Unit 5 - Dental Caries

Question 1

What are the characteristics of caries bacteria

Answer 1

Gram positive
Use oxygen
Lower available oxygen
Use sugars and fermentable CHO for energy
Use saliva for carbon source
Some form extra and intra cellular polysaccharides for later
Presence of food source plays major role in converting non-pathogenic plaque to cariogenic plaque

Question 2

What factors are operating together and involved in the caries process?

Answer 2

A caries prone tooth (susceptible)
Fermentable carbohydrates (dietary factors)
Specific types of bacteria
Time (associated with diet/saliva) host factors

Question 3

What is the plaque-host substrate theory?

Answer 3

The current understanding of caries ethology

Caries has a bacterial etiology that is interdependent on host factors, dietary factors and time

Question 4

What is pulpitis

Answer 4

Inflammation of the pulp

Question 5

What are the host factors in caries?

Answer 5

Composition of tooth structure
Morphology
Position
Clients age
Tooth surface
Salome
Dietary factors

Question 6

What role does tooth structure composition play in caries?

Answer 6

Fluoride levels in tooth surface

Surface enamel is more resistant than subsurface

Question 7

What role does morphology play in caries?

Answer 7

Presence of pits and fissures
Hypoplasia
Other defects that can trap plaque or render the tooth structure more susceptible to caries

Question 8

What role does position play in caries?

Answer 8

In self cleansing areas or in difficult areas for access by client plaque control

Question 9

What role does age play in caries?

Answer 9

Newly erupted teeth are more susceptible
Caries rate decreases after about 25yeaes (early adult)
Root caries increases in older individuals (increased root exposure)

Question 10

What role does tooth surface play in caries?

Answer 10

Some tooth surfaces are affected sooner than others as follows:
Maxillary-occ, mes, dist, ling, bucc
Mandibular - occ, mes, dist, bucc, ling
Posterior teeth sooner than anterior
Height of contour on teeth is typically above the gingival margin; the area apical to the height of contour lends itself to bacteria accumulation, and growth that is somewhat protected from oral self-cleansing mechanisms
Arch form and alignment may produce crowding and subsequent alignment which can create areas that harbour plaque

Question 11

What role does saliva play in caries?

Answer 11

Highly important
Maintenance of oral health including maintenance of tooth structure
Key component in protection against caries

Question 12

What are the properties of saliva?

Answer 12

Saliva enzymes
Salivary buffers
Pellicle components
Immunoglobulins
Minerals

Question 13

What role do salivary enzymes play in caries?

Answer 13

Have an antimicrobial effect
Lysozyme - cell wall destruction and cell lysis of gram positive bacteria
Lactoperoxidase - disruption of bacterial metabolic systems
Lactoferrin - binds iron that is essential for bacterial growth

Question 14

What role do salivary buffers play in caries?

Answer 14

Neutralize the pH of plaque when lactic and acetic acid are produced (main one in saliva is bicarbonate-carbonate)

Question 15

What role do saliva pellicles play in caries?

Answer 15

Saliva pellicle proteins may also serve a protective function since surface enamel is more resistant to bacterial acids than the subsurface mineral (surface salivary pellicle may stabilize the surface hydroxyapatite)

Add additional protection

Question 16

What role do immunoglobulins play in caries?

Answer 16

Contained in saliva

IgA is one major antibody found in saliva but there are several

Question 17

What minerals are in saliva to fight against caries?

Answer 17

Calcium
Phosphate
Fluoride
Bicarbonate 
Keep teeth intact by either participating in remineralization and/or buffering acids

Question 18

What are important factors in relation to remineralization/demineralization?

Answer 18

Rate of flow
Quantity
Viscosity

Question 19

How does the rate of flow in saliva have an effect on caries?

Answer 19

More inorganic components in slow flowing saliva

Eg. Calcium and phosphorous

Question 20

How does quantity of saliva effect caries?

Answer 20

Decreased amount of saliva promote increased caries

Question 21

How does viscosity of saliva effect caries?

Answer 21

Unclear effect

Probably affects the rate of flow and the ability to cleanse

Question 22

What is the difference between resting saliva and stimulated saliva?

Answer 22

The amount of calcium available
There are no minerals in resting saliva because they all leach out
Fresh saliva bring fresh minerals to neutralize acids & kill bacteria

Question 23

What is the interaction of sucrose and bacteria in the oral cavity over time?

Answer 23

Sugar is ingested - diffused into saliva and consumed by the bacteria
Bacteria produce acid as a byproduct and release it into the saliva
The acids drop the pH levels sharply and rapidly
Decalcification occurs below 5.5 (critical pH)

Question 24

What are the determining factors in the effect of sugar on dental caries?

Answer 24

Form and frequency of sugar intake and not quantify of sugar

Question 25

What does the amount of decalcification depend on?

Answer 25

Length of time the pH remains low (below 5.5)

Frequency of drop (diet *liquid or solid)

Question 26

How long does it take for the pH in your mouth to readjust from a decline in pH?

