Lecture 17 : Mechanisms of Caries and Prevention Flashcards
What bacterial Components of Dental Plaque cause dental caries?
in particular Strep. mutans, Strep sobrinus, and lactobacilli
What is a Mutacin?
antibiotic peptide produced by Strep. Mutans. Class of compounds called lantibiotics, which refers to the types of peptides it’s made up of
What are Caries?
—refers to the dissolution of tooth enamel and dentin. It starts in the pits, fissure, and interdentinal regions of the teeth, “stagnation areas” from which bacteria are difficult to remove.
How is the extent of caries measured?
The extent of caries is measured as the number of teeth diagnosed as decayed, missing, or filled due to caries- DMFT (Levine)
Refined Sugar =
Pure Sucrose
Unrefined Sugar =
unprocessed sweeteners, e.g., honey, agave nectar, molasses, raw sugar, maple syrup, palm sugar
What is Hydroxyapatite?
naturally occurring mineral form of calcium phosphate {Ca5(PO4)3(OH) or stoichiometricCa10(PO4)6(OH)2}. One hydroxyl group can be substituted by carbonate, fluoride, or chloride. Hydroxyapatite is the form of mineral which is found in bone and teeth, the hardest substance in the body
What is Fluoroapaptide?
—hydroxyapatite with a hydroxyl group substituted by fluoride atom. Because fluoride is more electronegative than hydroxyl group, it replaces the latter in the hydroxyapatite crystal structure without altering the overall structure, called an isomorphous replacement
What is Secondary Dentin?
formed after tooth formed as a layer on the root bordering pulp tissue
What is Tertiary Dentin?
created in response to trauma, stimulus like caries or wear on the tooth
What is Biofilm?
a group of microorganisms in which cells stick to each other on a surface. Adherent cells may be embedded within a self-produced matrix of polymeric extracellular substance or slime which also includes DNA, proteins and polysaccharides. Cells within a biofilm can exhibit special phenotypic and symbiotic characteristics
What is Fluorosis?
developmental problem also termed mottling of teeth which is caused by exposure to excessive concentrations of fluoride (>1ppm)
What is Remineralization?
the delivery of calcium and phosphate, from outside the tooth, into the enamel lesion, the presence of fluoride favors deposition of mineral onto the demineralized enamel surface
What is Endocarditis?
typically occurs when bacteria from another part of your body, such as your mouth, spread through your bloodstream and attach to damaged areas in your heart. Left untreated, endocarditis can damage or destroy your heart valves and can lead to life-threatening complications. Treatments for endocarditis include antibiotics and, in severe cases, surgery.
Endocarditis is uncommon in people with ____?
Health Hearts
People at greatest risk of endocarditis have _____?
A damaged heart valve, an artificial heart valve or other heart defects
Dental Abscess is the region of ______?
pus within teeth or gums usually initiated as a bacterial infection
What do Asaccharolytic bacteria use as their energy source?
metabolize Protein and Amino Acids
What do Asaccharolytic bacteria contribute to?
Asacharolytic bacteria contribute to the ability of advanced caries once we get into the denten and past the enamel and make the cavity or caries lesion even bigger
White spot lesion =
First enamel damage is beginning, it gets larger and larger until it encrouches on the vital pulp tissue of the tooth Might be more indicative of a carious lesion than a dark spot bc a dark spot may be a stain or a deep pit
What is the Chemical Composition of Enamel?
96% Calcium Hydroxyapatite Crystal 4% Organic Materials and water
True or False, Enamel is the most highly mineralized tissue in the body
True
What ends at tooth eruption?
Amelogenesis
What is Amelogenesis?
Formation of the enamel
When does Amelogenesis end?
When the tooth erupts
What is Dentin composed of?
45% Hydroxyapatite Crystals 33% Organic Material (Collagen, etc) 22% Water
How can Dentin be produced?
Dentin can be produced post-natally as when secondary dentin or tertiary dentin is formed
How is the Dentin Enamel Junction (DEJ) formed?
Dentin Enamel junction • Formed during development, the DEJ is a product of odontoblasts and ameloblasts and it bridges these two dissimilar mineral phases. DEJ is formed from odotoblasts and ameloblasts and its a barrier, so it’s really hard for the acids that cause caries to get through that really hard enamel. Once the acids have progressed all the way through, there’s one last body guard, the DEJ,
What does the DEJ act as a barrier for?
DEJ must be penetrated in order for decay to progress to the dentin and ultimately to the pulpal chamber.
What is required for the dissolution of enamel?
Primarily requires acid to dissolve the mineral hydroxyapatite.
What is required for the dissolution of the dentin?
Requires both specific collagenase and other proteases to breakdown collagenous matrix and also acid to dissolve the mineral crystals present.
Amelogenesis Chart explanation 9:10
- After the first layer of Dentin is formed, that starts it
- After the First Layer of Dentin is formed by Dentinogenesis, then a message is sent from those newly differentiated Odontoblasts to the inner enamel epithelia which cause the epithelial cells to further differentiate into the secretory ameloblasts.
