RESUMO
Hydroxyapatite (HA) from bovine bones has been used as a biomaterial in dentistry due to its biocompatibility and bioactivity. However, dense HA bioceramics still present inadequate properties for applications that require high mechanical performance, such as infrastructure. Microstructural reinforcements and control of ceramic processing steps are methods to improve these shortcomings. The present study assessed the effects of polyvinyl butyral (PVB) addition in combination with two sintering methodologies (2-step and conventional), on the mechanical properties of polycrystalline bovine HA bioceramics. The samples were divided into four groups (with 15 samples per group): conventional sintering with binder (HBC) and without binder (HWC) and 2-step sintering with (HB2) and without binder (HW2). HA was extracted from bovine bones, turned into nanoparticles in a ball mill, and subjected to uniaxial and isostatic pressing into discs, according to ISO 6872 standards. All groups were characterized by x-ray diffractometry (XRD), differential thermal analysis (DTA) and Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and relative density. Besides, mechanical analyses (biaxial flexural strength (BFS) and modulus of elasticity) were also performed. The characterization results demonstrated that adding agglutinants or the sintering method did not affect HA's chemical and structural characteristics. Even so, the HWC group showed the highest mechanical values for BFS and modulus of elasticity being 109.0 (98.0; 117.0) MPa and 105.17 ± 14.65 GPa, respectively. The HA ceramics submitted to conventional sintering and without the addition of binders achieved better mechanical properties than the other groups. The impacts of each variable were discussed and correlated to the final microstructures and mechanical properties.
Assuntos
Durapatita , Nanopartículas , Animais , Bovinos , Durapatita/química , Materiais Biocompatíveis/química , Espectroscopia de Infravermelho com Transformada de Fourier , Cerâmica/química , Propriedades de Superfície , Teste de MateriaisRESUMO
The aim of this study was to determine the prevalence of signs and symptoms of temporomandibular disorders (TMD) and otologic symptoms in patients with and without tinnitus. The influence of the level of depression was also addressed. The tinnitus group was comprised of 100 patients with tinnitus, and control group was comprised of 100 individuals without tinnitus. All subjects were evaluated using the research diagnostic criteria for temporomandibular disorders (RDC/TMD) to determine the presence of TMD and depression level. Chi-square, Spearman Correlation and Mann-Whitney tests were used in statistical analysis, with a 5% significance level. TMD signs and symptoms were detected in 85% of patients with tinnitus and in 55% of controls (P≤0·001). The severity of pain and higher depression levels were positively associated with tinnitus (P≤0·001). It was concluded that tinnitus is associated with TMD and with otalgia, dizziness/vertigo, stuffy sensations, hypoacusis sensation and hyperacusis, as well as with higher depression levels.
Assuntos
Transtorno Depressivo/complicações , Transtornos da Articulação Temporomandibular/epidemiologia , Zumbido/epidemiologia , Adulto , Brasil/epidemiologia , Estudos de Casos e Controles , Estudos Transversais , Tontura/complicações , Dor de Orelha/complicações , Dor Facial/complicações , Feminino , Perda Auditiva/complicações , Humanos , Masculino , Pessoa de Meia-Idade , Prevalência , Transtornos da Articulação Temporomandibular/complicações , Zumbido/complicações , Vertigem/complicações , Adulto JovemRESUMO
STATEMENT OF THE PROBLEM: Nickel-chromium alloys are indicated for the construction of resin-bonded fixed partial dentures; however, the potential toxicity of nickel has been a source of concern. Composite cements do not develop an adequate bond to air abraded noble alloys, which cannot be electrolytically etched. Tin-electroplating of noble alloys appears to be an alternative treatment for resin bonding. PURPOSE: This in vitro study investigated the effect of tin-electroplating on the bond of a composite cement to base and noble alloys. MATERIAL AND METHODS: Tensile tests were made with disks of four alloys that were cemented to each other with an adhesive composite cement after (1) air abrasion with 50 microns aluminum oxide and (2) air abrasion plus tin-electroplating. RESULTS: Tin-electroplating increased the bond strength of metal-ceramic gold alloy (Au,Pd,Pt) to a level comparable to the nickel-chromium alloy, but had a harmful effect on type IV gold alloy. CONCLUSIONS: Despite the recommendation for tin-electroplating of type IV gold alloys, this procedure did not improve bond strength to composite in this study.
