Retention of Zirconia Crowns Compared to Stainless Steel Crowns: An Ex-Vivo Study

The purpose of this study was to compare the retention of 3M stainless steel crowns^™ (SSCs), Kinder Krowns^® zirconia crowns (ZCs), and EZCrowns ZCs on extracted primary mandibular second molars ex-vivo.

A total of 45 extracted primary mandibular second molars were allocated randomly to either of the three groups. All teeth were mounted in Dentsply acrylic molds and then prepared for crown cementation. Crowns were cemented with glass ionomer cement (GIC). Retention testing was performed using Instron 5566A. Differences in retention between the groups were tested via Welch's analysis of variance (ANOVA), and post hoc comparisons were performed with the Games-Howell test.

Welch's ANOVA resulted in statistically significant differences between the three groups (P<0.001). The mean±SD force in Newtons (N) for the SSC group, Kinder Krowns^® group, and EZCrowns group were 337.0±137.1 N, 89.4±53.6 N, and 106.5±77.7 N, respectively. Post hoc comparisons with the Games-Howell test presented that the SSC group had significantly higher retention than both the ZC groups (P<0.001). There was no significant difference between the ZC groups (P=0.76).

Within the limitations of this ex-vivo study results, due to their statistically significant higher retention, stainless steel crowns should be selected over zirconia crowns when in need of a full coverage restoration. But if esthetics are a concern, dentists can choose freely between either of the ZCs tested in this study.