Voids and porosities in class I micropreparations filled with various resin composites

In this in vitro study, voids inside a minimal occlusal restoration using different consistencies of resin composite and various application techniques were investigated. One hundred and fifty-two simulated, minimally invasive preparations, including a prepared fissure and an excavated carious dentin lesion, were ground in perspex blocks. After applying an acrylic primer (Artglass Connector, Kulzer), the preparations were restored with the adhesive PhotoBond (Kuraray) and one of three resin composites: a packable composite (Prodigy Condensable-Kerr), a syringable composite (Clearfil Photo Posterior, Kuraray) and a flowable composite (Revolution, Kerr). The restorations were inserted according to eight protocols (n = 19). In three groups, the composite was placed in bulk. In another three groups, a layer of flowable composite was placed first, then cured, followed by a second layer of one of the three composites. In two groups, the first layer of flowable composite was left uncured before a second layer of a packable or syringable composite was inserted. The perspex blocks were sectioned and inspected for the presence of voids. Statistical analysis was conducted using Fischer's exact tests at p < 0.05. The results showed that restoring minimal preparations in the absence of porosities and voids was very difficult to achieve. Placing a layer of flowable composite that was left uncured, directly followed by injecting a medium-viscous composite, was the technique that resulted in the most homogeneous restoration.