# Root Canal Obturation by Electrochemical Precipitation of Calcium Phosphates
## 3 Results
### Oburation of Root Canals  
The volume available in the root canal cannot bear such an amount of precursor solution which is sufficient for root canal obturation. This resulted in the need for repeatedly applying precursor solution following precipitation and removal of fluids. Brushite initially precipitate at the surface of the BDD electrodes (Figure 9) but continuing treatment leads to deposition of biomaterial in the canal lumen (Figure 10). Characterization of these brushite depots by SEM revealed a close connection to the wall of the root canal and sealing of dentin tubules (Figure 11).  
Figure 8: Precipitate analysis via RAMAN spectroscopy. All sample data were background corrected using Crystal Sleuth software provided by the RRUFF Project [45]. Raman scans of brushite taken from the RRUFF Database (black line, RRUFF ID: R070554), positive sample (petrol, Carl Roth GmbH & Co. KG, Karlsruhe, Germany), precipitates at 6 V (blue), 8 V (green), 9 V (brown), 10 V (purple), 11 V (deep blue), 12 V (orange), 14 V (pale blue), 15 V (red) and 16 V (deep purple). Vertical red lines show matching peaks with database sample and positive sample. Experiments were carried out in triplicate and typical spectra are shown.  
Figure 10: Apical and coronal microscopic views of root canals from extracted human teeth following BDD-mediated obturation.  
Figure 9: Precipitation of brushite by a BDD electrode. Initial deposition of CaP at the cathode surface. (**a**) Cathode of the “wound-wire electrode” covered in precipitate. Please note that the anode is free of precipitate. (**b**) SEM micrograph of precipitate formed after a few seconds of current applied. Parameters are shown in the box at the bottom. ETD: Everhart-Thornley detector.  
With brushite being an electron-dense material, obturation of root canals can be verified radiographically. When sealing quality was monitored by X-ray and \(\upmu\)CT scans, for endodontic training blocks and extracted human teeth, BDD-mediated root canal obturation was visible in conventional with both methods (Figures 12 and 13). In addition, \(\upmu\)CT scans revealed maximal distance below 100 \(\upmu\)m between precipitate and canal wall (Figure 12).  
Figure 11: SEM image of tooth split in half after CaP obturation. The tooth was dried at 65 \({}^{\circ}\)C for 48 h prior to SEM imaging. Loose crystals were removed using compressed air. (**a**) Filled root canal; (**b**) crystals attaching to the root canals sealing the dentin tubules (left: crystals at the root canal surface; right: cross section of the dentin tubules). BSDE: back-scatter detector.  
Figure 12: Determination of the sealing quality in root canals. (**a**) X-ray images; (**b**) \(\upmu\)CT images of obturated root canals.  
Figure 13: Determination of the sealing quality in endo training blocks. (**a**) X-ray images; (**b**) \(\upmu\)CT images of obturated endo training blocks.  
For analysis of porosity, tomographic reconstruction of acquired \(\mu\)CT data and further data processing was carried out with the software X-AID (Figure 14). A total of 15 values were evaluated over a range of 3 mm for each sample (\(n=3\)). For the precipitated material, an overall porosity of 11.27% with a standard deviation of \(\pm\)7.47% was obtained.