Internal fit of lithium disilicate and resin nano-ceramic endocrowns with different preparation designs

Purpose: Investigation of different central cavity designs on internal fit of endocrowns fabricated from two materials. Materials and methods: Forty maxillary premolars were endodontically treated and divided into 8 groups [n ¼ 5]: LS10, LS6, LD10, LD6, ES10, ES6, ED10 and ED6 (“L” restored with Lava™ Ultimate [resin nano ceramic], “E” restored with IPS e.max® CAD [lithium disilicate], “S” shallow depth [3 mm], “D” extended depth [5 mm], “6”-degree and “10”-degree axial wall divergence). All restorations were fabricated using CEREC CAD/CAM system. Samples were tested for internal fit using CBCT imaging (Next Generation i-CAT scanner) before and after adaptation. Data was tabulated and statistically analyzed. Results: Lava™ Ultimate showed significant better internal fit compared to IPS e.max® CAD endocrowns both before and after adaptation [p ¼ 0.007 and 0.003, respectively]. Samples with 6-degree axial wall divergence showed significant better internal fit compared to those with 10-degree axial wall divergence before adaptation [p ¼ 0.041]. Before adaptation, group LS6 showed the best internal fit [403.00 ± 115.30 mm] followed by LD6, LD10, ES6, ES10, ED10, LS10 and ED6. After adaptation, group LS10 showed the best internal fit [394.80 ± 21.17 mm], followed by LS6, LD10, ED6, LD6, ES6, ED10, and ES10. Conclusion: Resin nano-ceramic endocrowns presented better internal adaptation compared to lithium disilicate endocrowns, regardless of the preparation design