干湿环境下循环载荷对氧化锆-饰面瓷叠层瓷结构抗弯强度的影响

目的:比较干燥和唾液浸泡环境下动态循环加载对氧化锆/饰面瓷叠层瓷结构抗弯强度的影响。方法:制作氧化锆/饰面瓷叠层瓷结构圆片试件30个,随机分为干燥和唾液浸泡两组,循环加载10000次后进行双轴弯曲测试,光学显微镜观察其表面损伤及断裂面形貌。结果:在干燥环境下,经过10000次循环疲劳实验后,表面裂纹主要为赫兹锥状裂纹,破碎模式主要为完全断裂。而在唾液环境下,经过疲劳实验后,表面裂纹除了赫兹锥状裂纹外还有环状裂纹,破碎模式主要为饰瓷脱瓷,而且在干燥环境下的样品抗弯强度比在湿润环境下平均要高70%。结论:口腔内氧化锆全瓷修复材料长期使用后出现性能下降的疲劳现象,与牙科陶瓷修复体处于充满唾液的水环境有关。     

Alternative Pretreatment Modalities with a Self‐Adhesive System to Promote Dentin/Alloy Shear Bond Strength

Purpose: The aim of this study was to evaluate alternative pretreatment modalities to enhance the dentin/alloy shear bond strength using a self‐etch adhesive system. Material and Methods: Ninety discs were fabricated and divided into three groups (n = 30). The discs of the first group were cast in gold palladium (Au‐Pd); those of the second group were cast in palladium silver alloy (Pd‐Ag); the discs of third group were cast in nickel chromium alloy (Ni‐Cr). Each group was further divided into three subgroups (n = 10) according to the dentin pretreatment used to lute the discs. Subgroup U (no pre‐treatment): Rely X Unicem resin cement. Subgroup GU: G‐Bond then Rely X Unicem. Subgroup ZU: Zinc‐Zeolite pretreatment then Rely X Unicem. Shear bond strength was determined using a compressive mode of force applied at the dentin/alloy interface using a monobevelled chisel‐shaped metallic rod. Data were collected and statistically analyzed to assess the effect of alloy type, pretreatment modality, and their interactions on the shear bond strength. Scanning electron microscopic examination (1000×) at the dentin/resin interface was performed. Two‐way ANOVA was used in testing significance for the effect of pretreatment, alloy, and their interaction. Duncan's post hoc test was used for pairwise comparison between the means when the ANOVA test was significant. The significance level was set at p≤ 0.05. Statistical analysis was performed with SPSS 15.0^®. Results: Regarding the pretreatment modality, the mean shear bond strength and 95% CI of subgroups ZU (18.00 MPa; 16.8 to 19.2) and GU (16.91 MPa; 15.4 to 18.4) were significantly higher than subgroup U (12.81 MPa; 11.4 to 14.2). Regarding the alloy type, the mean shear bond strength and 95% CI of Ni‐Cr groups (18.39 MPa; 16.9 to 19.9) were significantly higher than Au‐Pd (15.33 MPa; 13.8 to 16.8) and Pd‐Ag (13.99 MPa; 12.3 to 15.7). Conclusions: Pretreatment of dentin with G‐Bond and Zinc Zeolite improved the dentin/alloy shear bond strength. Base metal alloys provided superior bond strength values with any adhesive modality compared to noble alloys. Treatment of the dentin surface prior to the application of a self‐adhesive system is of great importance to enhancement of the dentin/alloy bond strength.     

Effect of 180 Days of Water Storage on the Transverse Strength of Acetal Resin Denture Base Material

