cons sheet # 6 - Mustafa Khandaq

Today we are going to talk about the dental caries….

Caries: are infectious microbiological disease of the teeth that results in localized dissolution and distruction of the calcified tissues.

Now there are important keywords in this definition:
1- infectious: that its an infection caused by a microbiological disease it means that there are microorganisms that cause this kind of disease which are the bacteria.
There are many factors that suggest where that bacteria would come from but in general during infancy we gain these microorganisms from our parents or siblings and it sticks with us for the rest of our life.

Some people have these microorganisms and as a result a lot of caries occur some people have fewer amounts of these microorganisms and therefore less caries can occur.

Localized dissolution and destruction of the tooth structure is the evidence of cavitations that we see in the tooth which is called caries.

We have four elements that develops caries or a carious region:
1-tooth surface: it could be enamel,dentin or even cementum (no tooth surface no caries) that means if we have artificial surface we don’t get caries, like removable partial denture or other restorative material.

2-cariogenic bacteria: like we said microorganisms is the causative factor of caries,these causative factors require a tooth surface plus food which resemble sucrose and any carbohydrates. In general proteins don't cause caries because bacteria can metabolite carbohydrate more than any other type of food.

3- Time: any caries that develop in a tooth needs time the time varies depending on the surface area and many other factors (ex. oral hygiene). So it doesn’t occur in one day it takes more than that.

Its very important to understand that caries doesn’t an inevitable out come it means that not all patients that have caries own the same carious progression and experience because it depends on many factors like oral hygiene, shape of the tooth and buffering capacity of their saliva.

Saliva is a very resistant factor against caries.

In general we have many factors but these the main ones and interaction between these factors determine if we have caries activity or not.

Dental caries happen in any tooth surface that is exposed to the oral cavity, any hidden surface in the oral cavity will not be exposed like Roots if its covered with gingival or dentin because its covered with enamel, unerrupted tooth.

Some times in deciduous teeth if the caries in the tooth is so extensive to the root for example this will cause an infection in the permanent teeth.

The most thing to consider is that caries is an infectious disease so we deal with such things by anti bioters so we have to remove all organisms that are causing this infection or disease.

So far dentistry is attending to deal with restorative approach rather than eliminating disease, it means that the dentist once he sees a carious region he just drill and fill it. This drilling and filling is wrong cause we should shift toward prevention of approaches.

Its not enough for us to cure or remove caries but we should treat the positive factor which is the infection it should be treated before the carious region.

We have demineralization in the carious region and this results in losing of the tooth structure but this process is highly variable. Like we said before there are different experiences with different individuals and also in the same tooth u cant predict the progression of the carious region inside a certain tooth, the process can be some times variable some times u predict that the caries is in all fissures of the tooth but it turns out that its on only one of them.

Like we said bacteria is the course of infectious caries but a single bacteria cant cause an infection there should be a collection of bacteria or whats called a colony of bacteria to cause caries.

There's some thing called dental plaque: it’s a gelatinous mass of bacteria adhering to the tooth surface.


Any bacteria that doesn’t adhere to the tooth surface doesn’t cause infection. These bacteria inside the plaque will metabolize carbohydrate to produce organic acid and this acid once its on the tooth it will cause demineralization and destruction of the tooth structure.

The carious region doesn’t happen and continue nonstop, the thing is in our teeth there 2 processes that is demineralization and Remineralization ,there is kind of a balance between these two processes if de-min is more than that of Re-min then we will have caries in that teeth but if Re-min is more than de-min caries wont happen.

This depends on many factors most important thing is the metabolic of bacteria inside the plaque the 2nd thing is the salivary buffering capacity in the mouth.

If we have low metabolic activity and high salivary buffering this will result in the process of Remineralization and vise versa.

So this balance occurs in the mouth between Re-min and de-min if it’s the same no caries occur. If de-min is more then caries will occur.

For example if we ate a meal that is rich with carbohydrates, saliva wont be able to puffer that amount of carbohydrate as a result de-min will occur.

