Crystal structure of a murine alpha-class glutathione S-transferase involved in cellular defense against oxidative stress

STATEMENT OF PROBLEM: The electric alloy brazed joints of removable partial denture alloys have failed frequently after routine usage. PURPOSE: A technique providing higher joint strengths was investigated. This investigation compared the tensile strengths of electric-brazed and laser-welded joints for a cobalt-chromium removable partial denture alloy. MATERIAL AND METHODS: Twenty-four cobalt-chromium standard tensile testing rods were prepared and divided into three groups of eight. All specimens in the control group (group 1) were left in the as-cast condition. Groups 2 and 3 were the test specimens, which were sectioned at the center of the rod. Eight specimens were joined by using electric brazing, and the remaining specimens were joined by using laser welding. After joining, each joint was ground to a uniform diameter, then tested to tensile failure on an Instron universal testing machine. Failure loads were recorded and fracture stress calculated. Statistical analysis was applied. RESULTS: The student-Newman-Keuls test showed a highly significant difference between the joint strengths of the as-cast control specimens, the electric-brazed and laser-welded joints. CONCLUSIONS: The tensile strengths of the as-cast joints were higher than those for the laser-welded joints, and both were higher than the electric-brazed joint strengths.     

Repair with a surveyed cast clasp while patient retains the partial denture

A technique is described that allows a removable partial denture with a broken clasp or a removable partial denture in which an abutment has been extracted to be restored by the reattachment of a new cast clasp component or a complete surveyed clasp assembly. The technique is applicable to most clasp designs and can include attachment to the acrylic denture base or the metal major connector. The technique is distinguished from other repair techniques by (1) providing a cast clasp replacement, (2) allowing the patient to retain the prosthesis during the repair, (3) generating a precisely formed surveyed clasp assembly by the laboratory, and (4) including an efficient transfer mechanism for the precision clasp created in the laboratory to be attached to the removable partial denture in the dental office. A two-step impression procedure is used to ensure proper relation of the partial denture to the abutments.     

Controlled temperature tissue fusion: argon laser welding of rat intestine in vivo. Part one

BACKGROUND AND OBJECTIVE: Thermal denaturation of proteins is recognized as a rate process governed by the local temperature-time response. Since rate processes are exponential with temperature, laser-assisted tissue welding was performed with and without temperature feedback control (TFC) to investigate the efficacy of temperature feedback in enhancing the photothermal welding process in vivo. STUDY DESIGN/MATERIALS AND METHODS: An automated system was developed for temperature feedback controlled laser irradiation. An experimental device incorporating co-aligned laser delivery and temperature detection was used to perform argon laser welded (with and without TFC) enterotomies. The weld strength and histology of laser welded and control sutured enterotomies were compared in an in vivo rat model. Animals (n = 41) were sacrificed at 1, 3, 7, and 21 days postoperatively, and the anastomotic site was removed for bursting/leaking pressure measurements and histological examination. RESULTS: Laser-welded (with and without TFC) and control sutured anastomoses in surviving animals healed comparably. Some laser-welded anastomoses without TFC ruptured spontaneously (4 out of 15) leading to the animals' death within the first 24-36 hours postoperatively. None of the animals in the other groups had this problem (control suture 0/6; laser with TFC 1 leak/8). The bursting/leaking pressures of the laser welded anastomoses were not significantly different than those of the sutured controls. CONCLUSION: TFC improves the quality of laser-welded rat intestinal anastomoses in vivo in the critical first postoperative 36 hours.     

Regulation of gene expression for lipogenic enzymes in the liver and adipose tissue of hereditary hypertriglyceridemic, insulin-resistant rats: effect of dietary sucrose and marine fish oil

The aim of this study was to investigate to what extent declining odour perception can be ascribed to dental status and oral hygiene habits, taking into account gender and age. Apparently healthy adults (n = 182), ranging from 53 to 93 years (mean age = 68.4) were tested. Information about oral hygiene habits (brushing teeth and cleaning dentures) and dental status was obtained by questionnaires. A validated objective procedure was used to measure sensory detection thresholds for isoamylacetate by an ascending method of limits. A significant negative correlation of odour perception with age was shown by the edentulous subjects which might reflect their wider age spread with many subjects over age 75. The evaluation of odour perception as a function of dental status shows no significant difference in odour perception between persons partial denture wearers, with natural teeth only or complete dentures. However, a tendency for lower odour perception was observed among male partial denture wearers, especially those reporting less frequent oral hygiene, which justifies further more detailed study.     

