Evaluation of Interfacial Gap Volume of Two Low-shrinkage Composites Using Micro-Computed Tomography

To investigate the efficacy of X-ray micro-computed tomography (μCT) in the detection and quantification of interfacial gap formation in standardized Class I and Class II resin composite restorations, to compare the interfacial gaps for two low-shrinkage resin composites with a methacrylate composite material, and to determine any correlation between the cavity configuration factor (C-factor) and the volume of gaps formed.

Sixty standardized Class I and Class II cavities were prepared and divided into six groups. Three types of composites, with their recommended self-etching adhesive systems, were used: Filtek Z250 XT; Estelite Sigma Quick; and Filtek P90. Each of the composite materials was placed in 10 Class I and 10 Class II cavities. The specimens were digitized using Skyscan 1172 μCT. They were examined for gap volume measurements, the thickness of the adhesive layer, and location of interfacial gaps.

There was a significant difference in the mean gap volume percentages of the three materials. The gap volume percent of Estelite Sigma quick was significantly lower than that of Filtek P90. No significant difference in the mean gap volume percentages of Class I and Class II restorations was found, except for Estelite Sigma Quick, in which the Class I gap volume percentage was higher than that of the Class II restorations.

μCT is an efficacious tool for the measurement of volumetric gaps formed at the tooth/restoration interface and for the evaluation of the adhesive layer. The differences in the C-factor do not always have a pronounced effect on the gap volumes of low-shrinkage composites.