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1.
Chron Respir Dis ; 21: 14799731241235213, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38476003

RESUMO

BACKGROUND: Smoking poses the most common risk factor for chronic obstructive pulmonary disease (COPD) and aggravates disease progression. Tobacco dependence inhibits smoking cessation and may affect smoking patterns that increase tobacco exposure and predispose to lung function decline. AIMS AND OBJECTIVES: We aimed to assess tobacco dependence in current smokers with and without COPD and evaluate its role in disease development. METHOD: This cross-sectional study was conducted in Greek rural areas. Current smokers completed the Fagerström Test for Nicotine Dependence and were classified into COPD and non-COPD groups based on spirometry parameters. RESULTS: Among current smokers, 288 participants comprised the non-COPD and 71 the COPD group. Both presented moderate tobacco dependence, but smokers with COPD started to smoke earlier in the morning. Multiple logistic regression analysis revealed higher COPD prevalence in smokers with higher scores in the Fagerström test (odds ratio OR = 1.12, 95% confidence interval [1.01 - 1.24]) and older age (OR = 1.06 [1.03 - 1.09]), independently of pack-years smoking index. Multiple linear regression analysis in smokers with COPD showed that the forced expiratory volume in the 1st second decreased by 2.3% of the predicted value for each point increase in the Fagerström Test and 0.59% for each year of age, independently of participants' sex and pack-years smoking index. CONCLUSION: The Fagerström score appears to indicate a higher probability for COPD and lung function deterioration when assessed along with age in current smokers. Smoking cessation support programs are fundamental to COPD prevention and management.


Assuntos
Doença Pulmonar Obstrutiva Crônica , Tabagismo , Humanos , Estudos Transversais , Grécia , Fumantes , Prognóstico
2.
ACS Omega ; 8(25): 22992-22997, 2023 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-37396219

RESUMO

We study the adsorption and mobility of a Li ion on the surface of the Mo2CS2 MXene by means of Density Functional Theory. We find that by substituting the Mo atoms of the upper MXene layer with V the mobility of the Li ion can be improved up to 95% while the material retains its metallic character. This fact indicates that MoVCS2 is a promising candidate for anode electrode in Li-ion batteries, where the materials need to be conductive and the Li ion needs to have a small migration barrier.

3.
Medicina (Kaunas) ; 59(7)2023 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-37512039

RESUMO

Phytobezoars constitute conglomerates of indigested plant fibers and are a rare cause of acute mechanical ileus. They exhibit an increased prevalence in the elderly population and people with specific predisposing conditions. Radiological imaging can often set a definitive diagnosis and dictate the optimal therapeutic approach, combined with the patient's clinical status. An 81-year-old male presented with deteriorating clinical symptoms of intestinal obstruction, and an exploratory laparotomy was performed following inconclusive radiological findings; multiple phytobezoars and incipient intussusception were revealed intraoperatively. A patient's medical history can often raise clinical suspicion of phytobezoars. However, a careful etiological investigation is imperative in all cases of mechanical ileus in advanced ages; early detection and dissolution of phytobezoars, when applicable, can reduce the need for surgical interventions.


Assuntos
Bezoares , Dispepsia , Íleus , Obstrução Intestinal , Intussuscepção , Idoso , Humanos , Idoso de 80 Anos ou mais , Intussuscepção/cirurgia , Intussuscepção/complicações , Obstrução Intestinal/etiologia , Obstrução Intestinal/cirurgia , Bezoares/complicações , Bezoares/cirurgia , Bezoares/diagnóstico , Íleus/etiologia
5.
Medicina (Kaunas) ; 59(5)2023 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-37241207

RESUMO

Melanoma is the most aggressive type of skin cancer. Half of melanoma cases are characterized by the mutation BRAF V600. The case presented concerns a 41-year-old patient with locally advanced melanoma, being positive in mutation BRAF V600. The patient underwent surgery and received additional targeted therapy as part of a clinical study. In subsequent disease progression, immunotherapy was used. When the disease progressed again while the patient was in a good performance status, targeted therapy was administered again, and a good response was noted, making the patient reach a statistically significant overall survival, exceeding four years. Targeted therapy has proven to be an important tool in the treatment of melanoma. The use of BRAFi targeted therapy does not exclude the option of readministration at subsequent disease progression (BRAFi rechallenge). Preclinical models suggest that the resistance mechanism of cancer cells to BRAFi therapy bends, as these cell clones lose their evolutionary advantage after stopping BRAFi. Cell clones sensitive to BRAFi may then outcompete, making the treatment effective again. Therapeutical dilemmas in the management of patients with locally advanced melanoma that progresses to metastatic cancer are discussed.


