Internal fit and marginal adaptation of CAD/CAM lithium disilicate endocrowns fabricated with conventional impression and digital scanning protocols. An in-vitro study

Aim: To evaluate the internal and marginal adaptation of computer aided design/computer aided manufacturer fabricated lithium disilicate endocrowns restoring endodontically treated maxillary molars and produced by conventional impression and digital scanning protocols.
Materials and methods: Thirty freshly extracted maxillary molars were prepared to receive endocrowns. Teeth were divided into two groups: conventional impression (n=15) and digital scanning (n=15). After restorations designing on CAD/CAM software, endocrowns were milled from Amber® mill lithium disilicate blocks. The internal gap was assessed by replica technique and stereomicroscope selecting 32 measurements for each restoration while, the mean marginal gap was assessed by stereomicroscope before and after cementation and thermocycling. Internal gap values were analyzed by Independent t-test, One Way ANOVA test for different landmark comparison, Tukey`s Post Hoc test for multiple comparisons, and Repetitive One-Way ANOVA test for marginal gap values before and after cementation.
Results: Statistically significant difference in marginal gap values was recorded between different impression protocols and regions (p < 0.05). digital scanning displayed significantly smaller gaps than conventional impression in all regions (p < 0.001). The largest gap was at pulpal floor in both groups. Marginal gap after cementation was larger than before cementation in both groups (p < 0.0001)
Conclusions: Digital scanning protocol produced endocrowns with superior internal and marginal adaption than those produced with conventional impression protocol. Pulpal floor showed the highest gap values in all tested regions while, margin showed the lowest gap. Cementation and thermocycling increased the marginal discrepancies but still within the clinically acceptable range.