Definitions and Descriptions

Caries is probably the most frequent disease in man (at least in western society) at the point that the affected population is actually the majority. The mechanism by which it forms is relatively simple.

The plaque bacteria, particularly some species, metabolize sugars and release a side product: lactic acid. Its action over the enamel at first causes a corrosion that decalcifies the surface (the white spot), and then the crumbling of the crystals in the affected area, thus leaving a tiny notch in the enamel.

From inside this little defect, the plaque starts to dig deeper into the tooth's body.

In its progressive advancing in the tooth's crown, the caries enlarges its cavity, approaching the pulp more and more. At the same time, the mechanical structure of the tooth gets weaker and some partial crown breaking may happen.

The majority of the caries actually doesn't hurt. This statement may sound odd, but it's the result of a slow evolution: those species (and those individuals in a species) which developed a good pain level control, have some advantage. Man also developed this skill and so it's possible to have various caries without actually feeling any symptom. As a matter of facts, a tooth that hurts may have a caries or not, but a tooth that doesn't hurt at all, is not sure to be sound and could as well hide one. For this very reason, a periodical checkup at your dentist's is very important.

One thing to be said is that caries is a multifactorial disease, meaning that it has not a unique cause. We're going to summarize the most important factors that may be involved.

a) Bacterial Plaque

It's a conglomerate of carbohydrates (sugars) and proteins directly coming from our nutrition and mixing with the mouth's resident bacterial flora. Plaque is not present in the foetus, and therefore it is aquired from the environment after birth. It's been proved that with the absence of bacteria, a kind of plaque is developed made up of alimentary remnants, but no caries starts. It's most clear that without bacteria there's no disease (see also "Hygene and prevention")

b) Saliva

The characteristics of viscosity, density and acidity of the saliva are inherited and have their influence in the developing of the caries process. Unfortunately there's no means to change the natural situation.

c) Enamel and Dentine

In a tooth, enamel's and dentine's resistance are inherited characteristics, but they can be improved by the general fluoride prophilaxis during infancy. Anyway, some teeth undoubtedly are more resistent against the developing of caries than others.

d) Diet

Since the plaque bacteria feed from carbohydrates and sugars coming from food, a diet which is too rich with those substances is bound to be favourable for the forming of caries. On the contrary, a diet rich in vegetable fibers helps the natural cleaning of the teeth set by means of the rubbing on the teeth's surfaces. The ideal diet from a dental point of view is therefore well balanced and rich in fibers, a thing that is also reccomended for general health anyway.

It consists of a latex sheet (or vinyl for allergic persons) through which some holes are made. The tooth to be treated, and often also the nearby ones are passed through these holes. The dam is fixed by means of a small steel clamp that embraces the tooth at neck height, right over the gum line and avoiding the sheet to slip off the tooth. The latex sheet is then held spread by means of an arch of various shape and material. This way, the dental sector to be worked on, is isolated from the rest of the mouth: this allows a better vision for the operator, a smooth compression on the gum, such as not having it interfering with the work, absence of humidity in the working field and the advantage of not having the patient in need of rinsing.

The rubber dam is strictly mandatory in all cases of dental filling (conservative dentistry), in endodontics, and anyway in all those cases in which the applying is possible.

It has to be underlined that the adhesive procedures, widely used in dentistry, are nowadays in absolute need of the dam deployment, otherwise the sticking strenght of fillings is weaker and may loose its characteristics in time.

In a scientifical and clinical environment, the lack of use of rubber dam in all those cases where it is not only reccomended but generally possible, can be nowadays be considered a technical deficiency!

Conservative dentistry deals with repairing the damages done by the caries, by removing the caries itself and replacing the lost tooth substance with a filling material.

In a certain sense, the caries cannot "heal" because lost enamel and dentine cannot regenerate and the tooth never gets its integrity back.

Modern filling materials and techniques allow a reliable and practically perfect restoration and function recovery.

