The patient, a female, presented to the local hospital with pain in the right lower posterior tooth, and the oral panoramic examination revealed an obstructed right mandibular wisdom tooth recommended to be transferred for extraction. On examination: the crown of the right mandibular blocked tooth did not erupt. The right mandibular blocked tooth was horizontally and lowly blocked, and the right lower second molar was destroyed and resorbed by the distal mesial root. The right lower obstructed tooth was removed minimally invasively under local anesthesia using ultrasonic bone knife to remove the bone and cut the crown, and the right lower second molar was retained. Elective treatment of the lower right second molar was recommended. The patient’s stitches were removed at the 1-week follow-up and healed well with no adverse effects. Post-extraction dental radiographs of the lower right obstructive tooth: showed no residual tooth fragments, and the lower right second molar I loosened and was retained. In this case, the mandibular wisdom tooth caused compression and resorption of the root of the adjacent tooth, and the extraction was late. Conventional tooth extraction is prone to complications such as mandibular fracture and nerve injury. Minimally invasive extraction using ultrasonic bone knife can minimize the complications.