Dental Restoration

A dental restoration or dental filling is a dental restorative material used to restore the function and integrity of missing tooth structure. The structural loss typically results from external trauma. It is also lost intentionally during tooth preparation to improve the aesthetics or the physical integrity of the intended restorative material. Dental restoration also refers to the replacement of missing tooth structure which is s upported by dental implants.

Dental restorations can be divided into two broad types: direct restorations and indirect restorations. All dental restorations can be further classified by their location and size. A root canal filling is a restorative technique used to fill the space where the dental pulp normally resides.

Tooth preparation


 Looking into the preparation, the white, outer enamel appears intact, while the yellow, underlying dentin appears recessed. This is because the dentin was decayed and was thus removed. This portion of the enamel is now unsupported, and should be removed to prevent future fracture.
Tooth preparation is usually required before placing a dental restoration. This process involves cutting the tooth usually with a dental drill to make space for the planned restoration, remove any dental decay and structurally unsound tooth. If permanent restoration cannot be carried out after tooth preparation, temporary restoration is done.
A tooth preparation is the finished product of a tooth's structure prior to restoration with a dental restorative material, such as gold, amalgam, composite, porcelain or any number of other materials.
There are two types of preparations.

In preparing a tooth for a restoration, a number of considerations will come into play to determine the type and extent of the preparation.  For the most part, the extent of the decay will define the extent of the preparation, and in turn, the subsequent method and appropriate materials for restoration.
Another consideration is unsupported tooth structure. When preparing the tooth to receive a restoration, unsupported enamel is removed to allow for a more predictable restoration. While enamel is the hardest substance in the human body, it is particularly brittle, and unsupported enamel fractures easily.

Direct restorations
This technique involves placing a soft or malleable filling into the prepared tooth and building up the tooth before the material sets hard. The advantage of direct restorations is that they usually set quickly. Since the material is required to set while in contact with the tooth, limited energy can be passed to the tooth from the setting process without damaging it. Where strength is required, especially as the fillings become larger, indirect restorations may be the best choice. It can be done in one visit with a dentist.

Indirect restorations


A gold inlay on tooth #3
This technique of fabricating the restoration 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 of the prepared tooth. The finished restoration is usually bonded permanently with a dental cement. It is often done in two separate visits to dentist. Common indirect restorations are done using gold or ceramics.
While the indirect restoration is being prepared, a provisory/temporary restoration sometimes is used to cover the prepared part of the tooth, which can help maintain the surrounding dental tissues.
Removable dental prostheses (mainly dentures) are considered by some to be 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 could be seen as a form of dental restoration.

Materials used in dental restorations

Metals and metallic alloys


Amalgam filling
These metals are mostly used for making crowns, bridges and dentures. Pure titanium could be successfully incorporated into bone. It is biocompatible and stable.
Precious metallic alloys

Base metallic alloys

Amalgam

Amalgam is widely used for direct fillings, and done in single appointment. Cast gold is used for indirect restorations.
Direct Gold

Although rarely used, due to expense and specialized training requirements, gold foil can be used for direct dental restorations.

Tooth colored
Dental composites are also called white fillings, used in direct fillings. Crowns and in-lays can also be made in the laboratory from dental composites. These materials are similar to those used in direct fillings and are tooth coloured. Their strength and durability is not as high as porcelain or metal restorations and they are more prone to wear and discolouration.
Composite resin
Dental composites, also called white fillings, are a group of restorative materials used in dentistry.  Compositions vary widely, with proprietary mixes of resins forming the matrix, as well as engineered filler glasses and glass ceramics. The filler gives the composite wear resistance and translucency. This is not recommended for molars.
Glass ionomer cement
A glass ionomer cement (GIC) is one of a class of materials commonly used in dentistry as filling materials and luting cements. These tooth-coloured materials were introduced in 1972 for use as restorative materials for anterior teeth.
As they bond chemically to dental hard tissues and release fluoride for a relatively long period modern day applications of GICs have expanded. The desirable properties of glass ionomer cements make them useful materials in the restoration of carious lesions in low-stress areas such as smooth-surface and small anterior proximal cavities in primary teeth. Results from clinical studies also support the use of conventional glass ionomer restorations in primary molars. They need not be put in layer by layer, like in composite fillings.
Porcelain (ceramics)
Full-porcelain (ceramic) dental materials include porcelain, ceramic or glasslike fillings and crowns (a.k.a jacket crown, as a metal free option). They are used as in-lays, on-lays, crowns and aesthetic veneers. A veneer is a very thin shell of porcelain that can replace or cover part of the enamel of the tooth. Full-porcelain (ceramic) restorations are particularly desirable because their color and translucency mimic natural tooth enamel.
Another type is known as porcelain-fused-to-metal, which is used to provide strength to a crown or bridge. These restorations are very strong, durable and resistant to wear, because the combination of porcelain and metal creates a stronger restoration than porcelain used alone.

Comparison

Restoration of dental implants

Dental implant

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.