Anesthesia

First of all the patients gets an anesthesia done, according to the specific situation (see appropriate section for details)

Rubber Dam mounting

In all dental fillings, the use of the rubber dam is peremptory, especially when a filling with aesthetic material is executed (composite resin or composite): the reason for this is that these materials are very influenced by humidity, loosing much of their adherence if not applied in a dry field (see section for details)

Caries removal

The caries is removed from the tooth by means of rotating burs mounted on turbines or micromotors, or hand driven instruments called excavators. The damaged tissue has to be removed provided the fact it can be safely distinguished from sound dentine. Some kinds of excavators are precisely designed to have more or less the hardness of sound dentine, a thing that consents to stop the excavation at the right point.

Cavity finishing

The cavity produced by caries removal needs to be shaped, and the task may be done through rotating or hand instruments. the aim is to give enamel and dentine a homogeneous and precise surface, more apt to receive a filling material. depending on which filling material is chosen, composite resin or amalgam, the cavity shaping may vary to quite some extent.

The composite resin is a plastic material having aesthetical properties and being able to stick to the tooth surfaces. The glueing procedure can be summarized in a defined sequence of chemicals that prepare the dental surfaces in order to receive the filling material.

The choice of the colour is done by observing the tooth and trying to harmonize the composite to the remaining structure. This is not always an easy task because the composite has different light reflection and refraction features from the tooth itself, nonetheless, an experienced dentist with a good knowledge of the product he is using can reach satisfying results.

Etching

The first substance to take contact with the finished enamel and dentine surface is an Acid that used as a conditioner (usually Orthophosphoric Acid 37% concentration): its function is to render a raw surface allowing the grip of the further substances. After its action, it's removed with a brief water spray.

Adhesion

According to the product used, there will be a Primer, which is a substance charged with creating a connection layer between tooth and resin: as a matter of fact it's a substance which is able of permeating the etched surface and connect it to the next layer.

As for next, the Adhesive is used, which is actually a fluid transparent sort of varnish and can be considered as the proper filling glue.

A thing to be pointed at is that some brands of dental adhesives mix these substances in one bottle: they are the so called "one step" adhesives. Every professional chooses his favourite product according to the published information and to his experience.

Filling

The actual filling material (composite) is delivered in small tubes or cartridges used with special dispensers. In any way, it is brought into the cavity with progressive quantities: it needs stratification.

This is mainly done to minimize a particularly unwanted effect that all the composites have, and that's to say polymerization retraction.

This issue deals with the fact that while the material hardens, it undergoes a volume contraction: if this is too heavy, it may cause a micro leakage between filling and cavity walls, too small to be noticeable but big enough to allow a second caries to pass through the gap.

Polymerization (hardening)

The composite hardening is achieved by exposing it to the light of a special lamp with a specific wavelenght emission. aminimum strenght of 550 mW/sqcm is required and below that value, a proper hardening cannot be guaranteed.

Finishing

The final part of the filling leads to the removal of the wedge, of the matrix and of the rubber dam. At this point the so called occlusal test is fulfilled: that means that the proper chewing dimensions are controlled, or easier said there's a check on the patient eventually feeling to be "touching" the filled tooth before the others. With the appropriate burs, retouching is done and as a next phase, the filling is polished using rubber burs, polishing paste or similar. Now the filling is complete.

The dental amalgam is a filling material consisting in a metal alloy existing now since more than a 100 years and having very good duration and stability characteristics.

Its good mechanical features allow very extensive dental reconstructions (see image), but its use requires a very high skill level.

We won't discuss here about its presumed toxicity, but to tell the truth it is a safely usable material, regardless of what's being said about it. A massive media campaign developed in the last years against amalgam, and the material was charged of causing the most various general diseases.

From a strictly medical and statistical point of view though, nothing has been clearly proved.

The enormous quantity of amalgam which is present in the world population, on the contrary is a proof for its general safety.

It's less used than it used to be and it's about to be abandoned, mainly because of its poor aesthetic qualities and because of the increased reliability of modern composite resins.