A follow-up study on changes in mastication after insertion of mandibular bilateral free end saddle denture by EMG]

The purpose of this study was to investigate changes in the mandibular shortened arch, whose occlusal deficit had been reconstructed by removable partial denture, during mastication by using the EMG analyzing system. A total of 5 shortened dental arch patients was provided with RPDs, and observed by a sophisticated masticatory analyzing system using EMG, before and one day, about 2 weeks, 3 months, after denture insertion. The conclusions were as follows: i) The elements of the shortened arch during mastication, that is, the duration, interval, and cycletime, were prolonged at the time of insertion of RPD, but 3 months after denture insertion, they were shortened to almost the same state as before treatment. ii) Prosthetic treatment for shortened dental arch improved revitalization of functional musculatures, and their rhythmicity of functional procedure. iii) The functional tongue room for optimal bolus position in mastication was provided by insertion of mandibular bilateral free end saddle removable partial denture.     

Effect of Postweld Heat Treatment on Microstructure, Hardness, and Tensile Properties of Laser-Welded Ti-6Al-4V

The effects of postweld heat treatment (PWHT) on 3.2-mm- and 5.1-mm-thick Ti-6Al-4V butt joints welded using a continuous wave (CW) 4-kW Nd:YAG laser welding machine were investigated in terms of microstructural transformations, welding defects, and hardness, as well as global and local tensile properties. Two postweld heat treatments, i.e., stress-relief annealing (SRA) and solution heat treatment followed by aging (STA), were performed and the weld qualities were compared with the as-welded condition. A digital image correlation technique was used to determine the global tensile behavior for the transverse welding samples. The local tensile properties including yield strength and maximum strain were determined, for the first time, for the laser-welded Ti-6Al-4V. The mechanical properties, including hardness and the global and local tensile properties, were correlated to the microstructure and defects in the as-welded, SRA, and STA conditions.     

Mechanical properties of titanium connectors

The tensile mechanical properties of welded titanium joints were studied, and intact titanium was used as controls. Welded joints were fabricated with either a stereographic laser-welding technique or a gas tungsten arc welding technique. The effect of heat treatment following a simulated porcelain application was also investigated. Heat-treated laser welds had significantly lower ultimate tensile strengths. Heat treatment had no effect on the modulus of elasticity or elongation, but generally significantly decreased the yield strength of the titanium specimens. The gas tungsten are welding specimens had significantly higher yield strengths and elastic moduli than the other two groups. The elongation of the control specimens was significantly greater than the elongation of the gas tungsten arc welding specimens, which was in turn significantly higher than that of the laser-welded specimens.     

Constructing cast crowns to fit existing removable partial denture clasps

A step-by-step procedure has been presented for fabrication of a cast crown to fit an existing partial denture clasp. The procedure can be accomplished in two appointments, and the patient need not be subjected to the incovenience of being without the partial denture between office visits. It is an accurate and easy technique which gives uniform results and eliminates the need for remaking an adequate removable partial denture.     

Reoperations on the biliary system]

As an increasing percentage of our population is growing older and suffering from chronic medical conditions, the ability of the dentist to treat these patients is becoming more important. The dentist must be aware of the these patients' physiology and changing anatomy as well as their psychosocial needs. Changes in oral and dental tissues related to aging, as well as limitations in this population's perceived dental care needs, are presented. Modifications in the practice of fixed, removable partial, and complete denture prosthodontics as related to the management of the geriatric patient by the general practitioner are discussed.     

Allelic polymorphism in the coding region of human T cell receptor V beta 12 gene

Many bilateral distal extension removable partial dentures possess insufficient guidance to control their dislodgement. When such a situation is observed, the tips of retentive clasps must be located in both an occlusogingival and mesiodistal (away from the denture base area) undercut. The specific location can be identified with a dental surveyor that has been adapted to function in two planes. Details of the adaptation process and use of the surveyor are described.     

Nitrogen absorption by iron and stainless steels during CO<Subscript>2</Subscript> laser welding

Nitrogen absorption by iron, Fe-20Cr-10Ni alloy, and SUS329J1 duplex stainless steel during CO₂ laser welding in an Ar-N₂ gas mixture was investigated and compared with equilibrium data predicted on Sieverts’ law and data on absorption during arc and YAG laser welding. The nitrogen absorption during CO₂ laser welding is lower than that during arc welding, but higher than that during YAG laser welding. Compared with arc welding, the lesser contact of monatomic nitrogen with the weld pool surface and the higher partial pressure of metal vapor in the keyhole may result in the lower nitrogen absorption during CO₂ laser welding, while the very low density of monatomic nitrogen in the atmosphere during YAG laser welding due to the low-temperature plume may lead to the lower nitrogen absorption during YAG laser welding than during CO₂ laser welding.     

