Effect of thiourethane on the polymerization and mechanical properties of composite resin: A systematic review.

Statement of problem: Thiourethane has high chemical affinity with polymeric materials and its addition has been suggested for improving adhesives and composite resin. However, a systematic review of thiourethane addition is lacking.

Purpose: The purpose of this systematic review was to analyze the articles in the dental literature that studied the effect of thiourethane added to the resin matrix of dental materials related to polymerization shrinkage and mechanical properties.

Material and methods: The systematic review was prepared in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines and was registered in the Open Science Framework (osf.io/sb9my). The population, intervention, comparison, outcome, and study design (PICOS) were the following: composite resin, thiourethane addition, composite resin without addition, evaluation of polymerization and mechanical properties, and in vitro experimental studies. Initially, 204 articles were found, 150 of which were excluded because of duplication. After reading the titles and abstracts based on the application of eligibility criteria, 21 articles were selected for reading in full, and all were included in the systematic review. Three reviewers evaluated the articles independently in 2 phases based on the eligibility criteria (selection of the title and reading of the article in full), with the reviewers' doubts and discrepancies being analyzed and resolved in a meeting with the authors.

Results: Most of the articles reported a significant improvement in the polymerization shrinkage and mechanical properties of experimental polymeric materials with the addition of oligomers.

Conclusions: Thiourethane added to resin dental materials improved their polymerization shrinkage values and mechanical properties.