Scanning Electron Microscopy Observations of Failures of Implant Overdenture Bars: A Case Series Report

Background: Soldered or cast bars are used as a standard of care in attachment systems supporting maxillary and mandibular implant overdentures. When failures of these bars occur, currently there is a lack of evidence in relation to their specific etiology, location, or nature. Purpose: To investigate the failure process of a case series of six failed soldered bars, four intact soldered bars, and one intact cast milled bar, which had been supporting implant overdentures. Materials and Methods: A total of 11 different overdenture bars were removed from patients with different configuration of opposing arches. A failed bar (FB) group (n = 6) had failed soldered overdenture bars, which were recovered from patients following up to 2 years of wear before requiring prosthodontic maintenance and repair. An intact bar (IB) group (n = 5) had both soldered bars and a single cast milled bar, which had been worn by patients for 2 to 5 years prior to receiving other aspects of prosthodontic maintenance. All bars were examined using scanning electron microscopy to establish the possible mode of failure (FB) or to identify evidence of potential failure in the future (IB). Results: Evidence of a progressive failure mode of corrosion fatigue and creep were observed on all the FB and IB usually around the solder areas and nonoxidizing gold cylinder. Fatigue and creep were also observed in all the IB. Where the level of corrosion was substantial, there was no evidence of wear from the matrices of the attachment system. Evidence of an instantaneous failure mode, ductile and brittle overload, was observed on the fracture surfaces of all the FB, within the solder and the nonoxidizing gold cylinders, at the solder/cylinder interface. Conclusion: Corrosion, followed by corrosion fatigue, appears to be a key factor in the onset of the failure process for overdenture bars in this case series of both maxillary and mandibular overdentures. Limited sample size and lack of standardization identify trends only but prevent broad interpretation of the findings.     

Anthropomorphic phantoms for assessment of strain imaging methods involving saline-infused sonohysterography

Two anthropomorphic uterine phantoms were developed that allow assessment and comparison of strain imaging systems adapted for use with saline-infused sonohysterography (SIS). Tissue-mimicking (TM) materials consist of dispersions of safflower oil in gelatin. TM fibroids are stiffer than the TM myometrium/cervix, and TM polyps are softer. The first uterine phantom has 3-mm-diameter TM fibroids distributed randomly in TM myometrium. The second uterine phantom has a 5-mm and 8-mm spherical TM fibroid, in addition to a 5-mm spherical and a 12.5-mm-long (medicine capsule-shaped) TM endometrial polyp protruding into the endometrial cavity; also, a 10-mm spherical TM fibroid projects from the serosal surface. Strain images using the first phantom show the stiffer 3-mm TM fibroids in the myometrium. Results from the second uterine phantom show that, as expected, parts of inclusions projecting into the uterine cavity will appear very stiff, whether they are stiff or soft. Results from both phantoms show that although there is a five-fold difference in the Young's moduli values, there is not a significant difference in the strain in the transition from the TM myometrium to the TM fat. These phantoms allow for realistic comparison and evolution of SIS strain imaging techniques and can aid clinical personnel to develop skills for SIS strain imaging.     

Hybrid spectral domain method for attenuation slope estimation

Attenuation estimation methods for medical ultrasound are important because attenuation properties of soft tissue can be used to distinguish between benign and malignant tumors and to detect diffuse disease. The classical spectral shift method and the spectral difference method are the most commonly used methods for the estimation of the attenuation; however, they both have specific limitations. Classical spectral shift approaches for estimating ultrasonic attenuation are more sensitive to local spectral noise artifacts and have difficulty in compensating for diffraction effects because of beam focusing. Spectral difference approaches, on the other hand, fail to accurately estimate attenuation coefficient values at tissue boundaries that also possess variations in the backscatter. In this paper, we propose a hybrid attenuation estimation method that combines the advantages of the spectral difference and spectral shift methods to overcome their specific limitations. The proposed hybrid method initially uses the spectral difference approach to reduce the impact of system-dependent parameters including diffraction effects. The normalized power spectrum that includes variations because of backscatter changes is then filtered using a Gaussian filter centered at the transmit center frequency of the system. A spectral shift method, namely the spectral cross-correlation algorithm is then used to compute spectral shifts from these filtered power spectra to estimate the attenuation coefficient. Ultrasound simulation results demonstrate that the estimation accuracy of the hybrid method is better than the centroid downshift method (spectral shift method), in uniformly attenuating regions. In addition, this method is also stable at boundaries with variations in the backscatter when compared with the reference phantom method (spectral difference method). Experimental results using tissue-mimicking phantom also illustrate that the hybrid method is more robust and provides accurate attenuation estimates in both uniformly attenuating regions and across boundaries with backscatter variations. The proposed hybrid method preserves the advantages of both the spectral shift and spectral difference approaches while eliminating the disadvantages associated with each of these methods, thereby improving the accuracy and robustness of the attenuation estimation.     

