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Figueira A, Monteiro A, Marques M, Carvalho A, Inácio D, Soares P, Reis T, Batel V, Pinto G. Pelvic radiotherapy: Do we really need high energy beams? Rep Pract Oncol Radiother 2013. [DOI: 10.1016/j.rpor.2013.03.611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Areias V, Neves I, Carvalho A, Duarte R. Mycobacterium tuberculosis, quanto tempo passeaste? REVISTA PORTUGUESA DE PNEUMOLOGIA 2013; 19:139-40. [DOI: 10.1016/j.rppneu.2012.12.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 12/20/2012] [Indexed: 10/26/2022] Open
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Santos MVC, Paiva MG, Macedo CRDP, Petrilli AS, Azeka E, Jatene IB, Castro Junior CG, Seber A, Miachon AS, Tanaka ACS, Castro MAS, Carvalho AC, Nars CCF, Terzian CN, Santos CCL, Guerra CCS, Silva DCB, Bassi DU, Feitosa FA, Hamamoto F, Szarf G, Lederman HM, Rigon Junior HJ, Mota ICF, Perrud JÁ, Soares Junior J, Gutierrez JA, Perin JPM, Catani LH, Tsai LY, Vianna LC, Santos MJ, Ishigai MMS, Diógenes MSB, Alves MTS, Piedade MTC, Parreiras M, Cypriano M, Negrini NS, Campos Filho O, Figueiredo PA, Novaes PE, Camargo PR, Maia OS, Petrilli R, Arduini RG, Gouveia RV, Teruya SBM, Moisés VA, Morais VLL. I Diretriz Brasileira de Cardio-Oncologia Pediátrica da Sociedade Brasileira de Cardiologia. Arq Bras Cardiol 2013; 100:1-68. [DOI: 10.5935/abc.2013s005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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104
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Carvalho A, Pelaez-Vargas A, Gallego-Perez D, Grenho L, Fernandes M, De Aza A, Ferraz M, Hansford D, Monteiro F. Micropatterned silica thin films with nanohydroxyapatite micro-aggregates for guided tissue regeneration. Dent Mater 2012; 28:1250-60. [DOI: 10.1016/j.dental.2012.09.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 08/12/2012] [Accepted: 09/07/2012] [Indexed: 11/29/2022]
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Areias J, Calinas F, Porto A, Carvalho A, Freitas D, Macedo G, Noronha R, Cotter J, Meliço-Silvestre A, Peixe R, Pratas J, Barrote D, Teixeira R, Augusto F, Carrilho I, Campante F, Velosa J, Carvalho L, Duarte MA, Guerreiro H, Pires C, Silva A, Cotrim I, Guedes F, Tomé L, Marcelino M, Gonçalves C, Ferreira E, Matos L, Peixe P, Esteves J, Valente T, Simões C, Marinho C, Jasmins L, Vieira MJ, Marinho R, Matos P, Estevens J, Carrasquinho J, Salcedo G, Parada P, Teixeira C. One year of Lamivudine therapy for portuguese patients with chronic hepatitis B. Clin Drug Investig 2012; 23:339-46. [PMID: 17535046 DOI: 10.2165/00044011-200323050-00004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVE To assess the efficacy of lamivudine treatment on hepatitis B e antigen (HBeAg) and/or hepatitis B surface antigen (HBsAg) seroconversion, on other virological and serological markers of response including hepatitis B virus (HBV) DNA and serum aminotransferases, and the safety of lamivudine treatment in hepatitis B patients. PATIENTS This phase III open-label study evaluated the virological and biochemical response to lamivudine in 70 Portuguese patients with HBeAg positive chronic hepatitis B. Patients were treated with lamivudine 100mg once daily for 12 months. METHODS Antiviral activity was assessed by measuring alanine aminotransferase (ALT)/aspartate aminotransferase (AST) levels at all protocol visits, and hepatitis B serology and HBV DNA were performed at baseline and at month 12 visits. Evaluation of safety and tolerance was based on clinical adverse events and laboratory analyses. RESULTS The primary endpoint was virological response at month 12, defined as loss of detectable HBeAg from serum with a reduction of HBV DNA to undetectable levels, and this was observed in 19/69 (27.5%) of patients. Almost half of the patients were HBV DNA negative by this time. Mean ALT values decreased steadily during treatment and by 12 months 61% of patients had values within the normal range. HBeAg seroconversion (HBeAg negative, HBeAb positive) was achieved in 27.9% of patients by 12 months, although all patients remained HBsAg positive. CONCLUSION Lamivudine was well tolerated and the incidence of adverse events was similar to those reported in previous studies. Lamivudine treatment resulted in virological and biochemical improvements in HBeAg positive chronic hepatitis B patients, with HBeAg seroconversion in one-third of patients.
