Effect of a Surface Sealant Agent on the Color Stability and Surface Roughness of Polymethyl Methacrylate and Nylon Denture Base Materials.

PURPOSE: To evaluate the effect of a surface sealant agent on the color stability and surface roughness (Ra) of two denture base materials: polymethyl methacrylate (PMMA) and nylon. MATERIALS AND METHODS: A total of 96 disk-shaped specimens (10 × 2 mm) were fabricated from heat-cured PMMA and nylon denture base materials (n = 48/material). Each of the color stability and Ra tests were performed on half of the samples in each material group (n = 24), and these subgroups were then subdivided according to the surface treatment applied: 12 specimens were conventionally polished, serving as the control group, and 12 specimens received a sealant on the surface in addition to the surface polishing. Color stability was assessed through measuring the CIEL*a*b* color parameters before and after immersion in coffee solution. Ra was measured and scanning electron microscopy (SEM) photomicrographs were taken before and after thermocycling. Statistical analysis was done using 2-way analysis of variance (α = .05). RESULTS: The surface sealant agent significantly increased the color stability of both materials (P = .047). However, it had no significant effect on the Ra of materials before (P = .600) or after (P = .583) thermocycling. Nylon had a significantly rougher surface than PMMA both before and after thermocycling (P < .001). Similarly, SEM observations show a more irregular texture for nylon than for PMMA. CONCLUSION: Although the sealant agent had no significant effect on the Ra before or after thermocycling, it significantly decreased the color change of nylon and PMMA disks. Based on both statistical analyses and SEM observations, the Ra of PMMA was lower than nylon denture base material.

Comparison of Generalized Estimating Equations and Quadratic Inference Functions in superior versus inferior Ahmed Glaucoma Valve implantation.

BACKGROUND: The celebrated generalized estimating equations (GEE) approach is often used in longitudinal data analysis While this method behaves robustly against misspecification of the working correlation structure, it has some limitations on efficacy of estimators, goodness-of-fit tests and model selection criteria The quadratic inference functions (QIF) is a new statistical methodology that overcomes these limitations. METHODS: We administered the use of QIF and GEE in comparing the superior and inferior Ahmed glaucoma valve (AGV) implantation, while our focus was on the efficiency of estimation and using model selection criteria, we compared the effect of implant location on intraocular pressure (IOP) in refractory glaucoma patients We modeled the relationship between IOP and implant location, patient's sex and age, best corrected visual acuity, history of cataract surgery, preoperative IOP and months after surgery with assuming unstructured working correlation. RESULTS: 63 eyes of 63 patients were included in this study, 28 eyes in inferior group and 35 eyes in superior group The GEE analysis revealed that preoperative IOP has a significant effect on IOP (p = 0 011) However, QIF showed that preoperative IOP, months after surgery and squared months are significantly associated with IOP after surgery (p < 0 05) Overall, estimates from QIF are more efficient than GEE (RE = 1 272). CONCLUSIONS: In the case of unstructured working correlation, the QIF is more efficient than GEE There were no considerable difference between these locations, our results confirmed previously published works which mentioned it is better that glaucoma patients undergo superior AGV implantation.

Knowledge, attitude, and practice of adults to the protective actions against sun in northwest Tehran, Iran.

BACKGROUND: Wrong beliefs about risky actions such as sunbathing and tanning are common due to media advertisements or general lack of knowledge. This work has focused on the knowledge and attitude of a group of citizens in Tehran, Iran and the protective actions they take regarding undesirable effects of the sun.    METHODS:   A descriptive-analytic cross-sectional study has been conducted on 400 randomly selected individuals from the citizens of Shahrak-E-Gharb, an area in northwest Tehran. A questionnaire comprising 24 questions including demographic information, individuals' knowledge about sun exposure, and their opinions and behaviors on protective actions towards solar radiation were used to assess study objectives. Crude and adjusted odds ratios and 95% confidence intervals for socio-demographic factors were calculated through univariate and multivariable logistic regression. RESULTS: The majority of participants had good knowledge about sun protective behaviors. Knowledge about sun exposure duration and tanning was higher among women and those with higher education. As for attitude, only 15% were concerned about skin cancer and 61.8% thought skin cancer can be prevented by sun protection. Higher education was associated with a more positive attitude towards tanning. Among respondents, 41% had suitable clothing to protect themselves against sun burn and only 32% used sunscreen most of the time. University graduates had significantly better practice towards using sunscreen cream compared to high school graduates. CONCLUSION: Although our study sample possessed good knowledge towards sun protection, their attitude and practices were unsatisfactory. Thereby, they need to be informed and educated as how to be safely protected against excessive sun exposure.