In the presence of contamination with saliva, use of bonding under the fissure sealant can reduce microleakage.

Background and Aim: With the advent of problem-based learning (PBL), pioneer universities across the world started using this method to improve learning quality. One of its modifications, hybrid-PBL, incorporates a combination of PBL and traditional teaching skills. This study compared the efficacy of hybrid PBL and the conventional instruction in terms of preclinical test scores and clinical procedural errors, representing dental students' knowledge and performance, respectively. Materials and Methods: This quasi-experimental study was conducted on 8 th (preclinical) and 9 th (clinical) semester dental students. Students at each educational level were randomly divided into two groups of conventional PBL and hybrid PBL using permuted block randomization. Students in group 1 received conventional PBL and those in group 2 received hybrid PBL for the preclinical course on endodontic diagnosis and treatment planning. Similarly, students who took the clinical course were divided into two groups, and received instructions on prevention of canal transportation and zipping. Both groups were compared at the end of the semester regarding level of knowledge and clinical performance of students in preclinical and clinical courses, respectively. The acquired scores were analyzed using independent t-test and the logistic regression analysis. Results: No significant difference was detected between the two learning methods regarding knowledge. The hybrid PBL caused a significant reduction in the frequency of transportation and zipping errors (P=0.0001). Conclusion: Hybrid PBL resulted in superior clinical performance with fewer transportation and zipping errors by dental students, while its effect was comparable to the conventional method on preclinical knowledge level of students.