Open Access

ARTICLE

Assessing Surface Roughness between Unishade and Conventional Composite Resins after Immersion in Different Staining Solutions: An In-Vitro Study

Sultan Binalrimal^1,*, Abdullah M. Alshehri², Mohammed Mustafa^2,*, Ali Robaian Alqahtani², Rasha Alharthi³, Basil Almutairi⁴

1 Restorative Department, College of Medicine and Dentistry, Riyadh Elm University, Riyadh, Saudi Arabia
2 Department of Conservative Dental Sciences, College of Dentistry, Prince Sattam bin Abdulaziz University, Al-Kharj, Saudi Arabia
3 Department of Clinical Dental Science, College of Dentistry, Princess Noura bint Abdulrahman University, Riyadh, Saudi Arabia
4 Department of Restorative Dental Science, College of Dentistry, King Saud University, Riyadh, Saudi Arabia

* Corresponding Authors: Sultan Binalrimal. Email: ; Mohammed Mustafa. Email:

(This article belongs to the Special Issue: Damage and Fracture of Polymer Composites)

Journal of Polymer Materials 2026, 43(1), 17 https://doi.org/10.32604/jpm.2026.075142

Received 26 October 2025; Accepted 20 February 2026; Issue published 03 April 2026

Abstract

Composite resin restorations are routinely exposed to acidic and chromogenic beverages that may alter their surface integrity over time. This in-vitro study evaluated the surface roughness behavior of two universal single-shade (Unishade) composites and two conventional multi-shade composites following immersion in commonly consumed staining solutions and assessed whether repolishing could restore smoothness after degradation. A total of 120 standardized disc specimens were fabricated and allocated to four material groups, with each group subdivided into distilled water, cola, and coffee immersion subgroups. Surface roughness was recorded at baseline, after one week, after one month, and following a final repolishing step using a standardized multi-step system. The findings demonstrated that Unishade composites exhibited more stable surface characteristics across all immersion periods, with changes consistently remaining below the threshold associated with biofilm accumulation. Conventional composites showed greater variability, particularly in cola, where roughness values increased significantly compared with distilled water and coffee. Repolishing substantially reduced immersion-induced roughness in all materials, although its effectiveness varied depending on composite formulation and beverage acidity. Cola produced the greatest surface alterations across all groups, highlighting the erosive potential of low-pH beverages. These results indicate that Unishade composites possess superior resistance to surface degradation, likely due to their nano-structured filler configuration and less hydrophilic resin matrices, while conventional materials appear more susceptible to acidic challenge. Within the limitations of this study, selecting surface-stable material types and applying appropriate finishing and repolishing protocols may enhance the long-term performance and esthetics of composite restorations.

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