Effect of Silane on Shear Bond Strength of Two Porcelain Repair Systems

Objectives: Ceramics have advantages such as optimal esthetics and biocompatibility. However, in the oral environment, they are subjected to high levels of stress due to masticatory forces, saliva, thermal changes and alterations of pH, which increase their risk of fracture. Since replacement of these restorations is costly and time-consuming, composite resin is often used for intraoral repair of these restorations. This study aimed to assess the shear bond strength of two porcelain repair systems by Pulpdent and Ultradent and evaluate the effect of number of silane layers on the shear bond strength.Methods: This invitro experimental study was conducted on 66 porcelain blocks measuring 3×5×8mm. In each kit, samples were randomly divided into three groups of 11. Silane was not used for group one. Groups two and three received one coat and two coats of silane, respectively. After surface preparation, composite was bonded to ceramic surfaces. Data were analyzed using two-way ANOVA.Results: The LSD test showed that application of Ultradent silane significantly affected the shear bond strength (P<0.05) while Pulpdent silane had no such effect (P=0.89). Application of one layer and two layers of silane was not significantly different (P=0.94).Conclusion: Ultradent ceramic repair kit yields higher shear bond strength at the ceramic-composite interface compared to Pulp dent ceramic repair kit. Use of one or two layers of silane does not make any significant difference with regard to the shear bond strength of ceramic to composite.

Effect of marginal design on fracture resistance of IPS e.maxall ceramic restorations: Chamfer versus shoulder finish lines

Background and Aim: One of the problems of all ceramic restorations is their risk of fracture due to occlusal loads. The aim of the present study was to compare the effect of two marginal designs (shoulder and chamfer) on the fracture resistance of IPS-emax all ceramic restorations. Materials and Methods: One extracted maxillary first premolar received chamfer 50' marginal preparation (0.8 mm). Twenty impressions were made using poly vinyl siloxane. Then, chamfer was converted to shoulder 90'(1mm). After impression, epoxy resin dies were fabricated. Impressions of each epoxy resin die were made and poured with die stone. Twenty Press crowns and twenty ZirCAD crowns were made on stone dies and ce-mented on resin dies. Then, samples underwent a fracture test in a universal testing ma-chine. Data were analyzed by one-way ANOVA. Results: The mean fracture resistance was 1426N for the chamfer ZirCAD samples, 1361.3N for the shoulder ZirCAD samples, 1059.9N for the chamfer Press samples and 1295.8N for the shoulder Press samples. One-way ANOVA revealed no difference among groups. (p=0.095). Conclusion: After porcelain application, marginal design does not affect fracture resis-tance of single IPS-emax posterior crowns. Fracture resistance was approximately the same in Press and ZirPress groups probably due to porcelain application, because in Zir-CAD group fractures occurred in the porcelain prior to the cor

Retracted: Stress Distribution in Three-Implant- Retained Mandibular Overdentures Using Finite Element Analysis

Background and Aim: Demand for implant-supported overdentures has increased due to the problems of conventional dentures. Despite the high success rate of implants, implant failure remains a major challenge. Implant overload can cause cortical bone loss and im-plant failure. Using finite element analysis (FEA), this study aimed to find the best design and type of attachments causing minimum stress in the alveolar bone. Materials and Methods: The geometrical model of the mandible was produced using computed tomography (CT) data and three ITI implants were placed in the midline and the location of the first premolar teeth. All conditions were simulated using finite element software. Three bar-ball, bar and ball attachments were considered to support the overdenture. Maximum von Mises stress was calculated in the supporting bone in differ-ent overdenture designs. Results: The greatest amount of stress in bone was around the upper thread and the neck of the implant. The ball and the bar-ball attachments applied the most and the least amount of stress to the peri-implant bone, respectively. Maximum stress was applied to the ball attachment in the bar-ball design. The maximum amount of movement was in bar-ball attachment. Conclusion: The bar-design decreased the stability of overdenture, as well as the stress in the peri-implant bone. Ball design increased concentration of stress in bone around the implant and increased the stability of overdenture

Comparison of the Effect of Feldspathic Porcelain and Zirconia on Natural Tooth Wear

