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Biomedical subjects

W M Liang

Publications and source records attributed to W M Liang.

11 recordsLinked to original sources
PubMed2004

Factors affecting the accuracy of elastometric impression materials.

OBJECTIVES: The purpose of this study was to evaluate the effects of (1) various impression materials, (2) different storage times and (3) the proportion of inorganic filler on the accuracy and stability of elastometric impression materials. METHODS: The impression materials studied included three alginate impression materials (Algiace Z, CAVEX and Jeltrate), five commercial silicone impression materials (Aquasil, Exaflex regular type, Express, Coltex fine and Rapid liner) and two experimental silicone impression materials designed for this study (KE106A and KE106B). Impressions were made of 10 metal dies that mimicked prepared crowns. After an impression was taken, dental stone was immediately poured into the alginate impressions, while the silicone impressions was poured 30 min later and waited for 1 h for setting. The second and third stone dies were made 1 and 24 h later, respectively. The diameters of the occlusal surfaces of the metal dies and stone casts were determined using photographs of the surfaces taken with a Kodak DC 290 digital camera. The pictures were then measured using a photomicrograph digitized integration system to calculate any discrepancy. Because each impression was used to make three rounds of stone dies, two-factor mixed factorial ANOVA was used to evaluate the effect of materials and storage time on the accuracy of the stone casts. The simple effects analysis, combined with multiple comparisons considering the per family type I error rate, was performed following confirmation that an interaction between the two factors was significant. RESULTS: The results showed that: (1) there was a significant interaction effect between materials and storage times on the accuracy of the impressions. (2) Two addition type silicone materials, Aquasil and Exaflex, had the greatest accuracy and stability. (3) The experimental material KE106A had the least accuracy in the first and second rounds and the alginate impression material CAVEX had the least accuracy in the third round. (4) The stabilities of CAVEX and Jeltrate were the least consistent of the 10 materials and decreased significantly with storage time. (5) When the experimental material had a low proportion of filler (KE106A), there was a significantly greater dimensional discrepancy compared to the same material with a higher proportion of filler (KE106B). CONCLUSIONS: The accuracies varied among the 10 impression materials over three rounds. Of all the materials, the addition type silicone materials, Aquasil and Exaflex, had relatively greater accuracy and stability. The discrepancy of the alginate impression materials increased with storage time. The large loading of filler showed less discrepancy.

Alginates↗
PubMed2001

Detection of Epstein-Barr virus DNA in the peripheral-blood cells of patients with nasopharyngeal carcinoma: relationship to distant metastasis and survival.

PURPOSE: Nasopharyngeal carcinoma (NPC) has been proved to be an Epstein-Barr virus (EBV)-associated cancer. By use of nested polymerase chain reactions (PCRs), we examined whether the presence of EBV DNA in the peripheral-blood cells (PBC) can serve as a prognostic indicator for NPC. PATIENTS AND METHODS: Peripheral blood from 124 patients with NPC who had no evidence of distant metastasis and 114 healthy volunteers with serologically positive findings for EBV infection was collected prospectively. Plasma and erythrocytes were separated. DNA was extracted from PBCs and analyzed by a nested PCR using primers specific to Epstein-Barr virus nuclear antigen 1 (EBNA-1). All patients were treated by radiotherapy with or without chemotherapy. Clinical parameters and status of EBNA-1 in PBCs were used for survival analysis using the Kaplan-Meier method and the Cox proportional hazards model. RESULTS: Positive rates of EBNA-1 DNA in PBCs of NPC patients and healthy volunteers are 71% and 14%, respectively (P =.001). No significant difference was observed with regard to the clinical characteristics of patients who were EBNA-1-positive (n = 88) and those who were EBNA-1-negative (n = 36). After a median follow-up period of 38 months (range, 24 to 56 months), 29 of 88 EBNA-1-positive patients and only one of 36 EBNA-1-negative patients developed distant metastases (P =.00015). Kaplan-Meier estimates of overall survival (P =.0010), metastasis-free survival (P =.0004), and progression-free survival (P =.0004) were significantly lower for the patients in the EBNA-1-positive group than for those in the EBNA-1-negative group. Multivariate Cox analysis confirmed the same results. CONCLUSION: The presence of EBNA-1 DNA in PBCs is a novel, important risk factor for patients with NPC that indicates a significantly higher risk of developing distant metastasis as well as a lower survival rate.

