Surface roughness and volume stability of amalgam replacement materials

Abstract

Objective: As of January 1, 2025, traditional silver amalgam is no longer available to the general population in the European Union as a filling material. The present study investigates five alternative restorative materials with regard to surface roughness and volumetric stability. The materials examined were Cention Forte (alkasite), IonoStar Molar, DeltaFil (conventional glass ionomer cements, GICs), Ketac Universal (high-viscosity GIC), and Equia Forte HT (glass hybrid). The primary objective was to assess changes in surface roughness influenced by different finishing methods over time and following artificial aging by thermocycling. Measurement of volumetric stability over time was another key outcome, as volumetric shrinkage, which can lead to marginal gap formation, and bacterial adhesion due to surface roughness are critical factors for the longevity of restorations. Methods: Surface roughness (Sa) was evaluated using optical 3D surface profilometry at three time points: immediately after finishing, after 30 days in distilled water, and following thermocycling. The effects of six different finishing methods, including burs and Sof-Lex discs, were analyzed. Volumetric changes were assessed using the Archimedean principle at six time points: immediately after polymerization, after 1 hour, 24 hours, 7 days, 30 days, and following thermal aging. Results: Surface roughness was significantly influenced by both the material and the finishing method. Sof-Lex discs produced the smoothest surfaces for most materials tested. Only the modified GIC and alkasite exhibited stable surface roughness over time. The glass hybrid material showed a significant increase in roughness following thermal aging. In terms of volumetric stability, modified GIC and high-viscosity GIC maintained a stable volume, whereas alkasite showed a reduction in volume after thermocycling. The glass hybrid material initially expanded, followed by contraction, while the conventional GIC showed continuous shrinkage. Conclusion: The study highlights the importance of the final finishing method in dental restorations. Appropriate finishing can reduce surface roughness and potentially enhance the longevity of restorations. Materials with smaller filler particles, such as modified GIC and glass hybrid, demonstrated more stable surface roughness over time. Volumetric stability was highest in high-viscosity GICs and glass hybrids. These findings suggest that modifications to GICs, such as PEG-PU micelles, may improve long-term surface smoothness and volumetric stability, making them promising alternatives to traditional amalgams. Future research should investigate these materials under more complex in vivo conditions.

Datum der Bewilligung	2025
Originalsprache	Englisch
Gradverleihende Hochschule	Medizinische Universität Graz
Betreuer/-in	Michael Payer (Betreuer*in), Gerd Leitinger (Betreuer*in) & Karl Glockner (Betreuer*in)