Browsing by Subject "Hot Temperature"
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Item Antibacterial efficacy of 0.12-percent and 2.0-percent chlorhexidine gluconate at 37˚C and 46˚C against enterococcus faecalis(2010) Thiessen, Craig B.D., 1978-; Vail, Mychel Macapagal, 1969-; Spolnik, Kenneth Jacob, 1950-; Zunt, Susan L., 1951-; Gregory, Richard L.; Legan, Joseph J.The purpose of this study was to investigate the antibacterial efficacy of 0.12-percent and 2.0-percent chlorhexidine gluconate (CHX) on eliminating Enterococcus faecalis from dentinal tubules, and whether this antibacterial effect was enhanced by heat. To date there have been no published articles that describe the heating of 2.0-percent CHX and its antimicrobial efficacy and clinical relevance towards E. faecalis within dentinal tubules in root canal systems. Ninety-five human extracted, single rooted, maxillary, anterior teeth were used to prepare dentin disk specimens. After proper sterilization, a 2.5-mm ISO-sized diameter lumen was prepared, and then the canals were filled with brain-heart infusion (BHI) broth infected with E. faecalis. The BHI was removed and the specimens in equally divided groups were rinsed with sterile saline and filled with saline, or 0.12 percent CHX or 2.0 percent CHX at ambient temperature (24°C) or experimental temperature (46°C) and incubated at oral temperature (37°C) or the experimental temperature (46°C), respectively. The specimens were frozen to -70˚C and pulverized in liquid nitrogen. Serial dilutions were prepared of 1:100 and 1:1000 and spiral plated on BHI agar plates in duplicate. They were incubated, and the number of bacterial colonies was recorded 24 hours later for data analysis. A two-way analysis of variance (ANOVA), with factors for solution, solution temperature, and the solution-by-temperature interaction was used to determine antibacterial efficacy. Pair-wise comparisons between groups were examined for significance using the Fisher’s Protected Least Significant Differences Method. The E. faecalis CFU were log-transformed to satisfy the assumptions required for the ANOVA. The results of this investigation demonstrated no statistically significant difference with the addition of heat to either test irrigation solution regarding the elimination of E. faecalis from dentinal tubules within the root canal system. There was a statistically significant difference in the antibacterial efficacy of CHX against E. faecalis in comparison with the concentration tested. A higher concentration of 2.0-percent CHX demonstrated a significantly higher antibacterial efficacy against E. faecalis compared with 0.12-percent CHX, and likewise with the saline control. It can be concluded that the use of a higher concentration of 2.0-percent CHX is advantageous as a final irrigation solution after copious amounts of NaOCl and EDTA have been utilized for effective antimicrobial efficacy and substantivity.Item The Effect of Thermocycling on the Failure Load of a Standard Orthodontic Resin in Shear-Peel, Tension, and Torsion(2006) Bunch, Jason Keith; Katona, Thomas R.; Baldwin, James J.; Hohlt, William F.; Moore, B. Keith; Shanks, James C.New products are frequently developed for bonding brackets. This continuum brings about incessant studies attempting to prove or disprove their value. The need to compare the results of bond failure studies is made difficult if not impossible by the variation of published testing methods. The purpose of this study is to compare the differential effects of thermocycling, as a lab protocol, on three debonding techniques, shear-peel, tension, and torsion when using a traditional orthodontic resin adhesive. A standard orthodontic resin, Transbond™ XT (3M Unitek, Monrovia, CA) was used to bond 102 flattened 0.018-inch stainless steel brackets (3M Unitek) to flattened bovine incisors. Two step acid etching and priming (37 % phosphoric acid gel and Transbond MIP Primer, 3M Unitek) was used to prepare the enamel for bonding. During bonding, the resin thickness was held consistent. The bonding was accomplished under controlled temperature and humidity. Half of the samples were thermocycled prior to debonding. The samples were debonded in shear-peel, tension, and torsion. The data showed no significant differences between thermocycling and nonthermocycling in shear-peel or torsion, but in tension the thermocycling group had a statistically significant higher failure load. Overall, was a trend toward increased bond strength in the thermocycled group. The increase is likely the result of continued polymerization during thermocycling. The statistical difference that is noted in tension is thought to be due to the location of the highest stress being in the center of the resin pad. This would be the location of the least initial polymerization. The use of thermocycling as a lab protocol during bracket failure studies in shear-peel and torsion is not necessary when using traditional orthodontic resin.Item The heat released during catalytic turnover enhances the diffusion of an enzyme(Nature Publishing Group, 2015-01-08) Riedel, Clement; Gabizon, Ronen; Wilson, Christian A. M.; Hamadani, Kambiz; Tsekouras, Konstantinos; Marqusee, Susan; Pressé, Steve; Bustamante, Carlos; Department of Cellular & Integrative Physiology, IU School of MedicineRecent studies have shown that the diffusivity of enzymes increases in a substrate-dependent manner during catalysis,. Although this observation has been reported and characterized for several different systems–, the precise origin of this phenomenon is unknown. Calorimetric methods are often used to determine enthalpies from enzyme-catalysed reactions