Chemical Strategies for Reducing Polymerization Shrinkage Stress in Experimental Dental Resin-Based Materials: A Scoping Review

Background: Polymerization shrinkage stress remains one of the main limitations of methacrylate-based dental resin composites, as it may lead to marginal gap formation, interfacial debonding, and long-term restoration failure. In recent years, numerous experimental monomers and alternative polymerization strategies have been proposed to mitigate stress development during polymer network formation. This scoping review aimed to map and summarize experimental and modified monomer systems investigated for reducing polymerization shrinkage stress in dental methacrylate-based composites. Methods: A comprehensive literature search was conducted in PubMed/MEDLINE, Scopus, Web of Science Core Collection, Embase, and Google Scholar to identify relevant studies published between 2010 and 2025. The search strategy combined terms related to dental resins, polymerization shrinkage, shrinkage stress, and experimental monomers (1678 papers found). After duplicate removal and screening of titles and abstracts, potentially relevant articles were assessed for full-text eligibility according to predefined inclusion criteria. In vitro studies investigating experimental monomers or modified resin systems with reported polymerization shrinkage stress measurements were included. Data extraction focused on monomer composition, chemical strategy for stress reduction, measurement methods, and reported shrinkage stress values. Results: A total of 33 studies met the eligibility criteria and were included in the qualitative synthesis. The reviewed studies investigated a wide range of molecular strategies, including thiol–ene and thiourethane chemistries, addition–fragmentation chain transfer (AFCT) networks, ring-opening or expanding monomers, high-molecular-weight dimethacrylates, ether-based monomers, and alternative reactive diluents. Reported polymerization shrinkage stress outcomes varied widely across studies because of differences in testing methods, specimen geometry, system compliance, curing protocols, reporting units, and control materials. Therefore, the results were synthesized descriptively, with emphasis on within-study comparisons between experimental systems and their respective controls rather than on direct numerical comparisons across studies. Thiol-based systems and adaptive polymerization mechanisms consistently demonstrated the greatest reductions in shrinkage stress compared with conventional dimethacrylate resin matrices. Conclusions: Experimental monomer design represents a promising strategy for controlling polymerization shrinkage stress in dental composites. Chemical approaches that modify polymerization mechanisms or network architecture may significantly reduce stress development during curing. Further studies are required to evaluate the long-term chemical, physical, and mechanical stability, as well as the clinical applicability, of these experimental and modified resin systems.