The influence of 2,4,6-trimethylbenzoyldiphenylphosphine oxide on the toxicity of dental resins: A systematic review of in vitro studies

Research question The 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO) has emerged as a prominent photoinitiator in resin-based compositions but its biological safety is questioned. The research question was: Does the presence of TPO in resin-based dental materials influence its cytotoxicity and genotoxicity? Material and methods This research followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline and was registered on the Open Science Framework (osf.io/sthvf). The literature was searched in the Science Direct, PubMed, Embase, Web of Science, Scopus, ProQuest and Google Scholar databases for articles published until July 2024. The inclusion criteria were studies evaluating the cytotoxicity and genotoxicity of TPO. The exclusion criteria were studies that did not evaluate TPO or that did not evaluate its cytotoxicity and genotoxicity in vitro or in vivo. Results 463 studies were identified, and after removing duplicates and applying the eligibility criteria, 5 were included and assessed qualitatively. Except for one study which presented a moderate risk of bias, the other five presented a low risk of bias. The heterogeneity of the studies` methodology and the results allowed qualitative analysis and discussion. Conclusions The main limitation of TPO is its high toxicity, with higher cytotoxic levels than other photoinitiators. Replacing other photosensitive systems for TPO may not offer adequate cost-benefit for biomedical applications.