Effect of crystallization and finish line curvature on the marginal integrity of lithium disilicate crowns

Purpose: This study aimed to investigate the effect of crystallization and finish line curvature on the integrity of lithium disilicate crowns fabricated by using partially crystallized (P) and fully crystallized (F) blocks.

Materials and methods: Forty-eight lithium disilicate crowns were fabricated based on the designated lithium disilicate blocks and finish line curvatures. The specimens were divided into four groups (n = 12 each): P block with a curved finish line (PC), P block with a straight finish line (PS), F block with a curved finish line (FC), and F block with a straight finish line (FS). Using the silicone replica technique and triple scan method, the absolute marginal discrepancy was measured at four surfaces. Using the triple scan method, five sections were segmented for each surface. Global deviation was measured by using a best fit alignment. Three-way mixed analysis of variance followed by Fisher least significant difference test and the Kruskal-Wallis test were used for statistical analyses (α = 0.05).

Results: The block crystallization had a significant impact on the marginal integrity in the triple scan method, showing a greater marginal discrepancy in the F block crowns (p < 0.001). The finish line curvature significantly influenced the marginal integrity in both measurement methods, with curved finish line crowns exhibiting a greater marginal discrepancy (p < 0.05). However, the areas with the greatest marginal discrepancies differed depending on the analytical method used.

Conclusions: The marginal discrepancies of the crowns differed according to the fabricated blocks and finish line curvature.