Background: Dental plaque accumulation remains the primary aetiological factor in dental caries and periodontal disease among adolescents, and conventional one-time oral hygiene instruction has shown limited success in producing sustained behaviour change in this age group.

Objective: To evaluate the effect of a motivational interviewing-based oral health education program on plaque index scores and self-reported oral hygiene behaviour among adolescent dental patients.

Method: This study uses simulated academic training data designed to resemble a prospective, single-group, pre-post interventional design. A hypothetical cohort of 70 adolescent patients aged 13 to 17 years attending an outpatient dental clinic received a structured four-session motivational interviewing-based oral health education program over four weeks. Plaque accumulation was assessed using the Silness-Loe Plaque Index, and oral hygiene behaviour was assessed using a structured self-report questionnaire, both administered before and after the intervention.

Results: Simulated analysis demonstrated a mean reduction in Plaque Index score from 1.84 to 0.96, and a mean increase in self-reported twice-daily brushing frequency from 38.6% to 71.4% of participants, with both changes statistically significant (p < 0.001).