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

Aim: 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.

Methods: 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.

Results: 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.

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