Assuntos
Melanoma , Neoplasias Cutâneas , Humanos , Adulto , Proteínas Proto-Oncogênicas B-raf/genética , Inibidores de Proteínas Quinases/uso terapêutico , Melanoma/genética , Neoplasias Cutâneas/patologia , Progressão da Doença , Mutação
6.
Am J Case Rep ; 24: e939117, 2023 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-37093778

RESUMO

BACKGROUND Gorlin syndrome, also known as basal cell nevus syndrome (BCNS), nevoid basal cell carcinoma syndrome (NBCCS), and Jaw cyst-Basal cell nevus-Bifid rib syndrome, is a rare multisystemic syndrome that can affect a remarkable number of tissues and organs in the human body. Patients with this syndrome are in jeopardy of developing basal cell skin cancer during puberty or early adulthood. CASE REPORT Herein, we report a case of a 58-year-old woman who had multiple pigmented skin lesions and a palpable tumor of the left scapula. The patient underwent surgical excision of the above-mentioned lesions. The histopathological examination revealed that 10 of them were basal cell skin carcinomas (BCCs); therefore, the patient was proven to have the syndrome. She had a history of similar skin lesions, which were removed before the age of 20. CONCLUSIONS This case highlights that rare phenomena, such as the presence of multiple BCCs, require additional investigations and a multidisciplinary approach since a rare and potentially life-threating condition might be the underlying cause. Early diagnosis of Gorlin syndrome is of paramount importance to facilitate the appropriate therapeutic approach, as directed by a multidisciplinary team. Patients with multiple skin lesions need to have regular assessments by their general practitioner or dermatologist, with dermoscopy serving as an important preventive measure. Furthermore, because pathogenesis of the syndrome is characterized by development of basal cell carcinomas, consecutive follow-up is of a great significance.


Assuntos
Síndrome do Nevo Basocelular , Carcinoma Basocelular , Transtornos da Pigmentação , Neoplasias Cutâneas , Feminino , Humanos , Adulto , Pessoa de Meia-Idade , Síndrome do Nevo Basocelular/diagnóstico , Síndrome do Nevo Basocelular/patologia , Detecção Precoce de Câncer , Neoplasias Cutâneas/patologia
7.
J Gastrointest Cancer ; 54(1): 237-246, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-35199298

RESUMO

BACKGROUND: Robotic liver surgery is a novel technique expanding the field of minimally invasive approaches. An increasing number of studies assess the outcomes of robotic liver resections (RLR). The aim of our meta-analysis is to provide an up-to-date comparison of RLR versus open liver resections (OLR), evaluating its safety and efficacy. MATERIALS AND METHODS: A systematic search of MEDLINE, Scopus, Google Scholar, Cochrane, and Clinicaltrials.gov for articles published from January 2000 until January 2022 was undertaken. RESULTS: Thirteen non-randomized retrospective and one prospective clinical study enlisting 1801 patients met our inclusion criteria, with 640 patients undergoing RLR and 1161 undergoing OLR. RLR resulted in significantly lower overall morbidity (p < 0.001), shorter length of hospital stay (p = 0.002), and less intraoperative blood loss (p < 0.001). Operative time was found to be significantly higher in the RLR group (p < 0.001). Blood transfusion requirements, R0 resection, and mortality rates presented no difference among the two groups. The cumulative rate of conversion was 5% in the RLR group. CONCLUSION: The increasing experience in the implementation of the robot will undoubtedly generate more prospective randomized studies, necessary to assess its potential superiority over the traditional open approach, in a variety of hepatic lesions.


Assuntos
Laparoscopia , Neoplasias Hepáticas , Procedimentos Cirúrgicos Robóticos , Robótica , Humanos , Procedimentos Cirúrgicos Robóticos/efeitos adversos , Procedimentos Cirúrgicos Robóticos/métodos , Estudos Retrospectivos , Estudos Prospectivos , Laparoscopia/métodos , Fígado , Hepatectomia/métodos , Neoplasias Hepáticas/cirurgia , Tempo de Internação , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/etiologia , Resultado do Tratamento
8.
Waste Manag Res ; 39(10): 1264-1269, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33586640

