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The thermosyphon is a type of heat exchanger that has been widely used in many applications. The use of thermosyphons has been intensified in recent years, mainly in the manufacture of solar collectors and various industrial activities. A thermosyphon is a vertical sealed tube filled with a working fluid, consisting of, from bottom to top, by an evaporator, an adiabatic section, and a condenser. The study of geyser-boiling phenomena, which occurs inside the thermosyphon is of extreme importance, therefore the experimental analysis of the parameters related to the two-phase flow (liquid-steam), such as void fraction, bubble frequency, bubble velocity, and bubble length are necessary, since these parameters have a significant influence on heat transfer. In this work, a pair of wire mesh sensors was used, a relative innovative technology to obtain experimental values of the reported quantities for measuring these parameters of slug flow in thermosyphons. An experimental set-up is assembled and the sensors are coupled to the thermosyphon enabling the development of the experimental procedure. Here is presented an experimental study of a glass thermosyphon instrumented with two wire-mesh sensors, in which the aforementioned slug flow hydrodynamic parameters inherent to the geyser type boiling process are measured. It was measured successfully, as a function of the heat load (110, 120, 130, 140, and 150 W), the void fraction (instantly and average), liquid film thickness, translation velocity of the elongated bubbles, lengths of the bubbles, and the liquid slug (displaced by the bubble rise up). It was observed that the higher the heat load, the lower is the bubble translation velocity. For all heat loads, based on the measured length of liquid slug (consequent displacement of liquid volume), caused by bubbles rise from evaporator to condenser, it could be affirmed to some extent that both boiling regime (pool and film) exist in the evaporator. The measured average void fraction (80%) and liquid film thickness (around 2.5 mm) during the elongated bubble passages were approximately constant and independent of the heat load. [ABSTRACT FROM AUTHOR]

Purpose: Edentulism usually leads to esthetic, functional, and emotional discomfort resulting in a loss of self-esteem and a decrease of the patient’s quality of life. Dental implants provide new possibilities to ensure the comfort and efficacy of prosthetic rehabilitation. The aim of this study was to evaluate the satisfaction level of patients rehabilitated using the Branemark protocol or overdenture implant-supported prostheses. Materials and Methods: Fifty-two patients were rehabilitated using the Branemark protocol and 23 using overdenture prostheses. Then, an adapted oral health-related quality of life questionnaire was administered in addition to a clinical exam to determine the condition of the dental implants and prostheses. The results for treatment expectation, understanding of the type of treatment, phonetic function, chewing comfort, pain, and self-esteem improvement were analyzed with Fisher exact test (P < .05). Results: Both treatments presented satisfaction of above 87%, with no statistical difference between them. Eighty-two percent of patients treated with overdenture prostheses and 80.8% of those treated with the Branemark protocol had no complaint of pain (P = .087). Conclusion: The treatments analyzed in this study were highly satisfactory with regard to functional and esthetic factors, resulting in an increase in self-esteem and quality of life. The psychological factor is a complex variable in patient satisfaction that directly influences quality of life. Considering the desires of patients in choosing the type of prosthesis is critical to treatment success. [ABSTRACT FROM AUTHOR]

The objective of this split-mouth clinical study was to compare a combination of in-office and at-home dental bleaching with at-home bleaching alone. Two applications of inoffice bleaching were performed, with one appointment per week, using 38% hydrogen peroxide. At-home bleaching was performed with or without in-office bleaching using 10% carbamide peroxide in a custom-made tray every night for 2 weeks. The factor studied was the bleaching technique on two levels: Technique 1 (in-office bleaching combined with home bleaching) and Technique 2 (home bleaching only). The response variables were color change, dental sensitivity, morphology, and surface roughness. The maxillary right and left hemiarches of the participants were submitted to in-office placebo treatment and in-office bleaching, respectively (Phase 1), and at-home bleaching (Phase 2) treatment was performed on both hemiarches, characterizing a split-mouth design. Enamel surface changes and roughness were analyzed with scanning electron microscopy (SEM) and optical interferometry (IFM) using epoxy replicas. No statistically significant differences were observed between the bleaching techniques for either the visual or the digital analyses. There was a significant difference in dental sensitivity when both dental bleaching techniques were used, with in-office bleaching producing the highest levels o f dental sensitivity after the baseline. Microscopic analysis of the morphology and roughness of the enamel surface showed no significant changes between the bleaching techniques. The two techniques produced similar results in color change, and the combination technique produced the highest levels of sensitivity. Neither technique promoted changes in morphology or surface roughness of enamel. [ABSTRACT FROM AUTHOR]

