Background/Objectives: The integrity of proximal contact and marginal adaptation in Class II composite restorations is essential for mechanical stability, interfacial integrity, and long-term clinical performance. These outcomes are strongly influenced by the matrix system used during restoration. This systematic review aimed to evaluate the performance of different matrix systems in restoring posterior proximal cavities, with a specific focus on their interaction with composite materials. Materials and Methods: A systematic literature search was performed in PubMed, Cochrane Library, ScienceDirect, and Scopus for studies published between 2014 and 2024. Clinical and in vitro studies comparing different matrix systems used in Class II posterior composite restorations were included. Sixteen studies met the eligibility criteria. Risk of bias was assessed using the RoB 2 tool for randomized clinical trials and the ROBINS-I tool for non-randomized studies. Results: Sectional matrix systems consistently demonstrated superior performance in achieving anatomically accurate and tight proximal contacts compared with circumferential and transparent matrix systems. Metal matrices generally showed better contact tightness and marginal adaptation than transparent matrices, likely due to their higher rigidity and improved resistance to deformation during composite placement and polymerization. The adjunctive use of separation rings and contact-forming instruments further enhanced proximal contact quality and marginal integrity. Regarding composite types, high-viscosity bulk-fill composites provided better marginal adaptation and proximal contact tightness than flowable bulk-fill and conventional composites. Conclusions: Within the limitations of the included studies, proximal contact quality and marginal adaptation in Class II composite restorations are influenced by the matrix system, composite material behavior, and clinical application protocol. Sectional metal matrix systems combined with separation rings appear to be associated with improved outcomes in the included studies, while auxiliary contact-forming instruments may further improve restorative outcomes.
Drouri et al. (2026) studied this question.