i
MARINA BARRÊTO PEREIRA MORENO
EFEITO DE DIFERENTES CORES E DO TEMPO
PÓS-FOTOATIVAÇÃO NA DUREZA KNOOP DO CIMENTO
RESINOSO
EFFECT OF DIFFERENT SHADES AND
POST-ACTIVATION TIMES ON KNOOP HARDNESS OF RESIN
CEMENT
PIRACICABA 2015
iii
UNIVERSIDADE ESTADUAL DE CAMPINAS FACULDADE DE ODONTOLOGIA DE PIRACICABA
MARINA BARRÊTO PEREIRA MORENO
EFEITO DE DIFERENTES CORES E DO TEMPO
PÓS-FOTOATIVAÇÃO NA DUREZA KNOOP DO CIMENTO
RESINOSO
EFFECT OF DIFFERENT SHADES AND
POST-ACTIVATION TIMES ON KNOOP HARDNESS OF RESIN
CEMENT
Dissertação apresentada à Faculdade de Odontologia de Piracicaba, da Universidade Estadual de Campinas, como parte dos requisitos para obtenção do título de Mestra em Materiais Dentários.
Dissertation presented to the Piracicaba Dental School of the University of Campinas in partial fulfillment of the requirements for degree of Master in Dental Materials.
Orientador: Prof. Dr. Lourenço Correr Sobrinho
____________________________________ Assinatura do Orientador
PIRACICABA 2015 Este exemplar corresponde à versão final da dissertação defendida por Marina Barrêto Pereira Moreno e orientada pelo Prof. Dr. Lourenço Correr Sobrinho.
vii RESUMO
A polimerização adequada de cimentos resinosos é fundamental para obter excelentes propriedades físico-mecânicas. Fatores relacionados à cerâmica e ao próprio cimento podem influenciar a passagem de luz, reduzindo a fotoativação e alterando o grau de polimerização dos cimentos. O propósito neste estudo foi avaliar a dureza Knoop após 15 min ou 24h de diferentes cores de cimento resinoso fotoativado, com ou sem a interposição da cerâmica, em diferentes profundidades. Amostras com 5 mm de diâmetro e 1 mm de espessura do cimento resinoso Variolink Veneer (Ivoclar Vivadent) nas cores HV+1, HV+2, HV+3, MV0, LV-1, LV-2 e LV-3, foram feitas em um molde de elastômero, cobertas com uma tira de poliéster e por um disco de cerâmica IPS e.max Press (Ivoclar Vivadent) na espessura de 0,7 mm e fotoativadas por 20 segundos usando o LED Radii-cal (SDI Limited), com 1.200 mW/cm2. O cimento resinoso foi transversalmente desgastado e submetido ao teste de dureza Knoop usando o aparelho HMV 2 (Shimadzu), com carga de 50g aplicada por 15 segundos, 15 min após a fotoativação e após armazenagem a 37o C por 24 horas. Cinco penetrações foram feitas na secção transversal a 100 e 700 µm da superfície de topo, sendo que vinte amostras foram confeccionadas para cada cor do cimento resinoso Variolink Veneer em cada período de armazenagem. Os dados foram submetidos à Análise de Variância em esquema de parcelas subdivididas (cor, tempo pós-ativação, modo de ativação e profundidade), seguido pelo teste de Tukey post hoc (α = 0,05). Significante diferença para a cor (p<0,0001), modo de ativação (p<0,001), tempo pós-ativação (p<0,0001) e profundidade (p<0,0001) foi detectada. Nenhuma diferença significante foi detectada entre as interações (p>0,05), exceto para a interação cor x tempo pós-ativação (p<0,0045) e modo de ativação x tempo pós-ativação (p<0,0003). A cor do cimento resinoso e a ativação indireta tiveram significante efeito na dureza Knoop. Houve um aumento significante na dureza Knoop, após 24 horas para todas as cores do cimento resinoso. A profundidade influenciou significantemente na dureza Knoop.
