Восстановление зубов: методы и материалы.

Treatments to restore function, integrity, and morphology of teeth

Dental restoration, dental fillings, or simply fillings are treatments used to restore the function, integrity, and morphology of missing tooth structure resulting from caries or external trauma as well as to the replacement of such structure supported by dental implants. They are of two broad types—direct and indirect—and are further classified by location and size. A root canal filling, for example, is a restorative technique used to fill the space where the dental pulp normally resides.

This technique involves placing a soft or malleable filling into the prepared tooth and building up the tooth. The material is then set hard and the tooth is restored. Where a wall of the tooth is missing and needs to be rebuilt, a matrix should be used before placing the material to recreate the shape of the tooth, so it is cleansable and to prevent the teeth from sticking together. Sectional matrices are generally preferred to circumferential matrices when placing composite restorations in that they favour the formation of a contact point. This is important to reduce patient complaints of food impaction between the teeth. However, sectional matrices can be more technique sensitive to use, so care and skill is required to prevent problems occurring in the final restoration. The advantage of direct restorations is that they are usually set quickly and can be placed in a single procedure. The dentist has a variety of different filling options to choose from. A decision is usually made based on the location and severity of the associated cavity. Since the material is required to set while in contact with the tooth, limited energy (heat) is passed to the tooth from the setting process.

In this technique the restoration is fabricated outside of the mouth using the dental impressions of the prepared tooth. Common indirect restorations include inlays and onlays, crowns, bridges, and veneers. Usually a dental technician fabricates the indirect restoration from records the dentist has provided. The finished restoration is usually bonded permanently with a dental cement. It is often done in two separate visits to the dentist. Common indirect restorations are done using gold or ceramics. While the indirect restoration is being prepared, a provisory/temporary restoration is sometimes used to cover the prepared tooth to help maintain the surrounding dental tissues. Removable dental prostheses (mainly dentures) are sometimes considered a form of indirect dental restoration, as they are made to replace missing teeth. There are numerous types of precision attachments (also known as combined restorations) to aid removable prosthetic attachment to teeth, including magnets, clips, hooks, and implants which may themselves be seen as a form of dental restoration. The CEREC method is a chairside CAD/CAM restorative procedure. An optical impression of the prepared tooth is taken using a camera. Next, the specific software takes the digital picture and converts it into a 3D virtual model on the computer screen. A ceramic block that matches the tooth shade is placed in the milling machine. An all ceramic, tooth colored restoration is finished and ready to bond in place. Another fabrication method is to import STL and native dental CAD files into CAD/CAM software products that guide the user through the manufacturing process. The software can select the tools, machining sequences and cutting conditions optimized for particular types of materials, such as titanium and zirconium, and for particular prostheses, such as copings and bridges. In some cases, the intricate nature of some implants requires the use of 5 axis machining methods to reach every part of the job.

Amalgams are alloys formed by a reaction between two or more metals, one of which is mercury. It is a hard restorative material and is silvery grey in colour. One of the oldest direct restorative materials still in use, dental amalgam was widely used in the past with a high degree of success, although recently its popularity has declined due to a number of reasons, including the development of alternative bonded restorative materials, increase in demand for more aesthetic restorations and public perceptions concerning the potential health risks of the material. The composition of dental amalgam is controlled by the ISO Standard for dental amalgam alloy (ISO 1559). Inorganic filler such as silica, quartz or various glasses, are added to reduce polymerization shrinkage by occupying volume and to confirm radio opacity of products due to translucency in property, which can be helpful in diagnosis of dental caries around dental restorations. The filler particles give the composites wear resistance as well. Compositions vary widely, with proprietary mixes of resins forming the matrix, as well as engineered filler glasses and glass ceramics. A coupling agent such as silane is used to enhance the bond between resin matrix and filler particles. An initiator package begins the polymerization reaction of the resins when external energy (light/heat, etc.) is applied. For example, camphorquinone can be excited by visible blue light with critical wavelength of 460 480 nm to yield necessary free radicals to start the process. After tooth preparation, a thin primer or bonding agent is used. Modern photo polymerised composites are applied and cured in relatively thin layers as determined by their opacity. After some curing, the final surface will be shaped and polished.

Composites and amalgam are used mainly for direct restoration. Composites can be made of color matching the tooth, and the surface can be polished after the filling procedure has been completed. Amalgam fillings expand with age, possibly cracking the tooth and requiring repair and filling replacement, but chance of leakage of filling is less. Composite fillings shrink with age and may pull away from the tooth allowing leakage. If leakage is not noticed early, recurrent decay may occur. A 2003 study showed that fillings have a finite lifespan: an average of 12.8 years for amalgam and 7.8 years for composite resins. Fillings fail because of changes in the filling, tooth or the bond between them. Secondary cavity formation can also affect the structural integrity the original filling. Fillings are recommended for small to medium sized restorations. Inlays and onlays are more expensive indirect restoration alternative to direct fillings. They are supposed to be more durable, but long term studies did not always detect a significantly lower failure rate of ceramic or composite inlays compared to composite direct fillings. Porcelain, cobalt chrome, and gold are used for indirect restorations like crowns and partial coverage crowns (onlays). Traditional porcelains are brittle and are not always recommended for molar restorations. Some hard porcelains cause excessive wear on opposing teeth.

The US National Institute of Dental Research and international organizations as well as commercial suppliers conduct research on new materials. In 2010, researchers reported that they were able to stimulate mineralization of an enamel like layer of fluorapatite in vivo. Filling material that is compatible with pulp tissue has been developed; it could be used where previously a root canal or extraction was required, according to 2016 reports.

Dental implants are anchors placed in bone, usually made from titanium or titanium alloy. They can support dental restorations which replace missing teeth. Some restorative applications include supporting crowns, bridges, or dental prostheses.

When a deep cavity had been filled, there is a possibility that the nerve may have been irritated. This can result in short term sensitivity to cold and hot substances, and pain when biting down on the specific tooth. It may settle down on its own. If not, then alternative treatment such as root canal treatment may be considered to resolve the pain while keeping the tooth.

In situations where a relatively larger amount of tooth structure has been lost or replaced with a filling material, the overall strength of the tooth may be affected. This significantly increases the risk of the tooth fracturing off in the future when excess force is placed on the tooth, such as trauma or grinding teeth at night, leading to cracked tooth syndrome.