Tensile Bond Strength, Fit Accuracy and Failure Types of Zirconia and Cast Gold Root Copings for Overdentures

To compare the tensile strength, dislodgement forces, marginal gap and failure types between digitally fabricated zirconia root copings and conventionally manufactured cast gold root copings.

Extracted human teeth (N=30) were prepared for the root copings and randomly divided into 2 groups: (1)zirconia root copings(ZC) and gold root copings(GC). The specimens were tested for tensile bond strength and dislodgement forces in a universal testing machine and the types of the coping failures modes were analyzed. In addition, the marginal gap was measured. Data were analyzed using one-way ANOVA and Pearson correlation test.

Mean tensile bond strength in the total horizontal adhesive area for ZC group was 7.5±2.8MPa and for GC group 10.5±4.8 MPa(p⟩0.05). The mean dislodgement forces for the ZC and GC groups were 242±107N and 311±118N, respectively and with no significant differences between the groups (p=0.12). The mean vertical marginal gap in the ZC group amounted to 27±11.05μm, while in the GC group it was 35.33±10.49μm, showing no statistically significant difference between the two groups (p=0.058). Mixed failure modes were more common (93%) in both groups.

In terms of all tested parameters, the zirconia root copings were comparable to the gold copings.