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Feeding supplemental choline and Met during the periparturient period can have positive effects on cow performance; however, the mechanisms by which these nutrients affect performance and metabolism are unclear. The objective of this experiment was to determine if providing rumen-protected choline, rumen-protected Met, or both during the periparturient period modifies the choline metabolitic profile of plasma and milk, plasma AA, and hepatic mRNA expression of genes associated with choline, Met, and lipid metabolism. Cows (25 primiparous, 29 multiparous) were blocked by expected calving date and parity and randomly assigned to 1 of 4 treatments: control (no rumen-protected choline or rumen-protected Met); CHO (13 g/d choline ion); MET (9 g/d DL-methionine prepartum; 13.5 g/d DL-methionine, postpartum); or CHO + MET. Treatments were applied daily as a top dress from â¼21 d prepartum through 35 d in milk (DIM). On the day of treatment enrollment (d -19 ± 2 relative to calving), blood samples were collected for covariate measurements. At 7 and 14 DIM, samples of blood and milk were collected for analysis of choline metabolites, including 16 species of phosphatidylcholine (PC) and 4 species of lysophosphatidylcholine (LPC). Blood was also analyzed for AA concentrations. Liver samples collected from multiparous cows on the day of treatment enrollment and at 7 DIM were used for gene expression analysis. There was no consistent effect of CHO or MET on milk or plasma free choline, betaine, sphingomyelin, or glycerophosphocholine. However, CHO increased milk secretion of total LPC irrespective of MET for multiparous cows and in absence of MET for primiparous cows. Furthermore, CHO increased or tended to increase milk secretion of LPC 16:0, LPC 18:1, and LPC 18:0 for primi- and multiparous cows, although the response varied with MET supplementation. Feeding CHO also increased plasma concentrations of LPC 16:0 and LPC 18:1 in absence of MET for multiparous cows. Although milk secretion of total PC was unaffected, CHO and MET increased secretion of 6 and 5 individual PC species for multiparous cows, respectively. Plasma concentrations of total PC and individual PC species were unaffected by CHO or MET for multiparous cows, but MET reduced total PC and 11 PC species during wk 2 postpartum for primiparous cows. Feeding MET consistently increased plasma Met concentrations for both primi- and multiparous cows. Additionally, MET decreased plasma serine concentrations during wk 2 postpartum and increased plasma phenylalanine in absence of CHO for multiparous cows. In absence of MET, CHO tended to increase hepatic mRNA levels of betaine-homocysteine methyltransferase and phosphate cytidylyltransferase 1 choline, α, but tended to decrease expression of 3-hydroxy-3-methylglutaryl-coenzyme A synthase 2 and peroxisome proliferator activated receptor α irrespective of MET. Although shifts in the milk and plasma PC profile were subtle and inconsistent between primi- and multiparous cows, gene expression results suggest that supplemental choline plays a probable role in promoting the cytidine diphosphate-choline and betaine-homocysteine S-methyltransferase pathways. However, interactive effects suggest that this response depends on Met availability, which may explain the inconsistent results observed among studies when supplemental choline is fed.
