Flexural strength, microhardness, and surface roughness of additively and subtractively manufactured zirconia: a systematic review and meta-analysis

Additive manufacturing (AM) has emerged as a promising alternative to conventional subtractive manufacturing (SM) for fabricating zirconia dental restorations. However, evidence comparing the flexural strength, microhardness, and surface roughness of AM and SM fabricated zirconia remains inconsistent. This systematic review and meta-analysis compared these properties between zirconia fabricated using AM and SM techniques. This systematic review and meta-analysis was conducted in accordance with the PRISMA 2020 guidelines. Electronic searches of PubMed/MEDLINE, Scopus, and Web of Science identified studies comparing AM and SM fabricated zirconia. Eligible studies were selected using predefined inclusion and exclusion criteria. Risk of bias was assessed using the Quality Assessment Tool for In Vitro Studies (QUIN) tool. Meta-analyses were performed using Review Manager (RevMan 5.4) with random-effects models. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated. Statistical significance was set at P < 0.05, and heterogeneity was assessed using the I² statistic. Twenty-five studies met the inclusion criteria. Meta-analysis of 20 studies demonstrated significantly higher flexural strength for SM zirconia than AM zirconia ( P = 0.03), although heterogeneity was substantial (I² = 92%). Subgroup analyses revealed that digital light processing (DLP) fabricated zirconia exhibited significantly lower flexural strength than SM zirconia ( P < 0.0001), whereas no significant difference was observed between stereolithography (SLA) and SM fabricated zirconia ( P = 0.33). No significant differences were identified for microhardness ( P = 0.12) or surface roughness ( P = 0.13). Funnel plot assessment suggested possible small-study effects for flexural strength. The findings of this review indicate that the effect of manufacturing approach on zirconia performance varied according to the property evaluated and the AM technology employed. Technology-specific differences should therefore be considered when interpreting the performance of AM zirconia. PROSPERO- CRD420251020607.