Shear bond strength comparison of implant-retained overdenture attachment pickup materials.

This study evaluated the shear bond strength (SBS) of 4 different retentive materials for the chairside pickup of dental implant attachments. Shear force was applied to determine the SBS of each material to denture acrylic resin. The difference between SBSs of polymethyl methacrylate and UBAR (claimed to bond to metal) to metal housings was also evaluated. There were no statistically significant differences among the SBSs of Jet Denture Repair Acrylic, EZ PickUp, and UBAR, but Quick Up had an SBS that was significantly lower than that of the other 3 materials. In addition, UBAR had a higher SBS to metal housings than did processed polymethyl methacrylate.

Bis-GMA affects craniofacial development in zebrafish embryos (Danio rerio).

Estrogen is a steroid hormone that is vital in vertebrate development and plays a role in a variety of developmental processes including cartilage and craniofacial formation. The effects of estrogen can be mimicked by other compounds found in the environment known as xenoestrogens. Bisphenol-A (BPA) is a known xenoestrogen and is combined with glycidyl methacrylate to make Bisphenol A glycidyl methacrylate (Bis-GMA), a major component in dental resin based composites (RBCs). Bis-GMA based RBCs can release their components into the saliva and bloodstream. Exposure to 1µM and 10µM Bis-GMA in Danio rerio embryos results in increased mortality of approximately 30% and 45% respectively. Changes to gross morphology, specifically craniofacial abnormalities, were seen at concentrations as low as 10nM. While the molecular pathways of Bis-GMA effects have not been studied extensively, more is known about one of the components, BPA. Further research of Bis-GMA could lead to a better understanding of xenoestrogenic activity resulting in improved public and environmental health.

Utilizing self-assessment software to evaluate student wax-ups in dental morphology.

Traditionally, evaluating student work in preclinical courses has relied on the judgment of experienced clinicians utilizing visual inspection. However, research has shown significant disagreement between different evaluators (interrater reliability) and between results from the same evaluator at different times (intrarater reliability). This study evaluated a new experimental software (E4D Compare) to compare 66 student-produced tooth wax-ups at one U.S. dental school to an ideal standard after both had been digitally scanned. Using 3D surface-mapping technology, a numerical evaluation was generated by calculating the surface area of the student's work that was within a set range of the ideal. The aims of the study were to compare the reliability of faculty and software grades and to determine the ideal tolerance value for the software. The investigators hypothesized that the software would provide more consistent feedback than visual grading and that a tolerance value could be determined that closely correlated with the faculty grade. The results showed that a tolerance level of 450 µm provided 96% agreement of grades compared with only 53% agreement for faculty. The results suggest that this software could be used by faculty members as a mechanism to evaluate student work and for students to use as a self-assessment tool.

Dental students' opinions of preparation assessment with E4D compare software versus traditional methods.

The aim of this study was to evaluate dental students' opinions regarding the utilization of a new grading software program for student self-assessment and a faculty-grading tool in a preclinical course. Using surface mapping technology, this program, called E4D Compare, yields a digital model of a student's preparation that is color-coded to show deficient areas. The program has now been used for two years at the James B. Edwards College of Dental Medicine at the Medical University of South Carolina, and the students previously assessed with E4D Compare have now entered into the dental clinics. For this study, students were asked to complete an anonymous survey for the investigators to evaluate students' attitudes and opinions on the effectiveness of this software in their preclinical courses to determine if this type of feedback helped them develop clinical skills. The survey also sought to collect students' opinions on the traditional objective criteria-based grading system. The survey was distributed to all members of the Classes of 2014 and 2015; it yielded a 59 percent response rate for the two classes, with a total of eighty-one students responding. Overall, the majority of students preferred the E4D Compare grading system over traditional hand-grading methods. The grading system provided instant, objective, and visual feedback that allowed students to easily see where their deficiencies were and encouraged them to work towards an ideal final product.

Regulation of extracellular glutamate in the prefrontal cortex: focus on the cystine glutamate exchanger and group I metabotropic glutamate receptors.

Microdialysis was used to determine the in vivo processes contributing to extracellular glutamate levels in the prefrontal cortex of rats. Reverse dialysis of a variety of compounds proved unable to decrease basal levels of extracellular glutamate, including Na+ and Ca2+ channel blockers, cystine/glutamate exchange (x(c)-) antagonists, and group I (mGluR1/5) and group II (mGluR2/3) metabotropic glutamate receptor (mGluR) agonists or antagonists. In contrast, extracellular glutamate was elevated by blocking Na+-dependent glutamate uptake (X(AG)-) with DL-threo-beta-benzyloxyaspartate (TBOA) and stimulating group I mGluRs with (R,S)-3,5-dihydroxy-phenylglycine (DHPG). The accumulation of extracellular glutamate produced by blocking X(AG)- was completely reversed by inhibiting system x(c)- with 4-carboxyphenylglycine (CPG), but not by Na+ and Ca2+ channel blockers. Because CPG also inhibits group I mGluRs, two additional group I antagonists were examined, LY367385 [(+)-2-methyl-4-carboxyphenylglycine] and (R,S)-1-aminoindan-1,5-dicarboxylic acid (AIDA). Whereas LY367385 also reduced TBOA-induced increases in extracellular glutamate, AIDA did not. In contrast, all three group I antagonists reversed the increase in extracellular glutamate elicited by stimulating mGluR1/5. In vitro evaluation revealed that similar to CPG, LY367385 inhibited x(c)- and that stimulating or inhibiting mGluR1/5 did not directly affect [3H]glutamate uptake via x(c)- or X(AG)-. These experiments reveal that although inhibiting x(c)- cannot reduce basal extracellular glutamate in the prefrontal cortex, the accumulation of extracellular glutamate after blockade of X(AG)- arises predominately from x(c)-. The accumulation of glutamate elicited by mGluR1/5 stimulation does not seem to result from modulating X(AG)-, x(c)-, or synaptic glutamate release.