Effect of microwave disinfection on mechanical properties of denture base acrylic resin

The microwave oven was used for sterilizing dentures contaminated with Candida albicans and other communicable diseases instead of disinfectant solutions. This study was carried out to evaluate the flexural properties, toughness, and impact strength of heat-cured acrylic resin sterilized by microwave oven either immersed in water or non-immersed for 5 and 15 min at full power. The results indicated that the microwave oven sterilization technique resulted in reduction of the load necessary to fracture the specimens, deformation at fracture, transverse strength, modulus of elasticity except disinfection at 5 min dry condition, toughness, and impact strength. This study concluded that the microwave oven is not acceptable for sterilization of dentures because of its weakening effects on the dentures that prone for fracture during clinical use. This method of sterilization increased the brittleness of acrylic resin specimens.     

Effect of thermal cycling and disinfection on microhardness of acrylic resin denture base

Abstract

The purpose of this study was to investigate the effect of thermal cycling and disinfection on the microhardness of acrylic resins denture base. Four different brands of acrylic resins were evaluated: Onda Cryl, QC 20, Classico and Lucitone. Each brand of acrylic resin was divided into four groups (n?=?7) according to the disinfection method (microwave, Efferdent, 4% chlorhexidine and 1% hypochlorite). Samples were disinfected during 60 days. Before and after disinfection, samples were thermal cycled between 5–55?°C with 30-s dwell times for 1000 cycles. The microhardness was measured using a microhardener, at baseline (B), after first thermal cycling (T₁), after disinfection (D) and after second thermal cycling (T₂). The microhardness values of all groups reduced over time. QC-20 acrylic resin exhibited the lowest microhardness values. At B and T₁ periods, the acrylic resins exhibited statistically greater microhardness values when compared to D and T₂ periods. It can be concluded that the microhardness values of the acrylic resins denture base were affected by the thermal cycling and disinfection procedures. However, all microhardness values obtained herein are within acceptable clinical limits for the acrylic resins.     

Quaternary ammonium silane-functionalized, methacrylate resin composition with antimicrobial activities and self-repair potential

The design of antimicrobial polymers to address healthcare issues and minimize environmental problems is an important endeavor with both fundamental and practical implications. Quaternary ammonium silane-functionalized methacrylate (QAMS) represents an example of antimicrobial macromonomers synthesized by a sol-gel chemical route; these compounds possess flexible Si-O-Si bonds. In present work, a partially hydrolyzed QAMS co-polymerized with 2,2-[4(2-hydroxy 3-methacryloxypropoxy)-phenyl]propane is introduced. This methacrylate resin was shown to possess desirable mechanical properties with both a high degree of conversion and minimal polymerization shrinkage. The kill-on-contact microbiocidal activities of this resin were demonstrated using single-species biofilms of Streptococcus mutans (ATCC 36558), Actinomyces naeslundii (ATCC 12104) and Candida albicans (ATCC 90028). Improved mechanical properties after hydration provided the proof-of-concept that QAMS-incorporated resin exhibits self-repair potential via water-induced condensation of organic modified silicate (ormosil) phases within the polymerized resin matrix.     

Effects of acrylic resin monomers on porcine coronary artery reactivity

The purpose of the present investigation was to assess the reactivity of porcine coronary arteries under in vitro conditions following their exposure to methyl methacrylate (MMA) and hydroxyethyl methacrylate (HEMA) monomers. Confirming previous studies using rat aortas, both MMA and HEMA induced acute/direct relaxation of coronary ring preparations, which was partly dependent on the endothelium. With prolonged tissue exposure, both monomers caused time- and concentration-dependent inhibition of receptor-mediated contraction of the vascular smooth muscle caused by prostaglandin F_2∝ (PGF_2∝), with HEMA causing more inhibition than MMA. Hydroxyethyl methacrylate, but not MMA, also produced impairment of non-receptor-mediated contraction of the coronary smooth muscle induced by KCl. On the other hand, neither HEMA nor MMA altered relaxation of the smooth muscle produced by the direct-acting pharmacological agent, sodium nitroprusside (SNP). While exposure to HEMA impaired endothelium-dependent vasorelaxation caused by bradykinin (BK), MMA markedly enhanced this endothelial-mediated response of the arteries. The enhanced endothelial response produced by MMA was linked to nitric oxide (NO) release. In conclusion, with prolonged tissue exposure, MMA causes less pronounced effects/adverse consequences on coronary smooth muscle function relative to the effect of HEMA, while enhancing vasorelaxation associated with release of NO from the endothelium. Accordingly, MMA-containing resin materials appear to be safer for human applications than materials containing HEMA.     