Adult↗
PubMed2001

Reinforcement of acrylic denture base resin by incorporation of various fibers.

This study was designed to evaluate improvements in the mechanical properties of acrylic resin following reinforcement with three types of fiber. Polyester fiber (PE), Kevlar fiber (KF), and glass fiber (GF) were cut into 2, 4, and 6 mm lengths and incorporated at concentrations of 1, 2, and 3% (w/w). The mixtures of resin and fiber were cured at 70 degrees C in a water bath for 13 h, then at 90 degrees C for 1 h, in 70 x 25 x 15 mm stone molds, which were enclosed by dental flasks. The cured resin blocks were cut to an appropriate size and tested for impact strength and bending strength following the methods of ASTM Specification No. 256 and ISO Specification No. 1567, respectively. Specimens used in the impact strength test were reused for the Knoop hardness test. The results showed that the impact strength tended to be enhanced with fiber length and concentration, particularly PE at 3% and 6 mm length, which was significantly stronger than other formulations. Bending strength did not change significantly with the various formulations when compared to a control without fiber. The assessment of Knoop hardness revealed a complex pattern for the various formulations. The Knoop hardness of 3%, 6 mm PE-reinforced resin was comparable to that of the other formulations except for the control without fiber, but for clinical usage this did not adversely affect the merit of acrylic denture base resin. It is concluded that, for improved strength the optimum formulation to reinforce acrylic resin is by incorporation of 3%, 6 mm length PE fibers.

Acrylic Resins↗
PubMed1999

Respiratory abnormalities among male foundry workers in central Taiwan.

The objectives of this study were to determine the relationship between exposure levels and respiratory abnormalities, to measure FVC and FEV1(1) changes per year based on work duties and to investigate the prevalence of and factors related to pneumoconiosis. A total of 583 male workers from 50 iron foundries in central Taiwan were investigated. First, workers' respiratory symptoms were categorized using a modified American Thoracic Society (ATS) questionnaire and then were verified by physician's examination. Next, pulmonary function tests were performed including: forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and forced expiratory flow rate. A chest radiograph was used to diagnose pneumoconiosis according to ILO criteria. Furnace workers were found to have the highest prevalence of chronic phlegm, thoracic disorders and chronic bronchitis. In general, smokers had a higher prevalence of respiratory symptoms as compared with non-smokers. Pulmonary function abnormalities and pneumoconiosis were closely linked to smoking and work duration. After adjusting for age, height and smoking there was a significant decrease based on work duration in FVC and FEV1 for furnace and moulding workers compared with after-processing and administrative workers. The overall prevalence of pneumoconiosis was 8.8%, highest among furnace (16.3%) and after-processing workers (11.4%) and lowest among administrative workers (2.5%). Using multiple logistic regression, the risk of developing pneumoconiosis (as compared with the administrative workers) for furnace workers was highest (8.98 times greater risk), followed by after-processing workers (6.77 times greater risk) and moulding workers (5.41 times greater risk). Prolonged exposure to free silica, and smoking habits, can result in respiratory abnormalities among foundry workers.

Adult↗
PubMed1997

A median-based test under informative dropout: the one-sample case.

We consider a clinical trial in which the outcome can be assessed by a continuous measure and where dropouts tend to have poorer efficacy than completers. When each subject can act as his/her own control, efficacy is measured by the difference between the outcome measurements at two times. When all subjects complete the protocol, a paired t-test can be used to test for a treatment effect, i.e., whether or not the mean difference is zero. When a patient does not return for the final evaluation, a measure of efficacy cannot be computed for that subject. Often, data from dropouts are ignored and only the observed pairs are used to analyze the data. When the reason for dropping out is not random, the result may be misleading. In this paper, we assume that (1) the distribution of the measure of efficacy (i.e., the change between two outcome measurements) is Gaussian, (2) dropouts would have worse efficacy than the median if they were observed, and (3) the dropout rate is less than 50%. We propose a median-based t-like statistic using the sample median in place of the sample mean. The variance of the median is estimated using only data from the complete half-sample, i.e., the half-sample with better efficacy. Simulations under five patterns of dropouts are performed to compare the proposed statistic with the paired t-test. The results show that the median-based statistic provides a conservative bound for the test of significance of the treatment. In contrast, because the paired t-test does not preserve its level of significance, except when the dropout mechanism is uniform, the paired t-test should not be used for trials in which dropouts tend to have poorer efficacy than completers.

