1病例报告患者男,20岁。因右上后牙经常有食物嵌塞,致牙龈肿痛,要求拔除。无拔牙禁忌证。查体:右上第2前磨牙位于牙列舌侧,无咬,其远中与第1磨牙近中舌尖紧密贴合,颊面与第1前磨牙舌面有0·5 mm间隙,有食物纤维嵌塞其中,其余牙咬良好。X线片提示牙根自根中1/2向近中弯曲,至根尖 1 case report patient male, 20 years old. Due to the upper right posterior teeth often have food impaction, causing swollen gums, requiring removal. No tooth extraction contraindications. Physical examination: The second upper right premolar was located on the lingual side of the dentition. There was no bite. The distance between the first premolar and the first molar was close to the middle tongue, the gap between the buccal surface and the first premolar was 0.5 mm, Among them, the remaining teeth bite well. X-ray tips root from the root 1/2 to the proximal bending, to the apical