Comparing ISO 4049 and Fourier-transform infrared spectroscopy for assessing ambient light sensitivity in dental resin composites

This study evaluated the sensitivity of dental resin composites to ambient light using the ISO 4049 standard and Fourier-transform infrared (FTIR) spectroscopy. It aimed to compare the working times measured by these two methods to assess FTIR's potential as an alternative to ISO 4049 for determining premature polymerization. Eight dental composites (three bulk-fill and five conventional) were exposed to simulated ambient light. Working time was assessed using the method described in ISO 4049 standard, which identifies premature polymerization via visually identifiable macroscopic changes. FTIR spectroscopy enabled an analysis of the progress of polymerization by measuring the degree of conversion of methacrylate C=C bonds. Working times were compared across composites and between methods, with statistical analyses performed using ANOVA and Pearson correlation. All composites met the minimum ISO 4049 working time of 60 s. However, significant differences in working times were noted between ISO 4049 and FTIR, with FTIR generally overestimating the working time. Pearson correlation indicated moderate alignment between the methods, particularly at higher working times, though FTIR was less sensitive to early polymerization changes compared to ISO 4049. In conclusion, FTIR spectroscopy shows potential for assessing ambient light sensitivity in dental resin composites, yet it lacks the sensitivity of ISO 4049 in detecting early-stage polymerization. This study underscores the need for standardized, sensitive methods in assessing resin composites' working times, especially as material compositions evolve in modern dentistry.