Periodontics › Aetiology
Periodontal Microbiology
High-yield revision notes with linked practice questions, written for dental students and candidates preparing for the ADC and other licensing examinations.
High-yield notes
In a healthy human being, bacterial population comprises of 2 kg of total body weight
Our body contains 10 times more bacteria than human cells.
H2O2 produced by S. Sangius is lethal to Actinobacillus actinomycetemecomitans.
Aggressive periodontitis is associated with a loss of colonization of S. sanguinis.
Bacterial plaque was first recognized by J Leon William.
Streptococcus salivarius and Streptococcus mitis are the first and most dominant oral microbes to colonize the oral cavity of newborn infants.
More than 500 different species are capable of colonizing the adult mouth.
Periodontal pathogens that are involved in the etiology of tonsillitis are Fusobacterium nucleatum and Prevotella intermedia.
One gram of plaque (wet weight) contains approximately 1011 bacteria.
Supragingival plaque causes gingivitis.
1 ml of saliva contains 750 million bacteria/ml
Examples of Secondary colonizers are E. corrodens,Fusobacterium, P. gingivalis.
Majority of oral microorganism are Facultative anaerobes.
After enamel has been exposed to bacteria, irreversible bacteria colonization takes place in about 2-4hr
After cleaning and pumicing the tooth surface, plaque begins to form within a few minutes
Pre requiste for plaque formation is pellicle
Materia alba has an irritating effect on gingiva
Materia alba is plaque without regular interval pattern and is disorganized and is LOOSELY ADHERENT TO TOOTH.
The inorganic component of sub-gingival plaque is derived from crevicular fluid.
Predominant bacteria found in two- days- old plaque is Streptococci
"Window of infectivity" for the acquisition of S. mutans at a mean age of 26 months (range 9 to 44 months)
Bacteria that adhere to tooth surfaces do not contact the enamel directly but interact with the acquired enamel pellicle.
Useful complex is purple complex.
Yellow complex organisms are the initial colonizer.
Bleeding on probing is caused by red complex organisms.
Key stone hypothesis was given by George Hajishengalis and colleagues.
Full mouth disinfection was given by Quirynen and co-workers.
The organism found in the necrotizing gingivitis periodontitis- Prevotella, spirochetes, fusobacterium (e.g. Treponema microdentium).
Lactoferrin acts against actinobacillus.
Specific and non-specific plaque hypothesis were put forward by Losche
Modified Koch's criteria as related to periodontal disease was given by Socransky
Microorganisms which uses steroids as growth factor P.intermedia
The number of bacteria in the oral cavity is greater in the morning.
Bacterial communication with each other in a biofilm is known as Quorum sensing
"Red complex" associated with bleeding on probing comprised of P.gingivalis, T.forsythia, T.denticola
+-----------------------------------------------------------------------+
| [Red complex]: Associated with bleeding on probing. |
| Tenerella forsythia, P. gingivalis, T. denticola | +=======================================================================+
| [Orange complex:] Red and orange complex organisms |
| are considered to be major etiological agents of periodontal |
| diseases. Eubacterium nodatum, Campylobacter rectus, Campylobacter |
| gracilis, Streptococcus constellatus | +-----------------------------------------------------------------------+
| [Yellow complex:] Streptococcus sanguis, S. Mitis, S. |
| Oralis, S. Gordonii, S. Intermedius | +-----------------------------------------------------------------------+
| [Green Complex:] Campylobacter concisus, Eikenella |
| corrodens, Aggregatibacter actinomycetem comitans serotype a. | +-----------------------------------------------------------------------+
| [Purple complex:] Veillonella parvula, Actinomyces |
| odontolyticus | +-----------------------------------------------------------------------+
| - Members of yellow, green and purple complex are considered to be |
| early colonizers. | +-----------------------------------------------------------------------+
24)Corncob appearance is seen in Supragingival plaque
Practice questions
Select an option to check your answer. Answers are shown below each question.
The yellow white, soft sticky, deposit of cellular debris and bacteria loosely adherent on tooth surface is
- APellicle
- BMateria alba
- CPlaque
- DCalculus
Composition of plaque formed on all restorative material surfaces is similar except that on
- AComposite
- BAmalgam
- CSilicate.
Bacterial communication with each other in a biofilm is through a phenomenon known as
- ACoaggregation phenomenon
- BCoadhesion phenomenon
- CCorncob phenomenon
- DQuorum sensing
''Coaggregation'' is mainly predominated by
- AInteraction between gram positive bacteria
- BInteraction between gram negative bacteria
- CInteraction between gram positive and gram-negative bacteria
- DInteraction between plaque and gram positive bacteria
Co-adhesion is a process of
- AAttachment of primary colonizers on the tooth surface
- BAttachment of new bacteria on the bacterial receptors
- Cformation of taste tube brush like appearance
- DIrreversible colonization of bacteria on tooth
Which of the tooth has most of the plaque?
- AGingival third
- BIncisal third
- CMiddle third
- DUniform on all surfaces
Who modified the Koch's postulates as related to periodontal disease?
- ASocransky
- BGlickman
- CRussel
- DGreene and Vermillion
'Corncob appearance' of plaque is seen on
- A1week old plaque
- B2weeks old plaque
- C3weeks old plaque
- D4weeks old plaque
Predominat bacteria found in two-days old plaque
- ASteptococci
- BBacteroids
- CSpirochetes
- DActinomyces
Corncob appearance of bacteria in plaque is seen towards
- ATooth surface
- BOuter surface
- CMiddle of plaque
- DAll of the above
Supragingival plaque causes
- AGingivitis
- BPeriodontitis
- CPericoronitis
- DApthous ulcers
- ELess than 2.5mm b. Greater than 3.5mm
''Red complex'' contains organisms that
- ACause periodontal disease
- BAssociated with bleeding on probing
- CContain early colonisers
- DContain late colonisers
"Port d' entrée" for periodontopathogens
- AGingiva
- BTeeth
- CTongue
- DPeriodontal ligament
After full-mouth extraction, the relative numbers of A. actinomycetemcomitans and P. gingivalis,
- ARemain unchanged
- BIs entirely eradicated
- CDecreased
- DIncreased
These notes are compiled from standard periodontology texts for study purposes. They are a revision aid, not a substitute for your own reading or current clinical guidelines. If you spot an error, please leave a comment.