Bias↗
PubMed1995

Emotional distress, coping, and adjustment in human immunodeficiency virus infection and acquired immune deficiency syndrome.

Fifty-seven ambulatory, human immunodeficiency virus (HIV)-infected patients at various stages of disease progression and 17 HIV seronegative controls were examined in a cross-sectional study with self-administered measures of emotional distress, coping, and adjustment to illness. All infected and control subjects were homosexual or bisexual and free of acute medical illness. The findings indicated that both uninfected and infected subjects had enhanced emotional distress in a variety of domains. However, while somatic and cognitive-ruminative complaints were greater in symptomatic subjects relative to controls, depression and anxiety were not. Professed coping strategies were heterogeneous and not particularly related to HIV diagnostic status, with the exception of planful problem solving which was decreased for acquired immune deficiency syndrome subjects. Disruption in several aspects of daily life adjustment was markedly increased in symptomatic subjects. The findings suggest that both HIV seropositive status and perceived risk for infection produce a sustained level of generalized psychological distress. Even in the absence of current medical illness, patients with advanced disease progression are concerned primarily with anticipated medical implications and cognitive effectiveness.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Cognitive deficits associated with human immunodeficiency virus encephalopathy.

The encephalopathy associated with direct nervous system infection by the human immunodeficiency virus (HIV) has been recognized as one of the major debilitating aspects of the acquired immunodeficiency syndrome (AIDS) and of pre-AIDS conditions. A comprehensive neuropsychological examination of symptomatic HIV-infected subjects without opportunistic cerebral disease demonstrated a distinctive pattern of cognitive deficits marked by prominent attentional impairment. Evidence of organizational and reasoning impairments also was observed, but language, visual-spatial, and memory consolidation abilities were relatively preserved. The findings suggest a profile of impairment similar to other cognitive syndromes involving dysfunction of predominantly anterior brain structures and projections and suggest a rationale for psychostimulant drug treatment.

AIDS Dementia Complex↗
PubMedDate not supplied

Understanding young children's health beliefs and diabetes regimen adherence.

Previous studies of chronic illness management in children have focused mainly on parents' health beliefs. However, children's health beliefs also can be an important factor in predicting adherence. Indeed, children 6 to 10 years old spend most waking hours away from home, are under less parental supervision, and are becoming more responsible for their own care. The purpose of this study was to develop a pictorial, multi-item instrument to measure dimensions of the Health Belief Model (HBM) and self-efficacy (SE), designed specifically for children with diabetes, thus making it possible to examine both the parent's and child's health beliefs; to explore the relationship between their beliefs; and to examine the extent to which these beliefs are predictors of adherence and metabolic control.

Attitude to Health↗
PubMedDate not supplied

Risk factors of pulmonary hemorrhage in very-low-birth-weight infants: a two-year retrospective study.

Pulmonary hemorrhage is a serious complications in very-low-birth-weight (VLBW) infants with respiratory distress syndrome (RDS). We undertook a 2-year retrospective study to investigate the predisposing factors and the incidence of pulmonary hemorrhage in VLBW infants. From January 1997 through December 1998, twenty infants were diagnosed with massive pulmonary hemorrhage (MPH) according to the following criteria: active bleeding from the endotracheal tube, acute drop in hematocrit (> or = 10%), and the development of multilobar infiltration on chest radiograph. The mean gestational age was 26.9 +/- 2.5 weeks, the mean birth weight was 909 +/- 290 g. Twenty historic controls with similar gestational age and birth weight were retrospectively identified during the study period. The incidence of MPH in VLBW infants was 5.9%(20/340). A lack of prenatal corticosteroid administration, surfactant replacement therapy for RDS, and a patent ductus arteriosus (PDA) with cardiovascular dysfunction requiring dopamine support were the significantly predisposing factors of MPH in the acute stage (< or = 7th day of life). To avoid MPH and decrease mortality and morbidity in the acute stage, prenatal corticosteroid administration, evaluation of the necessity of surfactant therapy, and early recognition and aggressive treatment of hemodynamically significant PDA were necessary.

Adrenal Cortex Hormones↗