Palavras-chave: Cerâmica, Materiais Dentários, Dureza, Cimentos de resina, Polimerização.
ix ABSTRACT
An adequate polymerization of resin cements is essential to obtain excellent physical and mechanical properties. Factors related to the ceramic and cement itself can influence the passage of light, decreasing the light curing and the degree of polymerization of the cement. The aim of this study was to evaluate the Knoop hardness number of different shades of resin cement light-cured either through or without the ceramic restoration and tested after 15 min or 24 h at different depths. The specimens with 5.0 mm in diameter and 1.0 mm thickness of the luting resin cement Variolink Veneer (Ivoclar Vivadent) in the HV+1, HV+2, HV+3, MV0, LV-1, LV-2 and LV-3 shades, were made in the elastomer mold, covered with a mylar strip and ceramic IPS e.max Press (Ivoclar Vivadent) disc in the thickness 0.7 mm and light-activated for 20 seconds using a LED Radii-cal (SDI Limited), with 1200 mW/cm2. The resin cement specimens were transversely wet-flattened and submitted to Knoop hardness using HMV 2 microhardness tester (Shimadzu), with a load of 50g applied for 15 seconds, 15 min after photoactivation and after storage at 37o C for 24 hours. Five indentations were made in the cross-sectional area at 100 and 700 µm from the top surface, being that twenty specimens were made for each shades of Variolink Veneer in each stored time. Data were submitted to ANOVA split-plot design (shade, post-cure time, mode of activation, and depth), followed by Tukey post hoc test (α = 0.05). The mean values of Knoop hardness are shown in Table 1. Significant differences for shade (p<0.0001), mode of activation (p<0.001), post-cure time (p<0.0001) and depth (p<0.0001) were detected. There was not significance in the interactions (p>0.05), except for shade x post-cure time (p<0.0045) and mode of activation x post-cure time (p<0.0003). The resin cement shade and indirect activation had a significant effect on the Knoop hardness. There was a significant increase in Knoop hardness after 24 h in all cements shades. The depth influenced significantly on the Knoop hardness.
xi
SUMÁRIO
DEDICATÓRIA ... xiii AGRADECIMENTOS ... xv INTRODUÇÃO ... 1 CAPÍTULO 1 ... 6Effect of different shades and post-activation times on Knoop Hardness of resin cement ... 6
CONCLUSÃO ... 21
REFERÊNCIAS ... 22
xiii
DEDICATÓRIA
À Deus pelo dom da vida e por guiar meus passos e decisões.
À minha mãe, Janice por todo amor a mim dedicado e por não medir
esforços para me apoiar sempre.
Às minhas irmãs, Flávia e Luísa pelo carinho, amizade e incentivo em
todos os momentos.
Às minhas sobrinhas, Maria Fernanda e Alice por toda alegria que
trazem a nossa família.
xv
AGRADECIMENTOS
Ao Magnífico Reitor da Universidade Estadual de Campinas, Prof. Dr. José Tadeu Jorge.
À Faculdade de Odontologia de Piracicaba, nas pessoas do seu Diretor, Prof. Dr. Guilherme Elias Pessanha Henriques e do Diretor associado Prof. Dr. Francisco Haiter Neto.
Ao meu orientador Prof. Dr. Lourenço Correr Sobrinho por me aceitar como orientada, pelos ensinamentos, paciência, atenção e acolhimento durante todo o mestrado.
Aos Profs. Drs. Mario Fernando de Goes, Simonides Consani, Mário Alexandre Coelho Sinhoreti e Américo Bortolazzo Correr titulares da área de Materiais Dentários e aos demais professores do corpo docente do curso de Pós-Graduação em Materiais Dentários pelos ensinamentos e apoio.
À Coordenadora do Programa de Pós-graduação em Materiais Dentários Profa. Dra. Regina Maria Puppin Rontani e ao ex-coordenador Prof. Dr. Marcelo Giannini.
Aos funcionários da Área de Materiais Dentários, Marcos Blanco Cangiani e Selma Aparecida Barbosa de Souza Segalla por estarem sempre dispostos a ajudar em todos os momentos.
À Profa. Dra. Glaucia Maria Bovi Ambrosano pela disponibilidade em fazer a estatística do trabalho.
Às Profas. Dras. Andréia Bolzan de Paula e Ana Costa Correr por toda ajuda durante a pesquisa.
Ao Prof. Dr. Hugo Lemes Carlo pela amizade e orientação durante a graduação e principalmente pelo incentivo dado para a realização deste mestrado. À Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES pela bolsa concedida.
