# Assessment of Fluoride-Releasing Materials in Remineralization of Adjacent Demineralized Enamel
## 2 Materials and Methods
### Micro-CT Scanning  
The teeth were scanned with micro-CT SkyScan 1275. Micro-CT scanners were used for all X-ray imaging to assess the change in the LD and MD. Digital sectional images included an acceleration voltage of 90 kV, a source current of 70 mA, and an isometric voxel size of 10 \(\upmu\)m. The samples were scanned at a standard resolution (1024 \(\times\) 1024 pixels). A 1 mm aluminum filter was used to reduce beam hardening. The hydroxyapatite phantom (0.25 and 0.75 gHA/cm\({}^{3}\)) was used to calibrate the MD. Each sample was scanned 2 times, using 360\({}^{\circ}\)-round scanning. Teeth were mounted in a holder with a silicone jig and placed in the scanner to minimize the field of view (FOV). The silicone jig was used to fix the position of the tooth when scanned for two periods. All samples were scanned in the same position using the same procedure, and calculations were made by one examiner. Cross-sections were reconstructed by using the NRecon program (version 2.0.0.5). Ring artifacts and beam  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Materials** & **Chemical Compositions** & **Lot Number** & **Manufacturer** \\ \hline Filtek Z350 XT (Nanofilled resin composite) & Urethane dimethacrylate, Bis-GMA, PEGDMA, Bis-EMA, TEGDMA, zirconia, silica & 10130616 (shade A3) & 3M ESPE, St. Paul, MN, USA \\ \hline  & Powder: inorganic fillers (Ba-Al-Ca-Ba-Al-F & & \\ Cention N & silicate glass, Ca-F silicate glass, YtF3) and & & \\ customized fillers & Z0232K & Ivoclar Vivadent, Schaan, \\  & Liquid: urethane dimethacrylate, tricyclodecan- & (shade A2) & Liechtenstein \\  & dimethacrylate & dimethacrylate & \\ \hline  & Powder: 100\% fluoroalumino silicate glass & & \\ GC Fuji II LC & Liquid: 20–22\% polyacrylic acid, & & \\ (Light-cured resin- & 30–40\% 2-hydroxyethyl) methacrylate (HEMA), & & \\ modified glass ionomer & 5–7\% trimethyl hexamethylene dicarbonate, & 2105081 (shade A3) & GC Corporation, \\  & 4–6\% triethylene glycol dimethacrylate, & (shade A3) & Tokyo, Japan \\  & \(<\)10\% urethane dimethacrylate, initiator, & & \\  & \(<\)1\% camphroquinone & & \\ \hline Equia Forte Fil (Glass hybrid self-cured glass ionomer cement) & Powder: 95\% strontium fluoroalumino silicate glass and 5\% polyacrylic acid & 2108031 (shade A3) & GC Corporation, \\  & Liquid: 40\% aqueous polyacrylic acid & (shade A3) & Tokyo, Japan \\ \hline \hline \end{tabular}
\end{table}
Table 1: Restorative materials and their compositions used in this study.  
hardening were routinely corrected during reconstruction to improve image quality. Many imaging errors could be corrected by white and dark flat-field correction (images taken without the sample in the field of view). LD and MD were analyzed by using the CT An program (version 1.20.8.0). The LD was investigated and calculated from the deepest point. The average MDs of each proximal enamel caries lesion were calculated from five different lesion levels (the lesion's deepest level and two levels over and underneath, respectively). The specific distance between each level was selected at 30 \(\upmu\)m (Figure 2A). The lesion area of interest 3000 \(\times\) 200 \(\upmu\)m\({}^{2}\) in size from the outer to the inner demineralized enamel surface was equal in every sample measurement (Figure 2B). In addition, the deepest point of the LD was reinvestigated prior to measuring MD to confirm that the MD was determined from the actual lesion depth. The intra-examiner reliability based on all LDs reinvestigated, computed using the intraclass correlation coefficient, was 0.98. LD and MD were evaluated at two different time points: baseline and after 14 days of pH cycling (post pH cycling).  
Figure 1: Flowchart of the study procedures.  
Figure 2: (**A**). Five different lesion levels (lesion’s deepest level and two levels over and underneath, respectively): each level was measured every 30 \(\upmu\)m. (**B**). Lesion area of interest size is 3000\({}^{\circ}\)200 \(\upmu\)m\({}^{2}\) from outer to inner surface.