RESUMEN

Two isomeric aspirin derivatives of isosorbide-5-mononitrate (ISMN) were prepared and evaluated as potential mutual prodrugs of aspirin and nitric oxide. The hydrolysis of both compounds was studied in pH 7.4 phosphate buffer solution, buffered alpha-chymotrypsin solution and 10% buffered rabbit plasma. The benzodioxin-4-one derivative was hydrolysed to salicylic acid and ISMN acetate in buffer solution (t(1/2) 32.1 h), 10% buffered rabbit plasma (t(1/2) 25.7 min) and alpha-chymotrypsin (t(1/2) 86.6 min). The carboxylic acid ester derivative ISMNA was hydrolysed via the salicylate ester in buffer solution (t(1/2) 48.5 h) but was rapidly and almost exclusively hydrolysed to aspirin and ISMN in plasma solution (t(1/2) 2.8 min). The hydrolysis appeared to be enzyme mediated as it was suppressed by co-incubation with eserine. ISMNA was evaluated for its ability to inhibit platelet aggregation in rabbit PRP in response to the following agonists: arachidonic acid (AA) (100 microM), ADP (1.2 microM), phorbol ester (0.5 microM), platelet activating factor (PAF) (5 nM) and the thromboxane mimic U46619 (1.5 microM). ISMNA suppressed platelet response to AA at 1 microM whereas 10 microM aspirin showed no inhibitory effects.

Asunto(s)

RESUMEN

Since the early 1990s ring-substituted derivatives of amphetamine have been abused widely in the Republic of Ireland. The main ring-substituted amphetamines being abused include methylenedioxyamphetamine (MDA), methylenedioxymethamphetamine (MDMA) and methylenedioxyethamphetamine (MDEA). A newer illicit synthetic analogue, which has been seized to a lesser extent by Irish police, is N-methyl-1-(3,4-methylenedioxyphenyl)-2-butanamine (MBDB). The work presented here involved the determination of the type of ring-substituted amphetamines being abused by a group of recovering opiate abusers participating in a methadone maintenance programme in a Dublin Drug Rehabilitation Centre. Urine samples which tested positive for amphetamines and ring-substituted amphetamines via EMIT immunoassay were subjected to further analysis using GC-MS with MBTFA flash derivatization. It was found that the methylenedioxypropanamines were being abused, as was amphetamine itself. However, no abuse of methylenedioxybutanamines or thioamphetamines was observed.

RESUMEN

PURPOSE: Computer programs have been developed for removable partial denture (RPD) design, but their educational impact has never been investigated. This study measured the effectiveness of computer-based RPD design simulations in a traditional RPD design course for second-year dental students. MATERIALS AND METHODS: Thirty-six students were randomly assigned to four groups, two simulation and two control groups, at the beginning of the RPD design module. A cross-over design compared the two strategies during laboratory exercises. First, the simulation group worked with the simulation, while the control group met in small-group seminars with faculty. Post-test 1 was given, and then students switched teaching methods and post-test 2 was given. Each post-test had two parts. Part 1 involved designing an RPD based on specific patient criteria. Part 2 involved choosing the more correct of the two designs. RESULTS: Results showed a significant difference (p = .0072) in two of four test groups. Although it was an initial evaluation, the computer simulation was shown to be equivalent to faculty-led small-group seminars. Students also responded positively to a questionnaire on their perceived effectiveness of the simulations. CONCLUSIONS: The results suggest that RPD design can be taught as effectively with computer-based simulations as with faculty-led seminars.

Asunto(s)

RESUMEN

This study compared the effects of various rotary instruments and polishing agents on tooth enamel. Topographical features of enamel were studied at consecutive stages of polishing with photoanalysis of scanning electron micrographs. The results indicate that enamel modified by diamond burs may be polished to produce the smoothest surface with white finishing stones, Ceramist finishing points, and flour of pumice.

Asunto(s)

RESUMEN

This report presents the experience gained from 26 patients treated with autogenic cultured epithelial grafts (auto-CEG). All auto-CEG were applied to wounds clinically defined as full skin thickness injury. In total 89 separate sites were grafted. The overall estimate of 'take' ranged from 0 to 98 per cent with a mean value of 15 per cent. The highest level of 'take' (43 per cent) was observed when auto-CEG were applied to wounds which had been previously covered with allogenic split-thickness skin grafts. An increased incidence of wound colonization with pathogenic species of bacteria corresponded with a decreased graft 'take'. Ps. aeruginosa and Staph. aureus were found to be present on 32.6 per cent and 60.5 per cent of wound swabs respectively, where 10 per cent or less 'take' of auto-CEG was seen, indicating that bacterial infection is in part responsible for graft failure. However, in 20.9 per cent of such instances, no growth of bacteria was detected, perhaps suggesting that certain wound beds may not present the correct physical environment necessary to support proliferating epithelial cells isolated from their underlying dermal component.

Asunto(s)

RESUMEN

This study compared the moduli of elasticity of three provisional crown and fixed partial denture resins. Eighteen specimens of each resin were reinforced with carbon graphite fibers and 18 resin specimens from each group contained no fibers. Six specimens of each resin, with and without fibers, were tested within 6 hours of fabrication, after 30 days, and after 60 days of water storage. The mean moduli of elasticity of all the resins increased significantly with fiber incorporation. Water storage did not have a significant effect on the moduli of elasticity of the resins tested.

