## 4 Discussion
If this variation is exclusively ascribed to dental amalgam, and assuming that the HgU levels reflect 24 h mercury excretion with approximately 50% of the mercury being eliminated via the urine, the mean HgU suggests a daily exposure of roughly 10 \(\upmu\)g. These findings imply that individuals with a considerable number of amalgam restorations--particularly those with more than 36 restored surfaces--are subjected to an additional mercury burden of 10-12 \(\upmu\)g per day [56]. It is not recommended against using amalgam fillings during breastfeeding. The mercury concentration in human breast milk, obtained immediately after delivery, has shown a significant correlation with both the number of amalgam restorations and the frequency of dietary intake [57]. To estimate the absorbed dose of mercury, three primary approaches are generally used: (1) measuring the concentration of mercury vapor (Hg\({}^{0}\)) released into the intra-oral air; (2) assessing the increase in mercury levels in blood; and (3) evaluating mercury concentrations in the urine. However, these methods have limitations: measurements of Hg\({}^{0}\) concentrations do not account for ionic mercury dissolved in saliva, while mercury levels in body fluids can be affected by dietary mercury intake [49; 58]. The chemical interaction between saliva and amalgam is highly complex. Therefore, it is common practice among researchers in this field to utilize synthetic saliva models rather than natural human saliva [59; 60; 61]. Aqueous media, including saline, distilled water, and saliva, have been employed to assess mercury release from amalgam specimens into liquids. Previous studies have reported varying release rates into saliva, ranging from 0.14 to 16.0 ng/(min \(\times\) cm\({}^{2}\)) [62]. In environments of natural or artificial saliva, where strong electrolytes such as KCl and NaCl serve as the primary and most concentrated components, various researchers have identified a mercury release ranging from 4 to 40 ng/(min \(\times\) cm\({}^{2}\)) [63; 64; 65]. Additionally, a buffer system, such as HCO\({}_{3}\)/CO\({}_{3}\) or H\({}_{2}\)PO\({}_{4}\)/HPO\({}_{4}\)\({}^{2}\), is included. Occasionally, a complex anion, such as SCN--which is present in relatively high concentrations in human saliva--is also incorporated. The mercury concentration in saliva is influenced by the emission rate of water-soluble inorganic mercury and the flow rate, which varies among individuals and increases with chewing gum stimulation. Therefore, the emission rate may be useful for evaluating amalgam effects. Measuring the mercury concentration in natural saliva is challenging due to external factors such as food and drink, which complicate the precise determination of true concentration levels. Consequently, artificial saliva was used in the present study, as it is a usual practice among investigators in this field to utilize synthetic saliva models rather than human saliva [63; 64; 65]. A spherical amalgam alloy commonly used in public dental clinics was selected for this study. Although both amalgam types contained a small amount of zinc, attributing any distinct effect on mercury dissolution solely to the presence of zinc is not considered feasible [66]. The quantity of mercury released from amalgam restorations substantially surpasses the total mercury exposure from other sources, such as water, air, and food [21, 67]. The emission of metal ions from restorations has been shown to be time-dependent and proportional to the surface area of the restoration [50]. The exposure to these metal ions, particularly mercury, presents a potential risk and could lead to harmful effects. In the experimental design of this study, the utilization of silver amalgam alloy capsules with a high copper concentration enabled the standardization of mercury levels across all test specimens.