Marginal Misfit Assessment in Common Restorative Materials for Cement‐Retained Fixed Implant Prostheses: An In Vitro Comparative Study

OBJECTIVES: To assess the vertical discrepancy at the abutment-crown interface (ACI) for cement-retained crowns fabricated from three commonly used restorative materials across implants featuring external and internal connections. MATERIALS AND METHODS: A total of 30 implants with external (EC) and internal (IC) connections were included in this study. Each implant received a prefabricated titanium abutment, which was randomly attached using the torque recommended by the respective manufacturers. Three types of restorative materials-metal-ceramic (MC), monolithic zirconia (MZ), and veneered zirconia (VZ)-were used to fabricate the crowns for each connection type and cemented to their respective abutments. Following 6000 cycles of thermal cycling between 5°C and 55°C, the vertical marginal misfit was evaluated using scanning electron microscopy. Data were statistically analyzed using repeated-measures ANOVA, followed by Bonferroni post-hoc test and paired t-test. RESULTS: The lowest marginal misfit was recorded for VZ restorations. Although the IC group showed lower mean misfit values compared to the EC group, this difference was not statistically significant (p = 0.980). Significant differences were found in the IC group between MZ and VZ (p = 0.016) and between MC and VZ (p = 0.035). Mean misfit values (µm) for each material were as follows: VZ = 18.7 (SD = 4.5), MZ = 42.2 (SD = 8.1), and MC = 39.9 (SD = 7.4). CONCLUSIONS: Cement-retained veneered zirconia restorations demonstrated less vertical ACI misfit compared to metal-ceramic and monolithic zirconia restorations. The connection configuration did not influence the marginal misfit. All measured misfit values were below 50 µm.