Dose-dependent effects of electron beam irradiation on dental materials: a systematic review of in vitro evidence.

BACKGROUND: Electron beam irradiation (EBI) is a non-chemical technique proposed for modifying dental materials, but evidence is contradictory. Some studies report gains in mechanical performance, others document discoloration, structural breakdown, or cytotoxicity at higher doses. OBJECTIVES: To systematically review effects of EBI on mechanical strength, surface characteristics, chemical stability, and biological responses in dental materials, and identify dose ranges where effects shift from beneficial to harmful. METHODS: PubMed, Scopus, and Web of Science were searched for laboratory studies published January 2001-March 2026 using the terms "electron beam irradiation" and "dental materials." Two reviewers independently screened records; a third resolved disagreements. Eligible studies were laboratory-based experiments evaluating dental materials under EBI. Data were extracted on post-irradiation mechanical, physicochemical, biological, and appearance outcomes. Risk of bias was assessed using RoBDEMAT and QUIN; certainty was rated using a modified GRADE approach. RESULTS: Of 897 records identified, 18 studies met inclusion criteria. Materials tested included composites, nanocomposites, fiber-reinforced composites, denture base polymers, orthodontic bracket materials and adhesives, alloy-resin bonding systems, monolithic zirconia, acrylic resins, glass ionomer cement, dental irrigants, cast titanium, and zinc oxide eugenol. Doses ranged from 1 to 200 kGy, with acceleration energies of 25 kV-10 MeV (two studies did not report beam energy). At low-to-moderate doses, most polymer-based materials showed improved flexural strength, fracture toughness, Vickers hardness, and wear resistance, whereas higher doses caused polymer degradation, discoloration, loss of structural integrity, and genotoxic/cytotoxic effects. QUIN classified 4 studies (22%) as low risk, 12 (67%) as medium risk, and 2 (11%) as high risk of bias. LIMITATIONS: All evidence was in vitro; studies were heterogeneous in materials, doses, and outcomes; irradiation parameters were inconsistently reported; modified GRADE certainty was very low across all outcomes. CONCLUSIONS: Current in vitro evidence indicates EBI modifies dental material properties, with mechanical improvements most consistent for dimethacrylate-based polymer systems at low-to-moderate doses (1-100 kGy), while color instability and dose-dependent degradation remain important barriers. Because the evidence base is entirely in vitro and of very low certainty, findings are preliminary; dose-optimization and in vivo studies are needed before clinical recommendations can be made. SYSTEMATIC REVIEW REGISTRATION: https://doi.org/10.17605/OSF.IO/HAVT8.