- Dentinogenesis is then dependent on signals from the differentiating inner enamel epithelium in order for that process to continue, reciprocal induction is what it’s called.
- It’s between the mesenchymal and epithelial cells
- Inductive stage - ameloblasts differentiate from the inner enamel epithelium
- Secretory stage - proteins in an organic matrix form a partially mineralized enamel
- Maturation stage - continues enamel maturation
What do Ameloblasts form?
Ameloblasts form individual enamel rods via their tome’s process.
EMP =?
Enamel Matrix Proteins
MMP = ?
Metalo Matrix Proteases
TP’s =?
Sticky outies, tome’s processes from which the enamel rods are forming.
Kind of forms out like spokes of oil, so they go around that dentin layer
RA = ?
Ruffle Ended Ameloblasts
10:46
???????????????????
Do a little bit better at a lower pH, nicely sealed
SA =?
Smooth ended ameloblasts,
they operate at a slightly higher pH and are a little more leaky
Maturation Stage =?
All of our enamel is fully hardening and mineralized
Transition Stage =?
Where it goes from secretory to maturation
loses a lot of ameloblasts, die from apoptosis
Function of Keratin, Study at work 14:00
The charts, Show the function of Keratin at work is required for the mechanical stability of tooth enamel, KRT75 polymorphism if there were people with problems with that, there were increased levels of caries.
14:22
Another diagram from that exact same study
Shows the first characterization that we know of specific epithelial hair keratins that are present in mature enamel and it links hair disorder associative polymorphisms in that KRT75 gene to increased susceptibility to dental defects and caries
Keratin association with teeth?
Where do Dental Caries initially start?
15:10
Fig 15.1
Severe dental carries usually start in pits and fissures
In patients with really poor hygiene, it’ll sometimes start on smooth surfaces and interproximal surfaces as well.
Figure shows it’s progressed away from those occlusal surfaces and is in some easy to clean areas
15:45 chart
Fig 15.2
DMFT compared against sugar consumption
The more sugar the kid eats, the more decay, missing, and filled teeth (DMFT)
1:10, the Mesolithic chart explanation
Step mutans, go to that time to watch explanation
What is Diet’s role in caries?
Much higher incidence of caries associated with the high carbohydrate diet (agricultural) versus high protein diet of the hunter-gatherers.
The less processed we are, the more caries we get?18:28
Historical View on the Mechanism of Caries
19:00
Rodents that didn’t have any bacteria didn’t get caries
Caries is a bacterial disease
Rats were given penicillin, blocked the formation of caries
Rat Study showed Caries if infectious 19:55
19:55
Giving rats penecilin, didn’t get caries
Put the rats in a cage w/ rats not treated with penicillin, those rats would get caries
Shows that it’s an infectious bacterial disease
They gave it to one generation rats, those rats didn’t develop caries, then their offspring didn’t develop caries either UNTIL they were infected by the rats that never got the Penicillin, >>>>passed it on to their offspring<<<<
How does Penicillin kill the bacterial cell?
By inhibition of cell wall synthesis
Mutans Streptococci Participate in _____?
Formation of biofilms on tooth surfaces
Grey on the bottom is the tooth surface
Purple is plaque, biofilm
Step in the biofilm is eating carbs producing lactic acid
then we get this carious lesion in response to the lactic acid that the Strep Mutans and other bacteria produce
What do Carbohydrate Interactions mediate?
Carbohydrate interactions mediate cell-pellicle and cell-cell interactions in the oral cavity.
What are the 3 steps to Biofilm formation?
- Attachment
- Colonization
- Biofilm Development
How does the PEP transport sugar into the cell?
PEP Group Translocation is also known as ______
Phosphotransferase System or PTS
What is PEP Group Translocation?
Pep Group Translocation or PTS is a distinct method used by bacteria for sugar uptake which uses phosphoenolpyruvate as an energy and phosphate source.
What enzymes does PEP Group Translocation involve?
Enzymes of the Plasma Membrane and the Cytoplasm
What is the Phosphotransferase System involved in?
The Phosphotransferase System is involved in transporting many sugars into bacteria
What sugars are involved in the PTS into Bacteria?
Glucose,
Mannose,
Maltose,
Fructose,
Cellobiose
True or False, PTS sugars can differ between bacterial groups
True
What do Bacterial groups try to do in regards to PTS sugars?
They try to mirror the most suitable carbon sources available in the environment.
What is the benefit of transforming glucose into glucose-6-phosphate?
It will not leak out of the cell,
so there will only be a one-way concentration gradient of glucose
What are the sources of bacterial lactic acid?
- ) Fructose (from sucrose)
- )Salivary amylase
- )Other Bacteria
- )The structure of Mutans is resistant to Digestion
Sources of Bacterial Lactic Acid
Fructose
(from sucrose) is transported as fructose-6-phosphate where it is phosphorylated to fructose-1,6-bisphosphate and metabolized to lactic acid by glycolysis.
Lactic acid is excreted but trapped at the tooth surface by the glucan capsule.
