The purpose of the present study was to evaluate the influence of different cement spaces on internal and marginal adaptation of posterior zirconia copings before and after cementation.
Methods:
Sixty mandibular first molar zirconia copings were fabricated using ZirkoDenta system, and divided into 4 groups (n=15), the first three groups were fabricated with three virtual cement spaces (70, 50, and 30 µm) respectively, and the fourth group was manually coated with two layers of die spacer. Measurements of internal adaptation were made using the replica technique with a stereomicroscope ×10 magnification. Measurements of marginal adaptation were made before and after cementation with glass ionomer cement, using direct view technique with an electronic microscope ×100 magnification. The data obtained were statistically analyzed using 1-way ANOVA, and student's test (α=0.05).
Results:
The axial & occlusal internal spaces of the manually applied die spacer group (52- 347µm) was significantly higher than that of the 70, 50 and 30 µm groups (25-209, 20-202, 24-252) µm respectively. Before cementation, the best marginal fit was for the 50 micron group (22 µm), with no differences among the 30 micron group (35 µm) and the manually applied die spacer group (33 µm). The marginal gap for the 70 µm group (46 µm) was higher than that for the 50 µm group. After cementation, the best marginal fit was for the 30 micron group (101 µm), with no difference with the 50 micron group (111 µm) and the manually applied die spacer group (129 µm). The marginal gap for the 70 µm group (153 µm) was more than that for the 50 & 30 µm groups
Conclusions:
Virtual cement spaces (30 & 50 µm) gave better marginal gap of posterior zirconia copings than the 70 µm and manually die spacer groups, when luted with glass ionomer cement.