Repeated Firing Shifted Lithium Disilicate Color but Not Strength in Lab Review

Edited by Dentaltown staff

Repeated firing cycles were most consistently associated with color change in lithium disilicate ceramics, while pooled effects on translucency and biaxial flexural strength were not statistically significant, according to a systematic review and meta-analysis published Sept. 7 in BMC Oral Health.

Researchers searched Scopus, Web of Science, PubMed/MEDLINE, the Cochrane Library, and Google Scholar following PRISMA 2020 guidelines. Forty studies were included in the systematic review, and 20 met criteria for quantitative synthesis.

The meta-analysis drew on 17 translucency datasets, 11 color-change datasets, and 13 comparisons of biaxial flexural strength. Effects were pooled using random-effects models and Hedges’ g.

Color change produced large standardized effects. For ?Eab, based on nine datasets, Hedges’ g was +3.58, with a 95% confidence interval of 3.13 to 4.03. For ?E00, based on two datasets, g was +4.08, with an interval of 3.76 to 4.41.

Translucency showed a small pooled effect of +0.20 that was not significant, with an interval running from -0.11 to +0.50. Biaxial flexural strength showed a pooled effect of +0.58, also not significant, with an interval from -0.28 to +1.44.

Responses varied by material and firing protocol across the four ceramics examined: IPS e.max CAD, IPS e.max Press, Amber Mill, and Amber Press. The authors reported that firings beyond five cycles may increase the risk of clinically unacceptable color alteration in some materials and settings, that IPS e.max CAD appeared comparatively stable across several tested protocols, and that the smaller evidence base for the Amber ceramics indicated greater optical variability.

Salma Issa Duhaim, Husniyati Roslan, and Ma’an Rashid Zakaria conducted the review.

The authors stated that the evidence remains entirely in vitro. The findings describe laboratory specimens rather than restorations in service, so they should be applied cautiously to clinical longevity.

Sources:
BMC Oral Health, “Effect of multiple firing cycles on optical and mechanical properties of lithium disilicate ceramics fabricated via pressable and CAD/CAM technologies: a systematic review and meta-analysis,” published online Sept. 7, 2026: link.springer.com/10.1186/s12903-026-09729-x