Effectiveness of a structured rubric-based assessment in preclinical crown preparation training: a randomized controlled trial

BACKGROUND: Crown preparation is a core but challenging skill for dental students, often assessed through subjective methods with limited reliability. Analytical rubrics provide a structured and transparent approach to teaching and evaluation. This study assessed the effectiveness of a rubric-based assessment system in preclinical crown preparation training. METHODS: A randomized controlled trial was conducted with 90 fourth-year undergraduate dental students who met predefined eligibility criteria (mean age: 22 ± 1.2 years). Participants were randomly allocated in a 1:1 ratio using a computer-generated sequence to a control group (n = 45) evaluated conventionally and a test group (n = 45) evaluated using a structured rubric. Both groups prepared an all-ceramic crown on tooth #21 following standard instruction. The primary outcome was the total crown preparation score. Assessments were performed independently by calibrated examiners at baseline and post-training; student blinding was not feasible. No adverse events were reported. Independent and paired t-tests with Bonferroni correction were applied, effect sizes calculated, and post hoc power analysis performed using a 95% confidence interval. Student perceptions were collected using a six-item Likert-scale questionnaire. RESULTS: Baseline comparisons had no significant differences (p = 1.0). At the end of training, the primary outcome show, test group demonstrated significantly higher scores across all parameters (all p < 0.001). Mean total score was 30.53 ± 4.99 in the test group versus 10.56 ± 4.34 in the control group (p < 0.001; Cohen's d = 4.21). Both groups improved significantly, with greater gains in the test group (22.91 ± 6.42 vs 2.93 ± 2.72). Post hoc power exceeded 0.99 for all outcomes. Student feedback was highly positive, with 95% affirming improved objectivity, self-reflection, and clarity of evaluation criteria. CONCLUSIONS: The use of an analytical rubric was associated with higher crown preparation assessment scores and positive student perceptions regarding clarity and objectivity of evaluation. These findings suggest that rubric-based assessment may support structured performance evaluation and learner understanding in preclinical prosthodontic training. TRIAL REGISTRATION: Not registered. This study evaluated an educational assessment intervention in a preclinical academic setting and did not involve patients or health-related clinical interventions as defined under ICMJE criteria.