Assuntos
Ligas Dentárias/química , Colagem Dentária/métodos , Galvanoplastia/métodos , Cimentos de Resina/química , Análise de Variância , Colagem Dentária/estatística & dados numéricos , Galvanoplastia/estatística & dados numéricos , Teste de Materiais/métodos , Teste de Materiais/estatística & dados numéricos , Propriedades de Superfície , Resistência à Tração , EstanhoRESUMO
A problem associated with resin-bonded fixed partial dentures is inadvertent dislodgment at the metal/cement interface. It has been suggested that Panavia Ex resinous cement requires only air abrasion of the alloy with 50 microns aluminum oxide particles to record reliable bond strength values. The purpose of this study was to discuss the consequences of changes in the type of air abrasion and surface oxidation of the alloy. Fifty pairs of disks of a Ni-Cr alloy were treated by five methods: (1) air abrasion with 50 microns aluminum oxide (control), (2) air abrasion with 50 microns glass beads, (3) air abrasion with a mixture of aluminum oxide and glass beads (ratio 1:1), (4) air abrasion with aluminum oxide and immersion in acid solution of potassium permanganate, and (5) air abrasion with aluminum oxide and immersion in aqueous solution of potassium permanganate. The disks were cemented to each other with Panavia Ex composite resinous cement and tensile tests were conducted at a crosshead speed of 0.5 mm/ minute. No statistically significant differences were recorded among the treatments for the alloys used in this study except air abrasion with glass beads, which exhibited the lowest bond strength values.
Assuntos
Ligas de Cromo , Colagem Dentária , Fosfatos , Cimentos de Resina , Condicionamento Ácido do Dente , Pressão do Ar , Óxido de Alumínio , Análise de Variância , Polimento Dentário/métodos , Vidro , Teste de Materiais , Oxirredução , Permanganato de Potássio , Estatísticas não Paramétricas , Propriedades de Superfície , Resistência à TraçãoRESUMO
This in vitro study evaluated the bond strength of metal frameworks cast using Ni-Cr, Ni-Cr-Be, Cu-Al, type IV gold, and noble metal ceramic alloy with and without tin electroplating. The castings were luted to human teeth using Panavia Ex resin. It was found that tin electroplating had a negative effect for the Cu-Al and type IV gold alloys and a positive effect for gold for metal ceramic restorations. The best results were obtained using the Ni-Cr alloy.
Assuntos
Ligas Dentárias , Colagem Dentária , Prótese Adesiva , Cimentos de Resina , Estanho , Adolescente , Análise de Variância , Ligas de Cromo , Cobre , Galvanoplastia , Ligas de Ouro , Humanos , Teste de Materiais , Ligas Metalo-Cerâmicas , Fosfatos , Resistência à TraçãoRESUMO
The development of composite resin cements that chemically bond to dental alloys has improved the construction of resin-bonded prostheses. Composite resins can be selected for various situations, but specific clinical situations may require different alloys. This study evaluated the ability of a composite resin cement to bond to various dental alloys of different compositions. Ten pairs of disks for each alloy (two NiCr, two NiCrBe, one CuAl, one gold type IV, and one gold for metal ceramic) were bonded to a composite resin cement after air abrasion was performed with aluminum oxide. The disks were then rinsed in tap water and were ultrasonically cleaned in distilled water for 2 minutes. The tensile tests exhibited greater values for alloys ultrasonically cleaned, and the best results were recorded by NiCr and NiCrBe alloys.
Assuntos
Resinas Compostas , Ligas Dentárias/química , Colagem Dentária , Cimentos Dentários , Fosfatos , Cimentos de Resina , Alumínio , Análise de Variância , Berílio , Ligas de Cromo/química , Cobre , Polimento Dentário/métodos , Análise do Estresse Dentário , Prótese Adesiva , Ligas de Ouro/química , Teste de Materiais , Ligas Metalo-Cerâmicas/química , Níquel , Propriedades de Superfície , Resistência à Tração , UltrassomRESUMO
Panavia Ex resin has been claimed to require only air abrasion of the alloy with 50 micrometers aluminum oxide particles to reach acceptable bond strength values. This study discusses the consequences of changes in the type of air abrasion and surface oxidation of the alloy. Thirty pairs of discs of a Ni-Cr alloy were treated by three methods: 1) air abrasion with 50 micrometers aluminum oxide (control); 2) air abrasion with glass beads; 3) air abrasion with a mixture of aluminum oxide and glass beads (ratio 1:1). The Tukey test showed statistical differences only for air abrasion with glass beads.
Assuntos
Ligas de Cromo , Colagem Dentária , Cimentos Dentários , Polimento Dentário/métodos , Fosfatos , Cimentos de Resina , Ar , Óxido de Alumínio , Análise de Variância , Ligas de Cromo/química , Colagem Dentária/métodos , Vidro , Teste de Materiais , Níquel/química , Propriedades de Superfície , Resistência à TraçãoRESUMO
Three phosphate bonded investments and three calcium type were studied observing the influence of investment on the final cast surface roughness. Increased dilution also incremented roughness for the phosphate investments. Between the two types of investments there was only significant difference concerning two specific commercial brands, but there were differences in the same type of investment among these different brands.