Improved Dimethyl Ether Production from Syngas over Aerogel Sulfated Zirconia and Cu-ZnO(Al) Bifunctional Composite Catalysts.

This work is dedicated to the study of the effect of the synthesis conditions (drying and calcination) of sulfated zirconia on the final catalytic behavior of bifunctional composite catalysts prepared by the physical mixing of the sulfated zirconia (methanol dehydration catalyst) with Cu/ZnO/Al2O3 (CZA; methanol synthesis catalyst). The main objective was to optimize the CZA-ZrO2/SO42- composite catalyst for its use in the direct production of dimethyl ether (DME) from syngas. Sulfated zirconia aerogel (AZS) and xerogel (XZS) were prepared using the sol-gel method using different solvent evacuation conditions and calcination temperatures, while the Cu-ZnO(Al) catalyst was synthesized using the coprecipitation procedure. The effectivity of CZA-ZrO2/SO42- composite catalysts for the direct production of dimethyl ether (DME) from syngas was evaluated in a flow reactor at 250 °C and 30 bar total pressure. The characterization of the sulfated zirconia aerogels and xerogels using different techniques showed that the mesoporous aerogel (AZS0.5300) exhibited the best textural and acidic properties due to the gel drying under supercritical conditions and calcination at 300 °C. As a result, the composite catalyst CZA-AZS0.5300 exhibited seven times higher DME production than its xerogel-containing counterpart (364 vs. 52 µmolDME·min-1·gcat-1). This was attributed to its well-matched metal surface, mesoporous structure, optimal crystallite size and, most importantly, its higher acidity.

Clinical Marginal and Internal Adaptation of Single Metal-Ceramic Crowns Fabricated with Casting, Milling, and Milling/Sintering Methods.

PURPOSE: To compare the adaptation of single metal-ceramic crowns (MCCs) fabricated with three different methods: lost-wax metal casting (LMC), milling of hard cobalt-chromium (HCC) blanks, and milling of soft presintered cobalt-chromium (SCC) blanks. MATERIALS AND METHODS: In this double-blind parallel randomized clinical trial, 60 single MCCs were fabricated using three different methods. Adaptation of the copings was evaluated radiographically, visually, and microscopically. Data were compared among the three groups using the Kruskal-Wallis test, followed by the Dunn post hoc test, one-way ANOVA, and paired t test (α = .05). RESULTS: Radiographic data showed that the frequency of crowns with no marginal discrepancy was significantly higher in the SCC group than the LMC group. Evaluation of marginal adaptation with an explorer revealed that crowns with excellent marginal adaptation had lower frequency in the LMC group than the HCC and SCC groups. In the silicone replica technique, the recorded data revealed no significant difference. Application of porcelain veneering did not affect the adaptation of the copings. CONCLUSIONS: The SCC and HCC groups showed better clinical outcomes compared to the LMC group. However, all MCCs fabricated with the LMC method, milling of HCC blanks, and milling of SCC blanks had acceptable clinical adaptation. Int J Prosthodont 2023;36:581-587.

Patient satisfaction with occlusal scheme of conventional complete dentures.

Occlusal scheme is a controversial topic that has been linked to patient satisfaction with conventional complete dentures (CCDs). This study aimed to compare the patient satisfaction with CCDs with four different occlusal schemes namely the lingualised occlusion (LO), buccalised occlusion (BO), fully bilateral balanced occlusion (FBBO) and partially group function occlusion (PGFO). In this clinical study, new CCDs were made for 121 patients; out of which, 97 patients (mean age of 57.87 ± 9.5 years) completed the 1-year follow-up. The CCD wearers were followed up at 1 month, 3 months and 1 year after CCD delivery. Data were collected via an interview and recorded in a checklist by a blinded examiner. The checklist included the demographic variables, the 19-item version of Oral Health Impact Profile for Edentulous Patients (OHIP-EDENT), and seven 100-mm line visual analogue scales (VASs) to assess the items related to patient satisfaction. The Kruskal-Wallis and Friedman tests followed by post hoc tests were used to compare the variables among the 4 groups and between the 3 follow-ups. P-value ≤ .05 was considered statistically significant for all tests. The patients with BO presented higher satisfaction scores for comfort, stability and retention at the 1-year follow-up compared with PGFO. Both PGFO and FBBO groups had higher physical pain scores compared with BO and LO. The psychological discomfort scores of FBBO group were significantly higher than those in LO group. Pairwise comparisons revealed no significant differences in the general patient satisfaction and total OHIP-EDENT scores between the 4 groups. For most items, within-group analysis showed significant improvement of the satisfaction scores and reduction of domain scores over time.

Factors Affecting the Learning of Fixed Prosthodontics Course by Students at Kermanshah University of Medical Sciences.

AIM: The objective of this study was to investigate the factors affecting the learning of fixed prosthodontics course from the viewpoint of students and faculty members of Kermanshah Dentistry School. MATERIAL AND METHODS: This research was a descriptive-analytical study conducted using the convenient sampling method. A total of 72 students and 5 faculty members were included in the study. Data were collected using a researcher-made questionnaire containing two sections. The first section consists of demographic information, and the second section consists of 14 questions to evaluate the factors affecting the learning of the fixed prosthodontics course. RESULTS: From the students' point of view, there was a significant relationship between the effect of using clinical points during a teaching on the learning efficacy of the fixed prosthodontics course and gender (P = 0.028). There was a statistically significant relationship between the level of professor's knowledge regarding the modern educational methods on the learning of fixed prosthodontics course (P = 0.034). The factor of displaying and implementing practical work on the real patient was considered important by students, and having knowledge about modern educational methods was considered important by faculty members. CONCLUSIONS: It is recommended that appropriate educational planning be implemented to enhance students' practical work on the real patient and increase professors' knowledge about modern educational methods.