First case was 32 years old male. He has bilateral otitis media, and underwent Rt intact canal wall mastoidectomy and tympanoplasty at 2 years ago.8 months ago,he underwent Lt intact canal wall mastoidectomy and tympanoplasty.But after Lt ear operation, his left hearing ability slowly deteriorated.Before Lt Bonebridge implantation,his pure tone average was 30dB at Rt and scale out at Lt.Because he underwent mastoidectomy, we implanted Bonebridge via retrosigmoid approach. During operation, his bone thickness was below 8.7 mm. So we exposed dura and used 4mm sized lift.After 6 weeks Bone bridge switched on,and he showed hearing improvement. Second case was 55 years old female.She has also bilateral otitis media,and underwent Lt canal wall down mastoidectomy and tympanoplasty at 15 years ago.Before Lt Bonebridge implantation, her pure tone average was 70dB at Rt and 80 dB at Lt. and air bone gap was 60dB at both. We perfomed Lt Bonebridge implantation and Rt canal wall up mastoidectomy and tympanoplasty.During operation, her bone thickness was below 8.7 mm. So we exposed dura and used 3mm sized lift. After 6 weeks Bone bridge switched on,and she showed hearing improvements.