Comparative wear behavior of lithium disilicate CAD/CAM ceramics under simulated mastication

To compare the two-body wear behavior of several commercially available lithium disilicate ceramics and their effects on steatite antagonists using a chewing simulator.

Fifty rectangular specimens (12.0 ×6.0 ×1.5 mm³) were prepared from CAD/CAM lithium disilicate blocks (n = 10): Amber Mill (AM), Amber Mill Direct (AMD), CEREC Tessera (CT), GC Initial LiSi Block (LiSi), and IPS e.max CAD (EM). AM, CT, and EM specimens were crystallized according to the manufacturer's instructions. Lithium disilicate specimens were opposed by steatite antagonists and subjected to 1,200,000 chewing cycles under a 49 N load. Volumetric material loss of both lithium disilicate and steatite specimens was quantified through a 3D optical profilometer (VR-6200, Keyence) and the analysis software (VR-6000 Analyzer). The Vickers microhardness of lithium disilicate ceramics was measured before and after chewing simulation. The microstructures of ceramics were evaluated with an SEM. Data were analyzed using one-way ANOVA for material loss and mixed ANOVA for microhardness (α = 0.05).

AM exhibited the lowest volumetric loss among the lithium disilicate ceramics, whereas CT and EM demonstrated the highest wear. Steatite antagonists opposing AM showed significantly higher volumetric loss compared with those opposing other materials. Before simulation, AMD and LiSi presented significantly higher microhardness values, while EM exhibited the lowest hardness. Following simulation, no significant differences in microhardness were observed among the materials.

Wear of lithium disilicate ceramics is primarily governed by microstructure. Material selection should consider both restorative materials and antagonist wear.