RESUMO

The scope of this paper is to examine the environmental and economic performance of an alternative household fermentable waste (HFW) management paradigm, developed within the framework of the HORIZON 2020 project Waste4think. In Greece, the business-as-usual scheme for the management of HFW is its disposal in landfills as part of mixed waste. Waste4think developed an alternative approach based on the benefits of source separation. Specifically, source separated HFW is taken to a drying/shredding plant, located in the municipality, for the production of a high-quality biomass product called FORBI. Alternative approaches have been examined for the exploitation of FORBI. In this work, the use of FORBI as an alternative fuel for the cement industry is assessed using life cycle assessment (LCA) and life cycle costing (LCC) tools. The results show that the proposed HFW management framework performs better than the baseline scenario both in economic and environmental terms. However, focus should be given to the optimisation of the drying/shredding process in order to reduce its energy intensity and environmental loadings.


Assuntos
Eliminação de Resíduos , Gerenciamento de Resíduos , Materiais de Construção , Alimentos , Instalações de Eliminação de Resíduos
9.
In Vivo ; 34(5): 2475-2484, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32871775

RESUMO

BACKGROUND/AIM: U-74389G and ascorbic acid protect the cells from oxidation. This study aimed to depict their role in ischemia-reperfusion injury in a renal rat model. MATERIALS AND METHODS: Sixty Wistars rats were randomized into six groups of 10 animals each. Group A Ischemia 30 min, reperfusion 60 min; Group B Ischemia 30 min, reperfusion 120 min; Group C Ischemia 30 min, ascorbic acid administration, reperfusion 60 min; Group D Ischemia 30 min, ascorbic acid administration, reperfusion 120 min; Group E Ischemia 30 min, U-74389G administration, reperfusion 60 min; Group F Ischemia 30 min, U-74389G administration, reperfusion 120 min. We then collected tissue and blood samples. RESULTS: Histology and the significantly decreased malondialdehyde and tumor necrosis factor-α levels indicated that ascorbic acid was superior to U-74389G, at pre-defined time intervals. CONCLUSION: Ascorbic acid and U-74389G ameliorated renal damage induced by ischemia-reperfusion injury, suggesting a therapeutic effect.


Assuntos
Pregnatrienos , Traumatismo por Reperfusão , Animais , Antioxidantes/farmacologia , Ácido Ascórbico/farmacologia , Modelos Animais de Doenças , Pregnatrienos/farmacologia , Ratos , Ratos Wistar , Traumatismo por Reperfusão/tratamento farmacológico
10.
Psychiatry Res ; 292: 113298, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32717710

RESUMO

INTRODUCTION: The aim of the study was to investigate mental health in university students in Greece, during lockdown due to COVID-19. MATERIAL AND METHODS: The data were collected online and anonymously, during lockdown; they included 1104 females (aged 22.08±4,96) and 431 males (aged 22.35±3.11). The analysis included transformation of the data with post-stratification method, descriptive statistics, Chi-square tests, Factorial Analysis of Variance and Relative Risk ratios RESULTS: : The results suggest that during, lockdown major depression was present in 12.43% with 13.46% experiencing severe distress. Risk factors were female sex, history of self-injury, suicidal attempts and following theoretical studies (RR=2-5.71). Conspiracy theories were accepted by 20-68%, with students of theoretical studies manifesting higher rates. DISCUSSION: The results of the current study confirmed that students are at high risk to develop depression and suicidality in relation to the COVID-19 outbreak. They also identified specific risk factors and pointed to the role of believing in conspiracy theories in copying with stress. They also identified populations with higher prevalence of these beliefs. Further targeted research is necessary as well as targeted intervention in vulnerable groups but concerning mental health as well as the reduction of believing in conspiracy theories.


Assuntos
Infecções por Coronavirus/psicologia , Saúde Mental/estatística & dados numéricos , Pneumonia Viral/psicologia , Angústia Psicológica , Quarentena/psicologia , Estudantes/psicologia , Adolescente , Adulto , Betacoronavirus , COVID-19 , Infecções por Coronavirus/epidemiologia , Feminino , Grécia/epidemiologia , Nível de Saúde , Humanos , Masculino , Pandemias , Pneumonia Viral/epidemiologia , Prevalência , Fatores de Risco , SARS-CoV-2 , Inquéritos e Questionários , Universidades , Adulto Jovem
11.
Psychiatry Res ; 290: 113111, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32450416

