Effect of two oxygen-inhibiting agents on the surface microhardness of giomer restorative materials

Giomers are bioactive hybrid restorative materials consisting of composite resin and glass ionomer filler pre-reacted on the surface, which maintain acceptable clinical qualities over time. One of the main factors that explains this is the surface hardness that is achieved by inhibiting the oxygen layer.

To compare the effect of blue and conventional Mylar strips used as oxygen inhibiting agents on the surface microhardness of giomer restorative materials.

A total 96 giomer specimens were prepared in disc-shaped molds 2 mm tall x 5 mm in diameter (ISO 4049: 2019-05). The specimens were grouped according to type of giomer: Beautifil II (BII) or Beautifil II LS (BIILS), and according to the type of Mylar strip: conventional, blue, or control group without strip. They were subsequently subjected to the Knoop (KHN) microhardness test. The database was analyzed with Stata SE v18 statistical software, and two-way ANOVA was performed.

Interaction was found between the type of giomer and Mylar strip (p=0.039). Significant differences were found between surface microhardness values according to the type of giomer (0.001) and the type of Mylar strip (0.001). Beautifil II LS presented significant differences between conventional Mylar strip vs. without Mylar strip (43.58 ± 1.65 vs. 40.44 ± 2.12) and between blue Mylar strip and without Mylar strip (44.69 ± 1.75 vs. 40.44 ± 2.12). In the Bonferroni Post hoc test, a significant difference was found between Conventional Mylar Strip and without Mylar Strip (p=0.001) and Blue Mylar Strip and without Mylar Strip (p=0.001).

The use of blue and conventional Mylar strips inhibits the oxygen layer on the Beautifil II and Beautifil II LS giomers, endowing them with high values of surface microhardness.