To test and compare the monotonic compressive strength of four different dental materials used for restorations
Method:
Four materials were used in this study: Group 1 (Tetric Evo Ceram - a light cured composite, Ivoclar Vivadent), Group 2 (Lava Ultimate - a resin nanoceramic CAD/CAM restorative, 3M ESPE), Group 3 (EmpressCAD - a leucite glass-ceramic, Ivoclar Vivadent) and Group 4 (e.maxCAD – a lithium-disilicate glass-ceramic, Ivoclar Vivadent). Ten specimens of each material were produced in cylinders for testing (12.7±0.63 mm in height by 6.35±0.03 mm in diameter) according to ASTM C1424-10, Standard Test Method for Monotonic Compressive Strength of Advanced Ceramics at Ambient Temperature. Group 1 specimens were produced by a filling polyvinyl siloxane mold in 2mm incriments and curing using a 1200mw/cm2 light. Groups 2-4 were milled using a cylinder model on a Cerec MCXL CAD/CAM milling unit. The glass-ceramics were fired according to the manufacturer’s instructions. Specimens were polished using Optrafine or Astrapol polishers. The specimen ends were then trued using 600-grit SiC to ensure parallel ends. The specimens were loaded at a rate of 1 mm/min using an Instron Univeral testing machine until failure.
Result:
Compressive strengths (MPa) were Group 1: 251.3±26.4, Group 2: 360.4±62.7, Group 3: 660.6±167.3, and Group 4: 1243.9±256.3. One-way univariate analysis of variance (ANOVA) indicated a significant difference in monotonic compressive strength, p < 0.05. Follow up multiple comparisons (Tukey HSD) indicated significantly higher compressive strength for Group 4 than all other groups. Group 3 was found to be significantly higher than both Groups 1 and 2. There was no significant difference in bond strength between Group 1 and Group 2.
Conclusion:
Within the bounds of this study, the glass-ceramic materials produced statistically higher compressive strengths than the resin matrix materials, with the lithium disilicate glass-ceramic statistically higher than the leucite glass-ceramic.