Purpose: To quantify hydrogen peroxide (H2O2) penetration into restored bovine teeth subjected to whitening treatment. Materials and Methods: Seventy-five enamel/dentin disks were divided into 5 groups (n = 15): intact disks (G1); cavity preparation only (G2); conventional adhesive system and composite resin (G3); resin-modified glass-ionomer cement (G4); and self-etching adhesive only (G5). After 24 h, the disks were placed into artificial pulp chambers containing an acetate buffer solution, and the first whitening session was performed using a 35% H2O2 (hydrogen peroxide) product. The disks were submitted to 10,000 thermal cycles and then stored for 1 year in deionized water. After this period, a second whitening session was performed. After each whitening procedure, the buffer solutions were analyzed for optical density in a spectrophotometer to assess the amount of H2O2 that had diffused. ANOVA and Tukey's test were used to compare the different groups and a Student's t-test was used to compare the different times (p ≤ 0.05). Results: Prior to aging, group 2 had the highest penetration of H2O2; the other groups showed similar, lower penetration. After thermocycling and aging, all groups showed a significant increase in H2O2 penetration. The greatest penetration of H2O2 into the pulp chamber was found in groups 2 and 5. Conclusion: Aged restorations allowed greater H2O2 permeation through the tooth structure. [ABSTRACT FROM AUTHOR]

This study evaluated the push-out bond strength of customized glass fiber posts in different regions of post space (cervical, middle and apical) submitted to mechanical cycling. Forty single-rooted human premolar teeth were submitted to endodontic treatment and divided into four groups, according to the type of fiberglass posts installed: customized or non-customized posts. Half of the samples were submitted to 1,200,000 mechanical cycles. Samples sections of approximately 1.3 mm thickness were obtained from each regional third and the samples were subjected to push-out bond test. Data were analyzed by two-way repeated measures ANOVA and Tukey's test (p = 0.05). There was no statistically significant difference between customized and non-customized fiberglass posts at the cervical region, regardless if the mechanical cycling was performed. (p = 0.18). In the middle third, the highest value of bond strength was observed in the non-customized group without mechanical cycling (12.90 ± 6.88 MPa), but it was not significantly different from the respective aged group (7.58 ± 4.72 MPa) (p > 0.05). Similar results observed in the apical region, where lower values were found for the customized groups. For customized fiberglass posts, the cervical region showed higher values of bond strength compared to the middle and apical thirds (p < 0.05) with or without mechanical cycling. The customization of fiberglass posts is not an essential clinical procedure since it does not improve the bond strength of fiberglass posts to dentin, independent of the mechanical cycling procedure. [ABSTRACT FROM AUTHOR]

The article discusses various aspects of a procedure for sealing a dental screw access channel using polytetrafluoroethylene (PTFE) tape, and it mentions dental techniques and in screw and cement-retained implant supported dental prostheses. Dental esthetics and oral rehabilitation are addressed, along with the utilization of dental materials such as polyvinyl siloxane, plastic, autopolymerizing acrylic resin, and cotton.

Purpose: To evaluate the clinical outcomes of minimally invasive ceramic restorations executed by dentists with different levels of experience. Methods: Sixteen professionals were divided into 4 groups according to their experience levels. These included G1: up to 2 years since graduation, G2: 2-5 years, G3: 5-10 years, and G4: more than 10 years. All professionals were trained to follow the same standardized clinical protocol, but were unaware of the research objectives. A single evaluator followed the clinical treatments and recorded the complications and errors that occurred during the execution of the protocol. Ninety-one full crowns, 137 veneers, and 46 no-preparation veneers were prepared from lithium disilicate. Follow-ups were performed immediately and at 30, 180, and 360 days after the cementation and the evaluation based on the modified United States Public Health Service criteria. Ceramic chipping/ fracture and debonding were considered failures. Fractures were replicated and submitted to fractographic analysis. Results: The highest number of failures were found in G1 followed by G3 and the lowest number of failures were found in G2. The level of success was 94% after 360 days. The fractographic analysis demonstrated the external surface of restorations as the critical area and suggested that failures might occur due to noncompliance with the clinical protocol. There was no correlation between professional experience and number of failures or patient satisfaction. Conclusions: Professional experience was not a decisive for patient satisfaction and success of minimally invasive ceramic restorations, and noncompliance with the clinical protocol was associated with early ceramic restoration failures. [ABSTRACT FROM AUTHOR]

Purpose: This study evaluated and compared bone heating, drill deformation, and drill roughness after several implant osteotomies in the guided surgery technique and the classic drilling procedure. Materials and Methods: The tibias of 20 rabbits were used. The animals were divided into a guided surgery group (GG) and a control group (CG); subgroups were then designated (G0, G1, G2, G3, and G4, corresponding to drills used 0, 10, 20, 30 and 40 times, respectively). Each animal received 10 sequential osteotomies (5 in each tibia) with each technique. Thermal changes were quantified, drill roughness was measured, and the drills were subjected to scanning electron microscopy. Results: Bone temperature generated by drilling was significantly higher in the GG than in the CG. Drill deformation in the GG and CG increased with drill use, and in the CG a significant difference between G0 and groups G3 and G4 was observed. In the GG, a significant difference between G0 and all other groups was found. For GG versus CG, a significant difference was found in the 40th osteotomy. Drill roughness in both groups was progressive in accordance with increased use, but there was no statistically significant difference between subgroups or between GG and CG overall. Conclusion: During preparation of implant osteotomies, the guided surgery technique generated a higher bone temperature and deformed drills more than the classic drilling procedure. The increase in tissue temperature was directly proportional to the number of times drills were used, but neither technique generated critical necrosis-inducing temperatures. Drill deformation was directly proportional to the number of times the drills were used. The roughness of the drills was directly proportional to the number of reuses in both groups but tended to be higher in the GG group. [ABSTRACT FROM AUTHOR]

