The “Root Removal First” strategy was applied in the NM group
tooth
PAD, SEPARATION, CREST
① Incision design: A longitudinal gingival incision was made from the mesio-buccal side of the M2, and an angular incision was made along the gingival margin to the retromolar pad. The mucoperiosteal flap was then raised buccally, and the buccal and occlusal aspects of the alveolar bone of the IMTM was exposed (Fig. The extraction of 38 according to the “Root removal first” strategy. ② Bone window creation: A bony window was then created to expose the IMTM by piezosurgery. In order to preserve at least 5 mm height of the buccal alveolar crest of M2, the main part of the bony window could only be made in the distal part of M2 using piezosurgery. The cervical region and part of the roots of IMTM would then be automatically exposed. Nevertheless, the main part of the crown was yet to be revealed. Subsequently, an extended micro bony window was made buccally to expose part of the crown of IMTM. (Fig. ③ Impacted tooth separation: The buccal and lingual bulbosities of the crown were both exposed. Similar to the tooth preparation for prosthetic crown, the circumference of the root was reduced by the fissure bur. IMTM was sectioned from the root with a fissure bur from the top to the bottom. The cutting line was at 45°-60° with the long axis of the tooth and the groove’s width was about 3 mm (Fig. ④ Root removal: The elevator was placed in the created gutter and the roots were elevated upward (Fig. ⑤ Crown removal: After the root was removed, an elevator was placed in the created groove of the mesio-buccal micro bony window. The crown was luxated distally by rotating the elevator. If necessary, the crown can be sectioned again, and the segments can be removed in pieces (Fig. ⑥ Wound care: The residual dental follicle and debris was removed completely(Fig. 