Knoop microhardness, surface roughness, and cytotoxicity analysis of arginine-modified experimental orthodontic...

The study aimed to evaluate the impact of incorporating 2.5%, 5%, and 7% arginine on the hardness, roughness, and cytotoxicity of 3M™ Transbond™ XT.

A total of 48 samples were divided into four groups (n=12): G1 - commercial resin 3M™ Transbond™ XT (TXT); G2 - TXT+2.5% arginine; G3 - TXT+5% arginine; and G4 - TXT+7% arginine. The hardness analysis was performed by a microhardness tester. The measurements of roughness were performed by a surface roughness measuring instrument. The surface morphology analysis was analyzed by digital images obtained with a scanning electron microscope (SEM). For the in vitro cytotoxicity test, dental pulp mesenchymal cells underwent a cell viability reduction assay. For statistical analysis, ANOVA (one-way/two-way) was used, followed by Tukey's test post hoc (P<0.05).

There was a reduction in the hardness of experimental resins compared to 3M™ Transbond™ XT commercial resin (P < 0.05). There was no difference between concentrations of 2.5% and 5%, but there was the largest reduction in resin with 7% arginine (P < 0.05). Surface roughness analysis showed there was no statistical difference between the samples (P ≥ 0.05). SEM also did not demonstrate changes in the surface roughness of the resins. All groups exhibited good cell viability at each timepoint. After 48h, an increase was observed for groups contaning arginine (P < 0.05).

Surface hardness was modified with arginine incorporation - to the Transbond™ XT resin formulation. No differences were observed for surface roughness. Due to the initial cytotoxicity of the resins, precautions regarding satisfactory photopolymerization and the distance of application in relation to the gingival tissues must be adopted.