New Bulk Fill Restorative With Robust 5mm Depth of Cure

Objectives: Bulk fill (BF) resin-based composites (RBCs) need to meet two important requirements: They must have low enough shrinkage stress and high enough depth of cure (DOC) for bulk placement and curing. This study reports DOC and stress measurements for a new BF composite, 3M EXP-BF. This study shows that EXP-BF can be placed in bulk up to 5mm deep in Class II restorations using multi-sided curing and up to 4mm in Class I restorations with shrinkage stress less than or equal to some common incrementally-placed RBCs.
Methods: 3M EXP-BF was cured using a multi-sided curing technique in 5mm deep Class II restorations placed in extracted human third molars. Relative cure was analyzed by measuring Knoop microhardness from occlusion to gingival floor (n=3).
Class I DOC measurements were performed as per ISO-4049, and were made in triplicate using a 4mm diameter by 15mm deep stainless steel mold and 20s cure time with a 3M ESPE Elipar™ DeepCure S light.
Shrinkage stress was measured by cusp deflection in 4mm deep by 4mm wide by 8mm long slots in aluminum molds to simulate an MOD preparation (n=3).
Results: In approximately 6mm deep Class II restorations EXP-BF achieved Knoop hardness at a depth of 5.1mm >89%±3.0% of the maximum tested hardness, which is well above the commonly accepted threshold of 80% hardness. This is considered robust because even at the gingival floor of the 6mm deep restorations the hardness is >86%±2.1% of the maximum tested hardness (Table 1).
Cusp deflection and DOC are reported in Table 2. Superscripts denote statistical grouping via ANOVA with Tukey’s comparison with 95% confidence.
Conclusions: 3M EXP-BF can be cured up to 5mm deep and has shrinkage stress less than or equal to incrementally placed composites, enabling the clinician to fill and cure up to 5mm deep increments.