In Vitro Comparison of Four Resin Composite Matrix Systems

To address the limited evidence regarding the performance of various matrix systems, this study investigated proximal contact quality and surface characteristics across systems differing in structural design and component configuration.

Forty Frasaco mandibular left first molars (ANKA-4 ZE 100, Frasaco GmbH, Tettnang, Germany) were used to prepare mesial proximal box cavities with standard dimensions. Cavities were restored with a bulk-fill light-cured resin composite using four different matrix systems (n = 10): precontoured stainless steel (Palodent V3, Dentsply Sirona, York, PA, USA), copper (TECCI Copper, TECCI Dental, Istanbul, Turkey), and polyester (TECCI Transparent, TECCI Dental) sectional, and non-dead soft steel circumferential (SuperMat Adapt SuperCap, KerrHawe, Bioggio, Switzerland) matrix systems. Pre- and post-operative scans were obtained using an intraoral scanner (Trios 3, 3Shape, Copenhagen, Denmark). Mesiodistal (MD) diameters were measured on the scans. Proximal contour and marginal adaptation were assessed by two blinded examiners. Surface roughness was evaluated using a profilometer (Mitutoyo SJ 301, Mitutoyo Corp., Kawasaki-shi, Kanagawa, Japan). Data were analyzed using One-Way ANOVA with Tukey's post hoc test for parametric comparisons, and Wilcoxon Signed-Ranks, Kruskal-Wallis with Dunn's post hoc test, Fisher's Exact test with Bonferroni correction, and Cohen's kappa for nonparametric analyses, with significance set at α = 0.05.

Significant differences were observed among matrix systems for MD diameters, proximal contour, marginal adaptation, and surface roughness (all p < 0.049). The stainless steel sectional matrix system produced the greatest MD diameter change and the highest incidence of cervical and lateral overhang. Only stainless steel and copper sectional matrix systems generated convex contours. Copper and stainless steel sectional matrices also exhibited greater surface roughness than the other systems (both p < 0.03).

Precontoured metal sectional matrices with rings achieve proper proximal contours and increase MD diameter. However, they require precise placement to avoid distortion, which may compromise surface smoothness.