The effect of grooves on the load to dislodgement of Procera crowns

Abstract

Statement of Problem: The objective of this study was to investigate the effect of grooves on a tooth preparation for a full coverage zirconia Procera restoration on the load to dislodgement of Procera zirconia crowns. Methods: Three standardized stainless steel dies were used to simulate a mandibular molar crown preparation with inadequate retention and resistance forms. The first die resembled a preparation with no grooves (control). The second die resembled a preparation with two grooves placed on the mid-mesial and distal walls. The third die resembled a preparation with two grooves as above; however, the grooves were placed after the dies were scanned. The stainless steel dies were scanned to fabricate zirconia abutments. After the addition of porcelain to the copings, the crowns were cemented with zinc phosphate cement. The load to dislodgement was tested via a universal load-testing machine. Data was analyzed using a one-way ANOVA statistical test followed by Tukey's HSD test. Results: There was a significant difference between the three experimental conditions (F = 213.69, p < 0.0001). Procera crowns cemented on the stainless steel dies with grooves prepared before scanning had a significantly higher load to dislodgement than all other groups (3850 ± 370 N). Procera crowns cemented on the stainless steel dies with grooves prepared after scanning exhibited the second highest load to dislodgement (2610 ± 250 N). The lowest value of load to dislodgement was when no grooves were present (2260 ± 300 N). Conclusion: Grooves placed before scanning of dies provided the most improvement load to dislodgement of Procera zirconia crowns.