Effect of Axial Groove and Resin Luting Cements on the Retention of Complete Cast Metal Crowns

BACKGROUND: The design of the tooth preparation and the cementing medium are important consid-erations in the retention of crowns and fixed partial dentures. The purpose of this invitro study was to determine the effect of axial groove on the retention of complete cast metal crowns using two resin luting cements. METHODS: Forty freshly extracted intact human molar teeth were prepared in their long axis to receive complete cast metal crowns. The specimens were randomly divided into two groups (one control and one study group). An axial groove of uniform size and shape was made on the prepared teeth under the study group. Axial surface area of prepared teeth specimens was measured. Complete cast metal crowns were fabricated for each specimen. Specimens of each group were divided into subgroups of 10 samples and were cemented with two resin luting cements, RelyX Unicem® and Calibra®, re-spectively. The cemented crowns were loaded in tension using a Universal Instron testing machine. The maximal tensile strength was recorded. Data were compared using the Mann-Whitney U test (α=0.05). RESULTS: No significant differences in the tensile stress values were noted between the control (mean: 5.76±0.392 MPa) and study (mean: 5.93±0.751 MPa) groups cemented with RelyX Unicem. No significant differences in the tensile stress values were noted between the control (mean: 4.92±0.641 MPa) and study (mean: 5.15 ±0.478 MPa) groups cemented with Calibra. However, significant dif-ference in the tensile stress values was found between the two resin cements in the control and study groups. CONCLUSION: Axial groove placed in tooth preparations for resin bonded complete cast metal crowns had no statistically significant effect on retention. The use of (RelyX Unicem®) yielded greater retention values when compared to Calibra®.