Copyright of Revista Eletrônica de Enfermagem is the property of Revista Eletronica de Enfermagem and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Rev Rene is the property of Rev Rene and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: To evaluate the torque stability of different UCLA retention screws of single implant-supported crowns submitted to mechanical cycling. Materials and Methods: Crowns fabricated from nickel-chromiummolybdenum alloy were attached to external-hexagon implants and grouped by the different retention screws used (n = 10): Ti, titanium screws (BRUNIHT, Biomet 3i); Au, gold-palladium screws with 24-carat gold coating (Gold-Tite, Biomet 3i); TiC, titanium alloy (Ti-6Al-4V) screw with diamondlike carbon coating (Neotorque, Neodent); and TiN, Ti-6Al-4V screw with aluminum-titanium-nitride coating (Ti-Tite, Conexão). Three initial removal torque (RT) values were obtained for each screw after torque insertion using an analog torque gauge. The final RT was measured after mechanical cycling (1 × 106 cycles at 2 Hz under 130 N). Data were submitted to analysis of variance and the Fischer test. Results: Statistically significant differences were observed between the initial RT in groups Ti and TiN, and between TiC and TiN. No statistically significant difference was seen between mean RT obtained before and after mechanical cycling, except for the Ti screws. All groups exhibited similar torque maintenance after mechanical cycling. Conclusion: Although no significant difference was observed among groups for the final percentage of torque maintenance, the final RT values of the coated screws were higher than those of the noncoated screws. [ABSTRACT FROM AUTHOR]

Copyright of Revista Espacios is the property of Talleres de Impresos Oma and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this study was to evaluate the degree of conversion of resin cements polymerized under different ceramic systems. Forty specimens of RelyX ARC (3M ESPE) and Maxcem Elite (Kerr) resin cements were polymerized under 5 types of dental ceramics: feldspathic, aluminum oxide-reinforced, aluminum oxide-based strengthened with zirconium oxide, leucite-reinforced, and lithium disilicate-reinforced. Measurements of the degree of conversion of the resin cements were performed 10 minutes, 1 hour, and 24 hours after curing using a Fourier transform infrared spectrophotometer. The values were subjected to a 3-way repeated-measures analysis of variance, and the means were compared with the Fisher protected least significant difference test (α = 0.05). The study findings showed that RelyX ARC resin cement displayed a higher degree of conversion than Maxcem Elite (P < 0.05). The degree of conversion was significantly lower for RelyX ARC polymerized under aluminum oxide ceramic and aluminum oxide ceramic strengthened with zirconium oxide (P< 0.05). For Maxcem Elite, there was no significant difference in the degree of conversion attained under the various ceramics (P > 0.05). For both cements, the degree of conversion increased gradually up to 24 hours after curing (P < 0.05). The ceramic system used directly influenced the degree of conversion of RelyX ARC. Both resin cements displayed an increase in the degree of conversion over time. [ABSTRACT FROM AUTHOR]

This work presents the use of electrical discharge machining (EDM) technology for manufacturing of three different types of axial microgrooves in heat pipes. This specific process, called wire electrical discharge machining (wire-EDM), allows the fabrication of microgrooves on the inner wall of a heat pipe with accuracy. Different from other capillary structures, such as composite wick and screen mesh, the material is removed from the pipe's container in order to conceive the capillary structure, which contributes with the mass reduction of the passive two-phase heat transfer device. The heat pipes were manufactured from a straight copper pipe with the external diameter of 9.45 mm, the inner diameter of 6.20 mm, and a total length of 200 mm. Three types of axial microgrooves were manufactured for constant width (35 µm) and varying the depth (from 30-48 µm), and thickness (from 35-70 µm). The number of microgrooves was also varied from 21-32 microgrooves. Water was used as the working fluid and the loading filling ratio was 60% of the evaporator volume. The condenser was cooled by air forced convection, the adiabatic section was insulated and the evaporator was heated by an electrical resistor and it was insulated from the environment with aeronautic thermal insulation. The thermal performance of the heat pipes are analyzed based on experimental results, so the heat pipes were tested at the horizontal and different inclinations under different low heat loads (from 5-50 W or a heat flux from 0.21-2.10 W/cm²). The experimental results showed that the axial microgrooves manufactured by the wire-EDM process worked satisfactorily in all analyzed cases and microgrooves of Type 1 showed a better thermal performance when compared with the others. [ABSTRACT FROM AUTHOR]