Crown Retention Provided by Four Provisional Cements

Provisional restorations provide an interim restoration while the final indirect restoration is prepared.  Ceramic preparations have shorter walls and are more convergent than gold veneer preparations and retention is comprised under these conditions. Retaining the provisional restoration on ceramic preparations is difficult. Objective:  The purpose of this study was to measure and compare the retention of castings on preparations with 20 degree taper when cemented with four different temporary cements.  Methods:  Fifteen recently extracted teeth were mounted in clear orthodontic resin, machined on a lathe to produce a uniform crown preparation.  Additionally, silicone impressions were made of the prepared teeth, dies and base metal castings were made for each preparation.  After divesting the castings and fitting them on the preparations, the crowns were sandblasted with alumina oxide.  The crowns were cast with a hook on the occlusal surface.  The crowns were cemented with one of four temporary cements following the manufacturers’ directions.  A 6 kg weight was placed on the crown until the cement hardened.  24 hours after cementation the crowns were placed in an Instron (model 1124) and a tensile load applied until failure at a 5 mm/minute crosshead speed. Following cementation the cement was removed from the casting and the preparation and the process repeated with another cement.  Peak failure loads were compared with ANOVA and Tukey B post hoc analysis.  Significance was set at .05.  n= 12.

Results:  Provisional cement                                        Peak failure load (N)

Temerex TNE provided significantly greater retention than any other cement (p<.05). Conclusion:  Temerex TNE should be used with preparations where retention is low.