Reference values of mechanical and thermal pain tests in a pain-free population

Quantitative sensory tests are widely used in human research to evaluate the effect of analgesics and explore altered pain mechanisms, such as central sensitization. In order to apply these tests in clinical practice, knowledge of reference values is essential. The aim of this study was to determine the reference values of pain thresholds for mechanical and thermal stimuli, as well as withdrawal time for the cold pressor test in 300 pain-free subjects. Pain detection and pain tolerance thresholds to pressure, heat and cold were determined at three body sites: (1) lower back, (2) suprascapular region and (3) second toe (for pressure) or the lateral aspect of the leg (for heat and cold). The influences of gender, age, height, weight, body-mass index (BMI), body side of testing, depression, anxiety, catastrophizing and parameters of Short-Form 36 (SF-36) were analyzed by multiple regressions. Quantile regressions were performed to define the 5th, 10th and 25th percentiles as reference values for pain hypersensitivity and the 75th, 90th and 95th percentiles as reference values for pain hyposensitivity. Gender, age and/or the interaction of age with gender were the only variables that consistently affected the pain measures. Women were more pain sensitive than men. However, the influence of gender decreased with increasing age. In conclusion, normative values of parameters related to pressure, heat and cold pain stimuli were determined. Reference values have to be stratified by body region, gender and age. The determination of these reference values will now allow the clinical application of the tests for detecting abnormal pain reactions in individual patients.

In vitro fracture strength and thermal shock resistance of metal-ceramic crowns with cast and machined AuTi frameworks

STATEMENT OF PROBLEM: AuTi alloys with 1.6% to 1.7% (wt%) Ti provide sufficient bond strength to veneering ceramics, but the strength of entire metal-ceramic restorations fabricated from these alloys is not known. However, this information is important to assess the clinical performance of such materials. PURPOSE: This in vitro study evaluated the fracture strength and thermal shock resistance of metal-ceramic crowns with AuTi frameworks produced by milling or casting. MATERIAL AND METHODS: Frameworks of the alloy Au-1.7Ti-0.1Ir (wt%) (Esteticor Vision) were produced by milling or casting (test groups). A high-gold alloy (Esteticor Special) was used as the control. The frameworks were veneered with ceramic (VMK 95). Specimens (n=7) were loaded until fracture. Loads at failure (N) were recorded and the mean values statistically evaluated using 1-way analysis of variance and a post hoc Dunnett test (alpha=.05). To assess the crazing resistance of the veneering ceramic, 6 additional crowns of each group were subjected to a thermal shock test. Fractured surfaces were documented by scanning electron microscopy. Coefficients of thermal expansion of the materials used were measured (n=2) to assess the thermal compatibility between alloys and ceramic. RESULTS: The mean fracture strength of the crowns with machined AuTi frameworks (1294 +/- 236 N) was significantly lower (P=.012) than that of the cast AuTi frameworks (1680 +/- 150 N), but statistically not different than the high-gold alloy (1449 +/- 159 N). Bonding failure to the AuTi alloy predominantly occurred at the alloy-oxide interface. For the high-gold alloy, more ceramic residues were observed. In the thermal shock test, crowns with milled AuTi frameworks showed significantly higher thermal shock resistance compared to the other groups. The coefficients of thermal expansion (Esteticor Vision cast: 14.5 microm/m.K; Esteticor Vision milled: 14.3 microm/m.K; Esteticor Special cast: 13.7 microm/m.K) did not correlate with the results of the thermal shock test. CONCLUSION: The in vitro fracture strength of crowns with milled AuTi frameworks is lower than that obtained with cast AuTi frameworks, but comparable to those crowns produced with a high-gold alloy.

Grain coarsening in contact metamorphic carbonates: effects of second-phase particles, fluid flow and thermal perturbations

Under contact metamorphic conditions, carbonate rocks in the direct vicinity of the Adamello pluton reflect a temperature-induced grain coarsening. Despite this large-scale trend, a considerable grain size scatter occurs on the outcrop-scale indicating local influence of second-order effects such as thermal perturbations, fluid flow and second-phase particles. Second-phase particles, whose sizes range from nano- to the micron-scale, induce the most pronounced data scatter resulting in grain sizes too small by up to a factor of 10, compared with theoretical grain growth in a pure system. Such values are restricted to relatively impure samples consisting of up to 10 vol.% micron-scale second-phase particles, or to samples containing a large number of nano-scale particles. The obtained data set suggests that the second phases induce a temperature-controlled reduction on calcite grain growth. The mean calcite grain size can therefore be expressed in the form D 1⁄4 C2 eQ*/RT(dp/fp)m*, where C2 is a constant, Q* is an activation energy, T the temperature and m* the exponent of the ratio dp/fp, i.e. of the average size of the second phases divided by their volume fraction. However, more data are needed to obtain reliable values for C2 and Q*. Besides variations in the average grain size, the presence of second-phase particles generates crystal size distribution (CSD) shapes characterized by lognormal distributions, which differ from the Gaussian-type distributions of the pure samples. In contrast, fluid-enhanced grain growth does not change the shape of the CSDs, but due to enhanced transport properties, the average grain sizes increase by a factor of 2 and the variance of the distribution increases. Stable d18O and d13C isotope ratios in fluid-affected zones only deviate slightly from the host rock values, suggesting low fluid/rock ratios. Grain growth modelling indicates that the fluid-induced grain size variations can develop within several ka. As inferred from a combination of thermal and grain growth modelling, dykes with widths of up to 1 m have only a restricted influence on grain size deviations smaller than a factor of 1.1.To summarize, considerable grain size variations of up to one order of magnitude can locally result from second-order effects. Such effects require special attention when comparing experimentally derived grain growth kinetics with field studies.

Vapor phase composition as an indicator of thermal stability of the Sm, Eu, and Yb chlorides

The Sm, Eu, and Yb tri- and dichlorides were investigated by Knudsen effusion mass spectrometry. It was found out by the analysis of mass spectra and ionization efficiency curves that the vapor composition is complex due to the partial high temperature decomposition/disproportionation of the samples. Up to five vapor species were identified for both LnCl3 (LnCl3, LnCl2, Ln2Cl4, Ln2Cl5, and Ln2Cl6) and LnCl2 (LnCl3, LnCl2, LnCl, Ln, and Ln2Cl4). The quantitative evaluation of vapor composition was made. It indicates that the disproportionation of SmCl2 and EuCl2 is negligible in the temperature range studied whereas that of YbCl2 and the decomposition of SmCl3 and YbCl3 cannot be neglected.