arch. The master casts are used to provide accurate information about the occlusion to the laboratory and construct the prosthesis. Occlusal registration: An occlusal registration is needed when providing extensive bridgework to allow the opposing casts to be related accurately. This may not be necessary if only a small number of teeth are to be restored. Temporary restoration: Temporary restorations should be fabricated if possible to protect and maintain the prepared teeth until placement of the final restoration. Try in: Confirm the clinical acceptability before cementing definitively. Assess the prosthesis on the master casts and identify the cause of any problems if present. A period of temporary cementation to assess clinical acceptability prior to definitive placement is sometimes used. Final placement: Once satisfied the prosthesis is clinically acceptable, cement and bond the bridgework definitively. Review: Assess the bridgework and manage any post-operative issues. Restoration fabrication As with single-unit crowns, bridges may be fabricated using the lost-wax technique if the restoration is to be either a multiple-unit FGC or PFM. Another fabrication technique is to use CAD/CAM software to machine the bridge. As mentioned above, there are special considerations when preparing for a multiple-unit restoration in that the relationship between the two or more abutments must be maintained in the restoration. That is, there must be proper parallelism for the bridge to seat properly on the margins. Sometimes, the bridge does not seat, but the dentist is unsure whether it is because the spatial relationship between the abutments is incorrect, or whether the abutments do not actually fit the preparations. The only way to determine this is to section the bridge and try in each abutment by itself. If they each fit individually, the spatial relationship was incorrect, and the abutment that was sectioned from the pontic must now be reattached to the pontic according to the newly confirmed spatial relationship. This is accomplished with a solder index. The proximal surfaces of the sectioned units (that is, the adjacent surfaces of the metal at the cut) are roughened and the relationship is preserved with a material that will hold on to both sides, such as PATTERN RESIN™ from the company GC America. With the two bridge abutments individually seated on their prepared abutment teeth, the resin is applied to the location of the sectioning to reestablish a proper spatial relationship between the two pieces. This can then be sent to the