Objective: to analyze the perceptions of undergraduate dental students of the level of difficulty and applicability of conventional dental impressions and to determine the percentage rate as well as the causes of failure of dental impressions . Methods and population:115 (fifth year students' pairs) and 50(Interns) were recruited to participate to this exhaustive cross-sectional study . All data were collected through a questionnaire and analyzed using Chi2 test and Student's t test .Results: Both interns and fifth year students had faced difficulties during dental impressions making (p=0.07). It was judged as a difficult stage by 58% of them. These difficulties were mainly related to the used impression materials (84.85%), to the patient (69%) and also to the lack of experience (49%). 461 dental impressions were re-made (289 because of inaccurate marginal detail, bubbles, tears, drags and pulls . Conclusion: Dental impression taking was considered as a difficult procedure regardless of the level of students because of the important failure rate specially when using C-silicon.