Background and Aim : Enamel wear is among the main disadvantages of ceramic restorations. Recently, use of full zirconia crowns without dental porcelain has been suggested. The aim of this study was to compare the effect of feldspathic porcelain and zirconia on the wear of natural teeth .   Materials and Methods : In this experimental study, 22 zirconia specimens were fabricated out of which, 11 specimens were polished and chosen as zirconia specimens while the remaining 11 were used to fabricate porcelain specimens. A total of 22 natural human teeth were also obtained. The natural teeth were photographed by a stereomicroscope in a fixed position and the distance from the cusp tip to a reference point was measured. Next, 11 teeth opposed zirconia and the remaining 11 opposed porcelain specimens in a chewing simulator and subjected to 120,000 masticatory cycles. The teeth were photographed again and the greatest difference between the before and after values ​​ was recorded .   Results : The mean (± standard deviation) wear rate was 153.8±95.68 and 306.3±127.74, in the zirconia and porcelain groups, respectively and the two groups had a statistically significant difference in this respect (p=0.007 ).   Conclusion : The mean wear was significantly lower in teeth opposing zirconia than in those opposing feldspathic porcelain

Evaluation of the frequency of ABO and Rh-Hr blood-group systems in different acquired cataracts type

Abstract Objectives This study evaluated the relationship between acquired cataract’s different types and the ABO and Rh blood classes. Methods Overall, 520 patients, by randomized sampling method, participated in this retrospective cross-sectional study. After reviewing the patient’s medical records and laboratory results, the patient’s demographics, ABO group, Rh, and cataract type were documented. Results A total of 520 patients were included in the research, with a mean age of 67.57 ± 11.85. Most of them were female (n = 286, 55%). Mix (n = 230, 44%) and nuclear sclerotic (NS) (n = 167, 32%) cataracts were the most common types. The posterior subcapsular cataract (PSC) prevalence in females was significantly higher than in males (16.1% vs.7.3% p = 0.002). Also, men had more NS cataracts than females (89, 38% vs. 78, 27.3%) (p = 0.009). Patients with PSC were significantly younger than others (all p-values  0.05). Conclusion Although our findings showed that cataract types are independent of blood group types and Rh, they can be compared with future studies on the association of other Blood-Group Systems in developing acquired cataracts

Risk of stroke in hospitalized SARS-CoV-2 infected patients: A multinational study

Background: There is an increased attention to stroke following SARS-CoV-2. The goal of this study was to better depict the short-term risk of stroke and its associated factors among SARS-CoV-2 hospitalized patients

SARS-CoV-2 and Stroke Characteristics: A Report From the Multinational COVID-19 Stroke Study Group

International audienceBackground and Purpose: Stroke is reported as a consequence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection in several reports. However, data are sparse regarding the details of these patients in a multinational and large scale. Methods: We conducted a multinational observational study on features of consecutive acute ischemic stroke, intracranial hemorrhage, and cerebral venous or sinus thrombosis among SARS-CoV-2–infected patients. We further investigated the risk of large vessel occlusion, stroke severity as measured by the National Institutes of Health Stroke Scale, and stroke subtype as measured by the TOAST (Trial of ORG 10172 in Acute Stroke Treatment) criteria among patients with acute ischemic stroke. In addition, we explored the neuroimaging findings, features of patients who were asymptomatic for SARS-CoV-2 infection at stroke onset, and the impact of geographic regions and countries’ health expenditure on outcomes. Results: Among the 136 tertiary centers of 32 countries who participated in this study, 71 centers from 17 countries had at least 1 eligible stroke patient. Of 432 patients included, 323 (74.8%) had acute ischemic stroke, 91 (21.1%) intracranial hemorrhage, and 18 (4.2%) cerebral venous or sinus thrombosis. A total of 183 (42.4%) patients were women, 104 (24.1%) patients were <55 years of age, and 105 (24.4%) patients had no identifiable vascular risk factors. Among acute ischemic stroke patients, 44.5% (126 of 283 patients) had large vessel occlusion; 10% had small artery occlusion according to the TOAST criteria. We observed a lower median National Institutes of Health Stroke Scale (8 [3–17] versus 11 [5–17]; P =0.02) and higher rate of mechanical thrombectomy (12.4% versus 2%; P <0.001) in countries with middle-to-high health expenditure when compared with countries with lower health expenditure. Among 380 patients who had known interval onset of the SARS-CoV-2 and stroke, 144 (37.8%) were asymptomatic at the time of admission for SARS-CoV-2 infection. Conclusions: We observed a considerably higher rate of large vessel occlusions, a much lower rate of small vessel occlusion and lacunar infarction, and a considerable number of young stroke when compared with the population studies before the pandemic. The rate of mechanical thrombectomy was significantly lower in countries with lower health expenditures