Comparison of (123)I and (131)I for whole-body imaging in thyroid cancer.

We compared the diagnostic sensitivities of (123)I and (131)I whole-body imaging in differentiated thyroid cancer. METHODS: Twelve thyroidectomized patients (3 previously treated with (131)I) were studied. After a period of thyroid hormone withdrawal, whole-body imaging was performed approximately 24 and 72-96 h after administration of 74-185 MBq (2-5 mCi) (123)I and 111-185 MBq (3-5 mCi) (131)I, respectively. RESULTS: Both (123)I and (131)I revealed residual thyroid tissue, present in 9 patients. (131)I detected metastases in 5 studies of 4 patients. In 4 of 5 studies, (123)I missed metastases shown by (131)I in 8 body regions including the neck, mediastinum, lungs, and bone and detected 3 other sites of metastasis only in retrospect. No lesion was better seen with (123)I than with (131)I. CONCLUSION: Although (123)I is adequate for imaging residual thyroid tissue, it appears to be less sensitive than (131)I for imaging thyroid cancer metastases.     

SELECTIVE ENDOSCOPY IN MANAGEMENT OF INGESTED FOREIGN BODIES OF THE UPPER GASTROINTESTINAL TRACT: IS IT SAFE?

During a four-year period, 308 patients presented following ingestion of foreign bodies. Ingestion was accidental in 272 cases (88.3%) and deliberate in the remainder. Symptoms at presentation included dysphagia, odynophagia, nausea and vomiting, chest pain and pharyngeal discomfort. Sixty-eight patients were asymptomatic. A policy of expectant management and selective endoscopy was employed. Following initial assessment 202 patients (65.6%) were discharged without treatment, 30 (9.7%) of whom were later reviewed as outpatients and did not require admission. Forty-nine patients (16%) were admitted for treatment; 27 had oesophagoscopy, five bronchoscopy and two had foreign body extraction with direct laryngoscopy. In nine patients who were endoscoped, no foreign body was identified. Twenty-seven others were referred to the otorhinolaryngology service in another hospital. There were no deaths in the group and morbidity was 1.2%. We conclude that a policy of selective endoscopy is safe and effective in the management of patients following ingestion of foreign bodies.     

Persistent diarrhea associated with AIDS

Chronic diarrhea and wasting are very common manifestations of AIDS in adults in developing countries. Etiologic studies show that protozoa (including Cryptosporidium parvum, Isospora belli , and Enterocytozoon bieniusi ) and Mycobacterium avium-intracellulara are the most frequently identified pathogens. Limited data in children suggest that common enteric pathogens are equally as likely in HIV⁺ and HIV^- babies. Preliminary analysis of an ongoing longitudinal study of 469 babies born to mothers with known HIV serostatus in Kinshasa, Zaire, reveals progression of acute to persistent diarrhea is six times greater in HIV⁺ compared to HIV^- babies, and 3.5 times greater in HIV^- babies born of HIV⁺ mothers in comparison to HIV^- babies with HIV^- mothers. HIV⁺ babies were also at greater risk than HIV^- babies to have recurrent episodes of diarrhea (RR = 2.3). Fifty percent of the deaths were due to acute or persistent diarrhea, and were strongly associated with HIV infection. Efforts to improve child survival in AIDS infected populations will need to address HIV infections in both mothers and infants.     

