CONSERVATIVE DENTISTRY
DENTAL CARIES
Caries is probably the most common disease in humans, so much so that the people who are affected (at least in Western society) are the majority of the population. The mechanism of caries formation is relatively simple.
Plaque bacteria, particularly some species, metabolize sugars and release a by-product: lactic acid. The action of lactic acid on the enamel causes a corrosion of the surface, which first decalcifies (white spot or white spot) acquiring a chalky appearance, and then crumbles causing the formation of a small notch in the surface of the tooth. Plaque proliferates within this notch and thus begins to make its way into the enamel.
In its progression inside the crown of the tooth, the caries digs a cavity of ever greater dimensions, getting closer and closer to the dental pulp, the vital part of the tooth. At the same time, the tooth's structure is also weakened and partial crown cracks may occur. Most cavities don't actually hurt at all. This statement may seem surprising, but it's the result of a slow evolution: those species (and those individuals within a species) that have a certain adaptability of their pain threshold are certainly favored: man too. has developed this particular ability, so that many cavities can be present at the same time without actually having any symptoms. In fact, a tooth that hurts probably has cavities, but a tooth that doesn't hurt could still be hiding one. For this reason, a periodic check-up by your trusted dentist becomes important.
One thing to note is that tooth decay is a multifactorial disease, meaning it doesn't actually have a single cause. We now give a summary of the factors that favor it.
a) BACTERIAL PLAQUE
Bacterial plaque is a conglomeration of carbohydrates (sugars) and proteins that come directly from nutrition and that mix with the bacterial flora of the mouth. Plaque is not present in the fetus, so it is acquired from the environment after birth. It has been shown that in the absence of bacteria a plaque from food residues develops, which however does not cause tooth decay: consequently, without bacterial plaque there is no disease. (see also "hygiene and prevention")
b) SALIVA
The characteristics of viscosity, acidity and consistency of saliva are hereditary and certainly have their influence in the so-called self-cleansing of plaque, but they cannot be influenced in any way.
c) ENAMEL AND DENTINE
The resistance of the enamel and dentin of a tooth are also inherited characteristics, but they can be improved by the action of fluorine taken in general with the fluoroprophylaxis in childhood. However, there are teeth that undoubtedly have a bigger resistance to the action of caries than others.
d) NUTRITION
Since plaque bacteria feed on sugars and carbohydrates, a diet excessively rich in these substances favors the formation of cavities. The intake of fibers (in particular vegetable fibers) can, on the contrary, help cleanse the teeth by rubbing the tooth surfaces. The type of diet recommended for prevention is therefore balanced and rich in fiber - which, among other things, is good for many other medical situations, and in general as a rule of good health.
DENTAL FILLING
Conservative dentistry deals with repairing the damage caused by caries, removing the cavity itself and replacing the lost tooth with a material called "filling".
In a certain sense, the patient is not "healed" from caries, because the lost enamel and dentin cannot be regenerated and the tooth never returns as it was before.
The materials and modern filling techniques, however, allow a reliable repair and a restoration of function practically similar to the original.
Anesthesia
First, the most suitable anesthesia for the specific case is applied to the patient. (see dedicated section for details)
Dam application
In all cases of dental filling, the use of the dam is mandatory, even more rigorously if an aesthetic material (composite resin or composite) is used: this because these materials are very affected by humidity, losing most of their adhesive capacity if not applied in a dry field. (see dedicated section for details)
THE RUBBER DAM
It is a latex sheet (or vinyl for allergy sufferers) on which small holes are made. The tooth to be treated, often together with the neighboring teeth, is so to speak "jacketed" by passing it through these holes. The fixing to the teeth takes place through a metal hook which, by embracing the tooth near the collar, prevents the dam from rising. The latex sheet is then held taut by a frame of various shapes. In this way, the sector of teeth on which it is necessary to operate is isolated from the internal environment of the mouth: this allows greater visibility to the operator, a slight compression on the gum so as not to interfere with the work, the absence of humidity in the field surgery, the advantage of not having to continuously rinse the patient.
The rubber dam is strictly applied in all cases of obturation (conservative dentistry), in root canal treatments (endodontics) and in any case in all cases in which it is possible to apply it.