RESUMO

The COVID-19 hit also Greece but due to early measures and their exceptional success, the death toll is one of the lowest in the world. Here we report the results from the analysis of the responses to an online survey, from the first 1000 university students, concerning the impact of the lockdown on their mental health. Overall, there was a 'horizontal' increase in scores; 42.5% for anxiety, 74.3% for depression, and 63.3% increase in total suicidal thoughts. Quantity of sleep increased in 66.3% but quality worsened in 43.0%. Quality of life worsened in 57.0% (same in 27.9%). There was a 25-3 fold increase in possible clinical cases of depression and an almost 8-fold increase in suicidal thoughts. Almost a third accept and one fifth are open to conspiracy theories concerning COVID-19. To our knowledge this is the first study reporting data concerning the impact of lockdown and quarantine on the mental health of university students. While the acute impact seems clear, the long-term consequences are unknown and although suicidal thoughts have risen substantially, it seems unlikely this will result in deaths. However, the results constitute a clear message that vulnerable populations are at a need for specific interventions concerning their mental health issues.


Assuntos
Ansiedade/epidemiologia , Infecções por Coronavirus/psicologia , Depressão/epidemiologia , Pneumonia Viral/psicologia , Quarentena/psicologia , Estudantes/psicologia , Adulto , Ansiedade/psicologia , Betacoronavirus , COVID-19 , Infecções por Coronavirus/prevenção & controle , Depressão/psicologia , Feminino , Grécia/epidemiologia , Humanos , Masculino , Saúde Mental , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Qualidade de Vida , SARS-CoV-2 , Sono , Ideação Suicida , Inquéritos e Questionários , Universidades
12.
Environ Sci Pollut Res Int ; 26(35): 35555-35564, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31069656

RESUMO

The present study focuses on the production of an alternative fuel (AF) for the cement industry from a food residue biomass (FORBI) product, generated from pre-sorted household food waste (HFW). FORBI is generated by drying and shredding the fermentable fraction of HFW collected door-to-door in the Municipality of Halandri, Greece. The key physicochemical properties such as the net calorific value (NCV), and the concentration of heavy metals and chlorine are subsequently determined using well-established international standards (EN and ISO). FORBI is evaluated as a potential AF in terms of technical feasibility and environmental impacts. Based on the characterization, FORBI is classified as a non-dangerous waste according to EWC 20 01 08, European Commission Decision 2014/955. According to EN 15359, it is classified as category 3, 2, and 1 with respect to NCV, Cl, and Hg respectively. The study concludes that FORBI is a suitable candidate as a secondary fuel for the cement industry, given its high calorific value along with its low humidity and ash content. Challenges for practical implementation include the relatively high chlorine content, the inclusion of alkalis in the cement produced, and the reduction of non-thermal NOx emissions.


Assuntos
Indústria da Construção , Materiais de Construção , Alimentos , Eliminação de Resíduos/métodos , Biomassa , Reatores Biológicos , Cloro , Grécia , Mercúrio , Metais Pesados
13.
Sci Rep ; 8(1): 9206, 2018 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-29907839

RESUMO

The magnitude time-series of the global seismicity is analyzed by the empirical mode decomposition giving rise to 14 intrinsic mode functions (IMF) and a trend. Using Hurst analysis one can identify three different sums of these IMFs and the trend which exhibit distinct multifractal behaviour and correspond to micro-, mid- and macro-scales. Their multifractal detrended fluctuation analysis reveals that the micro-scale time-series exhibits anticorrelated behaviour in contrast to the mid-scale one which is long-range correlated. Concerning the mid-scale one, in the range of 30 to 300 consecutive events the maximum entropy method power spectra indicates that it exhibits an 1/f α behaviour with α close to 1/3 which is compatible with the long-range correlations identified by detrended fluctuation analysis during periods of stationary seismicity. The results have been also verified to hold regionally for the earthquakes in Japan and shed light on the significance of the mid-scale of 30 to 300 events in the natural time analysis of global (and regional) seismicity. It is shown that when using the mid-scale time-series only, we can obtain results similar to those obtained by the natural time analysis of global seismicity when focusing on the prediction of earthquakes with M ≥ 8.4.

14.
Entropy (Basel) ; 20(8)2018 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-33265703

RESUMO

By employing the cross-correlogram method, in geo-electric data from the area of Kyrgyzstan for the period 30 June 2014-10 June 2015, we identified Anomalous Telluric Currents (ATC). From a total of 32 ATC after taking into consideration the electric current source properties, we found that three of them are possible Seismic Electric Signal (SES) activities. These three SES activities are likely to be linked with three local seismic events. Finally, by studying the corresponding recordings when a DC alternating source injects current into the Earth, we found that the subsurface resistivity seems to be reduced before one of these three earthquakes, but a similar analysis for the other two cannot be done due to their large epicentral distance and the lack of data.

