Opacity of a New Bulk Fill Equivalent to Universal Composites

Objectives: Bulk fill (BF) resin-based composites (RBCs) have long had to balance depth of cure with opacity. Typically, BF RBCs sacrifice opacity to achieve a reasonable depth of cure (DOC) for bulk filling and curing. The clinician, however, would like to have both properties maximized. This study presents opacity and depth of cure measurements of a new bulk fill composite (3M EXP-BF) and universal RBCs. This study shows the new BF RBC has an opacity in the range shown by the universal RBCs, yet has a DOC ≥4.0mm.
Methods: Two disks each (30mm diameter by 1mm thick) were cured from sixteen A2 shade RBCs typically used as universal composites. The opacity (contrast ratio) of each disk was measured on an X-Rite Color-i7 spectrophotometer using an “over-light/over-dark” measurement set-up. The EXP-BF was measured in the same way.
DOC measurements (n=3) were made using the ISO 4049 DOC method. Paste was filled into a 4mm diameter by 15mm deep stainless steel mold and cured 20s via a Deep-Cure S light (3M Oral Care). The plug of paste was removed from the mold, and uncured material scraped away. Reported values are the length of the cured plug divided by two.
Results: Results are summarized in the following table.
The universal RBCs range in opacity from 47.19 to 59.66. The EXP-BF is within that range. An ANOVA was run on DOC, using Tukey’s comparison with 95% confidence. As the superscript letters in the DOC column of the data table indicate, DOC for EXP-BF is statistically greater than all the other composites tested.
Conclusions: The EXP-BF has a contrast ratio in the range of universal RBCs, but still retains high (≥4.0mm) DOC for bulk filling. Such a combination of opacity and high DOC should allow clinicians to make more esthetic BF RBC restorations.