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Duarte R, Neto M, Carvalho A, Barros H. Improving tuberculosis contact tracing: the role of evaluations in the home and workplace. Int J Tuberc Lung Dis 2012; 16:55-9. [PMID: 22236846 DOI: 10.5588/ijtld.10.0511] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
SETTING In 2004, the tuberculosis (TB) contact screening strategy in Vila Nova de Gaia, Portugal, was changed from targeting only close contacts identified by interviews with the index patient (reflecting national policy) to include visits to the patient?s home and workplace. OBJECTIVE To find out 1) whether the new strategy increased adherence to TB screening procedures, 2) whether the strategy identified more at-risk contacts and 3) whether the strategy increased prevention of TB. METHODS We compared TB contact tracing during the periods 2001-2003 and 2004-2006. The numbers of identified and screened contacts and the results of screening procedures (number of patients with active TB and latent TB infection [LTBI] detected per index case) were analysed. The number of instances of active TB prevented and the numbers of contacts that had to be screened to prevent one such instance were calculated and compared for both screening strategies. RESULTS Home and workplace visits helped to identify more at-risk contacts (8.4 per index patient) than interview (2.5 per index patient), and improved adherence (87.3% of identified contacts were screened compared to 67.6% previously). More patients with active TB and LTBI were detected (1.4 per index patient compared with 0.75 per index patient previously), and more TB cases were prevented. CONCLUSION The newly implemented contact screening programme, featuring home and workplace evaluation of TB patient contacts, improved adherence to screening procedures, identified more at-risk contacts and should prevent more TB cases in the future.
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Carvalho B, Silva J, Cunha M, Viana P, Leite R, Stevenson D, Carvalho A, Oliveira C, da Silva JT, Póvoa A, Soares S, Calejo L, Sousa S, Xavier P, Sousa M, Barros A, Carvalho F. P33 Preimplantation genetic diagnosis for Portuguese familial amyloidotic polyneuropathy – 12 years' experience. Reprod Biomed Online 2012. [DOI: 10.1016/s1472-6483(12)60250-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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108
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Nascimento T, Cardoso M, Presado H, Carvalho A. 157 SEXUAL SATISFACTION IN MIDDLE AGE. Maturitas 2012. [DOI: 10.1016/s0378-5122(12)70268-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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109
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Monteiro A, Strunk A, Carvalho A, Tchepel O, Miranda AI, Borrego C, Saavedra S, Rodríguez A, Souto J, Casares J, Friese E, Elbern H. Investigating a high ozone episode in a rural mountain site. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2012; 162:176-189. [PMID: 22243863 DOI: 10.1016/j.envpol.2011.11.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 10/29/2011] [Accepted: 11/08/2011] [Indexed: 05/31/2023]
Abstract
A very high ozone episode with observed hourly values above 350 μg m(-3) occurred in July 2005 at the Lamas d'Olo air quality monitoring station, located in a mountainous area in the north of Portugal. Aiming to identify the origin and formation of this ozone-rich episode, a statistical analysis and a modelling approach were applied. A cross-spectrum analysis in the frequency domain and a synoptic analysis of the meteorological and air quality time series were performed. In order to go further in this analysis, a numerical modelling approach was applied. The results indicate that the transport of ozone and its precursors is the main responsible for the high ozone concentrations. Together with the local mountain breeze and subsidence conditions, the sea-breeze circulation transporting pollutants from the coastal urban and industrialized areas that reach the site during late afternoon turn out to be the driving forces for the ozone peaks.
