Dental caries

Question 1

Name 5 etiological factors involved in dental caries

Answer 1

Plaque micro-organisms
Dietary factors
Host physiology - eg salivary buffering
Teeth - oral hygiene/preventative measures
Time

Question 2

Name 4 methods to prevent teeth caries and example

Answer 2

Reduce carbohydrates in saliva-change diet /artificial sweeteners

Increase tooth resistance to acid- eg fluoride In water

Reduce tooth susceptibility eg seal fissures

Reduce /eliminate cariogenic microorganisms eg antibiotics

Question 3

Definition of a tooth carie

Answer 3

localised destruction of tooth tissues by bacterial fermentation of dietary carbohydrates

Question 4

what are the 2 stages of tooth decay

Answer 4

1. decalcification
2. dissolution of softened residue

Question 5

what is the critical pH and what does this mean

Answer 5

pH <5.5 - below this decalcification of tooth enamel starts to occur

Question 6

Name steps in plaque development

Answer 6

Adherence most importnat

Pellicle developed–>pioneering bacteria_adhere to pellicle_> bacteria proliferate and form microcolonies with extracellular matrix ___> secondary aerobic bacteria and extracellular polysaccharides aggregate and BIOFILM forms __> mature plaque

Question 7

How does a mature plaque cause tooth decay

Answer 7

Biofilm bacteria produce lactic acid from Fermentable carbohydrates which causesa pH drop which if it reaches critical pH 5.5 causes decalcification of the tooth enamelled increased softening and pourosity of the enamel so acid can penetrate deeper onto tooth and demineralize the subsurface.

Question 8

Name 3 places Where caries occur and percentage

Answer 8

Fissure caries ( >99%)
Approximal caries (5-60% )
Smooth surface caries ) 5%)

Question 9

What is the incipient phase of tooth caries also known as

Answer 9

White spot phase- demineralisation causing decalcification on enamel due to plaque

Question 10

What bacteria is noted to be prevalent pre care formation and in the incipient phase of tooth cary formation

Answer 10

Streptococci mutans ( increases 10-100fold )

Question 11

Who do we see root caries ( cementum caries ) in usually

Answer 11

Older patients who have exposed roots from - gingival recession ( age ) or decreased saliva production ( medications )

Also if too vigorous brushing damaging gums and exposing roots

Question 12

What is different in root surface caries vs other dental caries except for site

Answer 12

Critical pH is 6.7 not 5.5 !

Question 13

What are rampant caries and name a population these are seen in

Answer 13

Severe decay on multiple surfaces of multiple teeth seen in high risk groups such as “nursing bottle “ caries or decreased salivary flow (- irradiation /Sjogrens syndrome /medications )

Question 14

what are the 4 stages of caries

Answer 14

Depends on enamel damage :

1. Initial caries, also called “white spot -. matte light spot on the enamel surface at the place of enamel demineralization. Over time, the process can go from an acute form to a chronic one and pause for a while, the stain becomes dark.
   2
   Superficial caries. - in the area where the stain has formed, roughness appears, , the destruction of the enamel begins.
   3
   Medium caries. - the infection attacks and begins to destroy the dentin tissue.
   4
   Deep caries.( DENTINE caries ) A large carious cavity forms inside the tooth, the infection affects most of the dentin, gets very close to the pulp, or even inflame the pulp

Question 15

What are dentine caries

Answer 15

Advanced caries into dentine of tooth- see lots of lactobacilli bacteria but still some mutans streptococci

Question 16

what is white spot on teeth

Answer 16

demineralization creates white areas of decalcification of the enamel on teeth, resulting from the accumulation of bacterial plaque.-reversable if treated quickly

Question 17

What are the 2 main mutan streptococci in humans

Answer 17

Streptococcus mutans ( 70-80%)
Streptococci sobrinus (20-25%)

Question 18

Name the 4 virulence features of streptococcus mutans that makes it cariogenic

Answer 18

1.Produces extracellular polysaccharides -glucans and fructans from sucrose
2. Carbohydrate fermenter -lactic acid production
3.Aciduric
4. Can store polysaccharides intracellularly

Question 19

How does the production of extracellular polysaccharides glucan from St. Mutans ,cause caries

Answer 19

Glucans (by glucosyltransferase) driven by sucrose , causes polymerazation and branching of glucan ( so more insoluble ) and adheres to tooth allowing no diffusion in or out of plaque.
This blocks movement of Calcium ions ( so tooth not remineralised ) AND the tooth gets no nutrients - only St. Mutans gets nutrients

Question 20

How does the production of extracellular polysaccharides fructan from St. Mutans ,cause caries

Answer 20

Fructan promotes carbohydrate storage so prolonged acid production that means prolong lowered pH environement

Question 21

How doe St. Mutans ability to ferment carbohydrates cause caries

Answer 21

High fermentation rate of all simple sugars except mannitol and sorbitol - meaning high lactic acid rates (pH 3.13 )-tooth demineralisation occurs

Question 22

How is being acidic help st .mutans

Answer 22

Survives in low pH zones so at fermentation rates pH 5.5 survives

Question 23

How does storage of intracellular polysaccharides enable St.mutans to be cariogenic

Answer 23

When there is no exogenous carbohydrates it uses it stored polysaccharide s and glycogen to continue fermentation of sugars and continue the acid production and acidic environment

Question 24

What type /class bacteria are Streptococci mutans

Answer 24

Gram+ve facultative anaerobic cocci

Question 25

What is the lactobacillus bacteria and where is it found

Answer 25

Gram +ve micro-aerophilic rod bacterium found in severe caries. very acidogenic, makes lactic acid from carbohydrates

Question 26

What pH does lactobacilli metabolise in

Answer 26

Very acidic pH<4

Question 27

Do lactobacilli initiate cary formation

Answer 27

No - only in severe caries once formed