OTOL1 and hearing loss disorder: This study examined the plasma concentration of prestin, a potential biomarker for outer hair cell (OHC) function and noise-induced hearing loss (NIHL)/sensorineural hearing loss (SNHL), and otolin-1, a biomarker for vestibular dysfunction, in first-year (D1) and third-year (D3) dental students exposed to high-frequency dental instrument sounds during their training in dental school.