Effect of Mica Reinforcement on the Flexural Strength and Microhardness of Polymethyl Methacrylate Denture Resin

Purpose : Conventional denture base polymethyl methacrylate (PMMA) is low in strength, soft, and brittle on impact. Improvements in the mechanical properties of denture base materials have been sought by adding different reinforcing phases to the PMMA matrix. The purpose of this work was to study the effects of mica reinforcement on the mechanical properties, flexural strength, and microhardness of PMMA denture base resin. Materials and Methods : Wet ground muscovite mica and Lucitone 199 original shade denture base resin were used. Two micas were tested: W200 and P66 with average particle sizes (d50) of 131 μm and 30 μm, respectively. The mica was silane treated in a solution of 3‐methacryloxypropyl trimethoxysilane, ethanol, and water, and then dried. The specimens were fabricated using the denture base resin manufacturer's instructions with a powder : liquid ratio of 21 g/10 ml and a mixing time of 30 seconds. Five treatment groups were produced with differing amounts of mica added to the PMMA denture base resin: (A) control group with 0 vol% mica, (B) 10 vol% W200 mica, (C) 20 vol% W200 mica, (D) 10 vol% P66 mica, (E) 20 vol% P66 mica. The mica replaced equal volumes of the PMMA powder component to minimize changes in viscosity. The three‐point bending flexural strength specimens were 70 × 11 × 3 mm³. Seven specimens were prepared for each treatment group. The hardness specimens were prepared from the ends of the three‐point bend specimens after they were broken (N = 7). After deflasking, the specimens were polished with 600 grit silicon carbide paper to achieve smooth surfaces. A standard three‐point bending jig with a span length of 50 mm was attached to an Instron universal testing machine. The specimens were placed on the jig, and loading was carried out using a 1 mm/min crosshead speed until failure. Microhardness was measured using a Clark microhardness tester with a Knoop indenter. The load was set to 200 g and the dwell time to 15 seconds. ANOVA and Tukey tests were used for statistical analyses (Alpha = 0.05). Results : The flexural strength of the control group was between 77% and 94% higher than all the mica‐containing groups (p≤ 0.05). No significant differences were found within the four mica groups. Microhardnesses of the 20% mica groups (both fine and coarse) were 33% and 26% higher than the control (p≤ 0.05). The 10% mica groups had higher hardness than the control group, but the increase was not statistically significant (p > 0.05). Conclusion : Mica additions to denture PMMA reduced flexural strength; however, with the specimens containing highest mica concentrations (20%), microhardness significantly increased.     

Thoracic surgical management of colorectal lung metastases: a questionnaire survey of members of the Society for Cardiothoracic Surgery in great Britain and Ireland

Introduction

Distant metastases to liver and lung are not uncommon in colorectal cancer. Resection of metastases is accepted widely as the standard of care. However, there is no firm evidence base for this. This questionnaire survey was carried out to assess the current practice preferences of cardiothoracic surgeons in Great Britain and Ireland.

Methods

An online questionnaire survey was emailed to cardiothoracic surgeons in Great Britain and Ireland. The survey was live for 12 weeks. Responses were collated with SurveyMonkey^®.

Results

Overall, there were 75 respondents. The majority (83%) indicated thoracic surgery as a specialist interest. Almost all (99%) used thoracic computed tomography (CT) for staging; 70% added liver CT and 51% added pelvic CT. Fluorodeoxyglucose positron emission tomography was used by 86%. The most frequent indication for pulmonary resection (97%) was solitary lung metastasis without extrathoracic disease. Video assisted thoracoscopic surgery (VATS) was used by 85%. In addition, thoracotomy was used by 96%. A third (33%) used radiofrequency ablation. Synchronous liver and lung resection was contraindicated for 83% of respondents. Over three-quarters (77%) thought that scientific equipoise exists presently for lung resection for colorectal lung metastases but only 21% supported a moratorium on this type of surgery until further evidence becomes available.

Conclusions

The results confirm that the majority of respondents use conventional cross-sectional imaging and either VATS or formal thoracotomy for resection. The results emphasise the continuing need for formal randomised trials to provide evidence of any survival benefit from pulmonary metastasectomy for colorectal lung metastases.     

