What takes my dentist so long to do in my mouh?

Dentistry has hanged a lot.  In earlier times fillings were mainly cemented or simply pressed into the cavity.  Nowadays things are glued.  In order to give you a better view of the glueing procedure so that you might be able to keep calmer in the dentist’s chair, here are a few details.

A filling is said to be leaking when it no longer fits tightly against the tooth. If an amalgam filling is leaking, it has to be removed and replaced by another material; this is called amalgam replacement. The black edge gap between the tooth surface and filling is a sign of leakage. The patient does not usually feel any pain. During drilling, most mercury is released in the form of vapor, similar to that during filling placement. Luckily, the entire filling does not have to be removed. A cross cut is usually sufficient, as this causes parts of the filling to get separated. Less cutting causes less mercury exposure for both the patient and the doctor. To farther reduce mercury exposure during amalgam removal, dentists use a metal milling machine instead of a diamond coated drill. Amalgam discolorations are caused by deposits of amalgam filling in the dentin. Amalgam discoloration does not have to be removed. The general rule is to preserve as much tooth structure as possible. Whether or not the discolorations decrease the adherence between ceramic inlays and the dentin is subject to controversial scientific discussion; moreover, the difference between the various glue combinations should not play a role in actual clinical practice.

Bonding is an informal term used in dentistry to describe the gluing procedure of ceramic and/or plastic fillings. In contrast to the cementing process, surfaces to be glued must first undergo a special preparatory treatment. The individual steps involved are as described below.

 

Step one: etching the surfaces of restorations and/or teeth.

In the field of dentistry, etching gel is used to increase the area of the tooth surfaces used for bonding. In contrast to a cementing procedure, the surface to be bonded undergoes special preparation, which includes etching. During etching, the bonding surfaces of the prepared tooth cavity or ceramic inlay are roughened to create what is known as a microretentive pattern. The surface is initially smooth, but after a certain period of time, the etching gel penetrates into the tooth enamel and creates small lacunae (depressions) and caves. The etching gel is rinsed off after a few seconds (as specified by the manufacturer), leaving behind the surface irregularites. Let us consider the original area of the tooth cavity surface with the inlay as X. When one examines the bonding surface after the etching procedure, the area will have increased by a factor of Y. Because the bonding surface is not two- but three-dimensional, it has actually expanded more than what is seen. The etching procedure also conditions the surface, thus facilitating more stable bonding.

However, not all parts of the tooth cavity surface can be etched to an equal degree. The dentine layer lies below the enamel layer. Dentine comprises protein threads and small canals. Drilling can destroy these structures, leading to the development of a smear layer. This smear layer prevents the bonding adhesive from penetrating the enamel. If the etching gel is applied over the enamel and dentine for a similar period of time, the proteins released by the dentine will start to clump by a process known as denaturation. This process is similar to the grayish film that develops on the surface of chicken soup, which is caused by denaturated proteins. Because of this, the bonding adhesive cannot penetrate the dentine. Therefore, your dentist apply the gel initially to the enamel, and after a while, to the dentine, where it remains only for a few seconds. This allows the smear layer to be removed without causing protein denaturation, and it also allows the development of the necessary microretentive pattern. The bonding adhesive can now penetrate the dentine and enamel, which is the basis for optimal bonding.

The risk of complications during the etching procedure is negligible. However, in individual cases, complications requiring further treatment are possible. Every additional procedure carries its own risks, which may eventually lead to tooth loss. Complications specific to etching include the following:

  • Temporary tooth sensitivity to hot/cold sensations
  • Damage to the tooth nerve (pulp), necessitating root canal treatment in some cases

 

Step two: a primer is used to remove water from the dentin in order to dry out the protein strands

Because water prevents the glue from distributing well within the dentin.

 

Step three: although the protein strands are dry, they have collapsed

An adhesive is used at this point to make the protein strands stand up again, thereby promoting distribution of the glue.

 

Step four: the bonding agent is the preglue

Because it is very thin, it penetrates deeply into the cleaned and re-established protein strands as well as into the vacuoles/pores of the dentin.

Finally, the actual glue is applied. Although this is only a rough outline, it is clear that the gluing of dental fillings is an elaborate process. Good bonding results can be achieved only if the manufacturer’s instructions are followed and the tooth is kept clean throughout the procedure. This is why dentists always work with a rubber dam. A rubber dam is a rubber membrane used for complete isolation of teeth. There are various versions of rubber dam; the latex membranes are also available in various colors. Many materials used in dentistry are very sensitive to moisture. For example, a rubber dam should always be used while gluing ceramic inlays and/or plastic fillings. Likewise, root canal treatments should never be performed without a rubber dam because there are many bacteria in the saliva, which can trigger infections by making their way inside the open tooth canal. These bacteria can multiply without hindrance in the interior of the tooth, causing infections in the bone after weeks, months, or even years. This may even lead to tooth loss in many cases. Furthermore, any swallowing and/or breathing in (aspiration) of instruments, materials, or foreign objects is prevented by the rubber dam. Thanks to the rubber dam, a practitioner can concentrate on the working area with peace because he/she does not have to fight saliva, blood, and the tongue.

The last Step - Airblock. Airblock is the name of a dental product, but in expert jargon, it is also used as an expression for a step during the process of gluing a ceramic inlay. After hardening the glue quickly with a heat lamp, the surplus glue is removed. This is easily done because the interior of the glue is still soft. Now, airblock is applied before final hardening. This step enables the glue to completely harden. Through the use of airblock, the glue hardens much better, creating a smooth glue gap. This also decreases the risk of caries because adherence between the tooth and the inlay is optimal with airblock.

It’s not only fillings that are glued, however.  Tooth ornaments are also glued to the surface of the tooth.  Tooth ornaments are popular in dental cosmetics. All types of tooth ornaments share one thing in common: there is no drilling involved. Tooth ornaments can easily be fixed and removed without damaging the tooth in any way. The jewelry is gently glued onto the tooth, and the process is completely pain free. Healthy tooth substance used to be drilled in the past, but this practice is now frowned upon. After etching and conditioning the enamel, the desired ornament is glued to the tooth. Durability varies and depends heavily on the gluing procedure as well as on the individual’s eating and oral hygiene habits. Normally, the tooth ornament should last between two to five years. Nothing happens if the wearer swallows it.

However, such procedures belong in the hands of a dentist, not a cosmetic studio. In patients with poor dental hygiene, periodontitis, or caries, tooth ornaments should not be used. It is important that the enamel under the jewelry is completely healthy before they are glued onto the teeth. Ornaments cannot be glued onto artificial ceramic teeth. Well-glued ceramic inlays cannot be recognized, even by a dentist! The risks of bonding are negligible. Nevertheless, complications may occur in individual cases, possibly requiring additional measures. Every additional measure may in turn lead to complications, which may lead to tooth loss. At this point, we will only discuss the specific complications encountered with bonding, which include the following:

  • sensitive tooth necks;
  • toothache, which for example, may be caused by injury to the dental nerve;
  • leaking ceramic fillings or plastic fillings;
  • clogging of gaps between teeth;
  • and gum inflammation, which for example, may be caused by residual glue

 

This post is also available in: German

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