Composite Layering

Lutz and Kull (1980) were the first to demonstrate the good marginal adaptation of layered composite restorations in vitro. It should be noted that effective dentinal adhesives were not available at the time, and that composites were subject to greater polymerization shrinkage than current materials.

Through in vitro experiments several authors later demonstrated the effectiveness of layering in controlling polymerization stress (Lutz, Krejci, and Luescher, 1986; Lutz, Krejci, and Oldenburg, 1986; Tjan, Bergh, and Lidner, 1992; Park and colleagues, 2008).

Nevertheless, based on a comparison of the bulk technique and multilayered techniques, not all authors believe that layering can produce satisfactory margin quality (Versluis and colleagues, 1996; Jedrychowski, Bleier, and Caputo, 1998; Kuijs and colleagues, 2003).

In any case, in order to obtain adequate polymerization, the thickness of the material should not exceed 2 mm, even when high-intensity irradiation lamps are employed (Rueggeberg, Ergle, and Mettenburg, 2000). Therefore the composite must be layered (the number of increments will depend on the size of the cavity) using a thickness of 2 mm as a benchmark.

There are different layering techniques—horizontal, oblique, and vertical—but to date it is still unclear which one is the best (Ferracane, 2008).

Based on this information and my own clinical experience, I prefer to restore medium-sized Class I cavities with three increments of composite resin and use a four-increment technique for medium-sized Class II cavities (a medium-sized cavity is a cavity whose occlusal width is less than two thirds of the intercuspal distance).

In medium-sized Class I cavities the first increment consists of a thin layer of material (about half a millimeter of flowable composite), and the second is a layer of dentin mass, leaving enough room for the last layer of enamel mass. All layers are applied horizontally.

It must be noted that the use of flowable composite is controversial. In an in vitro study on Class V cavities, Kemp-Scholte and Davidson (1990) showed that an intermediate elastic layer placed between the bonding agent and the restoration decreased stress by 20% to 50% while preserving marginal integrity.

Many professionals have investigated this over the years, but no unequivocal conclusions have been reached. Some have shown that a layer of flowable composite improves marginal adaptation (Attar, Turgut, and Gungor, 2004; Li and colleagues, 2004, 2006), whereas others have found no improvement (Braga, Hilton, and Ferracane, 2003; Lindberg, van Dijken, and Horstedt, 2005). At the same time, however, no one has ever shown that the quality of restoration deteriorates. In my clinical experience, the use of flowable composite reduces postoperative sensitivity to practically zero.

Class II cavities are usually restored with four increments of material. The first is a layer of enamel mass that transforms the cavity into a Class I cavity by placing the composite against the matrix (the thickness of the proximal wall should be about half a millimeter). The Class I cavity can then be restored as usual.

The restoration is finished with abrasive disks and rubber wheels and is polished with brushes that have polishing agents embedded in the bristl/>