15.
BMC Nurs ; 16: 15, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28344515

RESUMO

BACKGROUND: In the healthcare sector, we often come across the burnout syndrome. It is an occupational syndrome which causes, physical and emotional exhaustion. More information is needed on the dangers of burnout and how often it occurs in healthcare. The purpose of this study was to investigate burnout and factors associated with the syndrome among nurses working with people that are mentally challenged. METHODS: A cross-sectional survey was conducted, among 180 nurses working in public health centers for the disabled in multiple regions of Greece. A self-administered questionnaire with questions about socio-demographic and work-related characteristics was used, as well as the Maslach Burnout Inventory (MBI) for burnout assessment. Univariate and multivariate analyzes were performed. RESULTS: The burnout dimensions of emotional exhaustion (Mean = 31.36) and depersonalization (Mean = 11.27) were at high levels while personal accomplishment was at low levels (Mean = 44.02). Female nurses had a higher personal accomplishment score (Mean = 44.82, p = 0.047) than men (Mean = 42.10, p = 0.047). Marital status, daily routine and relationships with supervisors were significantly related with emotional exhaustion and personal accomplishment and professional experience with higher levels of emotional exhaustion and depersonalization. Reason for professional selection was an independent predictor for depersonalization and personal accomplishment, with those that have selected the nursing profession randomly or because of the fear of unemployment having higher scores. Moderate relationships with colleagues was an independent predictor for all burnout dimensions. CONCLUSIONS: Nurses working in services for people with intellectual disabilities in Greece show increased burnout levels. Burnout can be prevented by offering more opportunities for professional advancement and education, new ways to provide supervisor support, provide incentives for nurses to initiate or participate in innovative programs. Specific training on conflict resolution, collaboration, reinforcement and stress coping techniques must be implemented.

16.
Eur J Orthod ; 36(1): 9-15, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22109942

RESUMO

The aim of the present work was to evaluate the biomechanical behaviour of the periodontal ligament (PDL) with respect to force development with different controlled loading velocities. For this purpose, an in vitro experimental study was performed on 18 minipig jaw segments. Displacements with variable increasing loading time were applied to one premolar crown of each jaw segment into the linguobuccal direction through a force sensor provided by a specialized biomechanical set-up. The predefined displacement values to be achieved were 0.1 and 0.2 mm. Each of the given displacement increments was applied on the specimens with a linear displacement increase employing the following time spans: 5, 10, 20, 30, 60, 120, 300, 450, and 600 seconds. Force values were measured during load application to register force/displacement diagrams and after the maximum displacement was reached force decay was monitored for a period of 600 seconds. Force/time curves for each tooth were plotted according to the data obtained. Diagrams of the maximum force values obtained from these plots and the force at the end of each measurement were extracted for all teeth. Forces at the point when maximum displacement was reached ranged from 0.5 to 2.5 N for the 0.1 mm activation and showed extreme variation with the specimens. The factor of volume and surface area of the individual roots were evaluated and found not to be responsible for these deviations. A comparable behaviour was recorded for the 0.2 mm deflection, however, on a higher force level. The results show that the force development at different displacement velocities is complex and dominated by the PDL biomechanical characteristics.


Assuntos
Dente Pré-Molar/fisiologia , Ligamento Periodontal/fisiologia , Animais , Fenômenos Biomecânicos , Análise do Estresse Dentário , Mandíbula/fisiologia , Estresse Mecânico , Suínos , Porco Miniatura , Coroa do Dente/fisiologia , Raiz Dentária/fisiologia
17.
Eur J Orthod ; 36(3): 350-63, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24062378