Effect of discontinuation of an antimicrobial stewardship programme on the antibiotic usage pattern

ObjectivesThis study aimed to analyse the effect of discontinuation of antimicrobial stewardship programme (ASP) activity on the usage pattern of antibiotics.MethodsAn interrupted time-series analysis assessing the trends in antibiotic use was conducted between September 2015 and August 2019 in an 859-bed university-affiliated hospital in Korea, where all ASP activities were discontinued in March 2018. The major activity of the ASP was a restrictive antibiotic programme.ResultsThe use of restrictive antibiotics increased immediately after the discontinuation of the ASP by 41.06 days of therapy (DOT)/1000 patient-days in the general ward (95% confidence interval (CI) 21.04–61.08) and by 391.04 DOT/1000 patient-days in the intensive care unit (ICU) (95%CI 207.56–574.51). In addition, there were positive changes in the slope for the use of restrictive antibiotics in the general ward (7.06 DOT/1000 patient-days per month, 95%CI 4.63–9.50) and ICU (35.95 DOT/1000 patient-days per month, 95%CI 18.70–53.19). The use of broad-spectrum antibiotics in the general ward significantly decreased (–87.54 DOT/1000 patient-days, 95%CI –149.29 to –25.79). For non-broad-spectrum antibiotics, there were positive changes in the slope in the general ward (16.54 DOT/1000 patient-days per month, 95%CI 12.99–20.09) and ICU (12.85 DOT/1000 patient-days per month, 95%CI 2.32–23.38).ConclusionsAfter discontinuation of the ASP, antibiotic usage patterns rapidly returned to the patterns prior to the implementation of the programme.     

Immunoregulatory and antimicrobial activities of myeloid cells

180 scientists recently met at the 20th Annual meeting of the European Macrophage and Dendritic Cell Society to discuss the interaction between interferons, myeloid cells, TLR, killing mechanisms and microbial pathogens.     

Reinforcement of acrylic denture base resin by incorporation of various fibers

This study was designed to evaluate improvements in the mechanical properties of acrylic resin following reinforcement with three types of fiber. Polyester fiber (PE), Kevlar fiber (KF), and glass fiber (GF) were cut into 2, 4, and 6 mm lengths and incorporated at concentrations of 1, 2, and 3% (w/w). The mixtures of resin and fiber were cured at 70 degrees C in a water bath for 13 h, then at 90 degrees C for 1 h, in 70 x 25 x 15 mm stone molds, which were enclosed by dental flasks. The cured resin blocks were cut to an appropriate size and tested for impact strength and bending strength following the methods of ASTM Specification No. 256 and ISO Specification No. 1567, respectively. Specimens used in the impact strength test were reused for the Knoop hardness test. The results showed that the impact strength tended to be enhanced with fiber length and concentration, particularly PE at 3% and 6 mm length, which was significantly stronger than other formulations. Bending strength did not change significantly with the various formulations when compared to a control without fiber. The assessment of Knoop hardness revealed a complex pattern for the various formulations. The Knoop hardness of 3%, 6 mm PE-reinforced resin was comparable to that of the other formulations except for the control without fiber, but for clinical usage this did not adversely affect the merit of acrylic denture base resin. It is concluded that, for improved strength the optimum formulation to reinforce acrylic resin is by incorporation of 3%, 6 mm length PE fibers.     

