Physical properties of composites light cured through ceramic spacers

Objectives: The objective of the present study was to assess the Color Stability/ΔE (after 7days dark/dry storage and 24hours after artificial aging/immersion in water at 60⁰C), Contact Angle/CA and Degree of Conversion/DC of 2 composites (Tetric in-ceram bulk-fill/TBF and Filtek Supreme/FS) polymerized through ceramic-spacers (E-max CAD blocks LTA3 and HTA3), with three thickness each: 0.7-, 1.4-, and 2mm; as well as a control group without ceramic interposition.
Methods: Five resin-disks were obtained for each group (6mm x 2mm) with aid of a PVS matrix and were used for the ΔE and CA tests. The respective ceramic-spacers (except for control groups) were interposed and resin was light-cured during 40s with a 1000mW/mm² LED light-curing unit. ΔE was assessed using a spectrophotometer (Easyshade), at baseline/immediately after light-curing, after 7days and 24h aging. For CA, the mean between the left and right angles was considered. DC was assessed with 4 specimens packed directly over the FTIR crystal.
Results: FS showed ≤ΔE up to 7days after light-curing comparing with TBF, except for group light-cured through the LT2mm spacer. After 24h artificial aging, both composites showed the same ΔE, except for LT2mm, in which TBF showed higher values. For both resins, the increase in thickness resulted in increased ΔE after artificial aging (LT2mm for FS and TBF). In addition, both composites showed ΔE higher than the threshold of 3.3 (clinically perceptible).
FS showed a decrease in the CA as the ceramic spacers increased in thickness and opacity. For TBF, no difference was observed. TBF showed higher angle of contact for all groups, except control and HT0.7mm groups. Considering DC, TBF showed higher values than FS, regardless of the group. For both resins, the only group with significant decrease in DC was LT2mm, but less pronounced for TBF.
Conclusions: For cementation of higher thickness/opacity restorations, TBF can be an interesting material.