Safety of transcatheter patent ductus arteriosus closure in small weight infants

Background: Patent ductus arteriosus (PDA) is a frequent congenital heart disease. Its transcatheter closure has become the treatment of choice in children and adults. However, the device closure of PDA in children with low weight is still challenging with high rate of complications. The aim of this study was to report further experience with trancatheter closure of PDA using the Amplatzer Duct Occluder(ADO) for children weighing less or equal to 8 kg. Methods: Twenty‐two patients (5 male, 17 female) underwent transcatheter closure of a PDA using ADO at a median age of 10 months (range 4 to 26) and a median weight of 7 kg (range 4.3 to 8). Follow‐up evaluations were performed with Doppler echocardiography at 24h, and at 6 and 12 months. Results: The device was implanted successfully in all patients. The median fluoroscopy time was 17.25 min (range 10 to 29). Within 24h, color Doppler revealed complete closure in 15 patients (68%), the other patients had a small residual shunt. No deaths were associated with the procedure. Two patients had a slight aortic protrusion of the device without coarctation and in one patient the device encroached partially on the left pulmonary artery without significant acceleration on Doppler echocardiography. All patients were discharged home the next day. All patients completed the 6‐month follow‐up with complete closure in 18 patients (81%). At the last evaluation in all patients at any time, there has been documentation of complete PDA closure in 20 (91%) of 22 patients. Conclusion: In patients weighing less or equal to 8 kg, percutaneous closure of PDA using an ADO is a safe and effective procedure. (J Interven Cardiol 2012;25:391–394)     

Oral health status in children with acute lymphoblastic leukemia

Leukemia is a malignancy of the bone marrow. Acute lymphoblastic leukemia (ALL) is the most common pediatric malignancy and accounts for nearly 75% of all newly diagnosed leukemias and 25% of all malignancies in childhood. The aim of the present study was to review the oral health status in children with ALL. Databases were explored using various combinations of the following keywords: "acute lymphoblastic leukemia", "children", "inflammation", "pediatric", "periodontal disease" and "periodontitis". Oral inflammatory conditions including chelitis, gingivitis, herpetic gingivostomatitis, mucositis, oral candidiasis, periodontitis and ulcerations are common manifestations in children with ALL. RESULTS: Periodontal inflammatory conditions and oral mucositis were reported to be significantly higher in children with ALL as compared to healthy controls. Tooth morphological disorders including agenesis, microdontia, short roots and developmental defects in the enamel and dentin were more often observed in children with ALL as compared to healthy controls. Children with ALL have a reduced salivary flow rate, which makes them more susceptible to dental caries as compared to healthy children. Malocclusion due to microdontia may also trigger temporomandibular joint disorders in children with ALL; however, this relationship needs further investigations. CONCLUSION: Oral inflammatory conditions including mucositis and gingivitis are common in children with ALL as compared to healthy children. Tooth morphological disorders including microdontia and enamel and dentin are common manifestations in children with ALL.     

Long-term effects of mustard gas on respiratory system of Iranian veterans after Iraq-lran war： a review

To review long-term respiratory effects of mustard gas on Iranian veterans having undergone Iraq-Iran war. Electronic databases of Scopus, Medline, ISI, IranMedex, and Irandoc sites were searched. We accepted articles published in scientific journals as a quality criterion. The main pathogenic factors are free radical mediators. Prevalence of pulmonary involvement is approximately 42.5%. The most common complaints are cough and dyspnea. Major respiratory complications are chronic obstructive pulmonary disease, bronchiectasis, and asthma. Spirometry results can reveal restrictive and obstructive pulmonary disease. Plain chest X-ray does not help in about 50% of lung diseases. High-resolution CT of the lung is the best modality for diagnostic assessment of parenchymal lung and bronchi. There is no definite curative treatment for mustard lung. The effective treatment regimens consist of oxygen administration, use of vaporized moist air, respiratory physiotherapy, administration of mucolytic agents, bronchodilators, corticosteroids, and long-acting beta-2 agonists, antioxidants, surfactant, magnesium ions, therapeutic bronchoscopy, laser therapy, placement of respiratory stents, early tracheostomy in laryngospasm, and ultimately lung transplantation. High-resolution CT of the lung is the most accurate modality for the evaluation of the lung parenchyma and bronchi. The treatment efficacy of patients exposed to mustard gas depends on patient conditions (acute or chronic, upper or lower respiratory tract involvement). There are various treatment protocols, but unfortunately none of them is definitely curable.