Answer 26

About 20-30 minutes to return to 5.5

Up to 2 hours before it returns to the original pH where acid is neutralized and removed for the pH to return to normal

Question 27

What factors are involved in the Stephan Curve in reference to fermentable carbohydrates?

Answer 27

Frequency of intake
Physical form and retentiveness
Length of time in mouth
Chemical composition in terms of a refined or complex CHO
Presence of other foods
Route of admission

Question 28

What are the pH outlines for demineralization?

Answer 28

Normal pH is 6.5-7
Critical pH is 5.5 for enamel and 6.2-6.7 for cementum
Dentin is somewhere in the middle

Question 29

What does research show is about the presence of bacteria and caries?

Answer 29

Germ free animals develop caries in the presence of bacteria
Oral bacteria can cause demineralization
Histological studies have shown bacteria in the enamel and dentin of various lesions

Therefore, bacteria need to be present for caries to happen

Caries associated bacteria indigenous to humans have a latent pathogenic potential

Question 30

Which bacteria are significant in pit and fissure caries?

Answer 30

Streptococcus mutans

Lactobacillus species

Question 31

What bacteria are significant in smooth surface caries?

Answer 31

S. mutans

Question 32

Which bacteria are significant in dentinal caries?

Answer 32

Lactobacillus species

Actinomyces naeslundi

Question 33

Which bacteria are significant in root caries?

Answer 33

A. viscosus
A. naeslundi
Filamentous rods

Question 34

Describe S. mutans

Answer 34

Cocci/spherical to elongated
No motility
Facultative aerobe
Forms and stores ICP’s, ECP’s ‘dextrans/levans’
Acidogenic/aciduric *most cariogenic; primary/supragingival plaque
Smooth surface, pits & fissure, root caries but not as significant there

Question 35

Describe lactobacillus

Answer 35

Rod/large irregular
Not motile (few motile)
Facultative aerobe
Metabolizes CHO’s but very little ECP’s
Needs retentive sites; established caries, P/Fs; secondary to S.mutans
P/F caries and progression of dentinal caries *needs acidic environment

Question 36

Describe Actinomyces viscosus

Answer 36

Bacilli/some branching
Not motile
Facultative aerobe
Metabolizes some ECP’s and ICP’s
Early colonizer, also associated with older plaque *acid producer; in supra plaque and in subging sulcar plaque
*RSC, mild and chronic gingivitis, early perio and calculus formation

Question 37

Describe A.naeslundi

Answer 37

Gram positive
Bacilli/some branching
Not motile
Facultative aerobe
Mild CHO metabolism
Some in plaque; prefers mucosa, tongue
Some root caries, perio, Actinomyces infections **opportunistic for post trauma infections

Question 38

What are characteristics of S mutans

Answer 38

Prolific producer of insoluble extracellular dextrans (ECP’s) which promote adhesion to tooth surface
Is highly selective for pellicle coated enamel surface (lives only on teeth)
Rapidly metabolizes sucrose to lactic acid and other organic acids which are believed to dissolve the enamel matrix
Can use sucrose in adaptive ways to foster its colonization while using every sugar in the diet for acid production
Ability to initiate and maintain microbial growth and continue acid production in acidic site
Can tolerate presence of acids; transmissible

Question 39

What are characteristics of Steptococcis sobrinus?

Answer 39

Much like S. mutans
Noted to be highly acidogenic and aciduric and found in high caries individuals
Some information referred to a higher amount in children, other similar to S. mutans in all caries associated biofilm

Question 40

What are characteristics of lactobacilli?

Answer 40

Considered important in PF caries
Can grow rapidly in anaerobic enviro (but can tolerate low O2 levels
Can produce both fermenting with and oxidative products (acids and carbon dioxide) depending on the primary fermentation product
Has ability to produce lactic acid and grow in acid created from fermentation
Role in caries still unclear- represents small % of organisms cultivated in caries
Have also been isolated in dentin of deep carious lesions
Proportions found in saliva far exceed those in dental plaque
Also colonize on tongue, vestibular mucosa&palate
Adherence is low-needs protection or other bacteria

Question 41

Characteristic of Actinomyces viscosus

Answer 41

A. viscosus is the dominant bacteria in root surface caries
A. naeslundii also frequently present in RSC along with A. Viscosus but have less affinity to tooth surface and more of an affinity for mucosal surfaces
Readily attach to proline-rich proteins found on saliva coated tooth surfaces and also adhere to polysaccharide receptor on cells of streptococcus sanguis
Tend to ferment sugars and can store ICP (contribute to prolonged acid release - yet not as acidogenic as S. mutans
Microorganisms tend to invade the cementum -along areas where sharpeys fibers were/may still be present

Question 42

What is the acidogenic theory (acid or demineralization theory)?

Answer 42

Acids produced by plaque bacteria result in demineralization of enamel
Carbohydrate + bacteria = acid
Acid + susceptible tooth = caries

Acid is the main destructive agent

Most widely accepted theory

Question 43

What is the proteolytic theory?