Assuntos
Aminoácidos , Metionina , Gravidez , Feminino , Bovinos , Animais , Metionina/metabolismo , Aminoácidos/metabolismo , Colina/metabolismo , Suplementos Nutricionais/análise , Dieta/veterinária , Metabolismo dos Lipídeos , Lactação , Período Pós-Parto/metabolismo , Leite/química , Racemetionina/metabolismo , Racemetionina/farmacologia , Betaína/metabolismo , Fígado/metabolismo , LecitinasRESUMO
Background: Clinical trials of neuroprotection in acute ischemic stroke (AIS) have provided disappointing results. Reperfusion may be a necessary condition for positive effects of neuroprotective treatments. This systematic review provides an overview of efficacy of neuroprotective agents in combination with reperfusion therapy in AIS. Methods: A literature search was performed on the following databases, namely PubMed, Embase, Web of Science, Cochrane Library, Emcare. All databases were searched up to September 23rd 2021. All randomized controlled trials in which patients were treated with neuroprotective strategies within 12 h of stroke onset in combination with intravenous thrombolysis (IVT), endovascular therapy (EVT), or both were included. Results: We screened 1,764 titles/abstracts and included 30 full reports of unique studies with a total of 16,160 patients. In 15 studies neuroprotectants were tested for clinical efficacy, where all patients had to receive reperfusion therapies, either IVT and/or EVT. Heterogeneity in reported outcome measures was observed. Treatment was associated with improved clinical outcome for: 1) uric acid in patients treated with EVT and IVT, 2) nerinetide in patients who underwent EVT without IVT, 3) imatinib in stroke patients treated with IVT with or without EVT, 4) remote ischemic perconditioning and IVT, and 5) high-flow normobaric oxygen treatment after EVT, with or without IVT. Conclusion: Studies specifically testing effects of neuroprotective agents in addition to IVT and/or EVT are scarce. Future neuroprotection studies should report standardized functional outcome measures and combine neuroprotective agents with reperfusion therapies in AIS or aim to include prespecified subgroup analyses for treatment with IVT and/or EVT.
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Timely detection of severe infratentorial hemorrhage in neonates is crucial, especially in case of life-threatening brain stem compression and/or acute obstructive hydrocephalus, which need lifesaving neurosurgical intervention. Although the detection of infratentorial hemorrhage by ultrasound scanning is often considered as difficult, the use of additional acoustic windows and recognition of characteristic ultrasound features facilitate early diagnosis. In this case series, we report on newborns with severe, symptomatic infratentorial hemorrhage detected primarily by cranial ultrasound. We demonstrate the characteristic ultrasound features present in all cases and discuss how ultrasound diagnosis contributed to early diagnosis and treatment.
Assuntos
Ecoencefalografia , Hidrocefalia , Hemorragia Cerebral/diagnóstico por imagem , Humanos , Hidrocefalia/cirurgia , Recém-Nascido , Procedimentos NeurocirúrgicosRESUMO
The objective of this experiment was to examine production performance responses to feeding rumen-protected choline (RPC) or methionine (RPM), or both, during the periparturient period. Fifty-four Holstein cows (25 primiparous, 29 multiparous) were used in a randomized block design experiment with a 2 × 2 factorial treatment structure. Cows were blocked by expected calving date and parity and assigned to 1 of 4 treatments: CON (no RPC or RPM); RPC (13.0 g/d of choline ion); RPM (9 g/d of dl-methionine prepartum; 13.5 g/d of dl-methionine postpartum); or RPC + RPM. Treatments were applied once daily as a top-dress from 3 wk before through 5 wk after calving. Dry matter intake and milk production were recorded daily, and milk samples were obtained once weekly. Data were analyzed for primi- and multiparous cows separately, using a repeated-measures mixed model that included random effects of cow and block and fixed effects of RPC, RPM, week, and their interactions; week served as the repeated effect. Initial BW and previous lactation milk yield were included as covariates in the statistical model for multiparous cows. Feeding RPC without RPM increased milk yield for multiparous cows by 8.7 kg/d, but this increase was not observed when RPC was fed with RPM. In multiparous cows, feeding RPM increased milk fat concentration and tended to increase milk fat yield. Because of this, RPM increased fat-corrected milk (FCM) by 2.8 kg/d at wk 2 postpartum, and this increase was sustained through wk 5 postpartum. In contrast, RPM did not affect overall milk fat yield and concentration for primiparous cows. Feeding RPC increased milk yield for primiparous cows by 3.5 kg/d irrespective of RPM inclusion, which is contrary to observations in multiparous cows, where RPC increased milk yield only in the absence of RPM. These results indicate that responses to RPC during the periparturient period may be dependent upon supply of methionine. Our observations also demonstrate that primi- and multiparous cows respond differently to RPC and RPM supplemented individually or simultaneously during the periparturient period. This variation in response could have been mediated by putative differences in choline and methionine requirements of primiparous versus multiparous cows, or by differences in the levels of milk production between the 2 groups (36 vs. 25 kg of FCM/d). However, cows in this study did not experience severe negative energy balance (mean nadirs of -6.6 and -5.0 Mcal/d for multiparous and primiparous cows, respectively), which likely affected their responses to RPC and RPM.
