Perioperative gum-chewing training prevents a decrease in tongue pressure after esophagectomy in thoracic esophageal cancer patients: a nonrandomized trial oleh Reiko Yamanaka-Kohno, Yasuhiro Shirakawa, Aya Yokoi, Naoaki Maeda, Shunsuke Tanabe, Kazuhiro Noma, Kazuyoshi Shimizu, Toshiharu Mituhashi, Yoshihide Nakamura, Souto Nanba, Yurika Uchida, Takayuki Maruyama, Manabu Morita, Daisuke Ekuni