Biofilm, Microbial Complexes & Calculus

How plaque biofilm forms

Acquired pellicle: salivary glycoproteins coat a clean tooth within minutes.
Early colonizers (mostly Gram-positive facultative): Streptococcus sanguinis, S. oralis, S. mitis and Actinomyces species attach to the pellicle.
Bridging organism: Fusobacterium nucleatum links early and late colonizers.
Late colonizers: Gram-negative anaerobes and motile organisms in deeper, subgingival biofilm.
Biofilms resist antimicrobials because of the matrix, slow growth and cell-to-cell signaling (quorum sensing), so mechanical disruption is the primary treatment.

Complex	Members	Meaning
Red	Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola	Linked to deep pockets and bleeding on probing; P. gingivalis is a 'keystone' pathogen (gingipains)
Orange	Fusobacterium nucleatum, Prevotella intermedia, Campylobacter rectus	Bridge to the red complex
Yellow, purple, blue, green	Streptococci; Veillonella and Actinomyces odontolyticus; Actinomyces; Capnocytophaga, Eikenella corrodens, A. actinomycetemcomitans serotype a	Mostly early colonizers compatible with health

Aggregatibacter actinomycetemcomitans (leukotoxin) is associated with the molar-incisor pattern of periodontitis in young patients, formerly called localized aggressive periodontitis.
Current view: dysbiosis. A shift in the whole community, plus the host response, drives disease (ecological plaque hypothesis).

Feature	Supragingival	Subgingival
Mineral source	Saliva	Gingival crevicular fluid (serum)
Color	White to yellow (stains with diet and tobacco)	Dark brown to black (blood pigments)
Hardness and attachment	Softer, easier to remove	Harder, more tenacious, often in ledges or rings
Common sites	Lingual of mandibular incisors (submandibular/sublingual ducts) and buccal of maxillary molars (parotid duct)	Interproximal and any pocket; distribution not tied to ducts

Main crystal forms: hydroxyapatite and octacalcium phosphate; whitlockite is more common subgingivally and posteriorly; brushite in young deposits.
Calculus itself is not the primary cause of disease: it is covered by live plaque and makes plaque removal harder.

Calling calculus the cause of periodontitis: the cause is the plaque biofilm and the host response; calculus is a retentive factor.
Saying subgingival calculus comes from saliva: its minerals come from crevicular fluid.
Putting Fusobacterium in the red complex: it is the orange-complex bridge.
Treating biofilm with antibiotics alone: mechanical disruption comes first.

Pick an answer to see right away whether it is correct and why.

Which organism is the classic bridge between early and late colonizers?
Which group makes up the red complex?
Where does supragingival calculus build up fastest?
Subgingival calculus is dark because of:
Which organism is most associated with the molar-incisor pattern of periodontitis in adolescents?

0 of 5 answered

Answer key: 1 D · 2 B · 3 D · 4 C · 5 C