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PubMed2004

Analysis of IR thermal imager for mass blind fever screening.

BACKGROUND: Obtaining meaningful temperature for the human body requires identifying a body site that will provide reliable data across a large population. It is important to understand that skin temperature does not solely depend on body-core temperature and may be affected by other physiological and environmental factors. Currently, there is lack of empirical data in correlating facial surface temperature with body core temperature. Present IR systems in use at airports/immigration checkpoints have not been scientifically validated particularly in regards to the false-negative rate. As a result, they may create a false sense of security by underestimating the number of febrile (and possibly infected) individuals. This article evaluates the effectiveness of thermal scanner when it is being used for mass blind screening of potential fever subjects such as SARS or bird flu patients. METHODS: Bio-statistics with regression analysis and ROC is applied to analyse the data collected (502) from the SARS hospital in Singapore and conclusive results are drawn from them. The results are vital in determining two very important pieces of information: the best and yet practical region on the face to take readings and optimal pre-set threshold temperature for the thermal imager. RESULTS: (1) The thermal scanner can be used as a first line tool for the mass blind screening of hyperthermia, (2) the readings from the scanner suggest good correlation with the ear temperature readings, (3) an imager temperature threshold should be determined by the environmental factors, outdoor condition in particular, the physiological site offset and the performance characteristics of thermal imager to warrant the most accurate and reliable screening operation. CONCLUSIONS: The analysis suggested that the thermal imager used holds much promise for mass blind screening when the readings from a specific region have a good correlation with the ear temperature. From the regression analysis, the best reading is taken from the maximum temperature in the eye region, followed by the maximum temperature in the forehead region. With ROC analysis, a randomly selected individual from the fever group has a test value larger than that for a randomly selected individual from the normal group in 97.2% of the time. The test can distinguish between the normal and febrile groups and an optimum threshold temperature for the thermal imager can be found. The pre-set threshold cut-off temperature for the current thermal imager was found to be 36.3 degrees C with reference to the associated environmental condition. Any temperature readings that exceed this reading will trigger off the alarm and a thermometer will be used to verify the whether the person is having fever.

Adult↗
PubMed2006

Temporal neural networks for downscaling climate variability and extremes.

This paper presents an application of temporal neural networks for downscaling global climate models (GCMs) output. Because of computational constraints, GCMs are usually run at coarse grid resolution (in the order of 100s of kilometres) and as a result they are inherently unable to present local sub-grid scale features and dynamics. Consequently, outputs from these models cannot be used directly in many climate change impact studies. This research explored the issues of 'downscaling' the outputs of GCMs using a temporal neural network (TNN) approach. The method is proposed for downscaling daily precipitation and temperature series for a region in northern Quebec, Canada. The downscaling models are developed and validated using large-scale predictor variables derived from the National Center for Environmental Prediction (NCEP) reanalysis data set. The performance of the temporal neural network downscaling model is also compared to a regression-based statistical downscaling model with emphasis on their ability in reproducing the observed climate variability and extremes. The downscaling results for the base period (1961-2000) suggest that the TNN is an efficient method for downscaling both daily precipitation as well as daily maximum and minimum temperature series. Furthermore, the different model test results indicate that the TNN model mostly outperforms the statistical models for the downscaling of daily precipitation extremes and variability.

Climate↗
PubMed2004

Estimation and classification of fMRI hemodynamic response patterns.

In this paper, we propose an approach to modeling functional magnetic resonance imaging (fMRI) data that combines hierarchical polynomial models, Bayes estimation, and clustering. A cubic polynomial is used to fit the voxel time courses of event-related design experiments. The coefficients of the polynomials are estimated by Bayes estimation, in a two-level hierarchical model, which allows us to borrow strength from all voxels. The voxel-specific Bayes polynomial coefficients are then transformed to the times and magnitudes of the minimum and maximum points on the hemodynamic response curve, which are in turn used to classify the voxels as being activated or not. The procedure is demonstrated on real data from an event-related design experiment of visually guided saccades and shown to be an effective alternative to existing methods.

Bayes Theorem↗
PubMed2005

Organic air pollutants inside and outside residences in Shimizu, Japan: levels, sources and risks.