Sources of Bacterial Lactic Acid
Salivary Amylase
attaches bacteria to teeth surfaces. Following a carbohydrate-rich meal, amylase digests these carbohydrates (starches) to maltose, which is transported into the cytosol similar to fructose-6-P. Within the bacteria, maltose is digested into to two molecules of glucose-6-phosphate and then metabolized to lactic acid.
Sources of Bacterial Lactic Acid
Other Bacteria
besides Strep. mutans can contribute to the production of lactic acid. Actinomyces spp. and viridans species of streptococci are common in the oral cavity and can bind to teeth surfaces via salivary proteins in the absence of sucrose.
Can make glucans and fructans which enhance adherence of Strep. mutans and acid production. S. mutans makes glucan binding proteins which facilitate adherence to these other bacterial glucans and help stabilize the capsule.
Sources of Bacterial Lactic Acid
Structure of Mutans is Resistant to Digestion
Structure of mutans is resistant to digestion with bacterial enzymes dextranase and fructanase.
What does Anaerobic metabolism yield?
Anaerobic metabolism of glucose yields lactic acid and a small amount of ATP.
This is the favored reaction wit/in plaque where the oxygen tension is low.
As we get through the enamel and into the dentin, we’re going to be involved with _____?
Advanced Caries
During the development of Advanced Caries, what will happen to the region?
- As the region becomes more acidic, the developing cavity promotes greater colonization by S. Mutans and even more acid-resistant bacteria
i. e. Lactobacillus ssp - The latter expand the cavity deeper into dentin.
- Asaccharolytic bacteria of the oral microbiota induce inflammation and abscesses within the pulp and periapical regions of a tooth affected with untreated late-stage dental caries.
What are the factors that determine dental caries severity?
27:50
Production of Saliva
The basic secretory units of salivary glands are clusters of cells called Asciny?
Secrete a fluid that contains water, electrolytes, mucus, enzymes, and they all flow out of the…
Assenus
into the Collecting Ducts
How is the production of Bicarbonate from Carbon Dioxide catalyzed?
• Production of bicarbonate from carbon dioxide is catalyzed by carbonic anhydrase enzyme which is present in saliva and salivary glands.
Really important in remineralization of the enamel,
can help the enamel get stronger.
• The reaction catalyzed by carbonic anhydrase is:
What are the effects of Saliva on carries?
Saliva flow over the teeth and its bicarbonate content are a major resistance towards caries.
Bicarbonate ion is huge with remineralization and making the enamel more resistant to caries.
Saliva washes away bacteria as long as they are not stuck on the teeth via the pellicle.
How does the shape and spacing of teeth affect caries susceptibility?
Clean and smooth surfaces of teeth, bacteria won’t stick to so Saliva washes it off.
The shape and spacing of teeth also affect saliva access and thus indirectly affect the development of caries,
i.e., orthodontic treatment
That’s why orthodontic treatment is not only for aesthetics
What does Amylase do?
Amylase breaks down Starch into Maltose
Maltase breaks down Maltose into Glucose
What are the benefits of Fluoride?
What is the agent associated with mottled teeth?
Fluoride
Fluorosis = Mottled Teeth
What did Fluoride studies show?
- Subsequent larger studies showed an inverse relationship between tooth decay and ingestion of fluoride
- Decay increased also when water supplies were changed to unfluoridated sources.
What is the optimal amount of Fluoride?
1.0 PPM Fluoride
How is Hydroxyapatite replaced with a Fluoride ion to make it more resistant to acid?
What happens with a tooth during a Sucrose attack?
Dynamic Process
HA is disintegratign as sugar is coming in,
the bacteria is eating it
waste product is acid
Causes HA to disintegrate, releasing phosphate ions into the oral fluid
The oral fluid has more minerals in it,
Phosphate ions buffer the acid results more minerals coming back into the enamel
At pH 5-6 we are demineralizing,
in more neutral territories we are remineralizing
At what pH would Fluoride possibly become ineffective?
4.5
Enamel normally at 5.5 breaks down
Fluoride can us to 4.5 pH
Fluoride is good at preventing lesions, but not super helpful when the lesions are already there
Prescribe to patients with a lot of carries going on to prevent future lesions from forming, make sure they know it won’t stop the caries they already have (needs to be treated in clinic)
What are the three mechanisms that Fluoride uses to protect against caries?
- Inhibition of demineralization
- Enhancement of remineralization
- Inhibition of bacterial enolase activity inhibiting lactase production from ingested carbohydrates
The relationship between Sugar and Acid
What is the relationship between sucrose and acid in dental biofilms?
- The mineral phase of bones and teeth is carbonated Hydroxylapatite.
- Dentin and enamel are composite materials of collagen and mineral.
- Hydroxyapatite is soluble in acid, i.e, at pH values less than 5.5
- Severity of Caries is related to the pH produced in dental biofilms (plaques) after ingestion of sucrose and other sugars,
- Caries related to the consumption of high carb diets which are metabolized by plaque…..
- generating lactic acid due to fermentation which demineralizes enamel and exposes underlying dentin
