and unsupported enamel fractures easily. A systematic review concluded that for decayed baby (primary) teeth, putting an off‐the‐shelf metal crown over the tooth (Hall technique) or only partially removing decay (also referred to as "selective removal") before placing a filling may be better than the conventional treatment of removing all decay before filling. For decayed adult (permanent) teeth, partial removal (also referred to as "selective removal") of decay before filling the tooth, or adding a second stage to this treatment where more decay is removed after several months, may be better than conventional treatment. Direct restorations 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 cleansible 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 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. Indirect restorations 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