and can therefore provide important insight into their reaction mechanisms,. The ensemble averages involved in traditional bulk calorimetry cannot probe the transient effects that the energy exchanged in a reaction may have on the catalyst. Here we obtain single-molecule fluorescence correlation spectroscopy data and analyse them within the framework of a stochastic theory to demonstrate a mechanistic link between the enhanced diffusion of a single enzyme molecule and the heat released in the reaction. We propose that the heat released during catalysis generates an asymmetric pressure wave that results in a differential stress at the protein–solvent interface that transiently displaces the centre-of-mass of the enzyme (chemoacoustic effect). This novel perspective on how enzymes respond to the energy released during catalysis suggests a possible effect of the heat of reaction on the structural integrity and internal degrees of freedom of the enzyme.Item Optimal Time and Temperature for Maximum Moment and Springback and Residual Stress Relief of Stainless Steel Wire(1970) Marcotte, Michael R.Stainless steel wire, Type 304, was tested using three measurements to indicate the best time and temperature for optimal spring properties. The measurements used were springback2 -springback1, relaxation-springback1, and maximum-moment values. It appears that the degree of improvement and stress relief obtained is time and temperature sensitive. Low temperature stress relieving appear to be of definite benefit and it certainly compliments what is known about sensitization phenomena. There was no uniform increase in springback as the temperature was increased. Springback and stress relief appear to be maximum at relatively low temperatures (650° to 750°F.) for 11 minutes. This research was done to help define some of the capacities of orthodontic materials. In the future, we must understand failure mechanisms with more accuracy and define mechanical properties, as they affect orthodontic appliances, with more meaningful tests and specifications.Item Reliability of pain intensity clamping using response-dependent thermal stimulation in healthy volunteers(Springer (Biomed Central Ltd.), 2015) Cruz-Almeida, Yenisel; Naugle, Kelly M.; Vierck, Charles J.; Fillingim, Roger B.; Riley, Joseph L.; Department of Kinesiology, School of Physical Education and Tourism ManagementBACKGROUND: Pain intensity clamping uses the REsponse-Dependent Stimulation (REDSTIM) methodology to automatically adjust stimulus intensity to maintain a desired pain rating set-point which is continuously monitored from a subject's real-time pain ratings. REDSTIM blinds subjects regarding the pain intensity set-point, supporting its use for assessing intervention efficacy. By maintaining the pain intensity at a constant level, a potential decrease in pain sensitivity can be detected by an increase in thermode temperature (unknown to the subject) and not by pain ratings alone. Further, previously described sensitizing and desensitizing trends within REDSTIM provide a novel insight into human pain mechanisms overcoming limitations of conventional testing methods. The purpose of the present study was to assess the test-retest reliability of pain intensity clamping using REDSTIM during three separate sessions. METHODS: We used a method for testing changes in pain sensitivity of human subjects (REDSTIM) where the stimulus temperature is modulated to clamp pain intensity near a desired set-point. Temperature serves as the response variable and is used to infer pain sensitivity. Several measures were analyzed for reliability including average temperature and area under the curve (AUC). Intraclass correlation coefficients were calculated for each measure at pain rating set-points of 20/100 and 35/100. RESULTS: Sixteen healthy individuals (mean age = 21.6 ± 3.9) participated in three experiments two days apart at both pain rating set-points. Most reliability coefficients were in the moderate to substantial range (r's = 0.79 to 0.94) except for the negative AUC (r = 0.52), but only at the 20/100 pain rating set-point. CONCLUSIONS: The present study supports the test-retest reliability of pain intensity clamping using the REDSTIM methodology while providing a novel tool to examine human pain modulatory mechanisms and overcoming common shortcomings of conventional quantitative sensory testing methods.Item The Role of Semidisorder in Temperature Adaptation of Bacterial FlgM Proteins(Elsevier B.V., 2013-12-03) Wang, Jihua; Yang, Yuedong; Cao, Zanxia; Li, Zhixiu; Zhao, Huiying; Zhou, Yaoqi; Department of Biochemistry & Molecular Biology, IU School of MedicineProbabilities of disorder for FlgM proteins of 39 species whose optimal growth temperature ranges from 273 K (0°C) to 368 K (95°C) were predicted by a newly developed method called Sequence-based Prediction with Integrated NEural networks for Disorder (SPINE-D). We showed that the temperature-dependent behavior of FlgM proteins could be separated into two subgroups according to their sequence lengths. Only shorter sequences evolved to adapt to high temperatures (>318 K or 45°C). Their ability to adapt to high temperatures was achieved through a transition from a fully disordered state with little secondary structure to a semidisordered state with high predicted helical probability at the N-terminal region. The predicted results are consistent with available experimental data. An analysis of all orthologous protein families in 39 species suggests that such a transition from a fully disordered state to semidisordered and/or ordered states is one of the strategies employed by nature for adaptation to high temperatures.