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At least 181 records · Page 10Linked to original sources
PubMed2001

The effect of acquired salivary pellicle on the surface free energy and wettability of different denture base materials.

OBJECTIVE: The objective of the present study was to evaluate the effect of salivary coating on the wettability and surface free energy of different denture base materials. METHODS: Five acrylic resin and two metallic denture base materials were investigated. Ten specimens of each material (20 x 15x1.5mm) were fabricated and a standardized method was used for polishing the test specimens. Whole unstimulated saliva was collected from a single healthy donor. The wettability properties of the materials were tested before and after organic layer formation. The wetting forces were determined according to the Wilhelmy Plate Technique. Diiodomethane, ethylene glycol and formamide were used as probe liquids. The contact angles, Lifshitz-van der Waals surface energy components, Lewis acid-base surface energy components and total surface energies were calculated using the equations described in the paper. The significance of the differences in the experimentally determined surface energies of different denture materials are calculated by statistical methods. CONCLUSIONS: Light-cured acrylic resin was the most wettable material with a significant basic character. Organic layers decreased the total surface free energies of all materials and at the same time imparted a more basic character. The coatings had a homogenizing effect in terms of the surface free energy components of the denture materials, nevertheless, their adhesive properties were still influenced by the substrate employed.

Acrylic Resins↗
PubMedDate not supplied

An in vitro study on restoring bond strength of a GIC to saliva contaminated enamel under unrinse condition.

OBJECTIVES: This study attempted to find a method of restoring the tensile bond strength of glass ionomer cement (GIC) to saliva contaminated enamel under unrinse condition. METHODS: One hundred and thirty human non-carious permanent teeth were divided into two major groups. Either treatment with air drying, acetone, polyacrylic acid, maleic acid, tartaric acid, Scotchbond primer or no treatment at all was applied to both clean and saliva contaminated enamel surfaces prior to GIC placement. Samples were debonded in tension after 7 days of storage in water using a universal testing machine. Statistical analysis was performed using one-way ANOVA, Tukey's studentized range test and Wilcoxon's rank sums test to determine the significance of the difference of tensile bond strengths within and between the two major groups. RESULTS: Bond strength of GIC to clean enamel was 2.46+/-0.79 MPa while the bond strength of GIC to wet contaminated enamel was significantly reduced to 1.28+/-0.32 MPa (p<0.01). However, the bond strengths were restored when the contaminated enamel surfaces were air-dried (2.19+/-0.38 MPa) or applied with either maleic acid (2.80+/-0.63 MPa) or Scotchbond primer (2.13+/-0.65 MPa) before placing GIC over the enamels. CONCLUSIONS: Air drying, or application of maleic acid or Scotchbond primer to the contaminated enamel without rinsing prior to GIC placement can restore the tensile bond strength to a level similar to that of non-contaminated control.

Acetone↗
PubMed1999

Quality assessment of defribrillation and advanced life support using data from the medical control module of the defibrillator.

What actually occurred during the two last links in the 'chain of survival': defibrillation and advanced life support (ALS), was studied in 156 patients with cardiac arrest of cardiac aetiology using the computer recording of the defibrillator and the Utstein-style data record. Ten patients (6%) survived. The ECG artefacts caused by chest compressions enabled a detailed analysis of compression rates (median 108 min(-1)) and duration of important compression free periods. The time from initiation of monitoring during asystole until chest compressions were initiated was median 29 s, significantly shorter than during electromechanical dissociation (EMD, 109 s; P < 0.001). These times were both significantly longer than the median time from initiation of monitoring until the first shock was given in cases with VF (19 s; P < 0.001). A total of 883 shocks (median six shocks) were administered to 110 patients with a significant difference in number of shocks between survivors and non-survivors, one versus seven, respectively. The success rate for the first shock and all shocks defined as non-VT/VF 5 s after the shock, was 75 and 63%, respectively. However, just 10% of all shocks resulted in a rhythm with a pulse and only 4% resulted in sustained return of spontaneous circulation (ROSC). An isoelectric period followed 38% of the shocks, and in 27% this lasted more than 20 s, with five patients obtaining electrical activity with a pulse after more than 30 s of isoelectric ECG. Thoracic impedance did not affect the shock efficacy. The method of analysing resuscitation we describe may be useful for quality improvement.

