All-ceramic crown preparations: An alternative technique

BACKGROUND

The aim of this study was to compare the crown preparation dimensions produced from two different techniques of preparation for posterior all-ceramic crowns.

METHODS

Twenty-four fourth year dental students undertook a course of advanced simulation training involving education in an alternative technique of preparation for a 36 all-ceramic crown. Crown preparations performed using the traditional technique were compared with an alternative technique for total occlusal convergence (TOC) and reduction difference (RD) using digital scanning and comparative software.

RESULTS

Groups that spent the most time performing the alternative technique produced crown preparations with significantly lower buccolingual (BL) TOC. The training resulted in crown preparations that were closer to ideal TOC and RD measurements.

CONCLUSIONS

The alternative technique of crown preparation for a posterior all-ceramic crown showed initial promise in creating a less buccolingually tapered and more ideally occlusally reduced crown preparation.

Structure-based design of 3-carboxy-substituted 1,2,3,4-tetrahydroquinolines as inhibitors of myeloid cell leukemia-1 (Mcl-1)

A novel Mcl-1 inhibitor chemotype based on a tetrahydroquinoline carboxylic acid was developed utilizing structure-based design, which was subsequently validated by a fluorescence polarization competition assay and HSQC NMR analysis.

Prevalence and severity of asthmatic symptoms in Grenadian school children: the Grenada National Asthma Survey

OBJECTIVE

The goal of this study was to determine the prevalence of asthma in school children in the tri-island Caribbean nation of Grenada.

SETTING, PARTICIPANTS AND OUTCOMES

This was a self-report study provided to the guardians of all primary school children between ages 6 and 7 throughout Grenada, Carriacou and Petite Martinique in 2013. Of the 2362 surveys provided, 1374 were returned, resulting in a response rate of 58.2%. Only responders listing birthdays between 1 January 2006 and 31 December 2007 were included in the analysis, resulting in 1165 qualifying responders. Asthma diagnosis was based on previous physician diagnosed asthma and/or self-reported presence of wheeze in the past 12 months (current wheeze). Severity of asthma, medication usage, environmental exposures, physician and emergency department visits were compared among respondents.

RESULTS

The prevalence of wheezing in the past year was 30.5±1.8%, and of these 68.4% were previously diagnosed with asthma. Of the current wheeze participants, 39.9±9.2% reported moderate to severe asthma symptoms and increased exposure to cigarette smoke, excessive dust, burning brush and landfills. Carriacou and Petite Martinique, the two smaller islands, had a lower incidence of current wheeze (14.1±7.7%) and exposure rates to cigarette smoke and burning brush as compared to the larger, denser island of Grenada. Although 65.7% of respondents diagnosed with asthma reported taking medication, the number of annual doctor and emergency department visits were high (2.82 and 0.86, respectively). Respondents with the most severe asthma symptoms reported the most emergency department visits with an average of 1.05 visits annually, whereas respondents with moderate asthma symptoms had the most doctor visits with an average of 3.33 visits annually.

CONCLUSIONS

This study indicates that the prevalence of childhood asthma in Grenada is very high and warrants policy consideration in public health and education to decrease its morbidity.

Bupivacaine-induced cellular entry of QX-314 and its contribution to differential nerve block

BACKGROUND AND PURPOSE

Selective nociceptor fibre block is achieved by introducing the cell membrane impermeant sodium channel blocker lidocaine N-ethyl bromide (QX-314) through transient receptor potential V1 (TRPV1) channels into nociceptors. We screened local anaesthetics for their capacity to activate TRP channels, and characterized the nerve block obtained by combination with QX-314.

EXPERIMENTAL APPROACH

We investigated TRP channel activation in dorsal root ganglion (DRG) neurons by calcium imaging and patch-clamp recordings, and cellular QX-314 uptake by MS. To characterize nerve block, compound action potential (CAP) recordings from isolated nerves and behavioural responses were analysed.

KEY RESULTS

Of the 12 compounds tested, bupivacaine was the most potent activator of ruthenium red-sensitive calcium entry in DRG neurons and activated heterologously expressed TRPA1 channels. QX-314 permeated through TRPA1 channels and accumulated intracellularly after activation of these channels. Upon sciatic injections, QX-314 markedly prolonged bupivacaine's nociceptive block and also extended (to a lesser degree) its motor block. Bupivacaine's blockade of C-, but not A-fibre, CAPs in sciatic nerves was extended by co-application of QX-314. Surprisingly, however, this action was the same in wild-type, TRPA1-knockout and TRPV1/TRPA1-double knockout mice, suggesting a TRP-channel independent entry pathway. Consistent with this, high doses of bupivacaine promoted a non-selective, cellular uptake of QX-314.

CONCLUSIONS AND IMPLICATIONS

Bupivacaine, combined with QX-314, produced a long-lasting sensory nerve block. This did not require QX-314 permeation through TRPA1, although bupivacaine activated these channels. Regardless of entry pathway, the greatly extended duration of block produced by QX-314 and bupivacaine may be clinically useful.