Assuntos
Colina/farmacologia , Suplementos Nutricionais , Lactação/efeitos dos fármacos , Metionina/farmacologia , Período Periparto/efeitos dos fármacos , Ração Animal/análise , Fenômenos Fisiológicos da Nutrição Animal , Animais , Bovinos , Colina/administração & dosagem , Dieta/veterinária , Metabolismo Energético/fisiologia , Feminino , Lactação/fisiologia , Fenômenos Fisiológicos da Nutrição Materna , Metionina/administração & dosagem , Leite/química , Paridade , Gravidez , Rúmen/metabolismoRESUMO
Mastitis is the leading cause of antimicrobial use on dairy farms. The potential for antimicrobial resistance has led to the examination of alternative strategies for controlling mastitis. One such alternative is PlyC, a potent peptidoglycan hydrolase derived from the streptococcal C1 bacteriophage that causes targeted lysis of the cell wall of Streptococcus uberis. At a concentration of 1.0 µg/mL, recombinant PlyC can induce lytic activity, suggesting that a low dose may successfully eliminate infection. We evaluated the dose effect of PlyC (1-50 µg/mL) on cytotoxicity and oxidative response on bovine blood polymorphonuclear leukocytes (PMN) obtained from 12 healthy, mid-lactation primiparous dairy cows. Following incubation at 0.5 and 2 h, cytotoxicity was characterized by measuring lactate dehydrogenase release from isolated cells. Oxidative burst response was characterized as the intensity of chemiluminescence produced in the interaction of reactive oxygen species generated in response to 0 or 1.6 µg/mL of phorbol 12-myristate-13-acetate (PMA) with a luminescent substrate with and without addition to PlyC to the incubation matrix. Data were analyzed as a complete randomized block design using mixed model procedures. Cytotoxicity of PlyC was not affected by concentrations up to 50 µg/mL. As expected, PlyC cytotoxicity on PMN varied across incubation time with greater cell toxicity measured at 2 h of incubation as compared with 0.5 h and is primarily attributed to the short life of PMN ex vivo. Concentrations of PlyC up to 50 µg/mL did not affect oxidative response; however, oxidative response was affected by incubation time and PMA concentration. In summary, varying doses of PlyC are nontoxic as estimated by lactate dehydrogenase release from cells and do not appear to alter PMA-stimulated reactive oxygen species production in bovine PMN. These early observations support continued work on the potential for application of this novel agent in combating mastitis.
Assuntos
Bacteriófagos , Endopeptidases/farmacologia , Mastite Bovina/prevenção & controle , Neutrófilos/metabolismo , Animais , Bovinos , Feminino , Lactação , Estresse OxidativoRESUMO
INTRODUCTION: Acquired demyelinating syndromes (ADS) are immune-mediated demyelinating disorders of the central nervous system in children. A nationwide, multicentre and prospective cohort study was initiated in the Netherlands in 2006, with a reported ADS incidence of 0.66/100,000 per year and MS incidence of 0.15/100,000 per year in the period between 2007 and 2010. In this study, we provide an update on the incidence and the long-term follow-up of ADS in the Netherlands. METHODS: Children < 18 years with a first attack of demyelination were included consecutively from January 2006 to December 2016. Diagnoses were based on the International Paediatric MS study group consensus criteria. Outcome data were collected by neurological and neuropsychological assessments, and telephone call assessments. RESULTS: Between 2011 and 2016, 55/165 of the ADS patients were diagnosed with MS (33%). This resulted in an increased ADS and MS incidence of 0.80/100,000 per year and 0.26/100,000 per year, respectively. Since 2006 a total of 243 ADS patients have been included. During follow-up (median 55 months, IQR 28-84), 137 patients were diagnosed with monophasic disease (56%), 89 with MS (37%) and 17 with multiphasic disease other than MS (7%). At least one form of residual deficit including cognitive impairment was observed in 69% of all ADS patients, even in monophasic ADS. An Expanded Disability Status Scale score of ≥ 5.5 was reached in 3/89 MS patients (3%). CONCLUSION: The reported incidence of ADS in Dutch children has increased since 2010. Residual deficits are common in this group, even in monophasic patients. Therefore, long-term follow-up in ADS patients is warranted.