The 1993 General Social Survey I: alcohol use in Canada

Natural dentitions of elderly people are often reduced and the remaining teeth are heavily restored. It is unknown whether they are satisfied or dissatisfied with this situation. To get more insight into this phenomenon 320 dentate non-institutionalized elderly subjects were clinically examined and interviewed by means of a questionnaire. Analysis of the data showed that only 13% of the subjects had at least a complete dentition from the right first molar to the left first molar; 50% had less than four occlusal units, 39% of the subjects were wearing a removable partial denture. Ninety per cent of the subjects was satisfied with the dental state and nearly all subjects mentioned they could chew well (97%), despite the fact that 91% of the subjects mentioned they had to deal with one or more dental discomforts. Satisfaction decreased significantly when the number of the occlusal units was reduced or a removable partial denture was present. The conclusion is drawn that although the dentitions of the elderly are often reduced they are, in general, satisfied with their dental state.     

The effect of carbon dioxide laser on acid resistance of human tooth enamel: an evaluation by wet chemical analysis and scanning electron microscopy

The use of the laser in improving acid resistance of tooth enamel has captured the imagination of most researchers. Man's susceptibility to dental caries presents itself as one of the most complicated problems to solve. The carbon dioxide laser at a wavelength of 10.6 microns is highly efficient for dental purposes as this wavelength is close to optimum absorption of dental enamel. A study was carried out using a pulsed carbon dioxide laser to find the effects of laser beam on human tooth enamel in an energy range of 2-20 J/cm2 at a pulse rate of 5 Hz. The effective resistance to acid was determined by wet chemical analysis whereas superficial changes seen on the surface were determined using the scanning electron microscope.     

Effects of cordocentesis on inferior vena cava velocity waveforms: differences between normally grown and growth-retarded fetuses

PURPOSE: The purpose of this investigation was to evaluate complete denture patients at pretreatment and postinsertion, 6 months and 18 months after denture delivery in order to develop an explanatory model of successful denture therapy to better understand patient acceptance of complete dentures. MATERIALS AND METHODS: Sixty complete-denture patients treated at a dental student clinic were followed through denture therapy and for 18 months thereafter. Subjects were examined and completed pretreatment questionnaires and posttreatment interviews. Three outcome measures of denture success were tested, and factors considered substantive in achieving a successful denture outcome were examined using multivariate analyses. RESULTS: At post-insertion, 76.7% of subjects were satisfied with their dentures, 74.6% said their expectations were met, and 66.7% said they adjusted easily to their new dentures; reports at 6 and 18 months were similarly high. Logistic regression findings suggest that psychological and interpersonal factors are more important determinants of denture satisfaction than anatomic or clinical factors. CONCLUSIONS: Subject characteristics including age, gender, race, income level, education, marital status, and maxillary and mandibular anatomy were not significantly associated with denture success as defined by the three outcome measures used in this study. Although these variables may represent important co-factors in the patient's acceptance of dental services and may affect the way a patient perceives dental care outcomes, statistically significant relationships were not found within our sample. Psychosocial variables, such as pretreatment expectations, satisfaction with the dental care received, and mental health showed a stronger relationship to a successful outcome.     

Mechanism governing nitrogen absorption by steel weld metal during laser welding

The existence of monatomic nitrogen in the plasma just over the keyhole during CO₂ laser welding was confirmed by the monochromatic image of a specific spectrum line emitted by monatomic nitrogen. The smaller reaction area of the molten pool with monatomic nitrogen is considered to lead to less nitrogen absorption during CO₂ laser welding than that during arc welding. The effect of the penetration mode shows that the nitrogen absorption during CO₂ laser welding mainly occurs on the upper surface of the molten pool. The nitrogen content in a reduced-pressure nitrogen atmosphere during CO₂ laser welding is in good agreement with that obtained during yttrium aluminum garnet (YAG) laser welding within the range of low nitrogen (partial) pressures. This result supports the supposition that the different behaviors of nitrogen absorption between CO₂ laser welding and YAG laser welding can be reasonably attributed to the lesser amount of monatomic nitrogen during YAG laser welding.     

Metals used to fabricate removable partial denture frameworks

This article will help the dental technician choose from among the many alloys available for fabricating dental prostheses. It will explain terminology and compare and explain inherent properties and characteristics of alloys. Although all of the materials discussed produce a clinically acceptable removable partial denture framework, the predominantly base alloys dominate the market because of the low cost of the metal, case of casting, high yield strength and modulus of elasticity.