A todos os amigos da Pós-graduação. Em especial a Renally Wanderley, Fabian Murillo, Gabriel Abuna, Juan Barrientos, Melissa Ruivo, Aline Girotto, Igor Alves, Dayane Oliveira e Ana Paula Ayres pelo apoio, companheirismo e amizade sempre.
xvi
À Renally Wanderley e Diego Nóbrega por estarem sempre presentes, sendo minha família em Piracicaba.
A todos os meus familiares e amigos por entenderem minha ausência e por todo apoio e incentivo.
1
INTRODUÇÃO
Nos últimos anos uma grande variedade de sistemas totalmente cerâmicos está à disposição dos cirurgiões dentistas no mercado odontológico. As restaurações confeccionadas em cerâmica tornaram-se amplamente utilizadas devido às propriedades mecânicas, estética, biocompatibilidade e estabilidade ao longo dos anos (Lührs et al., 2014). Entretanto, a friabilidade e a baixa resistência à tração, que podem causar susceptibilidade à fratura, são as maiores desvantagens do uso desse material (Lawn et al., 2004). Alguns sistemas cerâmicos podem fraturar em função da propagação de microtrincas na sua parte interna. Falhas e porosidades são inerentes a esses materiais, os quais quando submetidos à repetidas cargas no meio bucal, podem concentrar tensões nesses locais e levar o material à fratura (Wu et al., 2012).
Além das propriedades físico-mecânicas das cerâmicas, os agentes de cimentação são importantes para promover retenção, selamento marginal e longevidade dessas restaurações (Kesrak e Leevailoj, 2012). Os cimentos resinosos têm sido utilizados devido ao sucesso estético e a capacidade de união à estrutura dental e restauração protética quando associados aos sistemas de união, promovendo adequada adaptação marginal (Inokoshi et al., 1993). Esses cimentos podem apresentar ativação química, física ou dupla ativação. Normalmente, os fotoativados e os de dupla-ativação são indicados para fixação de restaurações onlays e inlays de cerâmica ou resina composta, e coroas de cerâmica, enquanto os quimicamente ativados são indicados para fixação de restaurações metálicas.
O procedimento de cimentação adesiva com cimentos resinosos reforça mecanicamente as restaurações totalmente cerâmicas, aumentando a resistência à fratura através da penetração do cimento em falhas e irregularidades, minimizando a propagação de trincas e permite que ocorra uma distribuição mais efetiva da tensão da restauração para a estrutura do dente. Além disso, pode influenciar na estética da restauração, considerando que o agente de cimentação
2
é capaz de alterar a cor final das restaurações cerâmicas. (Fleming et al., 2006; Karaagaclioglu e Yilmaz, 2008; Kesrak e Leevailoj, 2012). A polimerização adequada do cimento é de fundamental importância para obter excelentes propriedades físico-mecânicas e desempenho clínico satisfatório (Hofmann et al., 2001; Castro et al., 2012; Öztürk et al., 2013). Cimentos polimerizados de maneira inadequada podem promover alteração das propriedades físico-mecânicas e estabilidade dimensional, além de reduzir a força de união às estruturas dentárias, resultando em microinfiltração, alteração da cor, redução na biocompatibilidade e sensibilidade pós-operatória (Giráldez et al., 2011; Kilinc et al., 2011). De acordo com Caughman et al. (2001), os cimentos ativados por luz apresentam vantagens clínicas em relação aos quimicamente ativados, como maior tempo de trabalho e melhor estabilidade de cor. Porém, o uso desse cimento é limitado quando envolve cimentação de restaurações indiretas, as quais atenuam a passagem de luz dificultando a polimerização do agente de fixação.
Restaurações estéticas indiretas influenciam a passagem da luz, diminuindo a fotoativação e alterando o grau de polimerização dos agentes de fixação. (Öztürk et al., 2013). Como a cerâmica apresenta diversidade de componentes, é considerada um material opticamente heterogêneo. Apresenta em sua composição cristais com diferentes índices de refração, o que pode difundir a luz em direções diversas, reduzindo a intensidade da luz transmitida (Peixoto et al., 2007). Além disso, a transmissão da luz pode ser influenciada pela espessura, cor, composição e marca comercial da cerâmica (El-Mowafy e Rubo, 2000; Rasetto et al., 2004; Tango et al., 2007, Dias et al., 2008; Öztürk et al., 2012).
As composições dos sistemas cerâmicos possuem diferentes conteúdos cristalinos que podem influenciar as propriedades ópticas. Aumento no conteúdo cristalino, com a finalidade de obter maior resistência, normalmente promove maior opacidade (Bagis e Turgut, 2013). Em geral, as restaurações com maior espessura (Dias et al., 2008; Pazin et al., 2008) e tonalidade mais escura podem promover maior atenuação da luz (Peixoto et al., 2007). Os pigmentos das cerâmicas são capazes de absorver luz, resultando na diminuição da quantidade
3
de energia que atinge o cimento resinoso quando é usada cerâmica mais escura (Passos et al., 2014). A medida que a espessura do material restaurador aumenta, a dispersão ou absorção da luz também aumenta, reduzindo a quantidade da energia fornecida para fotoativação que atinge o cimento resinoso. As evidências mostram a existência de um efeito atenuador proporcional à espessura e à opacidade da cerâmica podendo acarretar menor microdureza dos cimentos resinosos. Assim, os cimentos fotoativados deveriam ser usados sob restaurações menos espessas e mais translúcidas em que é possível obter adequada transmissão de luz (Kilinc et al., 2011).
A polimerização dos cimentos resinosos também pode ser influenciada pela absorção e dispersão da luz no cimento, composição química e tamanho das partículas de cargas, além da irradiância emitida pela fonte de luz e do tempo de exposição (Musanje e Darvell, 2006; Reges et al., 2009). Essas características influenciam na profundidade de polimerização do cimento que está associada diretamente ao sucesso clínico da restauração (Reges et al., 2008).
A combinação da cor do cimento com a cerâmica é essencial para qualquer restauração. O comportamento óptico de restaurações cerâmicas é determinado pela cerâmica, cimento e cor da estrutura dentária. Diversas cores de cimentos resinosos estão disponíveis, considerando que o aspecto final das restaurações pode ser influenciado pela cor, opacidade e espessura do agente de cimentação (Öztürk et al., 2013). Alguns estudos têm mostrado que as cores mais escuras não permitem polimerizar adequadamente o material em maiores profundidades quando comparado às cores mais claras, devido às moléculas do pigmento promover efeito direto na dispersão e reflexão da luz (Onose et al., 1985; Ferracane et al., 1986; Leloup et al., 2002; Shortall, 2005; Guiraldo et al., 2009). Dessa forma, Reges et al. (2008) e Passos et al. (2014) recomendam que variações no método de fotoativação podem ser necessárias para diferentes situações clínicas e que cada cor pode necessitar de um método de ativação específica para maximizar a dureza.
4
Clinicamente, adequada polimerização deve ser alcançada de forma rápida para que o cimento resinoso possa resistir às cargas imediatas e atingir biocompatibilidade adequada (Reges et al., 2008). Um aspecto que tem sido levado em consideração é o fato de que cimentos resinosos podem mostrar polimerização residual após a fotoativação do material. Embora a polimerização residual do cimento pós-irradiação continue por aproximadamente 24 horas, a maior taxa de polimerização ocorre no tempo de 10 a 15 minutos após ser exposto à luz (Leung et al., 1983; Yan et al., 2010).
O teste de dureza é normalmente utilizado por ser um método simples e confiável que indica indiretamente o grau de conversão e a qualidade da polimerização dos cimentos resinosos (Rueggeberg & Craig, 1988; Oréfice et al., 2003; Tango et al., 2007; Jeong et al., 2009). Outras características como estrutura química dos monômeros e tipo e densidade das ligações cruzadas podem influenciar na dureza do material polimerizado (Reges et al., 2008; Jeong et al., 2009). De acordo com Pazin et al. (2008) quanto menor a dose de energia fornecida ao cimento resinoso, menor o grau de conversão e a dureza. Menores valores de dureza indicam polimerização inadequada do cimento resinoso, resultando em propriedades mecânicas deficientes (Castro et al., 2012).
A polimerização dos cimentos resinosos pode ser influenciada pelas características do material restaurador, fonte de luz e do próprio cimento. Alguns estudos tem avaliado o efeito da ativação indireta ou da profundidade de polimerização de diferentes cores de cimento resino, mas a influência da associação desses fatores ainda necessita de mais investigações. Dessa forma, o objetivo do presente estudo in vitro, composto por um artigo científico, foi:
1 – Avaliar através da dureza Knoop, a profundidade de polimerização de cimentos resinosos com diferentes cores fotoativados com interposição da cerâmica odontológica IPS e.max Press após 15 minutos e 24 horas (Capítulo 1).
As hipóteses testadas foram:
5
2- Os dois tempos de pós-ativação, 15 min e 24h tem influência similar na dureza;
3- Os modos de fotoativação direto e indireto têm potencial de polimerização similar;
6 CAPÍTULO 1
Effect of different shades, ceramic interposition and
post-activation times on Knoop Hardness of resin cement
Artigo submetido para publicação no periódico Brazilian Dental Journal.
Abstract
The aim of this study was to evaluate the Knoop hardness number of different shades of a resin cement light-cured either through or without the ceramic restoration, and tested after 15min or 24h at different depths. The specimens with 5.0 mm in diameter and 1.0 mm thickness of the luting resin cement Variolink Veneer (Ivoclar Vivadent) in shades HV+1, HV+2, HV+3, MV0, 1, 2 and LV-3, were fabricated in the elastomer mold, covered with a mylar strip and ceramic IPS e.max Press (Ivoclar Vivadent, shade HT A1) disc in the thickness 0.7 mm and light-activated for 20 seconds using a LED Radii-cal (SDI Limited), with 1.200 mW/cm2. The resin cement specimens were transversely wet-flattened to their middle portion and submitted to Knoop hardness using HMV 2 microhardness tester (Shimadzu), with a load of 50g applied for 15 seconds, at 15 min and after storage at 37o C for 24 hours. Five indentations were made in the cross-sectional area at 100 and 700 µm from the top surface, being that twenty specimens were made for each shades of Variolink Veneer in each stored time. Data were submitted to ANOVA split-plot design (shade, post-cure time, mode of activation, and depth), followed by Tukey post hoc test (α = 0.05). The mean values of Knoop hardness are shown in Table 1. Significant differences for shade (p<0.0001), mode of activation (p<0.001), post-cure time (p<0.0001) and depth (p<0.0001) were detected. There was not significance in the interactions (p>0.05), except for shade x post-cure time (p<0.0045) and mode of activation x post-cure time (p<0.0003).
7
The resin cement shade has a significant effect on the Knoop hardness. Indirect activation reduced significantly Knoop hardness. There was a significant increase in Knoop hardness after 24 h in all cements shades. The depth influenced significantly on the Knoop hardness.
Introduction
The interest in dental ceramics has increased in the last years in restorative dentistry most because of the excellent esthetic and mechanical properties.1 However, brittleness and susceptibility to fracture are major disadvantages to their use.2 In order to minimize these deficiencies and strengthen all-ceramic restorations, the adhesive cementation with resin cement has been suggested.3,4 Clinically, the success of ceramic depends on a great extent on the resin cement.
The resin cement is generally used for luting ceramics. These cements are classified according to their activation mode, that is chemical, photo, or dual curing.1,5,6 Light-cured cements offer the clinical advantages of extended working time, setting on demand, and improved color stability.7 After cementation, an adequate polymerization of resin cement is necessary to obtain high bond strengths.8 Inadequate polymerization is associated with lower color stability, poor mechanical properties, and an increased water sorption and solubility.9,10,11,12 Previous investigators have reported that intervening restorative ceramics might promote a significant effect of light attenuation on the bottom of the cavity, and compromise the photo-activation of the luting material.8,10,13,14,15,16,17 The intensity of this attenuation is dependent on the characteristics of the restorative material, shade, crystalline structure, thickness and opacity, which may interfere with light transmittance and, as result, inadequate polymerization.18,19,20,21,22,23
Besides, the polymerization of the resin cement may also be influenced by the characteristics of the cement as shade, chemical composition and filler particle size.24,25,26 These factors may interfere with the depth of cure of the resin cement and can be associated with the physical properties and satisfactory clinical
8
performances of the restoration.5 Some studies have evaluated the effect of indirect activation or the depth polymerization of different shades of resin cement.6,10,13,15,17,22,23,24,27,28,29 However, little is known about the combined influence of different shades of resin cements and indirect light-activation through ceramic.
