Search

Connective tissue growth factor (CCN2) has been associated with the pathogenesis of various fibrotic diseases, including oral submucous fibrosis (OSF). The chemical constituents of areca nut along with the mechanical trauma cause OSF. The coarse fibers of areca nut injure the mucosa and hence sphingosine-1-phosphate (S1P) is released at the wounded sites. Recent studies have shown that S1P is involved in wound healing and the development of fibrosis. The aims of this study were to investigate the effects of S1P on CCN2 expression in human buccal fibroblasts (HBFs) and identify the potential targets for drug intervention or chemoprevention of OSF. Methods: Western blot analyses were used to study the effects of S1P on CCN2 expression and its signaling pathways in HBFs and whether epigallocatechin-3-gallate (EGCG), the main and most significant polyphenol in green tea, could inhibit this pathway. Results: S1P significantly enhanced CCN2 synthesis in HBFs. This effect can be inhibited by c-Jun NH2-terminal kinase (JNK) inhibitor and extracellular signal-regulated kinase inhibitor but not by P38 mitogen-activated protein kinase inhibitor. Interestingly, EGCG completely blocked S1P-induced CCN2 expression via suppressing S1P-induced JNK phosphorylation. Conclusion: S1P released by repetitive mechanical trauma during AN chewing may contribute to the pathogenesis of OSF through upregulating CCN2 expression in HBFs. EGCG could be an adjuvant to the current offered therapy options or the prevention of OSF through suppression of JNK activation.

Background/purpose: Recently, dental education has put emphasis on the assessment of clinical competencies using an objective structured clinical examination (OSCE). The purpose of this study was to assess several clinical competencies required for dental graduates by having dental students and residents of different levels take the same set of OSCEs. Materials and methods: Twelve 5th-grade dental students (D5), 12 dental interns (Ri), and 12 1st-year dental residents (R1) were recruited to take the same set of OSCEs composed of six stations: Station 1, explanation of a treatment plan for restoration of a missing tooth; Station 2, taking a study cast impression with alginate; Station 3, explanation of a treatment plan for restoration of an inlay; Station 4, explanation to a mother for taking a radiograph of her child's tooth; Station 5, placement of a rubber dam on a designated tooth and Station 6, explanation of pulpitis diagnosis and treatment. The examinee's performance was graded using both global rating and checklist scores. Results: There were significant differences in the mean global rating and checklist scores of Stations 3, 5, and 6 among the three groups. In Stations 3 and 5, Ri performed best, followed by R1 and D5. In Station 6, R1 performed best, followed by Ri and D5. In Stations 1, 2, and 4, there were no significant differences among the three groups. However, Ri performed better than R1 in Station 1. Conclusion: More emphasis should be placed on professional communication skills in the resident training program.

Background/purpose: In order to evaluate properly the effect of different geometric designs of mini-implants on their mechanical behavior, finite element analysis (FEA) has long been a popular tool. The aim of the present study was to set up a standardized mechanical experiment to validate the effectiveness and accuracy of FEA. Materials and methods: Three commercially available mini-implants, Mondeal, Osstem, and Bio-Ray were inserted into artificial bone block with homogeneous density to remove the variability associated with bone. FEA and mechanical tests were performed. Results: For the bending test, a 7.57% error was found between the mechanical test and FEA. For relative and maximum displacements, results from FEA were compatible with those from mechanical tests. The results of the relative displacement from FEA (Mondeal > Osstem > Bioray) were consistent with those from mechanical tests that Mondeal provided the greatest mean displacement before failure, followed by Osstem and BioRay. Furthermore, after simulating a 2-mm cortical bone layer in the FEA test, the pullout resistance increased for all three mini-implants, yet the variations in between decreased dramatically. Conclusion: By incorporating FEA with real mechanical trial experiments, results from FEA have been validated and proved to be effective in studying the stress and strain distribution of mini-implants subjected to loading. FEA helps to evaluate how geometrical designs of mini-screws affect their clinical performance and may be useful in future improvement of screw designs. Based on our results, we have found that in clinical situations, the cortical bone layer plays an important role in the stability of the mini-implants.