WHAT IS A DENTAL FILLING?
This article will describe what is involved in tooth preparation and will include a review of some of the materials we use to 'fill" the tooth.
As a previous article discussed, cavities (Called caries in dental parlance) are the result of decalcification of tooth structure by the acid byproduct of carbohydrate (Sugars) breakdown by intra-oral bacteria. The surface of the tooth can start to break down. In some cases it has been shown that a cavity can take up to four years to form a deep lesion. What occurs is that the tooth surface will be decalcified and become chalky. This then forms a weak area where more bacteria can accumulate in the roughened surface. These areas are prone to continues decalcification once the process is initiated.
A cavity will progress through the more calcified and inorganic enamel surface layer till it penetrates the underlying dentin layer. This layer is lass calcified and is more organic in nature. What this means in practical terms is that the bacteria can break down the underlying dentin layer more quickly. The decay then spreads at a more rapid rate and can, in untreated cases, result in tooth death with the deep nerve becoming involved.This is why your dentist will schedule regular exams, cleanings and patient motivation sessions.
The latter get the patient involved in their own care and will be the major factor in prevention of oral disease. When there is significant tooth structure loss the dentist will intervene with what is called a filling. In dental parlance it is a "restoration". An x-ray will help determine the presence of decay and it will determine the extend of the decayed area. At this point local anesthetic is used to numb the tooth so that the process will be pain free. The procedure dictates the removal of all decay. Dental headpieces, called 'drills' by patients, are used to remove the decay.
The process is very fine tuned. The process involves removal of decay while not exposing the underlying nerve if possible. I say if possible, because in some cases deep decay can cause a pulp exposure. Once all the decay is removed the dentist will choose the type of filling material to rebuild the tooth to an anatomical size and form. For decades silver fillings were used. Today more of the white materials are used. There is some concern that silver fillings can cause problems due to the fact that hey contain mercury.
But there is no real evidence that this is scientifically accurate. The silver material does contain mercury but it is bound chemically in a silver filling. For example water is made of hydrogen and oxygen which are combustible. So chemical composition does not indicate a problem. Most dentists now use the white restoration materials. But as a professor of mine once told us, "don't be the first nor the last on the block,to try a new material" This was true of the white materials. When they first came on the market they were heralded as the answer to everything. But the new materials were off the market in a few years due to failures.
That was 30 plus years ago. Today we use materials and techniques that have been perfected and proven over time.The process is as follows. Once the tooth has decay removed and all weak areas are removed the "cavity" is cleansed. The area is etched with a mild acid. This 'roughens" the cavity surface. This in turn is washed off thoroughly and a liquid material is used as a bonding agent. This material is attracted to the wet cavity surface. It is what is called a polymer composite bonding material. In short it is an organic based material which enters the tooth, the material it is dissolved in alcohol or acetone.
When the bonding material is brushed on the cavity it enters the tooth. The dentin in particular is very porous, so the binding agent can penetrate the tooth. On exposure to air the alcohol or acetone evaporates and the plastic polymer portion starts to chemically interact. This forms millions of tiny 'pins' of a plastic retaining system. The material hardens; but, the surface remains unhardened, unpolymerized in dental parlance". So the cavity is now coated in the bonding agent. The filling material is added to the cavity preparation. In my practice I prefer a two material technique. I use a flowable material which adapts and bonds to the surface which has the bonding material coating.
Some materials will harden on their own. I prefer a light cured (Hardened) material. We use a light cured material. The light we use is a laser which had a visible spectrum blue light. The blue light causes several carbon molecules, in the filling material to bond to each other forming long chains chemically. This hardens the filling material while bonding it to the underlying layer. The remainder of the cavity is filled with a stronger material. This latter material is a polymer plastic with fine crystals of a glass material imbedded.
The surfaces of the very minute glass particles are treated in such a way that when the polymer plastic hardens the glass will be included in the mix. A suitable dental polymer must be bio compatible. That is it must be tolerated by the tooth. The ones today are very "Kind" to tooth structure. They also should have a contraction and expansion factor close to tooth structure. The early tooth polymers were not bonded to the teeth as they are now and in changes of temperature in the mouth occurred there was a difference in expansion and contraction rates,such that openings occurred at the tooth filling junction. The result was severe decay. These material were a good example of what my professor warned us about, "Do not be the first nor the last to try something new."
Today there are a variety of good materials available which are biocompatible in expansion, contraction factors, in biocompatibility with tooth structure and in strength for daily intraoral function. There are continuous developments and improvements of materials and one must keep abreast of independent evaluation and assessment. The overall result is satisfaction for the dental team in knowing that we can provide a great service. To the patient there is an assurance that this is available.
I can be contacted at mfpilon@gmail.com or you can check out my web site at http://www.drmichaelpilon.com/ Drop a line if you have any questions
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