Layering techniques for direct composite resin restorations might be complicated for inexperienced learners, as a number of materials and instruments are required at each step. The present study aimed to compare and assess the teaching effect of step-by-step and all-in-one teaching methods in layering techniques for direct composite resin restorations among undergraduate dental students.

A total of 68 junior dental students participated in this study, which was a prospective and single-blind trial. The students were randomly divided into a step-by-step group (experimental group, n  = 34) and all-in-one group (control group, n  = 34). The same teacher taught the two groups, ensuring a comparable teaching effect. The final score of each student was an average of scores by two experts who were blinded to the grouping. The scoring system was consisted by five parts. Each part was assigned scores of 3.0, 1.5, or 0. The total maximum score was 15 and minimum was 0. The total time taken by each group was also calculated.

The values of the quality of tooth restorations evaluated by experts for step-by-step and all-in-one groups were 11.29 ± 2.13 from 15 and 9.00 ± 2.71 from 15 (t = 3.88, P  < 0.001), respectively. In addition, the time spent by the experimental group was significantly lesser than that spent by the control group, which was 122.47 ± 2.82 and 137.18 ± 6.75 min, respectively (t = 11.72, p  < 0.001).

With regard to the layering techniques for direct composite resin restorations, the outcomes were better in the step-by-step group than in the all-in-one group.