Assuntos
Doenças do Sistema Nervoso Central/epidemiologia , Doenças Desmielinizantes/epidemiologia , Adolescente , Doenças do Sistema Nervoso Central/terapia , Criança , Pré-Escolar , Doenças Desmielinizantes/terapia , Feminino , Seguimentos , Humanos , Incidência , Masculino , Países Baixos/epidemiologia , Estudos ProspectivosRESUMO
The 4 major tocopherol isoforms differ in their biochemical reactivity and cellular effects due to basic chemical structural differences. Alpha-tocopherol has been well studied regarding effects on bovine polymorphonuclear leukocyte (PMN) function and its involvement in respiratory burst. However, no studies to date have identified the effects of supplementing a mixed tocopherol oil (Tmix) particularly enriched in non-α tocopherol isoforms (i.e., γ- and δ-isoforms) on fundamental immunometabolic changes in dairy cows. Therefore, the objectives of this study were to determine whether short-term feeding of vegetable oil-derived Tmix alters specific biomarkers of metabolism, whole-blood leukocyte populations, respiratory burst, immunometabolic-related gene expression of PMN, or gene expression of isolated PMN when challenged with lipopolysaccharides (LPS). Clinically healthy multiparous lactating Holstein cows (n = 12; 179 ± 17 d in milk, 40.65 ± 3.68 kg of milk yield) were fed Tmix (620 g/d) for 7 consecutive days. Jugular blood (EDTA anticoagulant) was collected from all cows on d 0 before treatment initiation and again on d 7 after Tmix feeding. Total stimulated respiratory burst activity (RBA) and leukocyte populations were assessed in whole blood, and tocopherol isoform concentrations, metabolites, and hormones were measured in plasma. For gene expression analysis, isolated PMN from cows before and after Tmix feeding were incubated with LPS at a final concentration of either 0.0 or 1.5 µg/mL. Feeding of Tmix for 7 d increased the concentrations of α- and γ-tocopherol. The Tmix did not alter plasma insulin but decreased cholesterol. The Tmix did not alter whole-blood RBA or the leukocyte populations. The LPS challenge increased the expression of proinflammatory genes TNFA and IL6. However, Tmix treatment did not alter the patterns of LPS-affected expression of genes (e.g., TNFA, ITGB2, PPARA, and RXRA) associated with the immune or metabolic response. In conclusion, short-term feeding of Tmix may have no negative effect on animal health as Tmix increased α- and γ-tocopherol concentrations in blood and did not impair whole-blood RBA or alter leukocyte populations. The data provide further support that the α- and γ-tocopherol isoforms do not interfere with normal immune or metabolic function.