Concentrations of 38 organic air pollutants including aromatic hydrocarbons (AHCs), carbonyl compounds (CCs), volatile organic halogenated compounds (VOHCs), and organophosphorus compounds (OPCs) were measured in indoor and outdoor air in an industrial city, Shimizu, Shizuoka Prefecture, Japan. Levels of pollutants tended to be higher indoors than outdoors in both summer and winter except for benzene, carbon tetrachloride, trichloroethylene, tetrachloroethylene, and dichlorvos (DDVP). This trend was especially pronounced for CCs such as formaldehyde and acetaldehyde. For the organic air pollutants, the concentrations of AHCs and VOHCs substantially increased in winter, but not those of CCs and OPCs; the trends were similar for both indoors and outdoors. We investigated possible indoor sources of pollutants statistically. Multiple regression analysis of corresponding indoor and outdoor concentrations and the responses to our questionnaire showed that indoor concentrations of certain AHCs were significantly affected by their outdoor concentrations and cigarette smoking. For formaldehyde, indoor concentrations were significantly affected by house age and the presence of carpet or pets. For p-dichlorobenzene (pDCB), the concentrations in bedroom trended to be higher than those in other indoors and outdoors, suggested that mothballs for clothes present in bedrooms are the principal indoor source of pDCB. We compared indoor and outdoor pollutant concentrations to acceptable risk limits for 11 organic air pollutants. In indoors without smoking samples, the geometric mean concentrations of benzene, formaldehyde, acetaldehyde, carbon tetrachloride, pDCB, and DDVP exceeded the equivalent concentration representing the upper bound of one-in-one-hundred-thousand (1x10(-5)) excess risk over a lifetime of exposure.

Air Pollutants↗
PubMed2004

Length stay, discharge disposition, and hospital charge predictors.

THIS STUDY EXPLORED the effect of patient, clinical, and treatment factors on length of stay (LOS), discharge disposition, and total acute care hospital charges for older adults undergoing elective total hip arthroplasty or total knee arthroplasty. A CAUSATIVE RETROSPECTIVE DESIGN was used, and data analysis included descriptive statistics, multiple regression, and logistic regression. SIGNIFICANT DIFFERENCES in predictor variables (ie, age, gender, living arrangement, comorbidities, postoperative complications) were found between patients who were discharged to home and those who were discharged to another facility. Only postoperative complications contributed significantly to LOS. Total surgical time and postoperative complications contributed significantly to hospital charges.

Aftercare↗
PubMed2001

Causal models for road accident fatalities in Yemen.

An identification of the causes of road accident fatalities is becoming more important with the growth of technology, population, number of vehicles and the need for their use. Many authors have addressed the problem in the past but no universal findings have been obtained. The problem tends to be different under different environments and for different geographical regions. The aim of this paper is to develop a model for the analysis and forecasting of road accident fatalities in Yemen considering data restrictions. The proposed data has a particular structure of accident occurrence that has not been reported in any existing research using data in other countries. The available data for the period 1978-1995 is used to build models to understand the nature and extent of the causes of fatalities. Part of the data is used for model building and part of it for test purposes. The issues of correlation and causality have been addressed and multiple collinearity is investigated and dealt with. Two alternative models are proposed based on both statistical grounds and that of practicality in viable decision making. The influence of consuming a locally grown stimulant called Qat on road users has been addressed and it is found that it increases the risk of accidents. This is not the common understanding within the authorities in Yemen as growing and consuming Qat is unregulated.

Accidents, Traffic↗
PubMed2003

Applying the random effect negative binomial model to examine traffic accident occurrence at signalized intersections.

Poisson and negative binomial (NB) models have been used to analyze traffic accident occurrence at intersections for several years. There are however, limitations in the use of such models. The Poisson model requires the variance-to-mean ratio of the accident data to be about 1. Both the Poisson and the NB models require the accident data to be uncorrelated in time. Due to unobserved heterogeneity and serial correlation in the accident data, both models seem to be inappropriate. A more suitable alternative is the random effect negative binomial (RENB) model, which by treating the data in a time-series cross-section panel, will be able to deal with the spatial and temporal effects in the data. This paper describes the use of RENB model to identify the elements that affect intersection safety. To establish the suitability of the model, several goodness-of-fit statistics are used. The model is then applied to investigate the relationship between accident occurrence and the geometric, traffic and control characteristics of signalized intersections in Singapore. The results showed that 11 variables significantly affected the safety at the intersections. The total approach volumes, the numbers of phases per cycle, the uncontrolled left-turn lane and the presence of a surveillance camera are among the variables that are the highly significant.

