Rethinking Dental School Admission Criteria: Correlation Between Pre-Admission Variables and First-Year Performance for Six Classes at One Dental School.

Admissions committees in dental schools are charged with the responsibility of selecting candidates who will succeed in school and become successful members of the profession. Identifying students who will have academic difficulty is challenging. The aim of this study was to determine the predictive value of pre-admission variables for the first-year performance of six classes at one U.S. dental school. The authors hypothesized that the variables undergraduate grade point average (GPA), undergraduate science GPA (biology, chemistry, and physics), and Dental Admission Test (DAT) scores would predict the level of performance achieved in the first year of dental school, measured by year-end GPA. Data were collected in 2015 from school records for all 297 students in the six cohorts who completed the first year (Classes of 2007 through 2013). In the results, statistically significant correlations existed between all pre-admission variables and first-year GPA, but the associations were only weak to moderate. Lower performing students at the end of the first year (lowest 10% of GPA) had, on average, lower pre-admission variables than the other students, but the differences were small (≤10.8% in all categories). When all the pre-admission variables were considered together in a multiple regression analysis, a significant association was found between pre-admission variables and first-year GPA, but the association was weak (adjusted R2=0.238). This weak association suggests that these students' first-year dental school GPAs were mostly determined by factors other than the pre-admission variables studied and has resulted in the school's placing greater emphasis on other factors for admission decisions.

The gross anatomy laboratory: a novel venue for critical thinking and interdisciplinary teaching in dental education.

Reports on the status of dental education have concluded that there is a need for various types of curricular reform, making recommendations that include better integration of basic, behavioral, and clinical sciences, increased case-based teaching, emphasis on student-driven learning, and creation of lifelong learners. Dental schools faced with decreasing contact hours, increasing teaching material, and technological advancements have experimented with alternate curricular strategies. At Southern Illinois University School of Dental Medicine, curricular changes have begun with a series of integrated biomedical sciences courses. During the process of planning and implementing the integrated courses, a novel venue-the gross anatomy laboratory-was used to introduce all Year 1 students to critical thinking, self-directed learning, and the scientific method. The venture included student-driven documentation of anatomical variations encountered in the laboratory using robust scientific methods, thorough literature review, and subsequent presentation of findings in peer review settings. Students responded positively, with over 75% agreeing the experience intellectually challenged them. This article describes the process of re-envisioning the gross anatomy laboratory as an effective venue for small group-based, student-driven projects that focus on key pedagogical concepts to encourage the development of lifelong learners.

Localized increases in corticotropin-releasing factor receptors in pulp after dental injury.

Corticotropin-releasing factor (CRF) binds to membrane-bound CRF receptors (CRF-Rs). Among the actions mediated by activated CRF-Rs is beta-endorphin (END) release from immune cells, increasing peripheral antinociception. For assessment of inflammatory regulation of CRF-R expression, rats underwent pulp exposure of left, first mandibular molars and recovered for 6 days. Control pulpal tissue consisted of contralateral, uninjured molars and left, first mandibular molars of uninjured animals. Pulp tissue specimens were incubated with antibodies directed against CRF-R (both isoforms), neurofilament, CD45, and END. We observed (1) increases in pulp CRF-R immunoreactivity after injury, (2) increased CRF-R immunoreactivity expressed in 3 distinct zones in relation to the injury, and (3) increased CD45 and END immunoreactivity in regions surrounding the pulpal abscess. CRF-Rs might provide an additional target for novel analgesics to treat pulpal pain.

Kv1.4 subunit expression is decreased in neurons of painful human pulp.

Kv1.4, a subunit of voltage-gated K(+) channels, plays a large role in regulating neuronal excitability. The level of Kv1.4 expression is unknown in human sensory neurons innervating healthy or painful tissue. Therefore, we examined Kv1.4 immunoreactivity in axons innervating both clinically diagnosed asymptomatic and painful symptomatic human tooth pulp. Antibodies directed against Kv1.4 and PGP9.5, a protein marker for axons, was used to determine the proportion of PGP9.5 immunopositive tissue that was also immunopositive for Kv1.4. We report that on pulpal axons innervating symptomatic teeth Kv1.4 immunoreactivity, a correlate of decreased Kv1.4 expression, is significantly decreased (p < 0.0001), suggestive of a factor responsible for facilitating chronic dental pain and decreases in currents produced, such as I(A), in neurons innervating painful pulp.

Expression of Nav1.9 channels in human dental pulp and trigeminal ganglion.

