Infrared spectroscopic analysis of restorative composite materials' surfaces and their saline extracts

This study aims at finding out if multiple attenuated internal reflection-infrared (MAIR-IR) spectroscopic analysis can be used as a tool to differentiate commercial resin composite brands and to find out if different resin composites will have different abilities of leaching materials that are cytotoxic to human gingival fibroblasts (HGFs) Tooth-colored resin fillings have become increasingly popular as restorative materials, which make it important to differentiate the commercial brands for forensic and biological purposes. Fourteen resin composite brands were used in the study. MAIR-IR spectroscopic analysis was used for surface characterization of the organic and inorganic parts of the resin composite samples which were studied as is and after 2 weeks of saline incubation. IR spectroscopy was also done on the saline extracts to find out if different resin composite materials would have different leaching abilities. The saline extracts were also used for the viability testing of HGF cell cultures. One-way analysis of variance test statistics was used to analyze the results. It was found that the resin composite brands have different spectra after saline soaking. It was also found that these resin composite brands possess different leaching abilities with regard to the amount and type of materials and different cytotoxic effects, which were found to be threshold dependent, meaning there is a critical or threshold value of leaching material at or above which the toxic effect will be significant and below which there is no toxic effect. Therefore, IR spectroscopy might be considered as a useful tool for dental resin composite characterization. However, more oral simulating environmental testing methods, different surface characterization methods, and more cell viability testing methods and assays must be considered for more specific results which relate more to the behavior of these dental resin composites in the oral environment.