So in general you should understand that its not a continuous phase in the mouth there are phases consisting of Re-min and de-min.
As long as we have Re-min and de-min it means that there is no cavitations in the region of that tooth so it means that the caries is irreversible when there is a cavitations it means whenever there is Re-min it wont affect that region with cavity it will affect the other parts of the tooth. And even intact teeth had these 2 phases and it depends on iso-tonicity and hyper tonicity regarding saliva that causes de-min and once the (PH) goes back re-min occur.

Question is asked about el kels….if the plaque stays a long time itg will absorb calcium and phosphate ions from saliva this will result in the hardness of plaque, if u brush ur teeth before the plaque absrbs these ions it will be removed otherwise it will be hardened and we can only remove by clinical polishing. hard plaque mostly occur in the gingival area.

As a conclusion once the plaque is formed caries will start to form.

Plaque formation occurs in stages (by assuming that the tooth is cleaned) :

1- (30min-1 hour): it forms acquired pellicle :very thin structureless, acellular film on the tooth structure that is formed by proteins from the saliva. First it’s a good thing but if we don’t clean it, pellicle will help in adherens of plaque afterwards. So this thin layer by itself helps in protection of enamel at the same time it produces a friction between the teeth because it’s a very thin for the proteins and the hard tissues of the teeth such as enamel so it kind of reduces the friction between teeth especially on the occlusal surface during mastication and another thing it forms a matrix for Re-min because ions in the saliva need some thing to stick to the tooth.

2- (12-24 hours): it’s the initial layer of the plaque, the first bacteria to be attached is the spherical bacteria this bacteria will adhere to pellicle and starts to spread horizontally on the tooth surface after that about 1-3 days that is if the patient didn’t clean his teeth if he did then he will go back to the pellicle stage where there is no caries otherwise filametous bacteria will grow on top of the cocci bacteria…why is that? Because filametous bacteria does not have the ability to adhere to the tooth structure unlike cocci bacteria.so in 1-3 days we can notice that the plaque increase in thickness, we said that in 24 hours bacteria will spread horizontally and with filametous bacteria it will spread vertically.

In one week the thickness will grow much more significantly and organization will occur on the surface it will take a corn shape like surface.

Organization of the surface depends on the type of bacteria.

Going back to the causes of caries we said that carbohydrates are the main causes especially sucrose more than fructose.

Now we will talk about a very important concept which is the (PH) we said that carbohydrates are metabolized by bacteria and the by product will be an organic acid this acid will cause a drop down in the ph of the oral cavity. Most of the ph in our body is neutral (ph around 7) if acid production occurs ph will drop down to a critical level if we it goes below that we will have de-min,if its above that we will have Re-min, this critical ph =5.5

We said that ions we need for Re-min comes from saliva its mainly composed of calcium and phosphate ions, we face acidity that occurs in our every day because in every meal we take the ph in our will drop down to a certain level depending on the kind of food we take for example if this meal is composed mainly of carbohydrates the ph will drop down significantly like pepsi or other sodas for example, the ph will drop down to 2 but on the other hand if we take proteins it wont drop down that much it will stay around 5.5

The key treatment of caries is to prevent de-min and stimulate the Re-min.

Scientists concluded that there are a certain number of microorganisms of bacteria that causes caries, that means not all bacteria causes caries. There are 2 main types of bacteria that causes caries and periodontal disease the fist one is the streptococcus bacteria (there are 8 serotypes of this bacteria) so in general we will call it as streptomutans , the other type is the lacto bacilli and its different from streptobacteria.

Why are these bacteria the main ones for caries formation?

Because streptococci has the ability to adhere to the tooth surface plus the the shape of lacto bacilli which is spherical also helps in the adherens to the surface ,they are also acidogenic that means they produce acids that lower the ph of the oral cavity and they also nourish on sucrose.

Cariogenic organism: are organism that cause caries.

One of the diagnostic mechanisms to discover caries is to do bacterial testing , if the patient has a high number of these 2 main bacteria that means he has a high carious activity.

Streptococcus is associated with the onset of the region when it has caries but lactobacilli come afterwards. Soso if u look at a tooth which is cavitated u will notice that number of lactobacilli is higher than streptomutans.

There is a very important enzyme in streptomutans which is called glycosyl tranferase this enzyme uses sucrose and convert it by polymerization into an extra cellular matrix this matrix attaches to the pellicle layer on the tooth.

Scientists tried to develop vaccines against this enzyme but so far nothing came out.