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Botelho F, Figueiredo L, Leite R, Carvalho A, Tomada N, Vendeira P. Predictive factors of a successful testicular biopsy and subsequent clinical pregnancy. Andrologia 2012; 44:237-42. [PMID: 22272771 DOI: 10.1111/j.1439-0272.2012.01276.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/25/2011] [Indexed: 11/27/2022] Open
Abstract
Forecast of success with testicular sperm extraction and intracytoplasmic sperm injection (ICSI) remains unknown, as predictive factors have rarely been studied. We evaluated the association among possible predictive factors and a successful biopsy and clinical pregnancy. A consecutive sample of men submitted to a testicular open biopsy in S. João Hospital was used. Patient's age, medical history, testicular volume, spermogram, genetic testing, endocrinologic results, biopsy results and clinical pregnancy information were collected. From the 113 men included, it was possible to retrieve spermatozoa in 79.6% of the cases, which resulted in 58 fertilisations and 22 clinical pregnancies. Retrieving viable spermatozoa on biopsy was associated with the identification of spermatozoa in the spermogram (100.0% versus 74.4%; P = 0.010), diseases causing obstructive infertility (100.0% versus 79.2%; P = 0.036) and no genetic causes detected (82.4% versus 54.5%; P = 0.030). Successful clinical pregnancy was only associated with lower female partner age (31.7 versus 36.0 year; P = 0.001) but not the quality of the spermatozoa or the time until the reproduction cycle. Identification of spermatozoa in the spermogram, diseases causing obstructive infertility and lack of genetic causes for infertility were associated with higher probability of viable spermatozoa retrieval but the female partner age remained the principal determinant of a successful pregnancy.
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Caetano Mota P, Carvalho A, Valente I, Braga R, Duarte R. Predictors of delayed sputum smear and culture conversion among a Portuguese population with pulmonary tuberculosis. REVISTA PORTUGUESA DE PNEUMOLOGIA 2012; 18:72-9. [PMID: 22277838 DOI: 10.1016/j.rppneu.2011.12.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 12/07/2011] [Indexed: 01/10/2023] Open
Abstract
INTRODUCTION Failure of sputum smear and/or culture conversion after 2 months of tuberculosis (TB) treatment has been considered a predictor of patient infectivity and treatment failure. We aimed to identify the factors associated with delayed sputum smear and culture conversion in patients with pulmonary TB who were given anti-TB treatment. MATERIAL AND METHODS Retrospective cohort of 136 adult patients with sputum culture-proven pulmonary TB referred to an urban Chest Disease Centre. Socio-demographic, clinical, radiological, microbiological, and therapeutic data were evaluated. RESULTS The median age was 41.0 (interquartile range [IQR] 18.0) years and 75.0% of patients were male. Delayed sputum smear and culture conversion occurred in 25.4% (30/118) and 27.2% (37/136) of patients, respectively. Multivariate analysis indicated that age ≥ 50 years (odds ratio [OR] 4.4, 95% confidence interval [CI] 1.5-13.3), male gender (OR 10.8, 95% CI 1.3-91.1), and smear grade > 1-9 acid fast bacilli (AFB)/field (3+) (OR 11.7, 95% CI 1.4-100.6) were significantly associated with persistent smear positivity after 2 months of treatment. Bilateral radiological involvement (OR 3.7, 95% CI 1.5-9.0) and colony count > 100 (3+) (OR 5.8, 95% CI 1.2-27.4) were significantly associated with persistent culture positivity. CONCLUSIONS Delayed sputum smear and culture conversion occurred in about one third of patients. Older age, male gender, and higher bacillary load were independently associated with delayed smear conversion. Bilateral radiological involvement and higher colony count were independently associated with delayed culture conversion.
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Martins V, Miranda AI, Carvalho A, Schaap M, Borrego C, Sá E. Impact of forest fires on particulate matter and ozone levels during the 2003, 2004 and 2005 fire seasons in Portugal. THE SCIENCE OF THE TOTAL ENVIRONMENT 2012; 414:53-62. [PMID: 22088423 DOI: 10.1016/j.scitotenv.2011.10.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 06/20/2011] [Accepted: 10/06/2011] [Indexed: 05/31/2023]
Abstract
The main purpose of this work is to estimate the impact of forest fires on air pollution applying the LOTOS-EUROS air quality modeling system in Portugal for three consecutive years, 2003-2005. Forest fire emissions have been included in the modeling system through the development of a numerical module, which takes into account the most suitable parameters for Portuguese forest fire characteristics and the burnt area by large forest fires. To better evaluate the influence of forest fires on air quality the LOTOS-EUROS system has been applied with and without forest fire emissions. Hourly concentration results have been compared to measure data at several monitoring locations with better modeling quality parameters when forest fire emissions were considered. Moreover, hourly estimates, with and without fire emissions, can reach differences in the order of 20%, showing the importance and the influence of this type of emissions on air quality.