Aged↗
PubMed2003

Locoregional recurrence after doxorubicin-based chemotherapy and postmastectomy: Implications for breast cancer patients with early-stage disease and predictors for recurrence after postmastectomy radiation.

PURPOSE: To compare rates of locoregional recurrence (LRR) after mastectomy, doxorubicin-based chemotherapy, and radiation with those of patients receiving mastectomy and doxorubicin-based chemotherapy without radiation and to determine predictors of LRR after postmastectomy radiation. METHODS: Kaplan-Meier freedom-from-LRR rates were calculated for 470 patients treated with mastectomy, doxorubicin-based chemotherapy, and postmastectomy radiation in five single-institution clinical trials. The LRR rates in these patients were compared to previously reported rates in 1031 patients treated without radiation in the same trials. RESULTS: Median follow-up was 14 years. Irradiated patients had significantly less favorable prognostic factors for LRR than did unirradiated patients. Despite this, in all subsets of node-positive patients, postmastectomy radiation led to lower rates of LRR. This included patients with T1 or T2 tumors and one to three positive nodes (10-year LRR rates of 3% vs. 13%, p = 0.003). Multivariate analysis of LRR for patients with this stage of disease revealed that no radiation, close/positive margins, gross extracapsular extension, and dissection of <10 nodes predicted for increased LRR (hazard ratios 6.25, 4.61, 3.27, and 2.66, respectively). Significant predictors of LRR for patients treated with postmastectomy radiation were higher number and >or=20% positive nodes, larger tumor size, lymphovascular space invasion, and estrogen receptor (ER)-negative disease. Recursive partitioning analysis revealed ER-negative status to be the most powerful discriminator of LRR in irradiated patients. CONCLUSIONS: Postmastectomy radiation decreases LRR for patients with breast cancer, including those with Stage II breast cancer and one to three positive lymph nodes.

Adult↗
PubMed1997

Meta-analysis and endocrinology.

It is likely that more studies that use meta-analysis will be published in the endocrinologic literature. Major strengths of meta-analysis are the systematic ascertainment of research on a given topic and the explicit delineation of reasons for accepting or rejecting studies as a basis for drawing conclusions. The tendency of meta-analysis to focus on a single estimate of effect and to ignore heterogeneity are problems both with the conduct of meta-analysis and the way in which it is interpreted. Meta-analysis cannot overcome bias in the original studies. It is difficult to perform a good meta-analysis and easy to perform a bad one. The critical reader should not be overawed by the results of a meta-analysis. Reading a meta-analysis should not substitute for careful reading of the primary studies on which the meta-analysis is based. Meta-analysis should not be used to stifle the conduct of original research.

Bias↗
PubMed2003

Who can best recruit to randomized trials? Randomized trial comparing surgeons and nurses recruiting patients to a trial of treatments for localized prostate cancer (the ProtecT study).

BACKGROUND AND OBJECTIVE: Recruitment to randomized trials is often difficult, but few studies have investigated interventions to improve recruitment. In a randomized trial nested within a trial of treatments for localized prostate cancer, we investigated the comparative effectiveness and cost-effectiveness of nurses and surgeons in recruiting patients. METHODS: Men with localized prostate cancer were randomized to see a nurse or urologic surgeon for an "information appointment" in which they were asked to consent to the ProtecT treatment trial comparing surgery, radiotherapy, and active monitoring. Analysis was conducted by intention to treat using chi-square with 95% confidence intervals for proportions and differences between groups. An economic evaluation was performed using the duration of appointments and grade of recruitment staff. RESULTS: Case-finding identified 167 men with localized prostate cancer. One hundred fifty (90%) took part in the recruitment trial. There was a 4.0% difference between nurses and surgeons in recruitment rates (67% nurses, 71% urologists, 95% CI -10.8% to +18.8%, P=.60). Cost-minimization analysis showed that nurses spent longer times with patients but surgeon costs were higher and nurses often supported surgeon-led clinics. CONCLUSION: Nurses were as effective and more cost-effective recruiters than urologic surgeons. This suggests an increased role for nurses in recruiting patients to randomized trials.