Effect of antimicrobial treatment on the course of an experimental Yersinia pseudotuberculosis infection in canaries

The efficacy of five antimicrobials administered via the drinking water was compared for the treatment of experimental Yersinia pseudotuberculosis infection in canaries. Groups of eight to 10 canaries were treated with ampicillin (2 g/1)(3) doxycycline (500 mg/1), enrofloxacin (150 mg/1), chloramphenicol (1 g/1) or sulphamerazine-trimetho-prim (1 g/1-200 mg/1) for 10 days, commencing 2 days after experimental infection. No clinical signs were observed in the group treated with enrofloxacin and there were no deaths and no isolations of Y. pseudotuberculosis from the spleen and liver at necropsy carried out at 35 days post-inoculation. In the groups treated with the other antibiotics morbidity varied between 50 and 100%, and mortality between 30 and 44%. Mortality and morbidity in an untreated infected control group of 12 canaries were 100%. Results indicate that enrofloxacin offers good possibilities for the treatment of pseudotuberculosis in recently infected canaries.     

Loss into water of residual monomer from autopolymerizing dental acrylic resin

A study has been made of the loss of residual monomer from samples of autopolymerizing acrylic resin immersed in water. Diffusion of monomer out of the resin into the water could account for only part of the loss. It was shown that free radicals continue to be present in the acrylic after completion of cure, and it is postulated that the residual monomer in an autopolymerized acrylic resin may be removed by further polymerization at these sites, as well as by diffusion out of the resin. The implications of this hypothesis are discussed.     

Effect of resin hydrophilicity and water storage on resin strength

This study evaluated the change in the ultimate tensile strength (UTS) of five polymerised resin blends of increasing hydrophilicity, after ageing in distilled water or silicon oil. Resin blocks were prepared from each resin blend by dispensing the uncured resin into a flexible, embedding mould, containing multiple cavities. The resins were polymerised in the moulds under nitrogen at 551.6 kPa and light-activated at 125 degrees C for 10 min. After dry ageing for 24 h at 37 degrees C, the middle third of each resin specimen was trimmed into an 'I' shape. Fifteen control specimens were randomly selected from each resin blend for baseline UTS evaluation. The UTS of the experimental specimens were determined after 1, 3, 6 and 12 months of ageing in water or oil. The UTS of each group of resins at different storage periods in water or oil were analysed using the Friedman multiple ANOVA on ranks and Dunn's multiple comparison tests at 95% confidence level. Significant reduction (p < 0.01) in UTS was observed in Groups II-V resins after 12-month storage in water, while the most hydrophobic Group I resin showed no significant change (p > 0.05) in the same period. The percentage reduction in UTS increased with the hydrophilicity of the resin blends. Long-term water storage of hydrophilic resin blends such as those employed in dentine adhesives, resulted in a marked reduction in their mechanical strength that may compromise the durability of resin-dentine bonds.     

Stereochemistry of poly(methyl methacrylate) acrylic resin denture base material

Nuclear magnetic resonance (NMR) 13C has been used to determine the tacticity of poly(methyl methacrylate) (PMMA) denture base materials. Curing cycle has no effect on tacticity. A tendency towards a mainly syndiotactic arrangement is shown. Industrially produced PMMA showed the same tacticity as the dental products.     