Studies on blood coagulation and fibrinolysis in patients bitten by Bothrops jararaca (jararaca)

The blood coagulation and the fibrinolytic systems of nine patients envenomed by Bothrops jararaca in S?o Paulo (Brazil) were studied. Five of the accidents were caused by young snakes (less than 50 cm). On admission, four patients had non-clotting and three partially-clotting blood. Fibrinogen levels were decreased due to the thrombin-like activity of the venom as expected. Consequent secondary activation of the fibrinolytic system was evident from the low levels of alpha-2-antiplasmin and the high titres of fibrin(ogen) degradation products. High titres of cross-linked fibrin fragment D (D-dimer) in seven patients together with decreased platelet counts and/or factor V, and/or factor VIII in some, suggests intrinsic thrombin formation as these factors are not consumed in the defibrinogenation induced by venom thrombin-like fractions such as Ancrod and Batroxobin. However, normal or increased levels of antithrombin III in all and normal levels of factor II in eight patients do not support this interpretation. The existence of variable concentrations of other proteins in the venom of B. jararaca such as botrocetin and thrombocytin isolated from B. jararaca and B. atrox or crotalocytin from Crotalus horridus venom should be considered. Such proteins are known to activate factors V, VIII, XIII, and platelets without affecting prothrombin (factor II) and antithrombin III. Slower recovery of the haemostatic disturbances after antivenom administration to patients bitten by young snakes suggests a more severe coagulopathy in such accidents. This is supported by clinical observations.     

阿克拉霉素A聚氰基丙烯酸异丁酯毫微粒冻干针剂体内外抗肝癌活性

阿克拉霉素A聚氰基丙烯酸异丁酯毫微粒的冻干针剂,能明显抑制体外培养人肝癌细胞株7703的生长,IC50为0.28μg·ml^-1。在0.8μg·ml^-1浓度时,克隆形成抑制率为90%,抑制作用有明显剂量依赖关系而未见明显时间依赖关系。静脉给药后,对常位移植人肝癌模型裸小鼠的抑瘤率为86.84%,肿瘤细胞增殖活性阳性率为20.83%。体内外均显示明显的抗肝癌活性,且体内抗肝癌活性比阿克拉霉素A冻干针剂强。     

Immunotoxicity of the commercial polybrominated diphenyl ether mixture DE-71 in ranch mink (Mustela vison)

Polybrominated diphenyl ethers (PBDEs) are persistent, bioaccumulative, organohalogen compounds that are increasing exponentially in the Great Lakes (Canada/USA) biota. The present study was undertaken to examine the immunological effects of a commercial PBDE mixture in ranch mink (Mustela vison). Twenty-week-old mink (n = 10 mink/group) were exposed to 0, 1, 5, or 10 ppm of DE-71 through their diet for eight weeks. The phytohemagglutinin-induced cutaneous reaction, and antibodies specific to keyhole limpet hemocyanin conjugated to dinitrophenol were measured. Liver microsomal ethoxyresorufin-O-deethylase (EROD) activity also was measured. Organs were weighed and spleens were examined histologically. No differences were found in the PHA-induced skin response in exposed mink; mink in the two highest treatments exhibited significant increases in antibody production over control mink. Systemic toxicity was apparent; significant body weight reductions were found in mink exposed to 5 and 10 ppm of DE-71. Exposed mink had significantly larger relative spleen, adrenal, and liver masses than control mink. Spleens of mink exposed to 10 ppm of DE-71 had significantly increased germinal center development and incidence of B-cell hyperplasia. The activity of EROD was induced in all treated mink relative to controls and was positively associated with the liver somatic index. Hematocrit in mink from the two highest exposure groups was significantly lower than control mink. Percentage neutrophils increased and percentage lymphocytes decreased significantly in mink from the higher two dosage groups. Our findings have direct relevance to wild mink in the Great Lakes ecosystem, because mink are top predators of the aquatic food web, providing evidence for the vulnerability of this species to the effects of environmental PBDE mixtures.