Accidents, Traffic↗
PubMed2002

A longitudinal study of breastfeeding and weaning practices during the first year of life in Dunedin, New Zealand.

OBJECTIVE: To investigate infant feeding practices during the first year of life in a group of white infants in Dunedin, New Zealand. DESIGN: Prospective study of infants from birth to 12 months of age. PARTICIPANTS: A self-selected sample of 74 white mothers and their infants born in Dunedin, New Zealand, between October 1995 and May 1996. Statistical analyses Regression analyses were performed to determine factors associated with successful breastfeeding initiation and duration. RESULTS: Among mothers, 88% (n=65) initiated breastfeeding, 42% (n=31) were exclusively breastfeeding at 3 months, and 34% (n=25) were partially breastfeeding at 12 months. Intention to breastfeed increased the likelihood of successful breastfeeding initiation. Mothers who reported that they did not have enough breastmilk tended to exclusively breastfeed for a shorter period of time. Tertiary education and exclusively breastfeeding at 1 month were associated with a longer duration of breastfeeding. Perception of breastfeeding in public as embarrassing was associated with a shorter duration of breastfeeding. Among infants, 45% (n=33) were given nonmilk foods before 4 months of age, and 69% (n=51) were given unmodified cow's milk as a beverage before 12 months. APPLICATIONS: Breastfeeding rates in this study, although higher than in many Western countries, were still lower than current recommendations. Our findings suggest that women should be taught how to increase their breastmilk supply. Parents should also be informed of the importance of delaying the introduction of nonmilk foods until their infant is 4 to 6 months of age and cow's milk until they are 12 months of age. Society also needs to address the social issue of embarrassment many mothers feel when breastfeeding in public.

Adult↗
PubMed1996

Relationship of hunger and food insecurity to food availability and consumption.

OBJECTIVE: To describe the relationship of new measures of hunger and food insecurity to household food supplies and individual food and nutrient intake. DESIGN AND SETTING: A questionnaire containing the Radimer/Cornell hunger and food insecurity items and questions on eating patterns and the frequency of fruit and vegetable consumption was administered to subjects during a personal interview in their homes. A 24-hour diet recall and a household food inventory were conducted at the initial interview and at a follow-up visit. SUBJECTS: Participants were 193 women drawn from a random sample of 308 women who had completed a previous health census in a rural New York State county. Subjects' ages ranged from 15 to 40 years. All had children living at home and less than 16 years of education. STATISTICAL ANALYSES: Regression analysis was used to test for linear trends across food insecurity groups for the household food inventory scores and for the frequency of consumption of fruits and vegetables. t Tests were used to assess differences between the food secure and food insecure groups for nutrient and food group means. A chi 2 test for trend was used to examine differences in the distribution of nutrient and fruit and vegetable intake between the food secure and food insecure groups. RESULTS: A significant decrease in the frequency of consumption of fruits and vegetables and the amount of food in the household and a significant increase in scores indicative of disordered eating patterns were associated with a worsening of food insecurity status. Potassium and fiber intake and fruit consumption differed significantly between the food secure and food insecure groups. The percentage of respondents consuming less than the Recommended Dietary Allowance for vitamin C and fewer than five fruits and vegetables per day was significantly greater among food insecure respondents than food secure respondents. APPLICATIONS/CONCLUSIONS: The quantity of food available in households and consumption of fruits and vegetables decreased with increasingly severe problems with food insecurity and hunger. In this rural population, the Radimer/ Cornell measures were useful in identifying households experiencing food insecurity and providing information about the nature of the food supply and the dietary intake problems experienced by food insecure households and persons, suggesting that these measures may be useful on community surveys designed to examine food insecurity issues.

Adolescent↗
PubMed1982

Maternal smoking and birth weight in relation to dietary habits.

A study on dietary and smoking behavior during pregnancy was performed between January, 1976, and September, 1979, at the St. Antoine Maternity Hospital in Paris. In addition to the routine clinical examinations at the third, sixth, eight, and ninth months of pregnancy, the women were systematically questioned about their dietary and tobacco habits. No dietary advice was given by the dietitians at any time, nor was there special counseling against smoking. Among 534 women who were followed up, 200 (37%) were smokers before pregnancy. At the sixth month, half of them had stopped smoking and the others had reduced their consumption. The analysis showed that the mean caloric intake and the gain in weight were the highest in the women who continued to smoke and the lowest in nonsmokers. Intermediate results were found in smokers who stopped. Birth weight was, on the average, 70 gm lower among smokers throughout pregnancy, compared with the other two groups, but this difference was not significant. These findings are consistent with the hypothesis that the negative effects of smoking on the fetus could be compensated for, to a great extent, by extra food.