Cytokine expression and accelerated tooth movement

It has been shown that inhibiting the expression of certain cytokines decreases the rate of tooth movement. Here, we hypothesized that stimulating the expression of inflammatory cytokines, through small perforations of cortical bone, increases the rate of bone remodeling and tooth movement. Forty-eight rats were divided into 4 groups: 50-cN force applied to the maxillary first molar (O), force application plus soft tissue flap (OF), force application plus flap plus 3 small perforations of the cortical plate (OFP), and a control group (C). From the 92 cytokines studied, the expression of 37 cytokines increased significantly in all experimental groups, with 21 cytokines showing the highest levels in the OFP group. After 28 days, micro-computed tomography, light and fluorescent microscopy, and immunohistochemistry demonstrated higher numbers of osteoclasts and bone remodeling activity in the OFP group, accompanied by generalized osteoporosity and increased rate of tooth movement.

Regional pattern of white matter microstructural changes in normal aging, MCI, and AD

OBJECTIVE

To cross-sectionally compare the regional white matter fractional anisotropy (FA) of cognitively normal (CN) older individuals and patients with mild cognitive impairment (MCI) and Alzheimer disease (AD), separately focusing on the normal-appearing white matter (NAWM) and white matter hyperintensities (WMH), and to test the independent effects of presumed degenerative and vascular process on FA differences.

METHODS

Forty-seven patients with AD, 73 patients with MCI, and 95 CN subjects received diffusion tensor imaging and vascular risk evaluation. To properly control normal regional variability of FA, we divided cerebral white matter into 4 strata as measured from a series of young healthy individuals (H1 = highest; H2 = intermediate high; H3 = intermediate low; H4 = lowest anisotropy stratum).

RESULTS

For overall cerebral white matter, patients with AD had significantly lower FA than CN individuals or patients with MCI in the regions with higher baseline anisotropy (H1, H2, and H3), corresponding to long corticocortical association fibers, but not in H4, which mostly includes heterogeneously oriented fibers. Vascular risk showed significant independent effects on FA in all strata except H1, which corresponds to the genu and splenium of the corpus callosum. Similar results were found within NAWM. FA in WMH was significantly lower than NAWM across all strata but was not associated with diagnosis or vascular risk.

CONCLUSIONS

Both vascular and Alzheimer disease degenerative process contribute to microstructural injury of cerebral white matter across the spectrum of cognitive ability and have different region-specific injury patterns.

Randomized clinical trial to determine the effect of nasogastric drainage on tracheal acid aspiration following oesophagectomy

BACKGROUND

The aim of this study was to investigate tracheal acid aspiration after oesophagectomy and to determine whether it is influenced by nasogastric (NG) drainage.

METHODS

Thirty-four patients undergoing oesophagectomy were randomized to one of three methods of NG drainage: a single-lumen tube with free drainage and 4-hourly aspiration, a sump-type tube on continuous suction drainage, or no NG tube. A tracheal pH probe was used to collect information on acid aspiration for 48 h after surgery. A pH < 5.5 was considered abnormal (normal pH 6.8-7.2). Total time with tracheal pH < 5.5, number of reflux episodes and longest reflux time were compared between groups.

RESULTS

There was significant and persistent tracheal acid aspiration in all patients. Patients with a sump-type tube had a significantly shorter total time with tracheal pH < 5.5 than those in the other groups (sump-type tube versus single-lumen tube, P = 0.0069; sump-type tube versus no tube, P = 0.0071). Patients randomized to no NG tube experienced more respiratory complications after surgery than those who had either single-lumen or sump-type tubes (seven of 12 versus four of 22 patients; P = 0.023). Insertion of a NG tube was necessary in the first week after surgery in seven of 12 patients in this group.

CONCLUSION

Routine NG drainage after oesophagectomy is necessary. A sump-type NG tube is better at preventing tracheal acid aspiration and may reduce the incidence of respiratory complications.

Possible mechanisms of acquired resistance to anti-angiogenic drugs: implications for the use of combination therapy approaches

The ultimate target of anti-angiogenic drugs is the genetically stable, activated endothelial cell of a newly forming tumor blood vessel, rather than the genetically unstable tumor cell population per se. This led to the notion that acquired resistance to such drugs may not develop as readily, if at all. While there is some evidence that this lack of resistance development may be the case for some direct-acting angiogenesis inhibitors, it is becoming apparent that resistance can develop over time to many types of angiogenesis inhibitors including, possibly, some direct inhibitors, especially when used as monotherapies. Possible mechanisms for such acquired or induced resistance include: (i) redundancy of pro-angiogenic growth factors when the drug used targets a single such growth factor or its cognate endothelial cell-associated receptor tyrosine kinase; (ii) the anti-apoptotic/pro-survival function of growth factors such as VEGF, which, in high local concentrations, can antagonize the pro-apoptotic effects of various angiogenesis inhibitors; (iii) epigenetic, transient upregulation, or induction, of various anti-apoptotic effector molecules in host-endothelial cells; and (iv) heterogeneous vascular dependence of tumor cell populations. It is suggested that long-term disease control with anti-angiogenic drugs can be best achieved by judicious combination therapy. In this regard, the great molecular diversity of anti-angiogenic drug targets, in contrast to chemotherapy, makes this a particularly attractive therapeutic option, especially when approved, commercially available drugs considered to have anti-angiogenic effects are used in such combination treatment strategies.