The influence of denture adhesives on the microhardness, color, and roughness of rigid reliners, before and after thermocycling.

The stability and functionality of complete dentures depend on various clinical and material factors, such as retention, adaptation, color change, microhardness, and surface roughness. Relining aims to re-establish the fit of the prosthesis to the supporting tissues, and it is carried out using materials such as acrylic resins. This study aimed to evaluate the color, microhardness and roughness properties of three relining acrylic resins: Kooliner (GC America, USA), TDV-Cold (TDV, Brazil), and Ufi Gel Hard C (VOCO, Germany), after combined use with three different adhesives (Corega, Fixodent - Haleon, UK; and Poligrip - P&G, USA) for 2 months, followed by aging by thermocycling (5.000 cycles). Color, microhardness, and roughness were analyzed on 120 samples at times T0 (initial), T1 (after 2 months), and T2 (after thermocycling). Additionally, characterization by energy-dispersive X-ray spectroscopy and scanning electron microscopy was performed at T0 and T2. The results showed that time had a significant influence on all the properties evaluated, with an increase in microhardness and roughness over time. Ufi Gel Hard C showed greater color stability and microhardness, even after aging, a behavior associated with the presence of elements such as silicon and barium in its composition. Roughness was also more evident in this relining acrylic resin, as confirmed by the SEM data and images. The reliners analyzed showed distinct behavior in response to aging and thermocycling, with Ufi Gel Hard C standing out for its greater stability. Time was the main factor influencing color, microhardness, and roughness properties.