1. School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan
2. Division of Prosthodontics, Department of Dentistry, Taipei Medical University Hospital, Taipei 110, Taiwan
3. School of Dental Technology, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan
4. Department of Otolaryngology, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Kaohsiung 833, Taiwan