Adult↗
PubMed1990

Serologic determinants of survival in patients with squamous cell carcinoma of the head and neck.

Specific circulating serum proteins may reflect unique properties governing the growth and progression of head and neck cancers. One hundred three previously untreated patients with squamous cell carcinoma of the head and neck were prospectively evaluated for serum IgA, IgG, and IgM and C1q-binding macromolecules. Immunoglobulins were assessed by the immunoturbidimetric technique. C1q-binding macromolecules (C1qBM) were measured utilizing the iodine-125 assay of Zubler et al (J Immunol 1976; 116: 232-5). Neither the level of serum immunoglobulins nor C1qBM values were correlated with the primary site, AJC (American Joint Committee on Cancer) stage of disease, or size of primary lesion. Likewise, comparison of serum IgA with C1qBM values demonstrated that these laboratory parameters were independent variables (r = 0.15 by Pearson linear regression). Univariate statistical analysis, utilizing the Cox proportional hazard model, showed serum IgA and C1qBM values to each contribute significantly to the ability to predict survival in patients with advanced squamous cell carcinoma of the head and neck (p = 0.01 and 0.003, respectively). Furthermore, multivariate analysis reveals that both C1qBM and serum IgA levels contribute significantly to the hazards model beyond staging in predicting survival (p less than 0.001). Predictive results were most apparent in patients with stage IV disease and related to the probability of both regional and distant metastatic recurrences. Conversely, serologic analysis provided no information in patients who were staged early. These results support pretreatment multiparametric serologic analysis of patients with squamous cell carcinoma of the head and neck.

Adult↗
PubMed1999

The Frail Elderly Functional Assessment questionnaire: its responsiveness and validity in alternative settings.

OBJECTIVE: To test the Frail Elderly Functional Assessment (FEFA) questionnaire for responsiveness (sensitivity to change) to low-level functional tasks in a frail elderly cohort and to evaluate its validity over the telephone or when administered to a caregiver proxy. SUBJECTS: Fifty-eight elderly patients from three urban inpatient rehabilitation settings and an outpatient geriatrics center. METHODS: A prospective, clinical, comparative trial. The FEFA questionnaire was administered serially. For validity, subjects were observed performing the tasks on the questionnaire within 24 hours of each interview. For responsiveness, repeat measures were performed within a 1- to 2-week period. Validity and sensitivity to change (responsiveness) of the questionnaire were determined by correlating patient responses to direct observations by rehabilitation staff. Responsiveness was also determined based on the Guyatt technique that divides clinically significant change by the normal variance, sigma/(2x [mean squared error])1/2, as well as by measures of effect size, standardized response means, and relative efficiency tests for responsiveness. To evaluate FEFA validity in alternative settings, kappa statistic and regression analyses were used based on the previously validated interviewer-administered format. RESULTS: Responsiveness was excellent with effect size (.35), standardized response means (.48), and relative efficiency (2.67) tests as well as Guyatt (1.26). There was 83% agreement when compared with FEFA task performance. Regression between change in FEFA score versus performance testing was significant (r2 = .33; p = .01). ANOVA was significant at a p = .03 for FEFA scores at first measure in rehabilitation compared to second. Correlation for caregiver proxy administration was .92 (p< or =.0001) and for telephone administration was .99 (p<.0001). CONCLUSIONS: The FEFA questionnaire, previously demonstrated to be reliable and valid, is sensitive to functional change (responsive) in frail elderly people. It is also valid when administered by phone or to a caregiver proxy.

Activities of Daily Living↗
PubMed1982

Correlation between serum antichlamydial antibodies and tubal factor as a cause of infertility.