Aged↗
PubMed2003

Early stopping in clinical trials and epidemiologic studies for "futility": conditional power versus sequential analysis.

Early stopping of a clinical trial is well accepted when there is enough evidence for a significant effect. However, during the course of a trial, there can be reasons to consider early termination for "futility." In epidemiologic studies, costly or destructive laboratory tests or slow case accrual can make it desirable to stop a study early for reasons of efficiency. Estimation of the conditional power (CP) is proposed as a decision tool to stop a study early or to continue it. We consider the disadvantages of this method. We propose (group) sequential continuation of the trial or study as a less arbitrary strategy. We re-analyzed two data sets from the literature to illustrate the advantages of a sequential approach. We conclude that (group) sequential analyses have several advantages over CP. More studies should consider a sequential design and analysis to enable early stopping when enough evidence has accumulated to conclude a lack of the expected effect. Such a strategy can save valuable resources for more promising hypotheses.

Antibodies, Viral↗
PubMed2003

Cranio-maxillofacial trauma: a 10 year review of 9,543 cases with 21,067 injuries.

INTRODUCTION: Cranio-maxillofacial trauma management requires pertinent documentation. Using a large computerized database, injury surveillance and research data describe the whole spectrum of injuries. The goal of this study was to assess the effect of the five main causes of accidents resulting in facial injury on the severity of cranio-maxillofacial trauma. PATIENTS AND METHODS: During a period of 10 years (1991-2000) 9,543 patients were admitted to the Department of Oral and Maxillofacial Surgery, University Hospital of Innsbruck with cranio-maxillofacial trauma. Data of patients were prospectively recorded including cause of injury, age and gender, type of injury, injury mechanisms, location and frequency of soft tissue injuries, dentoalveolar trauma, facial bone fractures and concomitant injuries. Statistical analyses performed included descriptive analysis, chi square test, Fisher's exact test, and Mann-Whitney's U test. This was followed by logistic regression analyses for the three injury types to determine the impact of the five main causes on the type of injury at different ages in facial trauma patients. RESULTS: Five major categories/mechanisms of injury existed: in 3,613 (38%) cases it was activity of daily life, in 2991 (31%) sports, 1170 (12%) violence, in 1,116 (12%) traffic accidents, in 504 (5%) work accidents and in 149 (2%) other causes. A total of 3,578 patients (37.5%) had 7,061 facial bone fractures, 4,763 patients (49.9%) suffered from 6,237 dentoalveolar, and 5,968 patients (62.5%) from 7,769 soft tissue injuries. Gender distribution showed an overall male-to-female ratio of 2.1 to 1 and the mean age was 25.8+/-19.9 years; but both varied greatly depending on the injury mechanism (facial bone fractures: 35.4+/-19.5 years, higher risk for males; soft tissue injuries: 28.7+/-20.5, no gender preference; dentoalveolar trauma: 18+/-15.6, elevated risk for females). For patients sustaining facial trauma, logistic regression analyses revealed increased risks for facial bone fractures (225%), soft tissue lesions (58%) in patients involved in traffic accidents, and dental trauma (49%) during activities of daily life and play accidents. When compared with other causes, the probability of suffering soft tissue injuries and dental trauma, but not facial bone fractures, is higher in sports-related accidents, 12 and 16%, respectively. CONCLUSION: This study differentiated between injury mechanisms in cranio-maxillofacial trauma. The specially trained surgeons treating cranio-maxillofacial trauma are the primary source of information for the public and legislators on implementing preventive measures for high-risk activities. In facial trauma, older persons are prone to bone fractures (increase of 4.4%/year of age) and soft tissue injuries (increase of 2%/year of age) while younger persons are more susceptible to dentoalveolar trauma (decrease of 4.5%/year of age).

Accidents↗
PubMed2001

Optimization of facilitation related to threshold in transcranial magnetic stimulation.

