Fig. 3
(a) diagram of preoperational cross-sectional measurements; (b) An actual preoperational cross-sectional measurement, the area of OLF was 187.4 mm2, the area of canal was 233.3 mm2, and the invasive proportion was 80.33%; (c) diagram of postoperational cross-sectional measurements; (d) An actual postoperational cross-sectional measurement, the area of OLF was 14.7 mm2, the area of canal was 233.2 mm2, and the invasive proportion was 6.30%