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Carvalho AC, Valadas E, França L, Carvalho C, Aleixo MJ, Mendez J, Marques R, Sarmento A, Doroana M, Antunes F, Branco T, Aguas M, Sarmento E Castro R, Lazarus JV, Barros H. Population mobility and the changing epidemics of HIV-2 in Portugal. HIV Med 2011; 13:219-25. [PMID: 22136745 DOI: 10.1111/j.1468-1293.2011.00963.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/30/2011] [Indexed: 11/29/2022]
Abstract
INTRODUCTION Portugal is the European country with the highest frequency of HIV-2 infection, which is mainly concentrated in West Africa. The cumulative number of notified HIV-2 infections in Portugal was 1813 by the end of December 2008. To better characterize the dynamics of HIV-2 infection in the country and to obtain data that may be of use in the prevention of the spread of HIV-2, we evaluated a large pooled sample of patients. PATIENTS AND METHODS Five Portuguese hospitals provided data on HIV-2-infected patients from 1984 to the end of 2007. Data concerning demographic characteristics and clinical variables were extracted. Patients were stratified according to date of diagnosis in approximately 5-year categories. RESULTS The sample included 442 patients, accounting for 37% of all HIV-2 infections notified in Portugal during that period. HIV-2-infected patients showed clearly different characteristics according to the period of diagnosis. Until 2000, the majority of HIV-2-infected patients were Portuguese-born males living in the north of the country. From 2000 to 2007, most of the patients diagnosed with HIV-2 infection had a West African origin, were predominantly female and were living in the capital, Lisbon. The average age at diagnosis and loss to follow-up significantly increased over time. CONCLUSION HIV-2 infection has been documented in Portugal since the early 1980s and its epidemiology appears to reflect changes in population movement. These include the movements of soldiers and repatriates from African territories during the independence wars and, later, migration and mobility from high-endemicity areas. The findings of this study stress the importance of promoting migrant-sensitive health care.
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Gomes J, Pereira T, Carvalho A, Brito C. Primary cutaneous actinomycosis caused by Actinomyces meyeri as first manifestation of HIV infection. Dermatol Online J 2011; 17:5. [PMID: 22136861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023] Open
Abstract
Primary cutaneous actinomycosis is very uncommon. We report a patient with cutaneous actinomycosis with multiple lesions without any detectable extra-cutaneous lesions. In our patient the actinomycosis was the presenting manifestation of HIV infection.
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Gomes J, Pereira T, Carvalho A, Brito C. Primary cutaneous actinomycosis caused by as first manifestation of HIV infection. Dermatol Online J 2011. [DOI: 10.5070/d30n05580m] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Abstract
Management of invasive aspergillosis in high-risk patients remains challenging. There is an increasing demand for novel therapeutic strategies aimed at enhancing or restoring antifungal immunity in immunocompromised patients. In this regard, modulation of specific innate immune functions and vaccination are promising immunotherapeutic strategies. Recent findings have also provided a compelling rationale for assessment of the contribution of the individual genetic profile to the immunotherapy outcome. Altogether, integration of immunological and genetic data may contribute to the optimization of therapeutic strategies exerting control over immune pathways, ultimately improving the management of fungal infections in high-risk settings.
