Ri, Song-Ung, Department of Ultrasonography, Hospital of Pyongyang University of Medical Science, Democratic People’s Republic of Korea. Ri, Un-Hui, Department of Ultrasonography, Hospital of Pyongyang University of Medical Science, Democratic People’s Republic of Korea. Ri, Won Chol , Agency for Testing of Biological Products, Food and Drug Administration, Ministry of Public Health, Democratic People’s Republic of Korea. Ri , Yon Hui , Okryu Children's Hospital Ri, Yong-Sil , Med. Dent Dentist, Department of Periodontal Disease, Rason Dental Hospital, Rason City, Democratic People’s Republic of Korea. Ri, Yongsu, Sinuiju University of Medical Sciences, Pynghwa Dong, Sinyuzu, North Phyongan province, Democratic People’s Republic of Korea. Ridha, Ameer Mohammed Rim, Ki Ho, a:1:{s:5:"en_US";s:40:"Pyongyang University of Medical Sciences";} Rim, Ki Ho, Department of Dental Caries and Oral Medicine Research, Faculty of Dentistry, Pyongyang University of Medical Sciences, Pyongyang, Democratic People’s Republic of Korea. Rim, Ki Ho, Department of Dental Caries and Oral Medicine Research, Pyongyang University of Medical Sciences, Pyongyang, Democratic People’s Republic of Korea Ro, Myong-Sung , Department of Dental Caries and Oral Medicine Research, Pyongyang University of Medical Sciences, Pyongyang, Democratic People’s Republic of Korea. Ryang, Ki-Hyon, Pyongyang University of Medical Science, Pyongyang, Democratic People’s Republic of Korea. Ryo, Pong Ae, Pyongyang University of Medical Sciences Ryo, Pong Ae, Pyongyang University of Medical Sciences, Pyongyang, Democratic People’s Republic of Korea. Ryong, Ryon-Hui , Pyongyang University of Medical Sciences