There is a higher incidence of local anesthetic failure in endodontic patients experiencing pulpal hyperalgesia. Up-regulation of Nav1.9, a voltage-gated sodium channel isoform, might play a key role in local anesthetic failure because Nav1.9 channels increase neuronal excitability and have low sensitivity to blockade by local anesthetics. Immunocytochemistry was used to examine Nav1.9 channel expression in axons of symptomatic (painful) versus asymptomatic human dental pulp and to determine Nav1.9 expression levels in neuronal somata of the human trigeminal ganglion. Nav1.9 channel immunoreactivity on pulpal axons was significantly increased in painful teeth. Nav1.9 channels were expressed in membranes and cytoplasm of human trigeminal ganglion neurons, with the highest expression in small neuronal somata. Nav1.9 expression in the trigeminal ganglion coupled with increased expression in symptomatic pulp might contribute to hypersensitivity of inflamed pulps and local anesthetic failure. Furthermore, the present study suggests that Nav1.9 channels are potential targets for novel anesthetics.

Development of gerbil medial superior olive: integration of temporally delayed excitation and inhibition at physiological temperature.

The sensitivity of medial superior olive (MSO) neurons to tens of microsecond differences in interaural temporal delay (ITD) derives in part from their membrane electrical characteristics, kinetics and timing of excitatory and inhibitory inputs, and dendrite structure. However, maturation of these physiological and structural characteristics are little studied, especially in relationship to the onset of auditory experience. We showed, using brain slices at physiological temperature, that MSO neurons exhibited sensitivity to simulated temporally delayed (TD) EPSCs (simEPSC), injected through the recording electrode, by the initial phase of hearing onset at P10, and TD sensitivity was reduced by block of low threshold potassium channels. The spike generation mechanism matured between P10 and P16 to support TD sensitivity to adult-like excitatory stimuli (1-4 ms duration) by P14. IPSP duration was shorter at physiological temperature than reported for lower temperatures, was longer than EPSP duration at young ages, but approached the duration of EPSPs by P16, when hearing thresholds neared maturity. Dendrite branching became less complex over a more restricted time frame between P10 and P12. Because many physiological and structural properties approximated mature values between P14 and P16, we studied temporal integration of simEPSCs and IPSPs at P15. Only a narrow range of relative onset times (< 1 ms) yielded responses showing sensitivity to TD. We propose that shaping of excitatory circuitry to mediate TD sensitivity can begin before airborne sound is detectable, and that inhibitory inputs having suboptimal neural delays may then be pruned by cellular mechanisms activated by sensitivity to ITD.

TRPM2 immunoreactivity is increased in fibroblasts, but not nerves, of symptomatic human dental pulp.

Transient receptor potential (TRP) channels function in diverse processes such as acting as second messenger systems, regulating of ionic concentrations, and aiding in thermoception. TRPM2 channels, members of the melastatin subfamily, mediate calcium influx in response to oxidative stress but during pathological states facilitate hyperexcitability and cellular necrosis via calcium excitotoxicity. We hypothesized that TRPM2 channel expression is upregulated in pulpal tissue of symptomatic teeth with signs of irreversible pulpitis. TRPM2 channel expression was significantly increased in pulp from clinically diagnosed symptomatic teeth compared with pulp from asymptomatic teeth. Additionally, increased TRPM2 expression in symptomatic pulp was the result of increased immunoreactivity in fibroblasts, whereas neural expression of TRPM2 was absent. We provide a possible mechanism explaining the association between TRPM2 channel expression with pain and necrosis. We suggest that TRPM2 channel antagonists could be administered in attempts to inhibit the progression of or even reverse pulpal degradation.

Optimizing synaptic architecture and efficiency for high-frequency transmission.

Bursts of neuronal activity are transmitted more effectively as synapses mature. However, the mechanisms that control synaptic efficiency during development are poorly understood. Here, we study postnatal changes in synaptic ultrastructure and exocytosis in a calyx-type nerve terminal. Vesicle pool size, exocytotic efficiency (amount of exocytosis per Ca influx), Ca current facilitation, and the number of active zones (AZs) increased with age, whereas AZ area, number of docked vesicles per AZ, and release probability decreased with age. These changes led to AZs that are less prone to multivesicular release, resulting in reduced AMPA receptor saturation and desensitization. A greater multiplicity of small AZs with few docked vesicles, a larger pool of releasable vesicles, and a higher efficiency of release thus promote prolonged high-frequency firing in mature synapses.