Effect of food-simulating liquids on flexural strength, Vickers microhardness, and surface roughness of IPS e.max Press and CEREC Tessera.

BACKGROUND

Lithium disilicate ceramics are widely used for indirect restorations, yet their mechanical performance may be influenced by fabrication route and chemical challenge from foods and beverages.

OBJECTIVE

To compare the effects of food-simulating liquids (FSLs) on flexural strength, Vickers microhardness, and surface roughness of pressed lithium disilicate (IPS e.max Press) and Computer-Aided Design and Computer-Aided Manufacturing (CAD/CAM) advanced lithium disilicate (CEREC Tessera).

MATERIALS AND

METHODS

One hundred fifty rectangular specimens were prepared using IPS e.max Press and CEREC Tessera (n = 75 each) and allocated into five groups per material (n = 15): one unconditioned control group, artificial saliva (7 days at 37°C), 0.02% citric acid, 20% ethanol, or 50% ethanol. Citric acid and ethanol groups underwent three 5-minute challenge cycles followed by re-storage in artificial saliva. Flexural strength was assessed by three-point bending. Microhardness (Vickers HV1/10) and surface roughness (Ra) were measured on independent specimens. Data were analysed using two-way analysis of variance with Tukey's post hoc test for flexural strength and surface roughness. For microhardness, factorial analysis was limited to the comparable shared conditions because ethanol-exposed IPS e.max Press specimens did not yield reliable Vickers measurements.

RESULTS

CEREC Tessera showed higher flexural strength than IPS e.max Press across conditions (control: 362.6 ± 15.4 vs 331.0 ± 8.5 MPa). Ethanol reduced strength in both materials, with the greatest reduction in 50% ethanol (238.0 ± 9.6 vs 147.4 ± 7.5 MPa). Across comparable conditions, CEREC Tessera also showed higher microhardness, while reliable Vickers measurements could not be obtained for ethanol-exposed IPS e.max Press specimens. Surface roughness increased after acidic and alcoholic exposure in both materials, although CEREC Tessera remained smoother overall (control: 0.06 ± 0.02 vs 0.67 ± 0.36 µm).

CONCLUSION

CEREC Tessera demonstrated superior flexural strength, microhardness, and surface integrity compared with IPS e.max Press after exposure to FSLs, suggesting that fabrication route influences laboratory performance under chemical challenge.