Assuntos
Ração Animal/análise , Bovinos/genética , Neutrófilos/imunologia , Explosão Respiratória , Tocoferóis/metabolismo , Animais , Bovinos/imunologia , Bovinos/fisiologia , Dieta/veterinária , Suplementos Nutricionais/análise , Feminino , Expressão Gênica , Lactação , Leucócitos/imunologia , Leucócitos/metabolismo , Leite/metabolismo , Neutrófilos/metabolismo , Tocoferóis/químicaRESUMO
Chromium (Cr) has been reported to enhance immune function and improve insulin sensitivity and performance in beef and dairy cattle. However, its effect on bovine macrophage inflammatory and metabolic response is unknown. The objective of this study was to characterize the effect of dietary Cr on the inflammatory and metabolic response of polarized macrophages ex vivo. Twelve primiparous and 16 multiparous healthy Holstein cows in mid lactation (143 ± 37 d in milk) were enrolled in this study. Cows were fed a common total mixed ration once per day that was top-dressed with 200 g of ground corn containing 1 of 2 dietary treatments: control (CTL, no Cr supplementation) or Cr propionate (CrP, 8 mg of Cr/cow per day) for 35 d. At d 1, 17, and 35 of treatment, blood monocytes were isolated and cultured to obtain 3 monocyte-derived macrophage (MDM) phenotypes: M0 (non-polarized), M1 (pro-inflammatory; IFN-γ polarized) and M2 (anti-inflammatory; IL-4 polarized). The experiment was set in a randomized complete block design. Neither dry matter intake nor milk yield was affected by treatment. Plasma concentrations of metabolites and the metabolic and inflammatory response of MDM in spent media were not affected by treatment. Neither the whole blood cell population nor the specific proportion of leukocytes was affected by the main effect of treatment. However, we did observe a trend for fewer circulating neutrophils in cows fed CrP than in cows fed CTL for 35 d, which may be partly attributable to a greater influx of neutrophils into peripheral tissues, a reduced pro-inflammatory response during disease, or both; this warrants future study. Expression of IGFI was increased in MDM-M0, and expression of CXCL11 tended to increase in MDM-M2 from cows fed CrP compared with cows fed CTL. Expression of SLC2A3 also tended to increase in MDM-M2 from cows fed CrP compared with cows fed CTL at 17 d. Our results suggest that CrP has minimal effect on the inflammatory and metabolic response of MDM for Holstein dairy cows in mid lactation. Future studies are warranted to evaluate the differential regulation of Cr on the inflammatory and metabolic response of leukocytes from dairy cows at different stages of lactation and parity.
Assuntos
Bovinos/fisiologia , Lactação/imunologia , Propionatos/farmacologia , Animais , Bovinos/imunologia , Indústria de Laticínios , Dieta/veterinária , Suplementos Nutricionais , Feminino , Macrófagos , Leite/metabolismo , GravidezRESUMO
Acquired demyelinating syndromes (ADS) can be a first presentation of multiple sclerosis (MS) in children. The incidence of these disorders in Europe is currently unknown. Children (<18 years old) living in the Netherlands who presented with ADS were included from January 1, 2007 to December 31, 2010 by the Dutch pediatric MS study group and the Dutch surveillance of rare pediatric disorders. Demographic and clinical data were collected. Eighty-six patients were identified over 4 years, resulting in an incidence of 0.66/1,00,000 per year. Most patients presented with polyfocal ADS without encephalopathy (30%), followed by polyfocal ADS with encephalopathy (24%), optic neuritis (ON, 22%), monofocal ADS (16%), transverse myelitis (3%), and neuromyelitis optica (3%). Patients with polyfocal ADS with encephalopathy were younger (median 3.9 years) than patients with ON (median 14.6 years, p < 0.001) or monofocal ADS (median 16.0 years, p < 0.001). Patients with polyfocal ADS without encephalopathy (median 9.2 years) were also younger than monofocal ADS patients (median 16.0 years, p < 0.001). There was a slight female preponderance in all groups except the ON group, and a relatively large number of ADS patients (29%) reported a non-European ancestry. Familial autoimmune diseases were reported in 23%, more often in patients with relapsing disease than monophasic disease (46 vs. 15%, p = 0.002) and occurring most often in the maternal family (84%, p < 0.001). During the study period, 23% of patients were subsequently diagnosed with MS. The annual incidence of ADS in the Netherlands is 0.66/1,00,000 children/year. A polyfocal disease onset of ADS was most common.
