range (close) interactions – bacterial adhesins to pellicle –
irreversible! (cannot be washed off)
Successive development of dental plaque III
polysaccharide
production
•Coaggregation and coadhesion
Fresh bacteria attach on the first
generation of cells and their
products
Coaggregation and coadhesion
late colonizers
early colonizers
Coaggregation and coadhesion
Streptococcus - Streptococcus
Mediated by lectins
•Actinomyces – Actinomyces
(carbohydrate binding protiens)
•Streptococcus – Actinomyces
and surface carbohydrates
Corn-cob formation
•Streptococcus - Corynebacterium matruchotii
•Veillonella – Eubacterium
Successive development of dental plaque III
•Climax community forms a biofilm
with high bacterial diversity and
large amount of extracellular matrix
•Detachment
Bacteria are continuously shedding
from the dental plaque
Calculus (tartar)
•Deposit of minerals
into the plaque
Risk of retaining
cariogenic bacteria
and conditions
Smooth surface (supragingival) dental plaque
Supragingival dental plaques II
•Fissure plaque:
mutans streptococci, Actinomyces, Veillonella,
Propionibacterium, Lactobacillus
•Approximal plaque:
mutans streptococci, Actinomyces, (n.b. relative lack of
anaerobes)
Subgingival dental plaques
•Gingival crevice plaque:
Streptococcus mitis group, S anguinosus group, oral
terponemes, Actinomyces, Rothia dentocariosa,
Porphyromonas, Prevotella, Fusobacterium
•Denture plaque:
mutans streotococci, Veillonella, Staphylococcus aureus,
Actinomyces Candida (yeast) species,
Synergestic nutrional interactions in dental plaque I
Collaborate breakdown of complex substrates (Host
glycoproteins)
•Streptococcus oralis utilizes carbohydrate sidechains
•Prevotella intermedia, P.oralis, Fusobacterium nucleatum
hydrolyses the protein core
•Peptostreptococcus micros and Eubacterium brachy extensive
amino acid fermentation
Synergestic nutrional interactions in dental plaque II
Utilization of bacterial polymers
•Fructan of Streptococcus salivarius is hydrolized and fermented
by:
•mutans streptococci, Streptococcus mitis group, Actinomyces,
Capnocytophaga, Fusobacterium
Synergestic nutrional interactions in dental plaque III
End product of primary feeder is utilized by a secondary feeder
Antagonistic interactions in dental plaque
•Competition for nutrients
•Bacteriocin production (oral streptococci, Corynebacterium
matruchotii, black pigmented anaerobes, A actinomycetemcomitans)
•hydrogen peroxide production
•low pH by organic acids
Dental caries
Localized destruction of tooth tissues by bacterial fermentation of
dietary carcohydrates i.e. multifactorial plaque-related infection
of enamel, cementum or dentin
•Initial caries lesion – white spot
still reversible
•Caviation
•Dentine infection
•Pulpitis, inflammation of dental pulpa
•Pulpal necrosis
early enamel caries
Multifactorial etiology of caries
Plaque microbes
Genetical background
•shape of teeth
•dentin/enamel
structure
•immunity
caries
duration of exposure
nutritional
factor
e.g.saccharose
Microbial etiology of caries
•Streptococcus mutans – most acidogenic oral bacterium (rapid lactate
producer)
•Lactobacillus – able to grow at low pH (<5.0), produce lactic acid,
involved in the progression of deep advancing carious process
•Actinomyces – root surface caries after gingival recession
•Veilonella – protective effect against dental caries due to secondary
feeding on lactic acid and producing less cariogenic acetic and
propionic acid
Caries Prevention
Eliminate as many cariogenic factor as possible!
•Nutrition:
•Cariogenic order of sugars and sugar derivatives:
saccharose > glucose > fructose >> mannitol > sorbitol >> xylitol
•Fluorid intake:
remineralization (of fluoriapatit)
inhibits bacterial glycolyis, polysaccharide synthesis
•Time factor:
•Regular elimination of plaques
(see next slide!)
A caries megelőzése
•Plaque microbes:
•Toothe brushing (mechanical effect)
•Antimicrobial components: (chlorhexidine), fluorids, timol, triclosan,
zinc compounds, enzymes: dextranase, glucanase
•Probiotics? – antagonistic bacteria (non- mutans Str.)
•Compenstaing host (genetic) factors:
•fissure sealing
•Immunization? – still at the stage of animal experiments