双链法对正畸牙牙间隙关闭的影响

目的 探讨双链法关闭正畸牙牙间隙的安全性及有效性。方法 选取72例不同上下颌牙列间隙的正畸患者,测量正畸治疗前后上下颌第一磨牙之间的所有牙齿的牙髓活力值,并进行统计学分析评估牙髓活力的安全性;使用双链法关闭正畸牙牙列间隙,分为拔牙组和不拔牙组各36例,观察周期为4周,测量成年组和未成年组的上下颌牙齿槽间距的治疗前后变化,计算正畸治疗前后总齿槽间距的差异,并进行统计学分析评估间隙关闭的有效性。结果 所有72例患者,治疗后未发现牙髓坏死及牙髓变性,治疗前后牙髓活力无改变,差异无统计学意义（P>0.05）;与矫治前相比,双链法矫治后4周,拔牙组和不拔牙组中的成年和未成年的病例上下颌槽间距值之和均明显减小,差异有统计学意义（P<0.05）。结论 双链法关闭正畸牙牙列间隙不会引起牙髓变性与坏死,具有临床使用的安全性;双链法关闭正畸牙牙间隙具有有效性,同时可简化临床操作,值得临床推广。     

正畸带环和树脂临时冠对牙隐裂的暂时性保护

背景：在牙隐裂的综合治疗过程中,采用正畸带环和树脂临时冠进行暂时性保护,能够有效防止牙体折裂,保护患牙,临床成功率较高。 目的：对比正畸带环和树脂临时冠对隐裂牙暂时性保护的临床效果差异。 方法：纳入牙隐裂患者189例,其中男97例,女92例,年龄19-65岁,随机分2组,分别采用正畸带环(n=93)、树脂临时冠(n=96)在综合治疗过程中对牙隐裂进行暂时性保护,观察两组患牙固位、牙周状况和患者满意度方面的临床效果。 结果与结论：正畸带环组出现3例带环松动和1例带环脱落;树脂临时冠组出现2例脱落,两组固位效果比较差异无显著性意义。正畸带环组11例出现牙龈炎或探诊出血,树脂临时冠组2例出现引起牙龈炎或探诊出血,树脂临时冠组牙周状况优于正畸带环组(P < 0.05)。正畸带环组有18例因带环颜色不美观、佩戴橡皮圈引起的膨胀感、带环凸出牙体表面引起不适等原因,满意度较低;树脂临时冠组有3例患者不满意,树脂临时冠组患者满意度高于正畸带环组(P < 0.05)。表明树脂临时冠在隐裂牙综合治疗过程中,其外形、色泽、舒适度等方面性能优异,具有良好的临床效果。 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

Effect of an acidic environment on the susceptibility ofHelicobacter pylori to trospectomycin and other antimicrobial agents

The susceptibility of 30 clinical isolates ofHelicobacter pylori to trospectomycin, ampicillin, metronidazole, clarithromycin, azitromycin and clindamycin under varying pH conditions was evaluated. An acidic environment was shown to affect unfavourably the activity of all the antimicrobial agents tested. This pH effect was most marked for the two macrolides and for clindamycin.     

光固化复合树脂修复成人正畸牙冠缺损的可行性

BACKGROUND:Because of good performance, beautiful and permanent color, and certain compressive strength, light-cured composite resin has been widely used in dental restoration. But there are less reports about its usage in adult crown restoration during orthodontic treatment.     

Effect of an antimicrobial stewardship programme on antimicrobial utilisation and costs in patients with leukaemia: a retrospective controlled study

ObjectivesTo examine the effectiveness of an antimicrobial stewardship programme on utilization and cost of antimicrobials in leukaemia patients in Canada.MethodsWe conducted a multisite retrospective observational time series study from 2005 to 2013. We implemented academic detailing as the intervention of an antimicrobial stewardship programme in leukaemia units at a hospital, piloted February–July 2010, then fully implemented December 2010–March 2013, with no intervention in August–November 2010. Internal control was the same hospital's allogeneic haematopoietic stem-cell transplantation unit. External control was the combined leukaemia–haematopoietic stem-cell transplantation unit at another hospital. Primary outcome was antimicrobial utilization (antibiotics and antifungals) in defined daily dose per 100 patient-days (PD). Secondary outcomes were antimicrobial cost (Canadian dollars per PD); cost and utilization by drug class; length of stay; 30-day inpatient mortality; and nosocomial Clostridium difficile infection. We used autoregressive integrated moving average models to evaluate the impact of the intervention on outcomes.ResultsThe intervention group included 1006 patients before implementation and 335 during full implementation. Correspondingly, internal control had 723 and 264 patients, external control 1395 and 864 patients. Antimicrobial utilization decreased significantly in the intervention group (p <0.01, 278 vs. 247 defined daily dose per 100 PD), increased in external control (p = 0.02, 237.4 vs. 268.9 defined daily dose per 100 PD) and remained stable in internal control (p = 0.66). Antimicrobial cost decreased in the intervention group (p = 0.03; $154.59 per PD vs. $128.93 per PD), increased in external control (p = 0.01; $109.4 per PD vs. $135.97 per PD) but was stable in internal control (p = 0.27). Mortality, length of stay and nosocomial C. difficile rate in intervention group remained stable.ConclusionsThe antimicrobial stewardship programme reduced antimicrobial use in leukaemia patients without affecting inpatient mortality and length of stay.     