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Doenças Autoimunes Desmielinizantes do Sistema Nervoso Central/epidemiologia , Pediatria , Adolescente , Criança , Doenças Autoimunes Desmielinizantes do Sistema Nervoso Central/líquido cefalorraquidiano , Doenças Autoimunes Desmielinizantes do Sistema Nervoso Central/classificação , Doenças Autoimunes Desmielinizantes do Sistema Nervoso Central/diagnóstico , Feminino , Humanos , Incidência , Angiografia por Ressonância Magnética , Imageamento por Ressonância Magnética , Masculino , Países Baixos/epidemiologia , Estudos Retrospectivos , Estatísticas não ParamétricasRESUMO
Familial hemophagocytic lymphohistiocytosis (fHLH) is an autosomal recessive disorder characterized by proliferation and infiltration of several organs by activated lymphocytes and macrophages. Without allogeneic stem cell transplantation, fHLH is fatal. We describe a previously healthy 11-month-old boy with a rapidly progressive encephalopathy. An older brother died at 8 months following a subacute encephalopathy diagnosed as meningoencephalitis. The family history led to the suspicion of a metabolic disease, but metabolic studies were unrevealing. MRI showed multiple inhomogeneous signal abnormalities in the cortex and white matter, most prominent in the cerebral hemispheres and around the dentate nucleus. Gadolinium-enhanced T1-weighted images showed a multitude of enhancing foci, suggestive of perivascular enhancement. Based on MRI pattern with multiple lesions, perivascular enhancement and family history, fHLH was suspected. DNA analysis showed that the patient was compound-heterozygous for the c.445 G>A (p.Gly149Ser) mutation in exon 1 and the c.757 G>A (p.Glu253Lys) mutation in exon 2 of the perforin 1 gene. The patient was treated according to the international HLH-2004 protocol (dexamethasone, etoposide, cyclosporine, intrathecal methotrexate and prednisolone) followed by allogeneic cord blood transplantation. He showed a significant neurological and radiological improvement. The reported case demonstrates that MRI pattern recognition can lead to early diagnosis of fHLH, with subsequent adequate treatment.
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Córtex Cerebelar/patologia , Córtex Cerebral/patologia , Linfo-Histiocitose Hemofagocítica/patologia , Proteínas Citotóxicas Formadoras de Poros/genética , Anti-Inflamatórios/uso terapêutico , Córtex Cerebelar/imunologia , Córtex Cerebral/imunologia , Quimioterapia Combinada , Heterozigoto , Humanos , Imunossupressores/uso terapêutico , Lactente , Linfo-Histiocitose Hemofagocítica/tratamento farmacológico , Linfo-Histiocitose Hemofagocítica/genética , Imageamento por Ressonância Magnética , Masculino , Mutação/imunologia , Perforina , Proteínas Citotóxicas Formadoras de Poros/imunologiaRESUMO
Infantile juvenile polyposis is a rare disease with severe gastrointestinal symptoms and a grave clinical course. Recently, 10q23 microdeletions involving the PTEN and BMPR1A genes were found in four patients with infantile juvenile polyposis. It was hypothesized that a combined and synergistic effect of the deletion of both genes would explain the condition. Subsequently, however, a patient with a larger 10q23 deletion including the same genes but with a mild clinical phenotype was identified. Here, we present four additional patients with 10q23 microdeletions involving the PTEN and BMPR1A genes. The sizes of the deletions were analyzed using single nucleotide polymorphism array analysis. All patients had macrocephaly, dysmorphic features, retardation and congenital abnormalities. One patient developed colorectal cancer. However, only one case had disease onset before 2 years of age and severe symptoms requiring colectomy. No clear correlation was found between ages at onset or severity of gastrointestinal symptoms and the sizes of the deletions. We conclude that patients with 10q23 microdeletions involving the PTEN and BMPR1A genes have variable clinical phenotypes, which cannot be explained merely by the deletion sizes. The phenotypes are not restricted to severe infantile juvenile polyposis but include childhood-onset cases with macrocephaly, retardation, mild gastrointestinal symptoms and possibly early-onset colorectal cancer.
