Effect of plaque-disclosing agents on biofilm removal: single-center randomized trial in fourth-year dental students

To assess whether plaque-disclosing agents (PDA) improve self-performed mechanical plaque removal and gingival health compared with standard instruction alone in dental students. Single-center, parallel-group randomized controlled trial (1:1), Istanbul Medipol University (Oct 2023–Jan 2024). 124 fourth-year dental students (age 20–30 years) randomized to test (n = 62) or control (n = 62). Both groups received standardized oral-hygiene instruction (Modified Bass; interdental cleaning guidance). The test group additionally received PDA before brushing as a visual aid; all outcomes were measured after triple rinsing. Between-group difference in change (Δ) in Plaque Index (PI) from baseline to week 1. ΔPI baseline→post-brushing and baseline→month 1; ΔGingival Index (GI) baseline→week 1 and baseline→month 1. Outcome assessor blinded at the time of measurement (after rinsing). All 124 randomized participants completed follow-up and were analyzed. Both groups showed short-term improvement (immediate reduction in PI post-brushing; GI improvement at week 1). The primary outcome showed no significant between-group difference in ΔPI from baseline to week 1. Secondary analyses similarly found no significant between-group differences in ΔPI or ΔGI at month 1. In a population with high baseline oral-hygiene proficiency, adding PDA did not confer a measurable advantage over standardized instruction alone on PI or GI change. PDA may be more informative in lay populations with lower oral-health literacy. ClinicalTrials.gov, NCT06080672, registered on October 12, 2023.