A temporary crown (provisional crown, interim crown) is a temporary (short-term) crown used in dentistry. Like other interim restorations, it serves until a final (definitive) restoration can be inserted. Usually the temporary crown is constructed from acrylic resins (monomethacrylate-based/polymethacrylate-based) or, chemical-cure/light cure composite (dimethacrylate-based), although alternative systems using aluminium crown forms are occasionally used. Temporary crowns function to protect the tooth, prevent teeth shifting, provide cosmetics, shape the gum tissue properly, and prevent sensitivity. Function The functions of temporary crowns are: Maintain the dental aesthetic Provisional restorations offer dental aesthetics purposes, especially for anterior teeth. A patient can evaluate the aesthetic of the temporary crown if that is to be changed in the definitive restoration. Maintain the tooth's function Overeruption of opposing teeth and drifting of adjacent teeth can be prevented by providing provisional restoration. Masticatory function for posterior teeth can be restored as well. Confirm that the tooth preparation is sufficient These include whether sufficient tooth has been prepared to accommodate the definitive restoration and any undercuts present will be removed. If deficiencies in the tooth prep are found, these can be rectified and the temporary crowns can be relined or remade. Prevent dentine hypersensitivity Exposed dentinal tubules in vital teeth can be covered with temporary crowns to prevent any dentinal fluid movement Prevent coronal leakage Temporary crowns block bacteria entry to prevent pulpal inflammation and maintain a good coronal seal to the root canal filling. Preformed crowns Problems preformed crowns are unlikely to fit perfectly, and need chair side adjustments a large bank of preformed crowns is required to fit all variations of tooth morphology Polycarbonate crowns A tooth-coloured shell that is slightly larger than the tooth preparation is selected and is reduced to the correct dimensions using a bur until it seats fully on the tooth preparation without bedding into the gingiva. Petroleum jelly is smeared over the tooth and acrylic resin is spread over the fitting surface of the crown. The shell is removed once the resin has polymerised and the restoration is trimmed until fit is satisfactory. 2. Plastic crowns Clear plastic crowns can be selected and trimmed with a scissors without traumatising the gingiva. Small holes can be made on the canine tips, incisal angles and cusps with a probe before filling crowns with acrylic resin to reduce risk of bubbles formation. Once the resin has set, the restoration can be checked for occlusion