# An Evaluation of the Demineralizing Effects of Various Acidic Solutions
## 2 Materials and Methods
The SEM parameters used for the measurements were 1000\(\times\) magnification, a 50 mm scale and 4.5 spot. The last step was to make bitewing radiographs of the initial situation. The tooth was placed in its silicone matrix and positioned over the image receptor. Using the parallel technique, the \(\chi\)-ray beam from the tube-head was oriented perpendicular to the tooth surface. Six types of demineralizing solutions were prepared:  
1. Hydrochloric acid gel 15% (Icon Etch, DMG); pH 1. 2. Orthophosphoric acid gel 35% (Vococid, Voco); pH 0.8. 3. Lactic acid 80%; pH 2. 4. Liquid 37% orthophosphoric acid; pH 1.5. 5. Formic acid 85%; pH 2.5. 6. An acid solution that contains 2.2 mM CaCl\({}_{2}\), 2.2 mM NaH\({}_{2}\)PO\({}_{4}\) and 0.05 M acetic acid; pH 4.5. In each acidic solution \(n=5\) teeth were immersed, each tooth having 2 demineralizing sites (one on the vestibular and one on the oral surface). Therefore, \(n=10\) treated sections were analyzed for each acid. The teeth were taken out of the silicone matrix and put in the demineralizing solutions for 30 min. Each tooth was washed under running tap water and scanned with the DIAGNODent(tm) pen, the Vita Easyshade(r) and SEM. Pictures and X-rays of the affected area were taken. The teeth were reinserted into the demineralizing solutions. After 1 h, they were taken out and washed, and all of the readings were performed again. Until the next day, the teeth were kept in saline water for rehydration. They were then reinserted in the demineralizing solutions for 24 h. All recordings were repeated for each tooth. \begin{table}
\begin{tabular}{c c} \hline
**DIAGNODent(tm) Reading Values** & **Tooth Tissues Status** \\ \hline
1–13 & Healthy enamel \\
14–20 & Enamel caries \\
21–29 & Deep enamel caries \\ \textgreater{}30 & Dentine caries \\ \hline \end{tabular}
\end{table} 
Table 1: The DIAGNODent(tm) pen readings classification. The last demineralizing cycle involved keeping the teeth in the prepared solutions for 96 h. The solutions were renewed every day. All determinations (DIAGNODent(tm) pen, Vita Easyshade(r), SEM, photograph and radiograph) were repeated for each tooth. The data were collected into an Excel database. The results were statistically analyzed to compare the variables of the demineralization periods in relation to the type of acidic solution. Therefore, the ANOVA one-way test was used to determine the statistical differences between the groups. For the post hoc comparisons, the Tukey test was applied, the significance level being set to \(a=0.05\). The statistical analysis was performed using the graphics from Origin2019b Graphing & Analysis (OriginLab), the results being considered significant for \(p\leq 0.05\). The present research was conducted as a pilot study, as extracted teeth without any caries lesions--even teeth without early-stage caries lesions--are difficult to collect, and increasingly so. The problem has been exacerbated by the COVID-19 pandemic, which has resulted in many patients having to postpone non-urgent dental care, including orthodontic treatment, which might have required the extraction of healthy teeth due to lack of space. In the future, we plan to repeat the demineralizing protocol on more teeth, using weaker concentrations of acids and including remineralizing cycles.