Problem-based learning versus a traditional educational methodology: a comparison of preclinical and clinical periodontics performance

To evaluate efficacy of a problem-based learning (PBL) pedagogy in preclinical and clinical teaching, test scores of 234 undergraduate dental students from the conventionally taught classes of 2003 and 2004 were compared with scores of 274 dental students from the PBL classes of 2005 and 2006. Although the groups' means were close together, t-test analysis of scores revealed that PBL students performed significantly better than traditional (TRAD) students on midterm (p=.0001) and final (p=.015) examinations taken on student partner/mock patients. ANOVA comparing the classes with each other showed significant differences for the midterm and final, but not for the clinical examination. Further multiple comparison tests (Tukey HSD) for the midterm and final revealed that differences specifically reflected superior performance of PBL classes against one of the TRAD classes (2004). There was no difference in performance between PBL (n=134) and TRAD (n=233) students on examinations taken with actual clinical patients who were undergoing nonsurgical periodontal treatment. Over a two-year period, PBL students rated their program instructors at a mean of 4.41 on a Likert-type scale of 1 (not helpful) to 5 (outstanding). The program provides a PBL model for teaching preclinical and clinical skills supported by a four-year evaluation of manual skills outcomes.     

Multicentric peripheral ossifying fibroma

Peripheral ossifying fibroma (POF) is a common solitary gingival growth thought to arise from the periodontal ligament. Though the etiology of POF remains unknown, some investigators consider it an inflammatory or reactive process, while others suggest it is a neoplastic process. In this report, we present and discuss a unique case of multicentric POF, affecting the maxillary and mandibular gingiva of a 49-year-old Caucasian female with meticulous oral hygiene and routine dental care. Though biopsy samples from multiple sites revealed similar histopathologic features, consistent with POF, the fact that there was a multicentric presentation is a unique phenomenon for this lesion. Multicentric lesions presenting in the oral and maxillofacial region are not typical, but have been observed in conditions associated with known genetic mutations, such as nevoid basal cell carcinoma syndrome (multiple odontogenic keratocysts), multiple endocrine neoplasia type II (multiple neuromas), neurofibromatosis (multiple neurofibromas) and Gardner syndrome (multiple neoplasms). This case is the first one to demonstrate that there may be a multicentric variant of POF that has not been previously recognized, and given the clinical presentation and multifocal nature of disease, the lesions in this patient are likely the result of genetic mutation(s) that predisposes to gingival soft tissue overgrowths containing mineralized product.     

Synthesis and characterization of high-throughput nanofabricated poly(4-hydroxy styrene) membranes for in vitro models of barrier tissue

Commercially available permeable supports with microporous membranes have led to significant improvements in the culture of polarized cells because they permit them to feed basolaterally and thus carry out metabolism in a more in vivo-like setting. The porous nature of these membranes enables permeability measurements of drugs or biomolecules across the cellular barrier. However, current porous membranes have a high flow resistance due to great thickness (20-40?μm), low porosity, and a wide pore size distribution with tortuous diffusion paths, which make them low-throughput for permeability studies. Here we describe an alternate platform that is more flexible, allows for more control over physical parameters of the membranes, and is high-throughput. This study reports on the synthesis, nanofabrication, and surface characterization of a 3-μm-thick transparent membrane based on poly(4-hydroxy styrene) (PHOST). The membranes are nanofabricated using electron beam lithography and deep ion plasma etching to achieve an organized array of straight pores from 50 to 800?nm in diameter, with at least 23 times less flow resistance. It also shows for the first time the potential utility of PHOST as a cell culture substrate without cytotoxicity, and suitability for nanofabrication processes due to temperature stability.     

PBL core skills faculty development workshop 1: An experiential exercise with the PBL process

This report describes the first in a series of foundation-building faculty development workshops focused on the instructional methodology of problem-based learning (PBL). The PBL Process workshop reported here introduced the learning theory topics supporting PBL and utilized an extended roleplay method to provide participants with personal experience with the PBL learning cycle. Overall, participants were satisfied with the methods and content of the workshop. A majority of survey respondents indicated that simulating a complete iteration of the PBL process was an effective way to learn about PBL. Participants expressed relatively greater difficulty understanding and performing activities related to qualitative assessment of learning processes. The workshop was developed to align with adult learning principles, and continued refinement of the workshop has enhanced the learning theory components underpinning PBL as well as the experiential aspects. These dual goals have resulted in blending the existing experiential workshop with an online distance-learning component addressing the learning theory topics relevant to PBL pedagogy.     

Keratin 19 downregulation by oral squamous cell carcinoma lines increases invasive potential.

Squamous cell carcinoma (SCC) of the head and neck is the sixth most frequent cancer worldwide. The survival rate is among the lowest of the major cancers and has not improved significantly in the past two decades. Extensive local invasion and regional lymph node metastasis are, in large part, responsible for the poor clinical outcome of these tumors. Keratin intermediate filaments are the most abundant cytoskeletal proteins in SCCs and regulate the migration of normal and transformed epithelial cells. Previous studies have shown that expression of the 40-kDa keratin K19 is dysregulated in SCCs arising from oral epithelium. Immunohistochemical experiments demonstrated that, while normal epithelium and dysplastic lesions expressed abundant K19 protein, invasive SCCs exhibited a patchy or negative staining pattern. We subsequently determined that K19 expression was consistently downregulated in seven SCC lines compared with normal epithelium. We therefore wanted to determine if K19 downregulation affected the invasive phenotype of these cells. We found that SCC lines which do not express K19 are significantly more invasive in vitro than those which retain expression of this gene. Stable expression of the K19 cDNA in K19 negative cell lines altered cell morphology and intercellular adhesiveness, and significantly decreased the number of cells able to migrate through a reconstituted basement membrane. Reduced invasiveness was not due to decreased metalloproteinase activity in the K19-expressing clones. We conclude that K19 overexpression in oral SCCs decreases their invasive potential by diminishing migratory capability.