Purpose: Acetal resin has been used as an alternative denture base and clasp material since 1986. The manufacturers claim that acetal resin has superior physical properties when compared to conventional denture base acrylic resins. Limited information is available about transverse strengths of acetal resin. The purpose of this investigation was to compare transverse strengths of pink and white acetal resins to transverse strengths of conventional heat‐polymerized polymethylmethacrylate (PMMA) resin in increasing durations of water storage. Materials and Methods: A transverse strength test was performed in accordance with International Standards Organization (ISO) specification No 1567. Twenty 65 × 10 × 2.5 mm³ specimens of each resin were prepared; five specimens of each resin group were subjected to three‐point bending test after 50 hours, 30 days, 60 days, and 180 days of water storage in distilled water at 37°C. Experimental groups’ transverse strengths were compared by three‐way ANOVA and Duncan's multiple range tests. Results: Transverse strength of PMMA denture base material was found to be in accordance with the requirements of ISO specification No 1567. Transverse strengths of white and pink acetal resin could not be calculated in this study, as white and pink acetal resin specimens did not break at the maximum applied force in the three‐point bending test. Flexural strength of acetal resin was found to be within the ISO specification limits. As the water storage time increased, the deflection values of PMMA showed no significant difference (p > 0.05). Both the white and pink acetal resin showed significant increase in deflection as the water storage time was increased from 50 hours to 180 days (p < 0.05). Conclusion: The results of this study indicated that transverse strength values of PMMA were within the ISO specification limit. Water storage time (50 hours, 30, 60, and 180 days) had no statistically significant effect on the transverse strength and deflection of PMMA. Acetal resin suffered from permanent deformation, but did not break in the three‐point bending test. Acetal resin showed significant increase in deflection as the water storage time was increased from 50 hours to 180 days. All materials tested demonstrated deflection values in compliance with ISO specification No 1567.     

Comfort-DA Ⅱ型义齿粘附剂的粘接性能评价

目的:研制新型高分子树脂类义齿粘附剂Comfort-DA Ⅱ型,评价其粘接性能。方法:运用统计学方法筛选出Comfort-DA Ⅱ型的最佳配比,测定配制后0h及浸泡人工唾液12h过程中粘接抗张强度值,与Protefix义齿粘附剂进行比较。结果:Comfort-DA Ⅱ型义齿粘附剂在配制0h的粘接抗张强度值,以及浸泡人工唾液后粘接抗张强度的平均值、最大值与第12h值均大于Protefix义齿粘附剂(P<0.05)。结论:Comfort-DA Ⅱ型义齿粘附剂具有较好的粘结抗张强度。     

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提要：全瓷修复因其优良的美观效果及生物相容性等诸多优点,成为口腔修复的发展趋势之一。各类全瓷修复体通过黏结性树脂黏结于牙体表面,合理有效的瓷表面处理技术是影响瓷与树脂黏结的首要因素。本文就牙科陶瓷几种表面处理方法的研究及其在口腔修复中的应用做一综述。     

An effect of immediate dentin sealing on the shear bond strength of resin cement to porcelain restoration

PURPOSE

The aim of this study was to determine differences in shear bond strength to human dentin using immediate dentin sealing (IDS) technique compared to delayed dentin sealing (DDS).

MATERIALS AND METHODS

Forty extracted human molars were divided into 4 groups with 10 teeth each. The control group was light-cured after application of dentin bonding agent (Excite® DSC) and cemented with Variolink® II resin cement. IDS/SE (immediate dentin sealing, Clearfil™ SE Bond) and IDS/SB (immediate dentin sealing, AdapterTM Single Bond 2) were light-cured after application of dentin bonding agent (Clearfil™ SE Bond and Adapter™ Sing Bond 2, respectively), whereas DDS specimens were not treated with any dentin bonding agent. Specimens were cemented with Variolink® II resin cement. Dentin bonding agent (Excite® DSC) was left unpolymerized until the application of porcelain restoration. Shear strength was measured using a universal testing machine at a speed of 5 mm/min and evaluated of fracture using an optical microscope.

RESULTS

The mean shear bond strengths of control group and IDS/SE group were not statistically different from another at 14.86 and 11.18 MPa. Bond strength of IDS/SE group had a significantly higher mean than DDS group (3.14 MPa) (P < .05). There were no significance in the mean shear bond strength between IDS/SB (4.11 MPa) and DDS group. Evaluation of failure patterns indicates that most failures in the control group and IDS/SE groups were mixed, whereas failures in the DDS were interfacial.

CONCLUSION

When preparing teeth for indirect ceramic restoration, IDS with Clearfil™ SE Bond results in improved shear bond strength compared with DDS.     

