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. As with other composite materials, a dental composite typically consists of a resin-based matrix, such as a bisphenol A-glycidyl methacrylate BISMA resin like urethane dimethacrylate (UDMA), and an inorganic filler such as silicon dioxide silica. 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. A coupling agent such as silane is used to enhance the bond between these two components. An initiator package begins the polymerization reaction of the resins when external energy (light/heat etc.) is applied. A catalyst package can control its speed. This is not recommended for molars.

After tooth preparation, a thin glue or bonding material layer is applied. Composites are then filled layer by layer and photo-polymerising each using light. At the end the surface will be shaped and polished.

COMPOSITE RESIN RESTORATIONS

General.

Composite resin is commonly used as a restorative material in anterior teeth because of its resistance to wear and its excellent aesthetics. The design of the cavity preparation will differ from the design of the amalgam, but most of the dental assistant's duties will be the same as those when amalgam is used. See figure 2-32 for steps of procedure when preparing restorations made of composite resin.

Varieties of Matrices:

Composite resin restorations require some kind of matrix to hold, shape, and protect them against stain and moisture contamination. Metal matrices, if used in conjunction with resin restorations, would stain the resin. Celluloid, which is issued in roll form, is normally the matrix of choice for proximal restorations. The celluloid matrix strip is approximately three-eighths of an inch wide and is cut to the desired length. Another celluloid-type matrix that is used with resin restorations is the cervical matrix. It is cylindrical or tabular in shape and is generally used on the facial and lingual surfaces of anterior teeth. This matrix offers the same protection against contamination, as do the celluloid strips. Crown forms are also made of celluloid and are shaped to match the morphology of the tooth. They come in numbered sets that vary in size, depending on the size and shape of the tooth involved. These crowns may also be used to prepare a temporary crown, to contain a sedative filling, or as a matrix for other types of restoration. If necessary, these crown forms may be modified and cut to fit the tooth being worked on. In order to hold many of these matrices in place and help them conform to an irregularly shaped tooth, a small wedge of wood is commonly available. Thus, we will always include a selection of wooden wedges in any setup.

Mixing Composite Resins.

Composite resins have largely replaced unfilled acrylic resins, because they last longer and have more desirable properties. They usually have a calcium hydroxide base. They are also very simple to mix and use. Most of these restorative kits contain the mixing instructions and mixing materials. If a crown form is not used to place the material, a plastic-coated plugger may be used. In using any of the compo- sites, it is always wise to follow the manufacturer's instructions. Failure to do so may result in a faulty restoration.

Completing the Restoration.

If resin is the restorative material, the matrix will be removed, and then the restoration will be smoothed and polished. Initially, the dentist may want to trim the resin restoration with a surgical scalpel. Therefore, a scalpel handle and a surgical knife blade should be included in the setup. For the remaining finishing to be done, different finishing materials may be used depending on the nature of the restoration. Proximal resin restorations are finished with abrasive strips known as cuttlefish strips. They vary in width from one- sixteenth to three-sixteenths of an inch and are six inches in length. These are available in three grits: Fine, medium, and coarse. Cervical resin restorations are usually finished by using sandpaper disks mounted on a snap-head type mandrel. The disk mounted on a mandrel is used in conjunction with the handpieces. The snap-head mandrel is readily identified by its pyramid-shaped head over which the disc with a brass fitting will snap into place.

Alternative Finishing.

A restoration of one of the composite resins may be initially trimmed with a surgical knife and surgical knife blade. Other finishing may be done with some type of finishing bur or with a diamond cone or abrasive wheel that is used in conjunction with handpieces. White and green stones may also be used for this procedure. After using the stones, cuttlefish strips and fine sandpaper disks might be employed as a final finishing measure.