The Perio-Resto Interface: In Vitro Comparison of Two Deep Margin Elevation Techniques on Surface Roughness, Marginal Adaptation and Material Integrity

<b>Background/Objectives:</b> Deep subgingival proximal carious lesions present significant restorative and periodontal challenges, especially when approaching the supracrestal attachment (SA). This study compared two established deep margin elevation (DME) tecniques-the modified matrix technique (MMT) and the matrix-free "R2 technique" (R2T)-with respect to surface roughness, marginal adaptation, surface integrity, voids and excess adhesive material. <b>Methods:</b> Forty extracted human mandibular molars were prepared with standardized proximal cavities 2-3 mm below the cementoenamel junction (CEJ) and randomly assigned to two groups (<i>n</i> = 20 each). Group 1 received DME with the modified matrix technique; Group 2 was treated with the R2T. In both groups, a flowable bulk-fill composite was applied. Surface characteristics and marginal adaptation were evaluated using scanning electron microscopy (SEM) and laser profilometry. Qualitative scoring and quantitative measurements were performed. Statistical analysis was conducted using GraphPad Prism (version 10.02.0). <b>Results:</b> The modified matrix technique resulted in significantly smoother composite surfaces (<i>p</i> < 0.001), whereas the R2T showed significantly fewer voids, better marginal adaptation, and less excess bonding material (<i>p</i> < 0.05). No statistically significant difference was observed in surface integrity between the groups. <b>Conclusions:</b> While the MMT produced smoother surfaces, the R2T resulted in superior marginal quality with fewer voids and less excess adhesive material. The findings suggest technique-specific advantages rather than overall superiority, indicating that both approaches appear feasible. Clinical decision-making should be guided by anatomical and operator-related factors.