OBJECTIVES: To attain the standardized procedure for optimal facilitation, we analyzed motor-evoked potential (MEP) responses to the degree of voluntary contraction and stimulus intensity. METHODS: Fifteen normal subjects were included. MEPs were elicited at thenar muscles during rest and at gradual voluntary contraction (MVC), using 10, 30, and 50% of MVC. During rest and each contraction, the excitability threshold at rest (RET) and at contraction (CET) were determined. Consecutive stimuli were applied, with the intensity of ratio increments (110-150% of ET). RESULTS: The RET showed a remarkable decrease after contraction. Shortening of latency reached a saturation level at 10% of MVC. Amplitude reached a saturation level at 30% of MVC with 62.7+/-8.5% of the maximum output, which is equal to 140% intensity of CET, and 110% of RET. The MEP amplitudes at rest and at 10% MVC were influenced by their ETs, but those measured above 30% of MVC were not related. CONCLUSIONS: The procedure recommended for optimal facilitation is as follows: to achieve minimal latency of MEPs, a minimal contraction (10% of MVC) with RET intensity is sufficient and for maximal amplitude, a moderate contraction (30% of MVC) with 110% of RET intensity is adequate.

Adult↗
PubMed2002

p values for pathogens: statistical inference from infectious-disease data.

Certain features of infectious-disease data-including the aggregated nature of the data, confounding variables, correlated variables, and non-linear relations-complicate the use of standard statistical procedures. Using data on a helminth infection, we review the use of three parametric tests (analysis of variance, linear regression, and logistic regression), address the complications arising from violation of the assumptions for these tests, and suggest methods of correction. We also compare the relative merits of parametric methods with equivalent non-parametric approaches, and illustrate the differences produced with results from a Kruskal-Wallis test and a t test. The value of using a resampling method-bootstrapping-is also shown. Finally, we discuss problems arising from use of a study design that requires data on the same attribute to be collected from the same individual over a period of time, and present three methods for overcoming this complication, showing that, in the example used, the mixed effect model and generalised estimating equation give similar results.

Analysis of Variance↗
PubMed2000

Comparison of genetic variability and parentage in different ploidy classes of the Japanese oyster Crassostrea gigas.

Chemical treatments with cytochalasin B were used to induce triploidy in the progeny of a mass fertilization of 3 male and 7 female Crassostrea gigas parents. Triploids were produced either by retention of the first (meiosis I (MI) triploids) or the second (meiosis II (MII) triploids) polar bodies. These animals, together with their diploid siblings, were divided for two experiments. One set was used to compare physiological performance, and the other set deployed to compare growth in two different natural environments. For both experiments, genetic variability in different ploidy classes was estimated using three microsatellite loci and eight allozyme loci. The microsatellite loci were highly polymorphic, allowing independent confirmation of ploidy status and the unambiguous identification of parentage for each oyster. Significant differences in parentage were found between ploidy classes, despite the fact they originated from the same mass fertilization. This indicates that the assumptions of a common genetic background among random samples of animals taken from the same mass fertilization may not be generally valid. Knowledge of parentage also allowed the more accurate scoring of allozyme loci. As expected, triploids were found to be significantly more polymorphic than diploids. However, MI triploids were not significantly more polymorphic than MII triploids. MII triploid genotypes were used to estimate recombination rates between loci and their centromeres. These rates varied between 0.29 and 0.71, indicating only moderate chiasma interference.

Alleles↗
PubMed1989

Assessment of coronary bypass surgery and percutaneous transluminal coronary angioplasty.

Coronary bypass surgery developed as another in a line of surgical procedures dating back more than 60 years. The medical profession at first assessed this procedure with time-honored anecdotal techniques. Gradually, for a variety of reasons, improved methods of comparisons worked their way into assessments of bypass surgery. Randomized controlled trials met resistance but have been very influential. Assessment of percutaneous transluminal coronary angioplasty has benefited from the knowledge generated during the last 25 years, but clinicians have been slower to apply the most advanced techniques.

Angioplasty, Balloon↗