RESUMO

BACKGROUND: Fixed-appliance treatment is a major part of orthodontic treatment, but clinical evidence remains scarce. OBJECTIVES: Objective of this systematic review was to investigate how the therapeutic effects and side-effects of brackets used during the fixed-appliance orthodontic treatment are affected by their characteristics. SEARCH METHODS AND SELECTION CRITERIA: We searched MEDLINE and 18 other databases through April 2012 without restrictions for randomized controlled trials and quasi-randomized controlled trials investigating any bracket characteristic. DATA COLLECTION AND ANALYSIS: After duplicate selection and extraction procedures, risk of bias was assessed also in duplicate according to Cochrane guidelines and quality of evidence according to the Grades of Recommendation. Assessment, Development and Evaluation approach. Random-effects meta-analyses, subgroup analyses, and sensitivity analyses were performed with the corresponding 95 per cent confidence intervals (CI) and 95 per cent prediction intervals (PI). RESULTS: We included 25 trials on 1321 patients, with most comparing self-ligated (SL) and conventional brackets. Based on the meta-analyses, the duration of orthodontic treatment was on average 2.01 months longer among patients with SL brackets (95 per cent CI: 0.45 to 3.57). The 95 per cent PIs for a future trial indicated that the difference could be considerable (-1.46 to 5.47 months). Treatment characteristics, outcomes, and side-effects were clinically similar between SL and conventional brackets. For most bracket characteristics, evidence is insufficient. Some meta-analyses included trials with high risk of bias, but sensitivity analyses indicated robustness. CONCLUSIONS: Based on existing evidence, no clinical recommendation can be made regarding the bracket material or different ligation modules. For SL brackets, no conclusive benefits could be proven, while their use was associated with longer treatment durations.


Assuntos
Braquetes Ortodônticos , Humanos , Desenho de Aparelho Ortodôntico , Braquetes Ortodônticos/efeitos adversos , Ensaios Clínicos Controlados Aleatórios como Assunto/métodos
18.
Eur J Orthod ; 35(6): 811-8, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23314330

RESUMO

The analysis of the non-linear and time-dependent viscoelasticity of the periodontal ligament (PDL) enables a better understanding of the biomechanical features of the key regulator tissue for tooth movement. This is of great significance in the field of orthodontics as targeted tooth movement remains still one of the main goals to accomplish. The investigation of biomechanical aspects of the PDL function, a difficult area of research, helps towards this direction. After analysing the time-dependent biomechanical properties of pig PDL specimens in an in vitro experimental study, it was possible to confirm that PDL has a viscoelastic anisotropic behaviour. Three-dimensional finite element models of mini-pig mandibular premolars with surrounding tissues were developed, based on micro-computed tomography (µCT) data of the experimental specimens. Tooth mobility was numerically analysed under the same force systems as used in the experiment. A bilinear material parameter set was assumed to simulate tooth displacements. The numerical force/displacement curves were fitted to the experimental curves by repeatedly calculating tooth displacements of 0.2mm varying the loading velocities and the parameters, which describe the nonlinearity. The experimental results showed a good agreement with the numerical calculations. Mean values of Young's moduli E1, E2 and ultimate strain ε12 were derived for the elastic behaviour of the PDL for all loading velocities. E1 and E2 values increased with increasing the velocity, while ε12 remained relatively stable. A bilinear approximation of material properties of the PDL is a suitable description of measured force/displacement diagrams. The numerical results can be used to describe mechanical processes, especially stress-strain distributions in the PDL, accurately. Further development of suitable modelling assumptions for the response of PDL under load would be instrumental to orthodontists and engineers for designing more predictable orthodontic force systems and appliances.


Assuntos
Ligamento Periodontal/fisiologia , Mobilidade Dentária , Animais , Dente Pré-Molar/fisiologia , Fenômenos Biomecânicos , Elasticidade , Análise de Elementos Finitos , Mandíbula/fisiologia , Modelos Animais , Modelos Biológicos , Estresse Mecânico , Suínos , Viscosidade
19.
Aust Orthod J ; 25(1): 63-75, 2009 May.
Artigo em Inglês | MEDLINE | ID: mdl-19634466

RESUMO

AIMS: To summarise the currently available evidence on the effects of microorganisms on the corrosion processes of biomaterials, with specific relevance to orthodontic alloys. METHODS: Factors related to the micro-environmental milieu, conditions, site characteristics, microbial species, enzymes and compounds released in response to their attachment to surfaces and formation of biofilms are analysed with respect to their contributory roles in corrosion. RESULTS: Application to orthodontics is projected from relevant evidence, albeit hypothetical due to the lack of extensive investigations of the subject. The micro-organisms involved and effects observed in orthodontic alloys are summarised. Finally, protective measures are proposed to minimise the potential for corrosion processes in orthodontic patients.


Assuntos
Corrosão , Ligas Dentárias , Aparelhos Ortodônticos/microbiologia , Aderência Bacteriana , Biofilmes , Genes Bacterianos/fisiologia , Leptothrix/metabolismo , Polissacarídeos Bacterianos/metabolismo , Streptococcus mutans/metabolismo , Bactérias Redutoras de Enxofre/metabolismo
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