We said that we have a lot of types of theories that explains the etiology of the caries the first one is the (non specific plaque hypothesis) which says that all plaque are cariogenic, you might not agree with this one because we said earlier that not all bacteria causes caries , there are certain types that does. Anyway this hypothesis was the first to be introduced. In this case we should remove all the plaque which is non sens. Because even in the most dedicated patients you cant totally eliminate plaque.

The 2nd one is the (specific plaque hypothesis) which states that there are certain microorganism inside the plaque that are responsible of causing disease that are either caries or periodontal disease and in this hypothesis we only need to take out the causative microorganism from the plaque but not all the plaque so its an easier way.

Depending on the specific plaque hypothesis there is a table that outlines the manegment of caries.

What is the etiology in caries? We said that we have mainly streptomutans and lactobacilli so the symptoms that follows infection will be de-min in teeth and as a result we have to drill and fill (restorative treartment) and treatment and elimination of streptococcus infection, after the treatment we should keep examining the teeth for any new caries.

What to do therapeutically? To continually measure the count of bacteria.

Buffering saliva helps in maintaining the ph in the oral cavity to approximately 5 when we have some metabolic activity for the caries ,in this case we will have whats called insipient region: noncavitated enamel region which has de-min bt without cavitation which is reversible type of caries. So buffering saliva helps in maintaining the ph bt under 5.5 so de-min occur without cavitation we’ll have intact enamel with de-min stopped surface.
The question is we said that in the inceptial region we’ll have de-min in the subsurface but the surface of enamel will stay intact how would that be? Bcz thye surface of the enamel is much more mineralized than the subsurface bcz its always exposed and the first to be Re-min before the subsurface and also the more u go toward the DEJ the more softer will be in structure.

How could we see the incipient region clinically?

If its dry It will appear as a whitish spot, but if its wet with saliva or water we cant see it bcz in de-min the spaces that was occupied by ions will be filled with water so it will take the same color as enamel but when its dry the water in the incipient region will go out and therefore it will appear whitish.

When the ph in the oral cavity drops to 3-4 either by high metabolic activity or a certain type of food,evidence of roughening of surface will be noticed and therefore cavitation will occur.

Ph=5.5 nthn happens.
Ph=5 incipient region.
Ph=3-4 cavitation.

Note: if we keep the low ph in the oral cavity for atleast 10 min de-min will occur.

Dietry sucrose changes both the thickness and the chemical nature of the plaque therefore more formation of ECM and it grows in thickness. The mutant streptococci and some of the plaque bacteria use the monosaccharide components of glucose and fructose and the energy of the disaccharide bond of sucrose, we will get two types of energy ,one from breaking the double bond and the other metabolizing sucrose itself.

We said that there are certain crystals that are in the enamel and dentin which hydroxyapatite, these apatite crystals which are composed of carbon,calcium ,phosphate and oxygen, once they start forming as in the newly erupted teeth they start uptaking floride.

Fluoride is a very advantageous for crystals bcz it makes crystals less soluble.

So crystals less in carbonate structure high in fluoride can be 10 times less soluble than crystals with high carbonate structure low in fluoride.

So food, drinks, tooth pastes… that are rich in fluoride help in carious prevention.

Note: the more salivation flow the least caries will occur.

There are different origins of caries it can be started from pits and fissures,smooth surfaces or roots. These are the main areas inside the oral cavity.

The shape of pits and fissures help in the generation of caries.
Smooth surfaces consist of any surface that doesn’t have any fissures like buccal,lingual and proximal surfaces.

For the fissures we have a very difficult oral hygiene bcz of the morphology of its shape, so plaque goes inside and u cant clean it, that’s why its highly encountered to find caries in pits and fissures.

The special thing about pits and fissures is the base to base spread in enamel and dentin but we can notice in dentin the base is wider than enamel bcz dentin is softer.

Last thing we need to know is that brushing our teeth wont prevent plaque accumulation in pits and fissures so we have whats called fissure sealing (not sure abt the spilling) it’s a composite but it doesn’t have filler particles so it flows on the fissures and obliterates them,once its obliterated cavities wont happen.

THE END

Gd luck for all.

Done bu: Mustafa Khandaq