Curing Capacity of Band-Bonding Resinous Adhesives Under 3D-Printed Molar Bands

To evaluate the curing efficiency of three resin composite adhesives applied beneath 3D-printed molar bands, by determining their degree of conversion (DC%) at different depths.

Fifteen 3D-printed metallic band specimens were divided into three groups and bonded with Band Lock Blue (BLB), Optiband Ultra Blue (OBU), or Transbond Plus (TRP). Adhesives were applied in 150 μm films and light-cured for 30 s (1200 mW/cm²). Degree of conversion (DC%) was measured at the top, middle, and bottom regions using attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR). Directly irradiated specimens served as controls. Statistical analysis of DC% values was performed with regression modelling at a 5% level.

A reduction in conversion beneath the bands compared to non-banded controls was seen, which was dependent on both the adhesive type and the region. For BLB, equally low DC% values were found for banded and non-banded specimens across all regions. Banded OBU specimens had significantly lower DC% compared to non-banded controls at all regions. Finally, TRP banded specimens had significantly lower DC% compared to non-banded controls at the middle and bottom regions, but not at the top region.

Curing capacity of band adhesives under 3D-printed bands is material-dependent. Blue-shaded OBU and dual-cured BLB showed more uniform conversion, whereas white-shaded TRP exhibited significant depth variations. However, conversion of the adhesives tested under 3D-printed metallic bands was acceptable when a high-intensity light-curing unit was used for an extended irradiation time for orthodontic applications (30 s).