Effect of In Situ Acid Erosion on Structural and Optical Properties of Nanoparticulated Bisacrylic Resin With Different Surface Treatments

Objective: To evaluate the influence of in situ acid erosion on the structural and optical properties of nanoparticulate bisacrylic resin with different surface treatments, evaluating surface roughness (Ra), knoop microhardness (KHN), color change (ΔE, ΔL, ΔC, ΔH), contrast (CR) and translucency (TP).

Methods: Eighty specimens were made (n = 10 per group) and the following surface treatments were applied: U_P-unpolished; A_p-polishing with Astropol rubber tips (Ivoclar); S_B-Biscover LV surface sealant (Bisco) and S_P-Palaseal surface sealant (kulzer). For the in situ experiment, 10 volunteers wore an intraoral appliance containing eight specimens (two specimens per experimental group), with only one specimen from each experimental group being subjected to the acid process. They were immersed in 150 mL of cola-based soda (pH = 2.3), 4 × 5 min/day for 14 consecutive days evaluating surface roughness (Ra), knoop microhardness (KHN), color change by CIEDE2000 (ΔE, ΔL, ΔC, ΔH), contrast (CR) and translucency (TP).

Results: The S_B and S_P groups adopted the lowest Ra values, with a significant difference from the others. The S_B group had the highest values of KHN and NP the lowest, with a significant difference from the others. The S_P group had the highest values of ΔE00, being the only one with a significant difference from the others. In all analyses, there was no significant change between the groups without and with acid administration.

Conclusion: The surface sealants were able to improve the surface roughness and microhardness of the bisacrylic resin, however, the Palaseal sealant generates unacceptable color change. The acid injection did not significantly influence the properties of the material, regardless of the surface treatment performed.