Do tutor expertise and experience influence student performance in a problem-based curriculum?

The purpose of this study was to evaluate the association between student performance and tutor expertise and experience in the Restorative Treatment course in a problem-based learning (PBL) dental curriculum. This retrospective study evaluated a cohort of 206 third-year dental students at Harvard School of Dental Medicine who were enrolled in the Restorative Treatment course between 2000 and 2005. Tutor expertise in prosthodontics and prior tutoring experience were measured against student performance in five areas: 1) tutorial session, 2) midterm examination, 3) final examination, 4) preclinical laboratory, and 5) overall cumulative course grade. Student performance in each of the five areas measured against combinations of tutor subject matter expertise and tutoring experience level showed no statistically significant difference between the groups in the overall course grade. However, student performance in the expert group showed a significant difference in the final examination compared to the nonexpert group (p<0.05). Also, students in the group consisting of expert tutors with no experience performed better on the final examination compared to those students who had expert tutors with experience (p<0.05). The results indicate that overall student performance in the problem-based Restorative Treatment course is not affected by tutor expertise or prior tutoring experience.

Invasion of human tissue ex vivo by Borrelia burgdorferi.

Borrelia burgdorferi sensu stricto is an etiological agent of Lyme disease. The lack of an adequate ex vivo system for human tissue infection is an obstacle to fully understanding the molecular mechanisms of invasion of tissue by B. burgdorferi and its adaptation within the human host. Here, we report on the development of such a system. We inoculated blocks of human tonsillar tissue with B. burgdorferi spirochetes, cultured them in a low-shear rotating wall vessel (RWV) bioreactor, and analyzed them using light and electron microscopy, nested polymerase chain reaction (PCR), and quantitative real-time PCR. Also, we evaluated the expression of the outer surface proteins (Osps) OspA and OspC by use of quantitative Western blotting. Light and electron microscopic analysis revealed multiple spirochetes localized extracellularly within the tissue, and their identity was confirmed by PCR. Quantification of spirochetes inside the RWV-cultured tonsillar tissue demonstrated that the number of B. burgdorferi exceeded the initial inoculum by an order of magnitude, indicating that spirochetes replicated in the tissue. Electron microscopic analysis showed that some spirochetes were arranged in cystic structures and that invading spirochetes differentially expressed surface proteins; both of these features have been described for infected tissues in vivo. The system we have developed can be used to study B. burgdorferi pathogenesis under controlled conditions ex vivo, in particular to explore the gene activation responsible for the adaptation of B. burgdorferi to human tissue that leads to Lyme disease.