Answer 43

Assumes caries is initiated by proteolytic enzymes in plaque that destroy the inter-Rod organic material and destabilizes the enamel crystals
Proteolytic enzymes: the main destructive force
Acids play a secondary role

Question 44

Recall plaque maturation process

Answer 44

Recall steps of biofilm formation - bacterial succession
Cocci replaced by rods and filaments
Cocci change: pH, nutrients, oxygen are critical in favouring growth of additional S. mutans/S. sobrinus and succession of others
S. mutans and lactobacilli increase

*review handout for more details

Question 45

What are some pathogenic factors in caries?

Answer 45

Acidogenic bacteria
Reduced salivary function
Frequency of fermentable CHO

Question 46

What are protective factors in caries?

Answer 46

Saliva flow - stimulated saliva
Salivary components
Proteins
Calcium
Phosphate
Fluoride
Antibacterial factors (chlorohexadine, fluoride) - in saliva and extrinsic
Sealants
Self care
Xylitol - not only stimulates saliva, but also changes the bacteria by changing not allowing the bacteria to stick to the surfaces.  Alter their sticky feet.

Question 47

Describe the demineralization process.

Answer 47

Stagnation of simple carbohydrates
Specific bacteria proliferate and produce acid - acids seep down the interrod spaces and begins to demineralize enamel rods from within
Critical pH is lowered creating an acid environment
Enamel becomes demineralization at a pH of 5.5 or lower
Eventually leads to cavitation (caries/decay)

Surface layer of enamel remains intact until it’s almost completely undermined
*as long as the outside surface layer of enamel is intact, remineralization can occur this, reversing the process providing the lesion has not reached the DEJ
Cavitation occurs when the surface layer is weakened and no longer supported by the underlying enamel rods and breaks through or collapses producing a cavitation (cavity)

Question 48

Describe the remineralization process

Answer 48

The replacement of mineral in tooth that was lost as a result of the caries process
A demineralization - remineralization equilibrium exists between saliva and oral hard tissues
Factors involved:
pH or acid levels (high acid low remineralization)
Mineral ion concentration carried in saliva (high mineral content = remineralization)
Salivary factors (increased flow and decreased viscosity favor remineralization)
Fluoride (oral presence of fluoride favours remin)
Frequency and severity of cariogenic environment (increased frequency = decreased remin)
Surface layer of enamel must stay intact for remin to happen

Question 49

Give an overview of the caries process in enamel

Answer 49

Decalcification extends from surface into rods as the bacteria produce acids and the acids break down the rods

Reversible if surface stays intact - but collapse of the surface is irreversible (carious lesion) - surface is remineralized

Question 50

Give an overview of the caries process after reaching the dentin

Answer 50

Dentin provides a source of nutrients for bacteria which favours growth -lateral spread (tufts and spindles)
Proteolysis of organic components - food sources
Decalcification from within the tubules - further bacterial invasion
Organic material - not remineralized therefore the acids and bacteria move laterally and downward

Question 51

What are the zones found in carious enamel?

Answer 51

Zone 1: surface zone - outer enamel appears intact and unaffected; can be remineralized if the lattice remains intact
Zone 2: body of lesion - area of greatest demineralization
Zone 3: dark zone - results from demineralization (always present but not always detectable); remineralization also happens here. Breakdown!
Zone 4: translucent zone - slightly more porous than sound enamel (not always present)

Incipient caries: subsurface not open enough to allow bacteria in, but demineralization of crystals occur developing these zones!

Question 52

What are the zone found in carious dentin?

Answer 52

Zone 5: brown zone - consisting of decomposed dentin (tubules destroyed along with mineral content)
Zone 6: bacterial zone - bacteria invades decalcification intact dentinal tubules
Zone 7: demineralized zone: decalcified dentin with no bacterial invasion
Zone 8: sclerotic zone - dentin sclerosis (Ca salt in tubules)
Zone 9: zone of fatty degeneration of odontoblastic process

Peritubular will breakdown first then the intertubular
Deadtracks = tubules

Question 53

What are protective responses of dentin?

Answer 53

Sclerotic dentin/transparent dentin:
Odontoblastic processes within the tubules degenerate - tubules become plugged with calcium salts and form a harder sclerotic dentin which slows the advancement of caries in those tubules
Dentin sclerosis occurs minimally in fast advancing caries and slowly in slowly advancing caries

Reparative or tertiary dentin:
Protective layer of dentin is laid down in the area of injury as a response to injury
Is secreted at the dentin/pulp interface

Both of the sclerotic and tertiary dentin differs from secondary dentin which is a biological process of continuous deposition of dentin at the pulp-dentin interface throughout life

Question 54

What are factors involved in the progression of the rate of caries development

Answer 54

Bacteria type
Nutrients available
Saliva - ability to remineralize/buffer - lack of saliva is huge (increased risk because the lack of ability to buffer and remineralize)
Optimal conditions - frequent snacks, newly erupted teeth, poor OH - if you want to build a breeding ground for bacteria (build it and they will come)
Speed of infiltration = variation in individuals - how fast the bacteria breaks down depend on every individual. Attack rate caries based on day/week/month/situation
Time