Cement Selection for Provisional Restorations -- Part II
Avishai Sadan, DMD
This author recommended the use of a durable cement (eg, zinc phosphate) for the cementation of provisional restorations for multiple-unit fixed partial dentures (FPDs) for any period of temporization. This cement can also be utilized for long-term temporization of single-unit restorations. The experienced clinician should be able to fabricate provisional single units and small provisional FPDs that exhibit excellent clinical fit on a routine basis. Even in ideal circumstances, however, it can be challenging to consistently achieve an exact fit in large provisional FPDs (with six or more abutments). Even if the fit of a large provisional FPD is adequate, the flexibility of the provisional materials may result in an incomplete seating of the prosthesis during cementation on some abutments. If not immediately detected, this will result in leakage and possible carious lesions. The use of zinc phosphate cement for temporization will provide a better seal at areas with a slightly less-than-ideal fit.
The use of such cement creates some clinical dilemmas that must be addressed. Possible complications associated with the use of this cement for temporization are dislodgment of post and core buildups and even fracture of abutments during the removal of the provisional restoration. One may think that if a buildup fractures during the removal of a provisional restoration that was cemented with zinc phosphate, it is of poor quality. Such thinking is incorrect, however, since the directions and magnitudes of the forces applied to abutment teeth during the removal of that provisional prosthesis are completely different from those the teeth are expected to withstand during normal function. The author suggests the following to minimize complications associated with the fabrication, cementation, and removal of these provisional prostheses:
1. Preparation of surface texture: Finalize the preparation to a smooth surface. Polished abutment teeth facilitate easy relining of the temporary, better flow of the impression material, and easy removal of the provisional restoration. Prior to the cementation of the definitive restoration, microetch the abutment with 50 µm aluminum oxide particles. A microetcher will roughen the abutment surface, increase retention, and clean the abutment surface more effectively than pumice.1
2. Mix the zinc phosphate cement to a "runny" consistency, which eases seating.
3. Lightly lubricate areas of junction between tooth structure and the core material. Coat a thin layer of petroleum gel on these areas to minimize the risk of dislodgment during the removal of the provisional prosthesis.
4. In multiple-unit restorations, create a lingual vertical slot at each provisional abutment restoration prior to the removal of the restoration. The slot will facilitate removal and decrease the transfer of forces to the abutment. If the provisional will be recemented at the end of the appointment, then after the removal of the provisional prosthesis clean the intaglio surfaces with a microetcher, seat the provisional intraorally, and seal the vertical slots using the "salt and pepper" technique. Polish and recement the restoration according to standard protocol.
There is no easy solution for the temporization of multiple-unit FPDs or the long-term temporization of single units. Clinicians should make every attempt to achieve an intimate fit of the multiple-unit FPD provisional restoration. At the same time, however, they should realize that, even if not clinically detectable, the fit of large provisional prostheses may be less than ideal. Thus, the use of a durable cement is recommended.
- Dietschi D, Spreafico R. Adhesive Metal-Free Restorations. Carol Stream, IL: Quintessence Publishing; 1999:154.
*Dean, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA.