Hotspot shelters stimulate frog resistance to chytridiomycosis.

Many threats to biodiversity cannot be eliminated; for example, invasive pathogens may be ubiquitous. Chytridiomycosis is a fungal disease that has spread worldwide, driving at least 90 amphibian species to extinction, and severely affecting hundreds of others1-4. Once the disease spreads to a new environment, it is likely to become a permanent part of that ecosystem. To enable coexistence with chytridiomycosis in the field, we devised an intervention that exploits host defences and pathogen vulnerabilities. Here we show that sunlight-heated artificial refugia attract endangered frogs and enable body temperatures high enough to clear infections, and that having recovered in this way, frogs are subsequently resistant to chytridiomycosis even under cool conditions that are optimal for fungal growth. Our results provide a simple, inexpensive and widely applicable strategy to buffer frogs against chytridiomycosis in nature. The refugia are immediately useful for the endangered species we tested and will have broader utility for amphibian species with similar ecologies. Furthermore, our concept could be applied to other wildlife diseases in which differences in host and pathogen physiologies can be exploited. The refugia are made from cheap and readily available materials and therefore could be rapidly adopted by wildlife managers and the public. In summary, habitat protection alone cannot protect species that are affected by invasive diseases, but simple manipulations to microhabitat structure could spell the difference between the extinction and the persistence of endangered amphibians.

Assessment of incident power density in different shapes of averaging area for radio-frequency exposure above 6 GHz.

Objective.The International Commission on Non-Ionizing Radiation Protection guidelines and IEEE C95.1-2019 standard for human protection from local electromagnetic field exposure above 6 GHz state that absorbed (or epithelial) power density (APD) and incident power density (IPD), averaged over a square area, are internal and external physical quantities, respectively, that set the exposure limit. Per exposure standards, the measurement procedure and evaluation of the IPD have been established in technical standards, where a circular averaging area is recommended only for non-planar surfaces in IEC/IEEE 63195-1 and -2. In this study, the effects of two averaging shapes on the APD and IPD are evaluated computationally to provide new insights from the viewpoint of exposure standards.Approach. The relation between the APD, IPD, and the steady-state temperature rise (heating factor) in rectangular and human models for exposure to a single dipole, dipole arrays, and the Gaussian beams is investigated computationally with finite-difference method.Main results. The maximum differences in the heating factor of the APD and IPD for square and circular averaging areas were 4.1% and 4.4% for the antenna-model distance >5 mm, respectively. These differences appear when the beam pattern on the model surface has an elliptical shape. For an antenna-model distance ≤5 mm and at frequencies ≤15 GHz, the heating factors for square averaging areas were not always conservative to those for circular ones (-7.8% for IPD), where only the antenna feed point are visible before beam formation.Significance. The heating factors of the APD and IPD for a circular averaging area are conservative for near-field exposure of canonical sources for frequencies up to 300 GHz, except for a beam with a significant major-to-minor axis ratio and an angle of 30°-60° to a square averaging area. This tendency would help bridge the gap between exposure and product standards.

Association between Rhythmic Variations of Mouse Body Temperature with 4-16-Minute Periods and Geomagnetic Undulations in Corresponding Frequency Range Pc5/Pi3.

The rhythmic variations of body temperature in two groups of mice located in Moscow and Novosibirsk were compared with geomagnetic undulations within Pc5/Pi3 (1-5 mHz) range measured in Borok and Novosibirsk middle-latitude geophysical observatories located at the same longitudes as the examined mice. The spectral maxima of geomagnetic undulations and body temperature variations were observed with greatest probability at the frequencies of 1.6, 2.3, and 3.1 mHz. At this, the mean square of the distance between the frequencies of spectral maxima of simultaneous oscillations was smaller than that of random intervals favoring the hypothesis on geomagnetic undulations as the synchronizer of biorhythms. In both groups of mice, the share of intervals with a high spectral coherency between geomagnetic undulations and body temperature variations had common maximum in the pre-midnight sector of local time and it was higher for the large-scale geomagnetic undulations. Dependence of geomagnetic undulations on spatial scale suggests that body temperature is affected by electrotelluric field.

Temperature Measurements of the Semicircular Canal During Green Laser Irradiation of the Canal: A Preliminary Study.

BACKGROUND: Laser irradiation of the semicircular canal (SCC) is a good treatment for intractable benign paroxysmal positional vertigo. However, there were few reports on the temperature changes during laser irradiation. OBJECTIVE: To measure the internal temperature of the SCC and vestibule during green laser irradiation of the SCC and investigate morphologic changes using human temporal bones. METHODS: After the lateral SCC was blue-lined, a thermocouple was inserted into the SCC through a hole made in the canal wall. Another thermocouple was inserted into the vestibule through the oval window. Green laser was irradiated to the lateral canal wall. After the irradiation, the tissues were inspected as paraffin using HE staining. RESULT: The internal temperature of the SCC rose from 33 ° to 52 °C by a single laser irradiation of 1.5 W × 2 seconds and 82 °C by a single laser irradiation of 1.7 W × 3 seconds to the canal wall with a black spot. Continuous laser irradiation of 1.5 W × 3 seconds, 10 times resulted in a temperature rise of 92 °C from 33 °C. Throughout the whole experiments, temperatures within the vestibule were unchanged. Histopathology showed that the irradiated areas of the lateral canal wall were partially deficient with or without carbonization after single irradiation. By continuous laser irradiations, the SCC bony wall showed a peroration of 40 µm in diameter with carbonized edges. CONCLUSIONS: Green laser irradiation of the SCC produced char formation with perforation in the canal wall. High temperatures within the SCC were recorded for a short period of less than 30 seconds. However, the vestibule didn't show temperature changes.

Assessment of absorbed power density and temperature rise for nonplanar body model under electromagnetic exposure above 6 GHz.

The averaged absorbed power density (APD) and temperature rise in body models with nonplanar surfaces were computed for electromagnetic exposure above 6 GHz. Different calculation schemes for the averaged APD were investigated. Additionally, a novel compensation method for correcting the heat convection rate on the air/skin interface in voxel human models was proposed and validated. The compensation method can be easily incorporated into bioheat calculations and does not require information regarding the normal direction of the boundary voxels, in contrast to a previously proposed method. The APD and temperature rise were evaluated using models of a two-dimensional cylinder and a three-dimensional partial forearm. The heating factor, which was defined as the ratio of the temperature rise to the APD, was calculated using different APD averaging schemes. Our computational results revealed different frequency and curvature dependences. For body models with curvature radii of >30 mm and at frequencies of >20 GHz, the differences in the heating factors among the APD schemes were small.

Effect of non-thermal radiofrequency on body temperature in mice.

Communication technologies based on radiofrequency (RF) propagation bring great benefits to our daily life. However, their rapid expansion raises concerns about possible impacts on public health. At intensity levels below the threshold to produce thermal effects, RF exposure has also recently been reported to elicit biological effects, resembling reactions to cold. The objective of the present study was to investigate the effects of non-thermal RF on body temperature in mice and the related mechanisms. 3-months-old C57BL/6 J mice were exposed to a continuous RF signal at 900 MHz, 20 ± 5 V.m-1 for 7 consecutive days, twice per day during the light phase, for one hour each time. The SAR was 0.16 ± 0.10 W.kg-1. We showed that body temperature patterns in mice change synchronously with the RF exposure periods. Average body temperature in the light phase in the exposed group was higher than in the control group. The expression of the TRPM8 gene was not affected by RF in trigeminal ganglia. Furthermore, the injection of a TRPM8 antagonist did not induce a temperature decrease in exposed mice, as this was the case for sham-controls. These findings indicate that 900 MHz RF exposure at non-thermal level produce a physiological effect on body temperature in mice. However, the involvement of TRPM8 receptors in the mechanism by which RF induced changes in body temperature of mice which remains to be further explored. It must then be assessed if this effect is extrapolable to man, and if this could lead to consequences on health.

Exposure to chronic light-dark phase shifts during the prepartum nonlactating period attenuates circadian rhythms, decreases blood glucose, and increases milk yield in the subsequent lactation.

Maintaining metabolic balance is a key factor in the health of dairy cattle during the transition from pregnancy to lactation. Little is known regarding the role of the circadian timing system in the regulation of physiological changes during the transition period. We hypothesized that disruption of the cow's circadian timing system by exposure to chronic light-dark phase shifts during the prepartum period would negatively affect the regulation of homeostasis and cause metabolic disturbances, leading to reduced milk production in the subsequent lactation. The objective was to determine the effect of exposure to chronic light-dark phase shift during the last 5 wk prepartum of the nonlactating dry period on core body temperature, melatonin, blood glucose, ß-hydroxybutyric acid (BHB) and nonesterified fatty acid (NEFA) concentrations, and milk production. Multiparous cows were moved to tiestalls at 5 wk before expected calving and assigned to control (CTR; n = 16) or phase-shifted (PS; n = 16) treatments. Control cows were exposed to 16 h of light and 8 h of dark. Phase-shifted cows were exposed to the same photoperiod; however, the light-dark cycle was shifted 6 h every 3 d until parturition. Resting behavior and feed intake were recorded daily. Core body temperature was recorded vaginally for 48 h at 23 and 9 d before expected calving using calibrated data loggers. Blood concentrations of melatonin, glucose, BHB, and NEFA were measured during the pre- and postpartum periods. Milk yield and composition were measured through 60 DIM. Treatment did not affect feed intake or body condition. Cosine fit analysis of 24-h core body temperature and circulating melatonin indicated attenuation of circadian rhythms in the PS treatment compared with the CTR treatment. Phase-shifted cows had lower rest consolidation, as indicated by more total resting time, but shorter resting period durations. Phase-shifted cows had lower blood glucose concentration compared with CTR cows (4 mg/mL decrease), but BHB and NEFA concentrations were similar between PS and CTR cows. Milk yield and milk fat yield were greater in PS compared with CTR cows (2.8 kg/d increase). Thus, exposure to chronic light-dark phase shifts during the prepartum period attenuated circadian rhythms of core body temperature, melatonin, and rest-activity behavior and was associated with increased milk fat and milk yield in the postpartum period despite decreased blood glucose pre- and postpartum. Therefore, less variation in central circadian rhythms may create a more constant milieu that supports the onset of lactogenesis.

Melatonin alleviates circadian system disruption induced by chronic shifts of the light-dark cycle in Octodon degus.

Modern 24-h society lifestyle is associated with experiencing frequent shifts in the lighting conditions which can negatively impact human health. Here, we use the degus, a species exhibiting diurnal and nocturnal chronotypes, to: (a) assess the impact of chronic shifts of the light:dark (LD) cycle in the animal's physiology and behaviour and (b) test the therapeutic potential of melatonin in enhancing rhythmicity under these conditions. Degus were subjected to a "5d + 2d" LD-shifting schedule for 19 weeks. This protocol aims to mimic lighting conditions experienced by humans during shift work: LD cycle was weekly delayed by 8h during 5 "working" days (Morning, Afternoon and Night schedule); during weekends (2 days), animals were kept under Morning schedule. After 9 weeks, melatonin was provided daily for 6h in the drinking water. The "5d + 2d" shifting LD schedule led to a disruption in wheel-running activity (WRA) and body temperature (Tb) rhythms which manifested up to three separate periods in the circadian range. This chronodisruption was more evident in nocturnal than in diurnal degus, particularly during the Afternoon schedule when a phase misalignment between WRA and Tb rhythms appeared. Melatonin treatment and, to a lesser extent, water restriction enhanced the 24-h component, suggesting a potential role in ameliorating the disruptive effects of shift work.

Ultradian Rhythms of Body Temperatures in Male Wistar Rats Maintained under Conditions of Constant Illumination.

We studied the dynamics of the body temperature in mature male Wistar rats maintained under condition of constant illumination. It was shown that body temperature under these conditions varied with a 3-5-h period. The daily dynamics of body temperature summed up over 20-23-day intervals showed a 4-h ultradian rhythm with maxima at 3.35-4.30, 7.35-8.30, 11.35-12.30, 15.35-16.30, 19.35-20.30, and 23.35-00.30 h. During these hours, pronounced (>0.9°C) increase in body temperature was observed by 1.6 times more often than in other eriods. Thus, there are periods during the day when the increase in body temperature in rats in the absence of light cues occurs more often than in other periods of the day. Hence, about 4-h ultradian rhythm of body temperature has an external synchronizer that differs from lighting conditions.

Circadian Responses to Fragmented Light: Research Synopsis in Humans.

Light is the chief signal used by the human circadian pacemaker to maintain precise biological timekeeping. Though it has been historically assumed that light resets the pacemaker's rhythm in a dose-dependent fashion, a number of studies report enhanced circadian photosensitivity to the initial moments of light exposure, such that there are quickly diminishing returns on phase-shifting the longer the light is shown. In the current review, we summarize findings from a family of experiments conducted over two decades in the research wing of the Brigham and Women's Hospital that examined the human pacemaker's responses to standardized changes in light patterns generated from an overhead fluorescent ballast. Across several hundred days of laboratory recording, the research group observed phase-shifts in the body temperature and melatonin rhythms that scaled with illuminance. However, as suspected, phase resetting was optimized when exposure occurred as a series of minute-long episodes separated by periods of intervening darkness. These observations set the stage for a more recent program of study at Stanford University that evaluated whether the human pacemaker was capable of integrating fragmented bursts of light in much the same way it perceived steady luminance. The results here suggest that ultra-short durations of light-lasting just 1-2 seconds in total-can elicit pacemaker responses rivaling those created by continuous hour-long stimulation if those few seconds of light are evenly distributed across the hour as discreet 2-millisecond pulses. We conclude our review with a brief discussion of these findings and their potential application in future phototherapy techniques.

Altered metabolic and hormonal responses in male rats exposed to acute bright light-at-night associated with global DNA hypo-methylation.

The association between light pollution and disruption of daily rhythms, metabolic and hormonal disorders, as well as cancer progression is well-recognized. These adverse effects could be due to nocturnal melatonin suppression. The signaling pathway by which light pollution affects metabolism and endocrine responses is unclear. We studied the effects of artificial light at night (ALAN1) on body mass, food and water intake, daily rhythms of body temperature, serum glucose and insulin in male rats. Daily rhythms of urine production and urinary 6-sulfatoxymelatonin (6-SMT2), as well as global DNA methylation in pancreas and liver tissues were also assessed. Mass gain was higher in ALAN rats compared with controls. Food intake, water consumption, glucose, insulin, and 6-SMT levels markedly lessened in response to ALAN. Conversely, urine production and body temperature were elevated in ALAN rats compared with controls. Significant 24-h rhythms were detected for all variables that were altered in mesor, amplitude, and acrophase occurrences under ALAN conditions. DNA hypo-methylation was detected in ALAN pancreatic tissue compared with controls, but not in hepatic tissue. Overall, ALAN affects metabolic and hormonal physiology in different levels in which flexible crosstalk between melatonin and both epigenetics and metabolic levels expressed as body temperature rhythm, is suggested to mediate the environmental exposure at the molecular level and subsequently physiology is altered. The flexibility of epigenetic modifications provides a potential therapeutic target for rectifying ALAN adverse effects by epigenetic markers such as melatonin and behavioral lifestyle interventions for confining ALAN exposures as much as possible.

Temperature dependence of thermal properties of ex vivo liver tissue up to ablative temperatures.

Thermal properties of ex vivo bovine liver were measured as a function of temperature, by heating tissue samples in a temperature-controlled oil bath over a temperature range from about 21 °C to about 113 °C. Results evidenced temperature-dependent non-linear changes of the thermal properties, with the temperature of 100 °C representing a break point: the thermal properties increased with temperature up to 99 °C and then decreased above 100 °C. The rate of increase appeared dramatic between 90 °C and 99 °C, owing to the onset of vaporisation of water contained in the tissue. In particular, at 99 °C, the thermal conductivity reported an increase of about four times with respect to the value measured at 90 °C, whilst about a two-fold increase was reported for both the volumetric heat capacity and the thermal diffusivity. Temperatures higher than 100 °C were reached only after complete vaporisation of water contained in the tissue, resulting in about 70% loss of weight from the tissue. An overall decrease of about 71% and 63% was reported for the thermal conductivity and volumetric heat capacity, respectively, in the temperature range 101 °C-113 °C. A decrease of about 25% was reported in the measured values of the thermal diffusivity in the temperature range 101 °C-108 °C, whilst a slight increase of measured values, not statistically significant, was observed in the temperature range 108 °C-113 °C. The temperature dependent changes of the thermal parameters were modelled with non-linear regression analysis to calculate the best-fit curves interpolating measured data. The proposed regression models could be used to numerically assess the changes in the thermal properties of biological tissues at supra-physiological temperatures relevant in thermal ablation procedures, as well as their effect on the prediction of the ablation zone dimensions in computational models for treatment planning.

Relationship between power density and surface temperature elevation for human skin exposure to electromagnetic waves with oblique incidence angle from 6 GHz to 1 THz.

This study presents an investigation of human skin exposure to obliquely incident electromagnetic waves at frequencies from 6 GHz to 1 THz. We aim to clarify the relationship between the power density and the skin surface temperature elevation under various exposure conditions. A Monte Carlo simulation was conducted to assess the transmittance and surface temperature elevation considering the variation of skin tissue thickness. For the case of TM wave injection, transmittance increases with increasing incidence angle from the normal incidence because of the Brewster effect. The normal incidence is confirmed as the worst-case exposure condition when the incident power density is defined in an area normal to the propagation direction. In addition, we investigated the power density required to obtain the equivalent temperature elevation over the skin surface. The analysis shows that the incident power density defined in the direction normal to the skin surface may underestimate the temperature elevation when TM waves are incident over the normal incidence up to the maximum transmittance angle. Our results also show that the power density inside the skin surface strongly correlates with the surface temperature elevation but less dependent on the frequency and independent of the oblique incidence angle and polarization. The findings of this study are expected to be valuable for discussing how to use the different definitions of power density based on dosimetric characteristics as measures in safety guidelines to protect humans from excessive temperature elevation by millimeter and submillimeter-wave exposure.

Importance of Exposure Duration and Metrics on Correlation Between RF Energy Absorption and Temperature Increase in a Human Model.

OBJECTIVE: This study investigated the influence of absorption metrics and averaging schemes on correlation between RF/microwave energy and induced temperature elevation for plane wave exposures. METHODS: A voxel-based, anatomically realistic model of the human body was considered. Correlation of electromagnetic fields and temperature increases were evaluated at several frequencies. Both specific absorption rate (SAR) and volume absorption rate (VAR) were considered. RESULTS: The best correlation with temperature increase occurs for exposure durations between 1 and 2 min both for SAR and VAR for most of the 700 to 2700 MHz frequencies considered. In this case, a 1 g mass or 1 cm3 volume appears to be optimal. However, for VAR, as frequency increases to above 900 MHz, a better correlation is achieved at slightly increased exposure times and volumes. For longer exposures, the maximum correlation coefficient is reduced, and the correlation favors larger averaging mass or volume. At steady-state (30 min), correlation of temperature increase with SAR is maximum for a mass of 9 g for all frequencies considered, whereas the volume for VAR maximum correlation is 15 cm3 for higher frequencies and 20 cm3 for lower frequencies. CONCLUSIONS: In general, SAR provides a better correlation with temperature compared to VAR for short exposures, while VAR renders better correlations for higher frequencies and longer exposures. SIGNIFICANCE: The correlation between electromagnetic absorption and temperature increases has implications in guidelines for limiting human exposure to electromagnetic fields and in biomedical applications such as imaging, sensing, and hyperthermia.

Bright light at night alters the perception of daylength in Indian weaver bird (Ploceus philippinus).

The brighter nights have posed new challenges to the wild species by affecting their temporal physiology. The present study on Indian weaver bird (Ploceus philippinus) investigated if exposure to bright light at different phases of night affects their clock-mediated daily functions. Birds were placed individually in specially designed activity cages under short days and long nights (8L:16D; L = 100 lux, D < 0.1 lux) for ∼3 weeks (19 days). Thereafter, they were divided into four groups (n = 6-9), and given ∼2 lux light either for the entire night (ZT 08-24; zeitgeber time 0 = time of light on; pattern A) or for 4 hr (pattern B), placed in 16 hr night such that its onset coincides with the onset of night (early night group, ZT 08-12), its end with the end of night (late night group, ZT 20-24), or the night was interrupted in the middle (midnight group, ZT 14-18). The results showed that bright light in entire night induced early onset of day activity and fragmented rest at night, however, if given at different phases of night, it made the days longer by delaying end (early night group) or advancing onset of daily activity (late night group). It also suppressed the melatonin levels and increased body temperature. These results suggest that bright light at night alters the perception of daylength and affects the underlying physiology. The findings may be useful in adopting a strategy for use of night light without disturbing species fitness in their environment.

Foraging strategy of wasps - optimisation of intake rate or energetic efficiency?

In endothermic wasps, foraging is an expensive activity. To maximise the benefit for the colony, wasps can optimise either the intake rate or energetic efficiency of a foraging trip. We investigated the foraging behaviour of vespine wasps under variable environmental and reward conditions. We trained them to forage for 0.5 mol l-1 sucrose solution from an artificial flower in a flow-through respiratory measurement chamber, and simultaneously measured their body temperature using infrared thermography to investigate interactions between thermoregulation and energetics. Measurement of carbon dioxide release (for energetic calculations) and load mass enabled the direct determination of foraging efficiency. An unlimited reward increased the wasps' energetic effort to increase the suction speed through high body temperatures. With reduced reward (limited flow), when an increased body temperature could not increase suction speed, the wasps decreased their body temperature to reduce the metabolic effort. Solar heat gain was used differently, either to increase body temperature without additional metabolic effort or to save energy. The foraging efficiency was mainly determined by the flow rate, ambient temperature and solar heat gain. In shade, an unlimited sucrose flow and a high ambient temperature yielded the highest energetic benefit. A limited flow reduced foraging efficiency in the shade, but only partly in sunshine. Solar radiation boosted the efficiency at all reward rates. Wasps responded flexibly to varying reward conditions by maximising intake rate at unlimited flow and switching to the optimisation of foraging efficiency when the intake rate could not be enhanced due to a limited flow rate.

The effect of 580 nm-based-LED mixed light on growth, adipose deposition, skeletal development, and body temperature of chickens.

Though previous study indicated that the 580 nm-yellow-LED-light showed an stimulating effect on growth of chickens, the low luminous efficiency of the yellow LED light cannot reflect the advantage of energy saving. In present study, the cool white LED chips and yellow LED chips have been combined to fabricate the white × yellow mixed LED light, with an enhanced luminous efficiency. A total 300 newly hatched chickens were reared under various mixed LED light. The results indicated that the white × yellow mixed LED light had "double-edged sword" effects on bird's body weight, bone development, adipose deposition, and body temperature, depending on variations in ratios of yellow component. Low yellow ratio of mixed LED light (Low group) inhibited body weight, whereas medium and high yellow ratio of mixed LED light (Medium and High groups) promoted body weight, compared with white LED light (White group). A progressive change in yellow component gave rise to consistent changes in body weight over the entire experiment. Moreover, a positive relationship was observed between yellow component and feed conversion ratio. High group-treated birds had greater relative abdominal adipose weight than Medium group-treated birds (P = 0.048), whereas Medium group-treated birds had greater relative abdominal adipose weight than Low group-treated birds (P = 0.044). We found that mixed light improved body weight by enhancing skeletal development (R2 = 0.5023, P = 0.0001) and adipose deposition (R2 = 0.6012, P = 0.0001). Birds in the Medium, High and Yellow groups attained significantly higher surface temperatures compared with the White group (P = 0.010). The results suggest that the application of the mixed light with high level of yellow component can be used successfully to improve growth and productive performance in broilers.

Effect of cell phone radiofrequency radiation on body temperature in rodents: Pilot studies of the National Toxicology Program's reverberation chamber exposure system.

Radiofrequency radiation (RFR) causes heating, which can lead to detrimental biological effects. To characterize the effects of RFR exposure on body temperature in relation to animal size and pregnancy, a series of short-term toxicity studies was conducted in a unique RFR exposure system. Young and old B6C3F1 mice and young, old, and pregnant Harlan Sprague-Dawley rats were exposed to Global System for Mobile Communication (GSM) or Code Division Multiple Access (CDMA) RFR (rats = 900 MHz, mice = 1,900 MHz) at specific absorption rates (SARs) up to 12 W/kg for approximately 9 h a day for 5 days. In general, fewer and less severe increases in body temperature were observed in young than in older rats. SAR-dependent increases in subcutaneous body temperatures were observed at exposures ≥6 W/kg in both modulations. Exposures of ≥10 W/kg GSM or CDMA RFR induced excessive increases in body temperature, leading to mortality. There was also a significant increase in the number of resorptions in pregnant rats at 12 W/kg GSM RFR. In mice, only sporadic increases in body temperature were observed regardless of sex or age when exposed to GSM or CDMA RFR up to 12 W/kg. These results identified SARs at which measurable RFR-mediated thermal effects occur, and were used in the selection of exposures for subsequent toxicology and carcinogenicity studies. Bioelectromagnetics. 39:190-199, 2018. © 2018 The Authors. Bioelectromagnetics Published by Wiley Periodicals, Inc.

Comparison of Different Energy Levels of Er:YAG Laser Regarding Intrapulpal Temperature Change During Safe Ceramic Bracket Removal.

OBJECTIVE: This study was done to compare the intrapulpal temperature change generated by different energy levels of Er:YAG laser used during debonding of ceramic brackets and find the most suitable level for clinical use. MATERIAL AND METHODS: Eighty polycrystalline alumina brackets were bonded on bovine incisor teeth, which were randomly divided into 4 groups of 20. One group was assigned as control. In the study groups, after laser exposure with 2, 4, or 6 Watt energy levels, brackets were debonded using an Instron Universal Testing machine. Adhesive remnant index (ARI) scores were recorded to evaluate the site of debonding. To assess intrapulpal thermal increase, 60 human premolar teeth that were prepared in the same way, at the same energy levels, by a thermocouple were used. RESULTS: When the debonding forces, intrapulpal temperature increases, and ARI of the groups were examined, statistically significant difference was observed between the groups. Mean temperature increases of 0.67°C ± 0.12°C, 1.25°C ± 0.16°C, and 2.36°C ± 0.23°C were recorded for the 2, 4, and 6 Watt laser groups. The mean shear bond strength was 21.35 ± 3.43 megapascals (MPa) for the control group, whereas they were 8.79 ± 2.47, 3.28 ± 0.73, and 2.46 ± 0.54 MPa for the 2, 4, and 6 Watt laser groups, respectively. CONCLUSIONS: Four watts is the most efficient and safe energy level to be used, utilizing Er:YAG laser with water cooling spray for 6 sec by scanning method during debonding of polycrystalline alumina brackets without any carbonization effects and detrimental temperature changes at debond sites.