## 3 Results  
### Basic Characteristic of Patients  
As demonstrated in Table 2, the largest proportion of study group were young non-smokers in the 16-26 age range, generally healthy people with a female predominance. There were insignificant differences in gender distribution, age, smoking, occupation, diseases, dietary supplementation, and vitamin D3 level between study and control group (\(p\) > 0.05 for all parameters). The reason for performing dental extractions for surgical reasons proved to be significantly statistical (\(p\) = 0.020). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Variable** & \begin{tabular}{c} **Total** \\ **(\(n\) = 69)** \\ \end{tabular} & \begin{tabular}{c} **LG Copper Area—No** \\ **(\(n\) = 20)** \\ \end{tabular} & \
\begin{tabular}{c} **LG Copper Area—Yes** \\ **(\(n\) = 49)** \\ \end{tabular} &
\begin{tabular}{c} **\(p\)-Value** \\ \end{tabular} \\ \hline Gender: & & & & \\ male & 16 (23.2) & 4 (20.0) & 12 (24.5) & 0.763 \\ female & 53 (76.8) & 16 (80.0) & 37 (75.5) & \\ \hline Age (years old) & 27.0 (22.0–31.0) & 25.0 (24.0–27.5) & 29.0 (22.0–32.0) & 0.305 \\  & [25.6–30.9] & [23.7–27.6] & [25.8–32.0] & 0.305 \\ \hline Age (years old): & & & & \\  16–26 & 34 (49.3) & 12 (60.0) & 22 (44.9) & 0.092 \\  27–37 & 29 (42.0) & 8 (40.0) & 21 (42.9) & 0.092 \\  38–45 & 6 (8.7) & 0 (0.0) & 6 (12.2) & \\ \hline Smoking & & & & \\ no & 61 (88.4) & 17 (85.0) & 44 (89.8) & 0.682 \\ yes & 8 (11.6) & 3 (15.0) & 5 (10.2) & \\ \hline Occupation: & & & & \\ student & 20 (28.9) & 5 (25.0) & 15 (30.6) & \\ worker & 10 (14.5) & 1 (5.0) & 9 (18.4) & 0.245 \\ white-collar worker & 39 (56.5) & 14 (70.0) & 25 (51.0) & \\ \hline Years of residence in the LG & & & & \\ copper district (n = 49): & & & & \\ \(\leq\)20 years old & 17 (34.7) & - & 17 (34.7) & - \\
21–30 years old & 19 (38.8) & & 19 (38.8) & \\ \(\geq\)31 years old & 13 (26.5) & & 13 (26.5) & \\ \hline Thyroid and parathyroid glands & & & & \\ diseases: & & & & \\ no & 62 (89.9) & 18 (90.0) & 44 (89.8) & 1.000 \\ yes & 7 (10.1) & 2 (10.0) & 5 (10.2) & \\ \hline Cardiac diseases: & & & & \\ no & 67 (97.1) & 19 (95.0) & 48 (98.0) & 0.498 \\ yes & 2 (2.9) & 1 (5.0) & 1 (2.0) & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Demographic, clinical, and laboratory characteristic of total study group and two subgroups of patients, divided according to place of residence. Descriptive data were presented as number of observation (percent) or median (Q1–Q3) and [95% CI]. Chi-square test, Fisher exact test, or Mann–Whitney test were used for the analysis of differences between two subgroups of patients. The Content of Toxic Metals in the Removed Teeth in Patients from the LG Copper Area and in Control Group  
As shown in Table 2, the concentrations of Fe and Pb were significantly higher in the teeth removed from patients from the LG Copper Area than in patients from the control group (\(p\) = 0.016 and \(p\) = 0.002, respectively). Risk Factors Determining the Accumulation of Toxic Metals in the Teeth of Patients Residing in the LG District  
The significant risk factors determining the accumulation of toxic metals, such as Mn, Cr, Ni, and Cu, in the teeth of patients residing in the LG Cooper Area are presented in Table 3.