Although salpingitis frequently produces tubal damage and infertility, many women with tubal factor as a cause of their infertility do not have a clinical history of salpingitis. In order to investigate whether or not some such cases might be due to subclinical chlamydial infections, we measured antichlamydial antibodies in the serum of 172 women consecutively undergoing evaluation for infertility. Only 16 (9.3%) had a prior history of salpingitis. Sixty-one (35%) had antichlamydial antibodies (S+), and of these 75% had tubal factor as a sole or contributing cause of their infertility, versus 28% of the seronegative (S-) women (x2 - 34, P less than 0.001). There was no association between chlamydial seropositivity and any infertility factor other than tubal factor in multivariant analyses. Subclinical infections with Chlamydia trachomatitis may be a major cause of tubal infertility in the United States, and chlamydial serologic studies may be useful in identifying the subset of infertile women likely to have tubal factor.

Adult↗
PubMed2003

Charts for cervical length in singleton pregnancy.

OBJECTIVES: To construct charts for cervical length in a low risk population measured by transvaginal ultrasonography. METHODS: Pregnant women of an apparently normal population were seen in the ultrasound division of the University Women's Hospital Basel between 20 and 34 weeks of gestation and underwent once (one measurement per subject) a transvaginal ultrasound measurement of the cervix under standardized conditions. In order to establish normal values of the cervical length, finally only women who delivered spontaneously at term (>37 weeks of gestation) remained in the study. Exclusion criteria were preterm labor, multiple pregnancies, cerclage or surgical intervention prior to pregnancy. For statistical evaluation, regression analysis and calculation of 5th and 95th percentiles were performed. RESULTS: A total of 669 cervical measurements were recorded. The number of measurements differed from 22 measurements at 23 weeks of gestation to 86 at 31 weeks of gestation. Cervical length gradually and significantly decreased as the gestational age progressed (between 20 and 34 weeks of gestation). New charts with the 5th, 50th and 95th percentile are presented and compared with previously published data. CONCLUSIONS: Our charts for cervical length in a limited risk population can be used for observing patients at high risk of preterm delivery and for clearly identifying a significant deviation or decline in the percentile for these subjects.

Adult↗
PubMed1998

Quantitative analysis of cholesterol and cholesteryl esters in human atherosclerotic plaques using near-infrared Raman spectroscopy.

Raman spectroscopy is a non-destructive analytical technique and previous results have shown that qualitative analysis of the lipid component of human atheromatous arteries is feasible. In this paper, we describe a quantitative analytical method for cholesterol and cholesteryl esters in human atherosclerotic plaques, combined with Raman spectroscopic results, using partial least-squares (PLS) regression, a statistical multivariate method based on factorial analysis. Twenty-nine human atherosclerotic pooled samples were studied and the results of Raman spectroscopy coupled with the PLS method were compared to biochemical results. The standard error of prediction was 16.1, 13.6, 1.9, 3.3 and 3.4 mg/g for total cholesterol, free cholesterol, palmitate cholesteryl, oleate cholesteryl and linoleate cholesteryl, respectively. The repeatability of Raman spectroscopy was found to be excellent. Our results show that Raman spectroscopy is a promising technique to obtain a consistent and non-destructive quantitative analysis of cholesterol and cholesteryl esters in human atherosclerotic lesions. In situ and in vivo analysis is a possibility in the near future.

Aged↗
PubMed1992

Factors associated with condom use among sexually active female adolescents.

A health belief model of condom use was used to identify factors associated with condom use in 390 sexually active female adolescents, aged 12 through 19 years, recruited at the time of a visit for reproductive health care. Fifty-six percent were white and the remainder black. Nineteen percent had genitourinary infections with Chlamydia trachomatis. Forty-six percent reported having had more than one sexual partner in the preceding year. Reported condom use for at least one specific reason (prevention of pregnancy, sexually transmitted disease, or acquired immunodeficiency syndrome) increased as behavioral, emotional, and sexually transmitted disease risk decreased, and as cognitive maturity and positive condom attitudes increased. Although uses of condoms to prevent pregnancy, sexually transmitted disease, and acquired immunodeficiency syndrome were positively intercorrelated, each made a contribution to explaining condom use at most recent coitus (odds ratios 2.95, 3.96, and 2.81, respectively). After statistical adjustment for the reported reasons for previous condom use, behavioral risk was the only additional factor associated with condom use at the most recent sexual encounter; women who participated in more risk behaviors (substance and alcohol use and minor delinquency) were less likely to have used a condom (odds ratio 0.61). Knowledge about sexually transmitted disease and acquired immunodeficiency syndrome, and concurrent use of contraceptive pills, were not related to condom practices. The data suggest that adolescents' perceptions about condoms, including the individual functions of condoms for contraception and for prevention of sexually transmitted disease, may be important in determining their use. Engaging in unprotected intercourse may be part of a larger behavioral domain that includes other unhealthy behaviors.

