Plaque Biofilm

Question 1

what are the two types of deposits?

Answer 1

Hard deposits: Dental CALCULUS [tartar]
Soft deposits: Acquired pellicle.
Plaque Biofilm.
Food debris.
Materia Alba.

Question 2

What is responsible for periodontal disease and caries?

Answer 2

plaque biofilm

Question 3

What is materia alba?

Answer 3

A loosely adherent mass of bacteria and cellular debris.
Forms on top of the biofilm.
A bulky, soft, white deposit that is easily visible without using any disclosing agent (something that shows the plaque).

Question 4

What is acquired pellicle?

Answer 4

A tenacious membranous layer composed of mainly of glycoprotein from the saliva.
Forms on the tooth surface, on calculus and even restorations – in about 2 hours.
Pellicle is pretty firmly attached to the tooth surface.

Pellicle appears as a homogeneous layer between plaque and the tooth mineral. Pellicle varies in thickness from about 1-10 microns, being thinnest on the occlusal surfaces due to abrasion. It is formed by the selective adsorption of salivary proteins and glycoprotein to the tooth.

The bacteria will cling to the pellicle

Question 5

What is the definition of plaque biofilm?

Answer 5

A whitish grey substance that is firmly adherent to the surface of the tooth – consists of a well organized, cooperating community of numerous microorganisms of different species – surrounded by a sticky matrix of salivary GP (glycoproteins) and extracellular PS (polysaccharides).

In ‘lay terms’(non jargon), “It is a whitish grey, STICKY film that forms on the surface of your teeth, Made up of thousands of many different type of bugs (bacteria) that could cause gum disease and decay.”

(it’s like the slippery layer on rocks in a river)

Question 6

How does the formaiton of biofilm begin?

Answer 6

Formation of a biofilm begins with the
attachment of free-floating microorganisms (the colonists) to the pellicle. The biofilm Initially is found along the gingival margin and Interproximal areas. If left undisturbed it may progresses to the rest of the crown as well as SUB GINGIVALLY.
The gingiva reacts to both, the quantitative & qualitative changes in the biofilm!….

Question 7

Howdo the first colonists adhere to the surface? (two mechanisms)

Answer 7

These first colonists adhere to the surface initially through weak, reversible Vander Waals forces. If the colonists are not immediately separated from the surface, they can anchor themselves more permanently using cell adhesion molecules such as Pili…..

Another mechanism of bacterial adhesion is calcium bridging which links (-) charged bacterial cell surfaces to the (-) charged pelliclevia interposed (+) charged, divalent Ca2+ ions from the saliva.

Question 8

What is the development of biofilm from pellicle?

Answer 8

pioneers, mainly strep. sp. –> grows by spreading laterally and upwards… –> secondary colonization by other species –> becomes mature biofilm –> initiates periodontal disease.

Question 9

What are the bacteria like at the beginning and toward end of the biofilm?

Answer 9

Biofilm present in clinically healthy gingiva comprises mainly of aerobic cocci/rods.During the development of chronic gingivitis, there is a shift to mostly anaerobic facultative organisms.Not only is there a change in quantity but there is also a change in the quality.

Question 10

How do the bacterial colonies communicate with each other?

Answer 10

ability of MO to communicate with eachother via signlaling molecules called homoserine lactones ?

Question 11

What type of bacteria are on clinically healthy gingiva?

Answer 11

aerobic gram + and gram - rods and gram + cocci.

Question 12

In gingivitis what are the bacteria like?

Answer 12

to mostly facultative anaerobes.

Question 13

What is the accumulation of biofilm affected by?

Answer 13

The accumulation of biofilm is affected bythe anatomy, position and surface features of the crown and root,friction at the tooth surface from the movement of saliva, type of food, chewing, lips and tongue, the anatomy of the gingiva and its relationship to the teeth.

Question 14

How were microorganisms studied in laboratory setting ?

Answer 14

Previously, MO were studied as they grew in culture plates. In a laboratory setting;- No Matrix is formed.- The colony is not well organized. Distributed haphazardly or at times, evenly. Antimicrobials have an effect! In nature however,- MO produce compounds that are not produced in the lab.- Antimicrobials have only a minimal effect on the MO in the mouth. (the matrix tend to protect the MO!)

traditional understanding of MO was based in their behavior of colonies grown from a single species in culture plates.

Question 15

How can you really tell if biofilms actually initiate gingivitis?

Answer 15

took a group of dental students and they cleaned the teeth and they were clean healthy tissues. One grop was told to not brush, flosh, or mouthwash for three weeks, then they checked their mouths. The control group they brought back and professionally scaled their teeth. So the test group in three weeks progressed to such an extent that it caused disease. They scaled the test group and the gingivitis disappeared and they returned to normal.

they concluded that gingivitis can be induced by withdrawing all measures of oral hygiene

From the now, classic studies done by Loe et al in the 60’s in Aarhus, Denmark.
Conclusion..

Gingivitis can be induced by withdrawing all measures of OH.

The removal of plaque results in clinically normal gingiva.

Question 16

What is the summary

Answer 16

SUMMARY

1.
Dental plaque is a complex biofilm growing on teeth which is the etiological agent of caries and periodontal disease.
2.
The movement of saliva around the mouth, mainly as a result of tongue action creates a shear force (in addition to mastication) which limits plaque accumulation to sheltered sites
3.
Plaque is initiated by the colonization and subsequent outgrowth of organisms competent to adhere to the tooth pellicle.
4.
The major “pioneer species” are Streptococcus oralis, Streptococcus mitis and Streptococcus sanguis. Others include Neisseria and Actinomyces….

5.
During and following outgrowth other species colonize the forming biofilm by adhering to the pioneer species. This process of co-aggregation can be highly specific.
6.
As secondary colonization progresses the species diversity of the biofilm increases.
7.
Eventually, a combination of secondary colonization and cell proliferation, moderated by detachment of organisms from the biofilm by shear force, produces a climax (stable) community.
8.
The climax community is stable and complex yet responsive to changes in the environment.

Question 17

What happens in the process of all of this formation of gingivitis and what not?

Answer 17

Cocci and rods to a 3 week old. Filamentous microorganisms dominate. Microorganisms expand from supra-gingival to sub-gingival.

When it is subgingival it is test tube brush appearance. It changes from gram positive to gram negative. As it deppens, the junctional epithelium will be worn away by the bacteria and it will move apically. When it does this it changes to periodontitis. The junctional epithelium is at the CEJ in gingivitis, but if it has migrated apically it is now periodontitis.

At the apex of the sulcus you will have adherent microorganisms and non-adherent microorganisms. The adherent are floating and are bad.

Bacterial invasion in the soft tissues  battle  dead cells.

Your body tries to get rid of these dead MO and dead WBC’s through the process known as necrosis and suppuration  pus. Creating a possible peridontal abscess if the escape route is blocked.

Question 18

T or F. The acquired tooth pellicle is also known as Nasmyth’s membrane

Answer 18

False. Althought this was thought to be the case a long time ago, the fact is, Nasmyth’s membrane is lost very shortly after tooth eruption.

Question 19

T or F. The acquired tooth pellicle is readily removed from teeth by tooth brushing.

Answer 19

False. It is not readily removed, you have to brush for some time.

Question 20

With the development of gingivitis, the sulcus bcomes predominantly populated by…

Answer 20

gram-negative organisms