and margins before being cemented in. 3. Composite crowns Preformed malleable composite crowns are soft and easily moulded to the tooth in situ. They can be partially cured for two to three seconds in the mouth and removed to be fully cured outside the mouth. Final check for occlusion, fit and margins can be carried out prior to cementing provisional restoration. 4. Metal-based crowns When a permanent crown needs replacement or sectioning for caries removal, the original crown can be modified and used as a temporary restoration. The crown can be relined with bis-acrylic composite resin and cemented on temporarily. Custom-formed resin replica temporary crown Chairside temporary crowns can be made in the mouth using a suitable mould. It is extremely useful in cases where the tooth to be prepared is structurally intact. The material used is usually that of a bis-acrylic composite material (e.g. ProTemp), or one which consists of the higher acrylics, usually a mixture of and . Custom-formed provisional crowns allow for shaping of the gingival tissues in order to achieve a satisfactory emergence profile of the definitive restoration. This is indicated particularly when restoring bone-level dental implants. How to make a custom-formed provisional restoration: A sectional impression of the tooth to be prepared is made. Prepare the tooth for the chosen design of restoration. A thin layer of petroleum jelly can be smeared onto the preparation to facilitate the removal of the provisional restoration from the tooth once the material is set Syringe the bis-acrylic composite resin into the sectional impression of the tooth that has been prepared, and relocate the impression in the mouth. Ensure that the impression is fully seated over the teeth – an obvious click can often be felt as the impression passes over the bulbosity of the remaining teeth. Remove the impression before complete polymerisation of the bis-acryl resin. At this stage, the resin will feel rubber. Once removed from the mouth or impression, any material flash and ledges can be removed with a high speed diamond bur or abrasive polishing discs. The marginal fit and occlusion are checked with the provisional restoration in situ and adjusted if necessary, ideally outside of the mouth. The provisional restoration can then be cemented with a temporary luting cement. Remove excess cement from the margins, carefully using dental floss interproximally. Cementing of the temporary restoration An ideal provisional cement should exhibit the following characteristics: