ABSTRACT
Objective: The aim of this study was to evaluate the effects of material and processing methods on the bond strength of orthodontic brackets. Material and Methods: Five types of brackets were tested: Conventional metallic (CM), metallic sandblasted (SB), ceramic (C), polycarbonate (PC), and metallic fabricated by melting injection molding (MIM). Shear bond strength (SBS) was conducted to check bond strength of the brackets bonded to bovine teeth (n=10/group), and tensile bond strength (TBS) (20 brackets/group) to check bracket retention to bonding material (n=20/group). Both, SBS and TBS were conducted with 1mm/min crosshead speed in a universal testing machine. Bond strength was calculated in Megapascal (MPa) based on force (N) and bracket area (mm 2). Data normality was verified, and One-way ANOVA was the statistical test with Tukey post-hoc (α=0.05). Results: SB and MIM presented higher SBS compared to C, PC, and CM (p<0.05). SB and MIM also presented significantly higher TBS compared to CM and PC (p<0.05). However, MIM was not different of C for TBS. Conclusion: The type of material and method of fabrication are determinant factors that affect bond strength of orthodontic brackets and melting injection molding (MIM) is a remarkable technology to improve brackets retention during the orthodontic treatment. (AU)
Objetivo: O objetivo deste estudo foi avaliar os efeitos dos materiais e métodos de processamento na resistência de união de bráquetes ortodônticos. Material e Métodos: Cinco tipos de bráquetes foram testados: Convencionais metálicos (CM), metálicos jateados (SB), cerâmico (C), policarbonato (PC), e metálico fabricado por injeção de metal fundido em molde (MIM). A resistência de união ao cisalhamento (SBS) foi conduzida para verificar a resistência de união dos bráquetes aderidos a dentes bonivos (n=10/grupo) e a resistência à tração (TBS) (20 bráquetes/grupo) para verificar a retenção do bráquete ao material adesivo (n=20/grupo). SBS e TBS foram conduzidas com relação carga/velocidade de 1mm/min em uma máquina de ensaios universal. A resistência de união foi calculada em Megapascal (MPa) com base na força (N) pela área do bráquete (mm 2). A normalidade dos dados e a estatística foi realizada utilizando One-way ANOVA e Tukey post-hoc (α=0.05). SB e MIM apresentaram os maiores valores de SBS comparados com C, PC e CM (p<0.05). Resultados: SB e MIM também apresentaram valores significativamente maiores de TBS comparados com CM e PC (p<0.05). Contudo, os valores de TBS para o grupo MIM não foram significativamente diferentes de C. Conclusão: O tipo de material e o método de fabricação são fatores determinantes que afetam a resistência de união de bráquetes ortodônticos e a injeção de metal fundido em molde (MIM) é uma tecnologia relevante para melhorar a retenção dos bráquetes durante o tratamento ortodôntico. (AU)
Subject(s)
Animals , Cattle , Orthodontic Brackets , Dental Cements , Shear StrengthABSTRACT
Abstract This study aimed to evaluate the effect of light attenuation through ceramic veneers and resin cement on degree of conversion (DC), cohesive strength (CS), and microshear bond strength (μSBS) of experimental adhesive systems. Experimental etch-and-rinse and self-etch adhesives were combined with different ratios of camphorquinone (CQ) and diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) photoinitiators: CQ-only; 3CQ:1TPO; 1CQ:1TPO; 1CQ:3TPO and TPO-only. Square-shaped ceramic veneer (IPS Empress Esthetic, Ivoclar Vivadent) (n = 10; 10mm long x 10mm wide x 0.5mm thick) and resin cement specimens (Variolink Esthetic LC, Ivoclar Vivadent) (n = 10; 10 mm long x 10 mm wide and 0.3 mm thick) were prepared. Light transmittance of a multiple-peak LED (Bluephase G2, Ivoclar Vivadent) was measured through restorative materials using a spectrometer (n = 5). Adhesive specimens were analyzed for DC, CS, and μSBS by light-curing the adhesive with or without (control) ceramic veneer, and with resin cement fixed to output region of the light-curing tip (n = 10). Data were submitted to ANOVA and Tukey's test (α = 0.05). Total light transmittance through the restorative materials was attenuated, and this attenuation was more evident for the violet spectrum. The DC for the TPO groups in ratios up to 1CQ:1TPO was similar to the control. 1CQ:3TPO showed lower values for CS. μSBS was reduced for all groups with light attenuation, but lower values were observed for 1CQ:3TPO and TPO-only. In conclusion, light transmission was reduced with interposed restorative materials. Adhesives combined with CQ and TPO up to 1CQ:1TPO showed greater cure efficiency and mechanical properties compared with a higher amount of TPO.
ABSTRACT
The aim of this study was to evaluate the effect of different commercial silanes on microshear bond strength of resin cement to lithium disilicate ceramic. Twenty ceramic samples with 10 mm in length, 10 mm wide and 3 mm in thickness were fabricated, etched with 10% hydrofluoric acid for 20 seconds, and divided into 5 groups, according to the commercial silane applied: G1- RelyX Ceramic Primer (3M ESPE), G2- Angelus Silane, G3- Prosil (FGM), G4- Dentsply Silane (Dentsply) and G5- Bis-Silane (Bisco). Silanes were applied in accordance to manufacturers' recommendations. Addition silicone molds with 1 mm in thickness, 10 mm in diameter and 3 perforations with 1 mm in diameter each one, were placed on ceramic and filled with the resin cement RelyX ARC (3M ESPE) in all groups. Light activation was performed with LED Bluephase G2 (Ivoclar Vivadent) at 1200 mW/cm2, for 30 seconds. Samples were maintained in 100% humidity at 37°C for 24 hours and submitted to microshear test. The data (MPa) were submitted to one-way ANOVA and Tukey test (α=0.05). The results obtained for each group were: G1: 22.39±2.99; G2: 23.35±4.08; G3: 26.05±5.46; G4: 18.56±4.09; G5: 25.26±4.10. Statistical analysis showed significantly lower microshear bond strength for G4. Fracture pattern analysis showed predominance of adhesive failures in G1 and G2. G3 and G5 presented higher percentage of cohesive failures in ceramic, and G4 showed mixed, adhesive and cohesive fractures with similar percentages. It was concluded that different silanes showed influence on the lithium disilicate ceramic resin cement bond strength
O objetivo neste estudo foi avaliar o efeito de diferentes silanos comerciais na resistência de união ao microcisalhamento do cimento resinoso à cerâmica de dissilicato de lítio. Foram confeccionadas 20 amostras de cerâmica (10mm de comprimento, 10mm de largura e 3mm de espessura), condicionadas com ácido fluorídrico a 10% por 20 segundos e divididas em 5 grupos, de acordo com o silano aplicado: G1- RelyX Ceramic Primer (3M ESPE), G2- Silano Angelus, G3-Prosil (FGM), G4- Silano Dentsply e G5-Bis-Silane (Bisco). Matrizes de silicone por adição (1 mm de espessura, 10 mm de diâmetro e 3 perfurações com 1 mm de diâmetro) foram colocadas sobre a cerâmica e preenchidas com cimento resinoso RelyX ARC (3M ESPE). A fotoativação foi realizada com LED Bluephase G2 (Ivoclar Vivadent) a 1200 mW/cm2, por 30 segundos. As amostras foram mantidas em 100% de umidade a 37°C por 24 horas e submetidas ao teste de microcisalhamento. Os dados (MPa) (G1: 22,39+2,99; G2: 23,35+4,08; G3: 26,05+5,46; G4: 18,56+ 4,09; G5: 25,26+4,10) foram submetidos a análise de variância e ao teste de Tukey (p<0,05). A análise estatística mostrou valor de resistência de união significantemente menor para G4. A análise do padrão de fratura mostrou predominância de falha adesiva para G1 e G2. G3 e G5 apresentaram maior porcentagem de falha coesiva em cerâmica, e o G4 apresentou fraturas mista, adesiva e coesiva em igual porcentagem. Concluiu-se que os diferentes silanos apresentaram influência na resistência de união do cimento resinoso à cerâmica de dissilicato de lítio