Effect of estrogens on the myeloperoxidase-mediated antimicrobial system.

Estradiol 17 beta prevented the fall in the microbicidal activity of the myeloperoxidase-H2O2-halide system induced by high H2O2 concentrations. In contrast, when the H2O2 (and halide) concentrations were low the myeloperoxidase-H2O2-halide antimicrobial system was inhibited by estradiol. These properties of estradiol 17 beta were shared by estradiol 17 alpha, estrone, estriol, ethinyl estradiol, and phenol, but not by estradiol-3-benzoate, testosterone, progesterone, hydroxyprogesterone, cortisone, hydrocortisone, or deoxycorticosterone.     

Influence of the activator in an acrylic bone cement on an array of cement properties

In all but one of the acrylic bone cement brands used in cemented arthroplasties, N,N-dimethyl-4-toluidine (DMPT) serves as the activator of the polymerization reaction. However, many concerns have been raised about this activator, all related to its toxicity. Thus, various workers have assessed a number of alternative activators, with two examples being N,N-dimethylamino-4-benzyl laurate (DMAL) and N,N-dimethylamino-4-benzyl oleate (DMAO). The results of limited characterization of cements that contain DMAL or DMAO have been reported in the literature. The present work is a comprehensive comparison of cements that contain one of these three activators, in which the values of a large array of their properties were determined. These properties range from the setting time and maximum exotherm temperature of the curing cement to the variation of the loss elastic modulus of the cured cement with frequency of the applied indenting force in dynamic nanoindentation tests. The present results, taken in conjunction with those presented in previous reports by the present authors and co-workers on other properties of these cements, indicate that both DMAL and DMPT are suitable alternatives to DMPT.     

Evaluation of persistent antimicrobial effects of an antimicrobial formulation

Context:

Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) is becoming more prevalent in healthy athletic populations. Various preventive measures have been proposed, but few researchers have evaluated the protective effects of a prophylactic application of a commercially available product.

Objective:

To compare the persistent antimicrobial properties of a commercially available antimicrobial product containing 4% chlorhexidine gluconate (Hibiclens) with those of a mild, nonmedicated soap (Dr. Bronner''s Magic Soap).

Design:

Cross-sectional study.

Setting:

Microbiology laboratory, contract research organization.

Patients or Other Participants:

Twenty healthy human volunteers.

Intervention(s):

The test and control products were randomly assigned and applied to both forearms of each participant. Each forearm was washed for 2 minutes with the test or control product, rinsed, and dried. At, 1, 2, and 4 hours after application, each forearm was exposed to MRSA for approximately 30 minutes.

Main Outcome Measure(s):

Differences in numbers of MRSA recovered from each forearm, test and control, at each postapplication time point were compared.

Results:

Fewer MRSA (P < .0001) were recovered from the forearms treated with the test product (4% chlorhexidine gluconate) than from the forearms treated with the control product (nonmedicated soap).

Conclusions:

The 4% chlorhexidine gluconate product demonstrated persistent bactericidal activity versus MRSA for up to 4 hours after application.