Assuntos
Receptores de Proteínas Morfogenéticas Ósseas Tipo I/genética , Cromossomos Humanos Par 10 , Gastroenteropatias/genética , Polipose Intestinal/genética , PTEN Fosfo-Hidrolase/genética , Deleção de Sequência , Anormalidades Múltiplas/genética , Idade de Início , Pré-Escolar , Neoplasias Colorretais/etiologia , Feminino , Gastroenteropatias/complicações , Gastroenteropatias/patologia , Humanos , Lactente , Recém-Nascido , Deficiência Intelectual/genética , Polipose Intestinal/complicações , Polipose Intestinal/patologia , Masculino , Análise de Sequência com Séries de Oligonucleotídeos , FenótipoRESUMO
The combination of composite resins with adhesive intermediate agents and techniques is still questionable with respect to application to posterior regions of the dentition. To add data to the information already available about the clinical behavior and longevity of class II composite resin restorations, a longitudinal study has been started; its design is discussed in this paper.
Assuntos
Resinas Compostas/química , Restauração Dentária Permanente/métodos , Cimentos de Resina , Adolescente , Adulto , Ensaios Clínicos como Assunto , Amálgama Dentário , Feminino , Humanos , Estudos Longitudinais , Masculino , Metacrilatos/análise , Dente Molar , Quartzo , Projetos de Pesquisa , Propriedades de SuperfícieRESUMO
The shear strength of composite resin restorative systems bonded to dentin was measured and marginal integrity of class V restorations was assessed. A correlation between bond strength and marginal adaptation could not be demonstrated. The application of an intermediate layer of unfilled resin or the use of low-stiffness composite resins to improve the strain capacity of the restoration significantly influenced the quality of the marginal integrity.
Assuntos
Resinas Compostas/química , Colagem Dentária , Restauração Dentária Permanente , Animais , Bovinos , Intervalos de Confiança , Esmalte Dentário/ultraestrutura , Dentina/ultraestrutura , Elasticidade , Microscopia Eletrônica de Varredura , Variações Dependentes do Observador , Estresse Mecânico , Propriedades de SuperfícieRESUMO
The use of adhesive resin composites for restoration of Class V lesions often results in cervical marginal gap formation due to polymerization contraction. In this laboratory study, flexible linings applied between the bonding agent and the bulk restorative appeared to preserve the marginal integrity of Class V restorations during curing. Measurements of the polymerization contraction stress showed 20 to 50% relief due to various flexible intermediate materials. Apparently, reduction of the total stiffness by application of an intermediate layer can render the total restoration sufficiently flexible to compensate for that part of the stress that would otherwise exceed the bond strength.
Assuntos
Resinas Compostas , Forramento da Cavidade Dentária , Restauração Dentária Permanente/métodos , Cimentos de Resina , Animais , Bis-Fenol A-Glicidil Metacrilato , Bovinos , Cimentos Dentários , Análise do Estresse Dentário , Cimentos de Ionômeros de Vidro , Propriedades de SuperfícieRESUMO
When one uses composite resins, the curing contraction, the stiffness of the material, and the strength of the vulnerable dentinal bond are important factors in determining the marginal adaptation of the restoration. Calculations based on these intrinsic material properties have indicated that both bulk placement and incremental placement of the restorative material in the cervical cavity inevitably lead to marginal gap formation. Sealing of this gap with an unfilled low-viscosity resin, directly after the composite resin is cured, may lead to perfectly closed restoration margins, provided that composites with low linear curing contraction and low Young's modulus are used. These conditions were experimentally shown to be valid for laboratory and clinical situations.