Asunto(s)

RESUMEN

A questionnaire was used to rate patients' satisfaction, expectations, and level of discomfort associated with implant treatment. The questionnaire was sent to 262 patients who had been treated with Core-Vent implants between 1984 and 1988. Over 60% of the patients contacted completed the questionnaire. The distribution of the respondents was evaluated according to age, sex, occupation, and marital status. Statistical interpretation of the data revealed that (1) measures of the level of satisfaction and expectation were significantly less for housewives when compared with other occupations; (2) satisfaction significantly correlated with measures of expectations and lack of discomfort; and (3) expectations correlated with lack of discomfort. In general, most subjects were extremely satisfied with the treatment they received.

Asunto(s)

RESUMEN

This study examined the tensile bond strength and failure sites of one heat-cured (Microlon) and two visible light-cured (Triad and Extoral) denture resins to two types of denture teeth. The resins were processed into cylinders against denture teeth milled to the same size. Half of the specimens were thermocycled. After tensile testing, statistical analysis (p 0.05) showed that the strongest bond was achieved with the heat-cured resin Microlon, whereas Triad resin displayed the stronger bond between the two light-cured resins. Scanning electron microscopic analysis showed that the nature and location of the fracture sites was different among the three resins tested.

Asunto(s)

RESUMEN

Oestradiol-17-b release from silastic implants of different length was determined in vitro over periods of up to 511 days. Sink conditions were provided by either Sodium lauryl sulphate (1%) or polyethylene glycol 400 (50%) in aqueous based media. Drug release profiles were fitted to the kinetic expression for matrix controlled release from a cylindrical delivery system, thus allowing prediction of both the rate and extent of release with time. A linear relationship was found between the cumulative amount of drug released in vitro and that released in vivo; the latter being measured from implants recovered from animals slaughtered in the period 96-515 days post implantation. A linear relationship was also obtained between serum oestradiol concentrations in the period 14 to 84 days post implantation and the in vitro release rate.

Asunto(s)

Asunto(s)

RESUMEN

Fabrication of complete dentures is dependent upon making accurate final impressions that capture the movable tissues in their functional state. Border-molding a custom tray with compound prior to making final impressions is a well established technique for recording these tissues. However, many practitioners avoid or abandon this technique because there appear to be more cost effective and/or easier techniques available. This article reviews proper border-molding procedures for maxillary impressions and graphically demonstrates the difference between impressions made with and without border-molding.

Asunto(s)

RESUMEN

Judgement skills and critical thinking in dentistry are developed through: (1) a systematic approach to gathering and processing information, and (2) an essential amount of practical experience. A new system of interactive videodisc patient simulations titled 'Dental Diagnosis and Treatment' or 'DDx & Tx' has been developed to provide students or practicing dentists an opportunity to develop and practice their critical thinking skills. The DDx & Tx system consists of patient simulation software, a laser-reflective videodisc with its accompanying database, a patient simulation management system, and documentation. An authoring tool is under development. Faculty-authored simulations require students to gather information, formulate diagnoses, order appropriate treatments and properly sequence those treatments. The students' performance is automatically scored and a critique is provided as a review.

Asunto(s)

RESUMEN

Patients often attempt to repair denture fractures at home by using cyanoacrylate. Cyanoacrylate is difficult to remove and may prevent the fractured sections from being reassembled properly. This method permits aligning the fractured sections in the mouth before repairing the denture.

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

Standard and interpenetrating polymer network acrylic resin denture teeth were milled into cylinders 8 mm in diameter and processed against cylinders of the three different resins. The specimens were reduced by milling to a diameter of 6 mm in the region of the tooth-resin interface and thermocycled for 24 hours. Specimens were then subjected to tensile loading until fracture. Group means were compared by using the Duncan multiple range test at the 5% level of significance. The strongest bond occurred between the heat-cured resin and the standard acrylic resin teeth. Intermediate strength was achieved with the heat-cured resin to the IPN teeth and the autopolymerizing resin to both types of teeth. Lowest strength was measured with the light-cured resin to both types of teeth.

Asunto(s)

Asunto(s)

Asunto(s)

RESUMEN

The long-term dimensional stability of three non-aqueous elastomeric impression materials, a silicone, a polyether and a polysiloxane, were investigated. The testing apparatus was an A.D.A. specification No. 19 test block and mould. The impressions were measured by the use of a travelling stage reflecting microscope and a Quantimet 720 Image Analyzing computer at time zero and again at 4, 24 and 48 h, and at 1, 2, 3 and 4 weeks. Impressions poured immediately had the greatest accuracy for all the materials. The polysiloxane (0.025 mm) and polyether (0.033 mm) showed very little change in dimension after 4 weeks when compared to the test block. However, the silicone showed significant change at 4 h (0.14 mm) and 0.2 mm after 4 weeks. After 4 weeks the polysiloxane maintained the best surface detail, the polyether was adequate but the silicone lost much of its detail in as little as 24 h. The reasons for these findings are discussed.

Asunto(s)