Adolescent↗
PubMed2003

Facial moulage: the effect of a retarder on compressive strength and working and setting times of irreversible hydrocolloid impression material.

STATEMENT OF PROBLEM: Irreversible hydrocolloid is widely used as an impression material for fabrication of extraoral maxillofacial impressions. A disadvantage of irreversible hydrocolloid, however, is its limited working time. PURPOSE: This study tested the compression strength (elastic recovery) and working and setting times for an irreversible hydrocolloid impression material after a retarder was added. MATERIAL AND METHODS: The irreversible hydrocolloid (Jeltrate) was mixed with water in a standard water/powder mixture of 18 mL (1 unit) of water and 7 g (1 unit) of the impression material. Test specimens (n = 3) were prepared by adding 2, 4, 6, and 8 drops of monobasic sodium phosphate (the retarder) to each. Three other specimens, to which no retarder was added, served as the control. Specimens were prepared according to the American National Standards Institute/American Dental Association's specification no.18 guidelines for irreversible hydrocolloid impression material. Immediately after the specimens were prepared, the flat end of a polished rod of poly(methyl methacrylate) was placed in contact with its exposed surface and quickly withdrawn. The working-time experiment was a pass/fail test conducted 30 seconds before the initial setting time. The initial setting time was established as extending from the start of the mix to the time when the impression material no longer adhered to the end of the rod. To determine how the compressive strength of the modified irreversible hydrocolloid (with retarder added) compared with that of the control, the mean stress at maximum load (Mpa) was analyzed. The compressive strength (MPa) was calculated. Statistical analysis consisted of descriptive statistics and regression analyses. RESULTS: The results of this experiment demonstrated that the elastic recovery of the irreversible hydrocolloid did not change with the addition of sodium phosphate (2 to 8 drops). The percent recovery with was 95.95% +/-.42%, 96.33% +/-.82%, and 96.28% +/-.53% for 0 (control), 2 and 8 drops, respectively. Average setting times for control specimens were 2 minutes 20 seconds +/- 0 seconds for the control specimen (0 drops) to 11 minutes 20 seconds +/- 1 minute 50 seconds for the test specimen with 8 drops. There was a direct relationship (R(2) = 0.85) between the number of drops added and the setting time. All control specimens and test specimens containing 2, 4, 6, and 8 drops of monobasic sodium phosphate produced acceptable levels of elastic recovery (> or =95%). CONCLUSION: Within the limitations of this study, predictable longer working and setting times were demonstrated for the irreversible hydrocolloid specimens with 1 to 8 drops of the sodium phosphate solution tested. The specimens with 8 drops of retarder solution exhibited variable setting times and would not be suitable for clinical use. The compressive strength of the modified irreversible hydrocolloid material tested was compromised because of the addition of sodium phosphate solution; however, recovery from deformation remained satisfactory as retarder solution was added.

Alginates↗
PubMed1996

Color stability: denture base resins processed with the microwave method.

Several quick heat-cured denture base resin systems and microwave processing resins have been introduced to provide easier and faster processing. The microwave processing method is the fastest of the heat-cured processing methods. Conventional acrylic resins processed with the microwave method seem to possess adequate physical properties, and one study indicated that a microwave acrylic resin was reasonably color stable under conditions of accelerated aging, although manufacturers do not recommend using them for microwave processing. The purpose of this study was to evaluate the color stability of seven conventional and one microwave heat-cured denture base materials processed with the microwave method. The samples were subjected to conditions of accelerated aging to test for color stability. The color stability was quantitatively measured and color measurements were made before weathering and at 300, 600, and 900 hours. The mean color change for each sample group was statistically analyzed with polynomial regression to determine the pattern of color change over time. The differences in color change for the acrylic resins were significant for all materials, but the color change for Lucitone Hy-pro was not noticeable on visual examination. The results of this study revealed that color changes occurred after accelerated aging in heat-cured denture base resins and Acron GC microwave acrylic resins processed with the microwave method. Hy-pro and TruTone materials exhibited the least color change; Hy-pro material was the most color stable material.

Acrylic Resins↗