Loss of muscle strength, mass (sarcopenia), and quality (specific force) and its relationship with functional limitation and physical disability: the Concord Health and Ageing in Men Project

OBJECTIVES: To determine the association between loss of muscle strength, mass, and quality and functional limitation and physical disability in older men. DESIGN: Cross‐sectional study of older men participating in the Concord Health and Ageing in Men Project (CHAMP). SETTING: Elderly men living in a defined geographical region in Sydney, Australia. PARTICIPANTS: One thousand seven hundred five community‐dwelling men aged 70 and older who participated in the baseline assessments of CHAMP. MEASUREMENTS: Upper and lower extremity strength were measured using dynamometers for grip and quadriceps strength. Appendicular skeletal lean mass was assessed using dual X‐ray absorptiometry. Muscle quality was defined as the ratio of strength to mass in upper and lower extremities. For each parameter, subjects in the lowest 20% of the distribution were defined as below normal. Functional limitation was assessed according to self‐report and objective lower extremity performance measures. Physical disability was measured according to self‐report questionnaire. RESULTS: After adjusting for important confounders, the prevalence ratio (PR) for poor quadriceps strength and self‐reported functional limitation was 1.91 (95% confidence interval (CI)=1.10–2.40); for performance‐based functional limitation the PR was 1.81 (95% CI=1.45–2.24). The adjusted PR for poor grip strength and physical disability in instrumental activities of daily living (IADLs) was 1.37 (95% CI=1.20–1.56). The adjusted PR for low skeletal lean mass (adjusted for fat mass) and physical disability in basic activities of daily living was 2.08 (95% CI=1.37–3.15). For muscle quality, the PR for lower extremity specific force and functional limitation and physical disability was stronger than upper extremity specific force. CONCLUSION: Muscle strength is the single best measure of age‐related muscle change and is associated with physical disability in IADLs and functional limitation.     

我国灾害医学救援体系建设

在我国,要充分认识和发挥军队卫勤力量的优势和特色,通过平时训练、为军服务,以及实战的积累,加强军队卫勤力量的建设,把军队卫勤力量建成国家应急医学救援的主力军。从国家层面讲,应在整个中国范围内,根据地缘环境、医疗水平和基础设施情况,通过规范救援体系、加强装备建设、形成药械存储机制、加强人才培养,由国家统一建立以军医大学为核心的区域性突发灾害医疗卫生救援中心,协调各类救治与防护力量,实行划区保障。     

Characterization of acute adverse-effect profiles of selected antiepileptic drugs in the grip-strength test in mice

The aim of this study was to assess the acute adverse effects (neurotoxic) of several antiepileptic drugs (clonazepam, lamotrigine, oxcarbazepine, phenytoin, phenobarbital and topiramate) by measuring skeletal muscular strength in mice using the grip-strength test. Linear regression analysis of grip-strength in relation to drug dose-response allowed us to determine D₅₀ values, the dosages of antiepileptic drugs that reduced grip-strength in mice by 50% compared to control animals. Each of the antiepileptic drugs studied reduced skeletal muscular strength in mice in a dose-dependent manner. The D₅₀ for clonazepam was 31.7 mg/kg, lamotrigine – 47.7 mg/kg, oxcarbazepine – 87.3 mg/kg, phenobarbital – 128.7 mg/kg, phenytoin – 69.7 mg/kg, and topiramate – 509.5 mg/kg. In conclusion, the grip-strength test can aid in evaluating acute adverse effects of drugs with respect to their influence on muscular strength in experimental animals.     

How safe is the use of prosthetic materials in the repair of abdominal-wall defects in malnourished subjects?

Incisional hernias and abdominal-wall defects consume large amounts of healthcare resources. Use of mesh is effective in treatment of these disorders and can decrease the rate of recurrence. This experimental study focused on the safety of mesh use in the setting of malnutrition, a condition that impairs wound healing. Rats were divided into two groups: normally fed and food-restricted. An abdominal-wall defect, 2 by 2 cm, was covered with polypropylene mesh, 2.5 by 2.5 cm. After sacrifice of the rats at the 21st and 60th days, tissue samples were sent for tensiometric and histopathological studies. No significant difference in infectious complications was observed between the two groups. Tensiometry revealed no significant differences between the groups. On histopathological examination, the only difference noted was in the vascularization scores of normally fed rats. For malnourished subjects that survived after surgery, the use of polypropylene mesh appeared safe in the closure of abdominal-wall defects, with no increase in infection rate and satisfactory wound healing.