It should also be emphasized that the adhesive procedures (gluing) that are widely used in dentistry now absolutely require the use of the dam, otherwise the adhesion power of the fillings is considerably reduced, partially compromising their success over time.
In the scientific and clinical environment, the failure to use the dam in all cases where it is not only possible but necessary, is now considered a technical deficiency!
CAVITY PREPARATION
CARIES REMOVAL
Caries is removed from the tooth by means of rotating burs mounted on turbines or micromotors, or with hand tools called excavators. Carious tissue should be removed until it can be distinctly separated from healthy dentin. Some types of very sharp excavators are built to match the hardness of healthy dentin, meaning that they cannot remove it, thus allowing the dentist to stop the excavation at the right point.
CAVITY FINISHING
The cavity produced with the eradication of caries, needs a shaping, which can also be performed with rotating instruments or by hand. The aim is to give the enamel walls a linear and homogeneous surface, suitable to receive the filling material. Depending on whether the filling is performed with composite resin or amalgam, the type of finishing and shaping of the cavity can vary greatly.
COMPOSITE FILLING
The composite resin is a paste of plastic material that has aesthetic features, and is able to physically stick to the tooth. The bonding procedure involves the application of a series of chemicals that prepare the cavity's surface to receive the filling.
The color shade choice obviously takes place by observing the tooth and trying to harmonize the composite with the remaining structure. This is not always an easy task, because the composite has different light refraction and reflectance characteristics than the tooth, however a dentist with a fair amount of experience and with a good knowledge of the product he is using, can achieve satisfactory results.
a) ETCHING
The first substance that goes into contact with the finished dentin and enamel is an acid with the aim of preparing the surface (usually 37% orthophosphoric acid): it has the function of roughening the surfaces and allowing the bonding process. It is removed with a short jet of water.
b) BONDING
Depending on the product used, you may use a Primer, which is a substance in charge of creating a connecting layer between the tooth and the resin: in fact it's capable of microscopically infiltrating the prepared surface and binding to it. Finally, Bonding is used, which is nothing more than a transparent fluid resin: it could also be considered as the "glue" of the filling.
It should be noted, that some brands of bonding materials offer all these steps in one bottle: they are so-called "one step" adhesives. Every dentist chooses the best product based on published studies and his experience.
c) FILLING
The actual (composite) filling material can be carried in tubes called syringes, or in capsules mounted on special guns. In any case, it is brought into the cavity in a progressive quantity: by stratification, that is. This happens in order to minimize a particular undesirable effect that all composites show, namely polymerization shrinkage.
Simply told, it represents the fact that while hardening, the composite undergoes a contraction in volume: if this is excessive, it can cause a micro detachment from the cavity walls, too small to be noticed immediately but large enough to infiltrate a new caries.
d) POLYMERIZATION
The hardening of the composite is achieved by exposing it to the light of a particular lamp emitting a light beam at a certain precise wavelenght and intensity. The minimum intensity is considered to be 550 mW / cmq: below this power it cannot be guaranteed that the composite hardens appropriately.
e) FINISHING
The final stage of filling involves removing the wedge, matrix and dam. At this point the so-called occlusal check is carried out: the chewing dimensions are checked: if the patient, closing his mouth and making his teeth match, first "touches" the reconstructed tooth. Then the necessary retouching is carried out and the polishing phase is performed by means of pastes, brushes or rubber pads. At this point, the filling is complete.
AMALGAM FILLING
Dental amalgam is a filling material consisting in a metal alloy that has existed for over 100 years and has excellent durability and stability characteristics.
Its high mechanical characteristics make it possible to carry out extremely extensive dental reconstructions, but certainly its use requires particularly careful manual skills.
We will not discuss its alleged toxicity here, however it is in fact a perfectly usable material, as far as known. A massive media campaign against amalgam has developed in recent years, blaming it for the most disparate general diseases.
However, from a medical and statistical point of view, nothing has been proved.
The enormous quantity of amalgam present in the world population, if anything, proves the absolute safety of the material.
However, one of its peculiar characteristics is that it does not adhere to the tooth cavity in a chemical / physical way like the composite. It is therefore only a filler, even if the seal is probably almost perfect.
It was abandoned mostly due to its poor aesthetic qualities and the greater reliability of modern composites.