Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 5 3 2008 09 15 111 114 N. Sargolzaee Associate Professor, Department of Periodontics, School of Dentistry, Mashhad University of Medical HR. Arab Associate Professor, Department of Periodontics, School of Dentistry, Mashhad University of Medical A. Moeintaghavi Associate Professor, Department of Periodontics, School of Dentistry, Mashhad University of Medical M. Radvar Associate Professor, Department of Periodontics, School of Dentistry, Mashhad University of Medical 2015 10 03 Objective: The aim of this study was to investigate the existence of human T-lymphotropic virus type 1 (HTLV-1) in subgingival plaque of HTLV-1 seropositive pa-tients. Materials and Methods: A total of 18 patients including 13 females and fivemales, with a mean age of 37 years participated in this descriptive study. Half of them were HTLV-1 carriers and the others were in HTLV-1 associated myelopathy tropical spastic paraparesia (HAM/TSP) stage.Subgingival dental plaque samples were taken using sterile paper points and examined to detect HTLV-1 using polymerase chain reaction (PCR). Results: None of the carrier stage patients revealed HTLV-1 virus, while only one patient in the HAM/TSP group was found with the virus. Conclusion: This study showed that the existence of HTLV-1 virus in subgingival plaque of patients suffering from HTLV-1 in carrier and HAM/TSP stages with healthy periodon-tium is rare. Studies with larger samples are recommended. https://fid.tums.ac.ir/index.php/fid/article/view/157 https://fid.tums.ac.ir/index.php/fid/article/download/157/157