📌 POINTS TO PONDER
🔺Dental plaque can be defined as the soft deposits that form the biofilm adhering to the tooth surface or other hard surfaces in the oral cavity, including removable and fixed restorations.
🔺Dental plaque is broadly classified as supragingival,subgingival or peri-implant plaque based on its positionon the tooth and implant surface.
🔺Supragingival plaque is found at or above the gingival margin.
🔺Subgingival plaque is found below the gingival margin, between the tooth and the gingival sulcular tissue.
1. Supragingival plaque
2. Subgingival plaque
🔸Tooth associated
🔸Tissue associated
3. Peri-implant plaque
🔺 Materia alba differs from dental plaque as it lacks organized internal structure. Due to which material alba can be easily displaced with water spray.
🔺Corn cob and test tube brush structures are theexamples of coaggregation in dental plaque.
🔺 Fusobacterium nucleatum bridges between primary and secondary colonizers during plaque maturation.
📌 VIVA VOCE
Q1. Who coined the term biofilm?
Ans. Bill Costerton in 1978 coined the term biofilm.
Q2. Which organism is believed to be important in bridging between primary and secondary colonizers during plaque maturation?
Ans. F. nucleatum is believed to be important in bridging between primary and secondary colonizers during plaque maturation.
Q3. Give examples of coaggregation.
Ans. Examples of coaggregation are:
👉 Interaction of secondary colonizers with early colonizers: Corncob and test tube brush are the examples of coaggregation:
🔹F. nucleatum with S. sanguinis
🔹P. loescheii with A. viscosus
🔹C. ochraceus with A. viscosus.
👉 Interaction among secondary colonizers:
🔹F. nucleatum with P. gingivalis
🔹F. nucleatum with T. denticola.
Q4. What are corncob structures?
Ans. Corncob structure: Structures which have inner core of rod-shaped bacterial cells, such as F. nucleatumand over the surface of which attach the coccal cells, such as Streptococci or P. gingivalis.
Q5. What is cryptitopes?
Ans. These are hidden receptors for bacterial attachment.
🔹Hidden segments of salivary acidic proline-rich proteins (PRPs) become exposed when the molecules undergo a conformational change as they adsorb to apatitic mineral of the tooth (cryptic, meaning hidden, and topo, meaning place).
🔹Certain bacteria keenly bind to salivary acidic PRPs adsorbed onto apatitic surfaces and they do not interact with PRPs in solution.
🔹PRP molecules evidently undergo a conformational change when they adsorb to hydroxyapatite and these hidden segments become exposed and these adhesins of bacteria recognize cryptic segments.
Q6. What is quorum sensing?
Ans. It is a way of cell to cell communication that regulates gene expression by sharing information on cell-population density.
Q7. What are heat shock proteins (HSPs)?
Ans. HSPs belong to the family of stress proteins which are usually synthesized by bacterial cells when exposed to the environment.
Q8. Who gave ecological plaque hypothesis?
Ans. In 1991, PD Marsh gave ecological plaque hypothesis.
Q9. What are the phases of plaque formation?
Ans. • Pellicle formation.
- Initial colonization of microorganisms.
- Secondary colonization and maturation ofmicrobes.
Q10. Which phase is the prerequisite for the development of plaque?
Ans. Pellicle formation is the prerequisite for the development of plaque.
📌 MULTIPLE CHOICE QUESTIONS (MCQs)
💡The first bacteria to be deposited on the tooth in bacterial plaque formation are:
A. Gram-negative rods
B. Gram-positive rods
C. Gram-positive cocci
D. Gram-negative cocci
Answer : C
💡Non-specific plaque hypothesis was put forward by:
A. Genco
B. Listgarten
C. Loesche
D. None of the above
Answer : C
💡Radius of action of toxins in the bacterial plaque is:
A. Less than 2.5 mm
B. Greater than 3.5 mm
C. Less than 1.5 mm
D. 1.5-2.5 mm
Answer : D
💡1 mg of plaque contains approximately:
A. 2 × 108 bacteria
B. 2 × 109 bacteria
C. 2 × 1010 bacteria
D. 2 × 1011 bacteria
Answer : A
💡Corn cob formation in dental plaque is an example of:
A. Adhesion
B. Symbiosis
C. Attachment
D. Coaggregation
Answer : D
💡Materia alba differs from dental plaque in:
A. Absence of microorganisms
B. Presence of desquamated epithelial cells
C. Lack of internal structure
D. Duration of adherence to tooth
Answer : C