Fig. 1. Schematic of the endoscopic swept OCT root canal imaging system. (a) Diagram of the system structure; (b) data processing flow

Fig. 2. Schematic of endoscope probe light guide structure

Fig. 3. Experimental adjustment device

Fig. 4. Schematic of the relative position and angle adjustment between the probe and the root sections. (a) Change relative position; (b) change the relative angle

Fig. 5. Representation of the root fractures on the OCT images. (a) “Bright line”; (b) “dark line”; (c) shadows between the two “bright lines”

Fig. 6. Comparison of histological features and OCT scanning images of root section samples. (a)(b) Samples without fractures; (c)(d) samples without fractures being misdiognosed; (e)(f) samples with two fractures

Fig. 7. OCT scanning image when the inner wall of the root canal is a regular circle (width of root fractures larger than 30 μm). (a) Stereo microscope gold standard image; (b) contrast image of position adjustment of OCT probe, (b1) before adjustment, (b2) after adjustment

Fig. 8. OCT scanning images when the inner wall of the root canal is a long flat oval (width of root fractures less than 30 μm). (a) Stereo microscope gold standard image; (b1)-(b3) contrast images of position adjustment of OCT probe

Fig. 9. OCT scanning images when the inner wall of root canal is an irregular shape (width of root fractures less than 30 μm). (a) Stereo microscope gold standard image; (b) contrast images of position adjustment of OCT probe

Fig. 10. Three-dimensional model images of the root canal. (a) Cross-sectional image; (b) root canal wall image

Fig. 11. OCT scanning two-dimensional images before and after 10° rotation. (a) Before rotation; (b) after rotation