Voids at the Bottom of Cavities With Various Bulk Fill Composites and Depth

Objectives: Over the past years, it has drawn great attention to fill large dental cavities, such as Class I and II ones, with bulk fill composites. Challenges of this technique have been identified by researchers and clinicians, such as depth of cure and potential voids (such as bubbles and gap formation) at bottom of a restoration. This research is to study the voids at the bottom of cavities with various bulk fill composites, which employee different curing and filling characteristics.
Methods: Four group of bulk fill composites, with corresponding bonding agents, were used in this study: 1) Bulk EZ (Danville), with Prelude One (Danville); 2) SonicFill (Kerr), with OptiBond Solo Plus (Kerr); 3) Filtek Bulk Fill Posterior (3M), with Scotchbond Universal (3M); 4) SureFil SDR (Dentsply), with Xeno V (Dentsply). All A2 shade. In pre-fabricated cavities (made with RockCore, Danville) with sizes of 4mm (width) X 6mm (length) X depth (3, 4, 5, 6mm), bonding agents were applied according to each IFU. Each composite was used to fill up these cavities and cure according to IFU. Cured specimens were then sectioned to expose interfaces, which were examined by optical microscope and SEM (scanning electronic microscope).
Results: Typical SEM images of interface are shown in Figure 1. Only Bulk EZ shows 100% of continuous interface in all depth. All other composites show voids (detached gaps or bubbles) at interfaces between composites and adhesives at all depth.
Conclusions: Within the limitation of this study, the self-curing flowable composite Bulk EZ shows the best interface integration when applied on large tooth cavities.