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Carvalho A, Brito P, Santos J, Caramelo FJ, Veiga G, Vasconcelos B, Pires JN, Botelho MF. Evaluation of two dental impression materials using a robot arm. BULLETIN DU GROUPEMENT INTERNATIONAL POUR LA RECHERCHE SCIENTIFIQUE EN STOMATOLOGIE & ODONTOLOGIE 2011; 50:36-37. [PMID: 22750598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Accepted: 09/20/2011] [Indexed: 06/01/2023]
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118
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Botelho F, Figueiredo L, Leite R, Carvalho A, Tomada N, Vendeira P. UP-01.136 Which Men Have More Likelihood of Success with a Testicular Biopsy? Urology 2011. [DOI: 10.1016/j.urology.2011.07.688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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119
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Lima-Brito J, Castro L, Coutinho J, Morais F, Gomes L, Guedes-Pinto H, Carvalho A. Genetic variability in Sambucus nigra L. clones: a preliminary molecular approach. J Genet 2011; 90:e47-52. [PMID: 21873774 DOI: 10.1007/s12041-011-0066-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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120
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Carvalho A, Paiva S, Viegas C, Scarpelli A, Ferreira F, Pordeus I. P1-274 Prevalence and predisposing factors for malocclusion among Brazilian preschool children. Br J Soc Med 2011. [DOI: 10.1136/jech.2011.142976e.66] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Marchioni D, Carvalho A, Carlos J, Selem S, Teixeira J, Verly E, Fisberg R. SP3-78 Validity and reproducibility of a food frequency questionnaire developed based on a representative sample of adolescents from SAo Paulo, Brazil. Br J Soc Med 2011. [DOI: 10.1136/jech.2011.142976o.78] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Carvalho AC, Paiva SM, Scarpelli AC, Viegas CM, Ferreira FM, Pordeus IA. Prevalence of malocclusion in primary dentition in a population-based sample of Brazilian preschool children. EUROPEAN JOURNAL OF PAEDIATRIC DENTISTRY 2011; 12:107-111. [PMID: 21668282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
AIM The purpose of the present study was to assess the prevalence of malocclusion in the primary dentition in a randomised representative sample of Brazilian preschool children. MATERIALS AND METHODS A cross-sectional survey was carried out in Belo Horizonte, Brazil, involving 1069 male and female preschool children from 60 to 71 months of age, randomly selected from public and private preschools and daycare centers. A questionnaire addressing demographic data was sent to parents/guardians in order to characterise the sample. The oral examination of the children was performed by a single, previously calibrated dentist (kappa inter-examiner agreement value = 0.82). The criterion for the categorisation of malocclusion was at least one of the following conditions: posterior crossbite, overjet (> 2 mm), anterior crossbite, anterior open bite and deep overbite. Univariate analysis was performed using the SPSS software RESULTS The prevalence of malocclusion was 46.2%. Deep overbite was the most prevalent alteration (19.7% of the sample). Posterior crossbite was diagnosed in 13.1% of the children; 10.5% had accentuated overjet; 7.9% had anterior open bite; and 6.7% had anterior crossbite. CONCLUSION Malocclusion in primary dentition is becoming a significant problem. The prevalence in the present study was high, especially vertical and transversal malocclusions.
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Gabelle J, Augier F, Carvalho A, Rousset R, Morchain J. Effect of tank size on
k
L
a
and mixing time in aerated stirred reactors with non‐newtonian fluids. CAN J CHEM ENG 2011. [DOI: 10.1002/cjce.20571] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Carvalho A, Celikkol B, Coutinho J, Briddon PR. Surface-phosphorus interaction in Si nanocrystals. ACTA ACUST UNITED AC 2011. [DOI: 10.1088/1742-6596/281/1/012027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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125
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Silva EL, Coutinho J, Carvalho A, Torres VJB, Barroso M, Jones R, Briddon PR. Electronic structure of Zn, Cu and Ni impurities in germanium. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:065802. [PMID: 21406934 DOI: 10.1088/0953-8984/23/6/065802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present a density functional modelling study of Zn, Cu and Ni impurities in hydrogen-terminated germanium clusters. Their electronic structure is investigated in detail, especially their Jahn-Teller instabilities and electrical levels. Interstitial and substitutional defects were considered and the latter were found to be the most stable defect form for nearly all Fermi level positions. Relative formation energies are estimated semi-empirically with the help of the measured formation energy of the single Ge vacancy. We find that while Zn is a double shallow acceptor, Cu and Ni are deep acceptors with levels close to the available experimental data. Donor levels were only found for interstitial Cu and Zn.
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