(PR003) In Vitro Zirconia Crown Retention after Endodontic Access and Subsequent Restoration

Objective: The aim of this study was to evaluate the effect of 2 different restorative materials on the retention of anterior zirconia crown retention after endodontic access preparation. We hypothesis that endodontic access preparation will reduce the retention of anterior zirconia crowns because it partially removes an axial wall which is a key factor in retention. After the access is restored with composite resin (CR), the original crown retention will be increased, but the initial retention will be lower when restored with a temporary restorative material such as Cavit. Currently, there are no studies describing the effect endodontic access preparation has upon maxillary anterior zirconia crown retention nor the effect when restoring these openings.

Methods: 30 maxillary central incisor crown preparation dies were milled from a PMMA puck. A zirconia crown was fabricated for each die. The control group (n=10) was tested for retention using the Instron machine. The other samples then had endodontic access preparation performed and were restored with Cavit (n=10) or CR (n=10). These groups were then tested for retention.

Results: The preliminary results of this study indicate that the zirconia crowns lost retention when an endodontic access preparation was performed and filled with a Cavit. However, the retention was fully regained and surpassed after being restored with CR.

Conclusion: These preliminary results conclude that the original zirconia crown retention can be exceeded after endodontic access is restored with CR. This could provide valuable insight for endodontists in their decision when restoring or temporizing anterior zirconia crowns.