Abstract
This in vitro study examined the margin integrity of sculptable and flowable bulk-fill resin composites in Class II cavities of primary molars. Standardized Class II cavities were prepared in human primary molars and restored with the following resin composite materials after application of a universal adhesive: a sculptable bulk-fill composite (Tetric EvoCeram Bulk Fill (TEC) or Admira Fusion x-tra (AFX)), a flowable bulk-fill composite (Venus Bulk Fill (VBF) or SDR), or a conventional composite (Filtek Supreme XTE (FS)). The bulk-fill materials were applied in 4 mm layers, while the conventional composite was applied in either 2 mm (FS2, positive control) or 4 mm layers (FS4, negative control). The specimens were exposed to thermo-mechanical loading (TML) in a computer-controlled masticator. A quantitative margin analysis was performed both before and after TML using scanning electron microscopy, and the percentage of continuous margins (margin integrity) was statistically analyzed (α = 0.05). All composites showed a significant decline in margin integrity after TML. AFX exhibited the significantly highest margin integrity of all materials after TML (97.5 ± 2.3%), followed by FS2 (79.2 ± 10.8%), TEC (73.0 ± 9.1%), and FS4 (71.3 ± 14.6%). SDR (43.6 ± 22.3%) and VBF (25.0 ± 8.5%) revealed the lowest margin integrity. In conclusion, the tested sculptable bulk-fill materials show similar or better margin integrity in primary molars than the conventional resin composite placed in 2 mm increments.
Highlights
Today, carious primary teeth are mostly restored by using tooth-colored filling materials such as glass ionomer cements, compomers, and resin-based composites [1]
An inherent problem of resin composites is the fact that they shrink during the polymerization process, which leads to contraction stresses within the material and at the tooth–restoration interface [3]
The null hypothesis to be tested was that there would be no significant differences in margin integrity between cavities restored with conventional or bulk-fill composite materials
Summary
Carious primary teeth are mostly restored by using tooth-colored filling materials such as glass ionomer cements, compomers, and resin-based composites [1]. Among these materials, the lowest failure rates have been reported for resin composites [2]. Various incremental layering techniques and modified light curing approaches have been established to counteract the consequences of contraction stress [6,7]. These approaches are technique-sensitive which, in particular, is a problem when treating children. Light curing several composite layers consecutively in deep cavities is time consuming and may lead to the incorporation of air bubbles or contaminants, especially when the compliance of a young patient is lacking [8]
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