Influence of filler composition on the refractive index of four different enamel shades of composite resins

Abstract

Aim and Objective: The purpose of this study was to measure the refractive index of four commercially available enamel resin composites, using optical coherence tomography (OCT) and their relationship with the atomic composition of the composite resin fillers utilizing an energydispersive X-ray fluorescence spectrometer (EDX). Materials and methods: Four different enamel composites, namely Enamel HRi color UE3, Enamel HFO color GE3, Vit-l-escence color Pearl Frost, and Amelogen Plus color Enamel White were tested. For each composite, disks with different thicknesses were fabricated and then lightcured according to the manufacturer’s instructions. The disks were then stored in deionized water under 36.5 °C for at least 7 days. Each of the samples from the four different groups was measured in five distinctive points to analyze the optical and physical length using optical coherence tomography (OCT). Elemental analysis of all four different enamel shades of the composite was done using an EDX. Results: The filler contents showed interesting differences in elemental composition and concentration; however, Si seemed to be a common filler component. The HRi composite presented a distinctive composition compared to other materials and was the only composite that showed a smaller percentage of SiO2, and also was the only composite that contained compounds, such as P2O5, ZnO, CaO, La2O3, and V2O5. The optical coherence tomography analysis showed the refractive index values of all tested enamel composites. Among the four different enamel composite resins tested, the enamel HRi composite demonstrated the most ideal refractive index to mimic natural enamel. Conclusion: The enamel HRi composite demonstrated a distinctive filler composition and this could be the main reason behind its higher refractive index. Nonetheless, it remains unclear how much of an impact this feature has in the final esthetic outcome of anterior composite restorations, where many other optical phenomena are also important. Clinical significance: The clinical success of any esthetic restorative procedure depends on diagnosing the proper treatment plan and also on executing this treatment with the right materials. On direct esthetic restorations, knowing the optical properties of such materials is fundamental, as they should be able to replicate both natural enamel and dentin.