Therefore, the aim of this study was to evaluate the Knoop hardness number (KHN) of different shades of a light-cured resin cement Variolink Veneer with the material light-activated either through or without the ceramic restoration, and tested after 15 min or 24 h. The null hypotheses tested were: 1) hardness is similar for different cement shades; 2) the two post-cure times, 15 min and 24 h have similar influence on hardness; 3) direct and indirect photo-activation modes would have similar polymerization potentials; 4) hardness would be similar at different depths.
Material and Methods
Discs with 10 mm in diameter and 0.9 mm thickness were fabricated with a lithium disilicate glass ceramic IPS e.max Press (Ivoclar Vivadent, Schaan, Liechtenstein, shade HT A1), according to manufacturer’s instructions. The resulting disc was submitted to wet polishing with 320-, 400-, 600- and 1200-grit SiC papers (Norton SA, São Paulo, SP, Brazil) in order to obtain a disc with 10 mm in diameter and 0.7 mm thickness and ultrasonically cleaned in distilled water for 10 minutes, and dried with compressed air. The thickness of the disc was measured using a digital caliper (Mitutoyo Corporation, Tokyo, Japan).
The light-cured Variolink Veneer luting resin cement (Ivoclar Vivadent, Schaan, Liechtenstein), at seven shades HV+1, HV+2, HV+3, MV0, LV-1, LV-2 and LV-3, was tested. The resin cement was placed into an elastomer (Express putty – 3M ESPE, St. Paul, MN, USA) mold (5 mm in diameter x 1 mm thickness). A transparent polyester strip was placed over the filled mold and manually pressed using a microscope slide to remove excess of the resin cement. The ceramic disc
9
was placed on the polyester strip over the resin cement and light-activation was conducted through the ceramic (indirect mode - I), for 20s, using a LED Radii-cal (SDI Limited, Bayswater, Victoria, Australia) with an irradiance of 1.200 mW/cm2. Figure 1 shows the experimental setup of the study.
Figure 1 – Experimental setup of the study. Past of the resin cement Variolink Veneer inserted into the elastomer mold; Polyester strip placed over the filled mold; ceramic disc positioned over the resin cement; light curing unit placed onto the ceramic surface for photo-activation.
Twenty specimens were obtained for each resin cement shade. Half of these specimens were tested after 15 min, and other half after dry storage at 37ºC for 24 h in light-proof containers. Another, twenty specimens for each resin cement shade were obtained by light-activation without ceramic (direct mode - D), with half tested after 15 min and half 24 h.
Next, in order to obtain a smooth and plane surface for hardness testing, the specimens were fixed in an acrylic resin die (Buhler, Lake Bluff, IL, USA) with sticky wax and transversely wet-flattened with 320-, 400-, 600- and 1200-grit SiC papers (Norton SA, Sao Paulo, SP, Brazil) in a water-cooled automatic polisher (APL4; Arotec, Cotia, SP, Brazil). Knoop hardness measurements were performed
10
with a microhardness tester (HMV-2; Shimadzu Corp., Tokyo, Japan) under a load of 50 g for 15 s. Five indentations were made in the cross-sectional area at 100 and 700 µm from the top surface (Figure 2). The average value of the five readings was recorded as the Knoop hardness number (KHN). The surface top layer of the specimens was not tested because it is normally low-polymerized due to oxygen inhibition, and would probably yield lower hardness values.5
Figure 2 – Cross-sectional area of the flatted cement specimen for Knoop hardness readings at different depths.
The exploratory data were performed before analysis of variance (ANOVA) split-plot design. The plot was represented by shade, post-cure time and mode of activation with their respective double and triple interactions. The sub-plot was represented by the depth factor and all interactions of the deep with other factors. The significance interactions were outspread and submitted to Tukey post hoc test (α = 0.05).
Results
The mean values of Knoop hardness are shown in Table 1. Significant differences for shade (p<0.0001), mode of activation (p<0.001), post-cure time (p<0.0001) and depth (p<0.0001) were detected. There was not significance in the interactions (p>0.05), except for the interaction between shade x post-cure time (p<0.0045) and between mode of activation x post-cure time (p<0.0003).
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When shades were compared, the mean value of Knoop hardness of the shade MV0 was significantly higher than other shades (p<0.05). The HV +3 shade showed lower hardness values (p<0.05), independent regardless of the cement depth, the mode of activation or the post-cured time. No significant difference was found among LV 1, LV 2 and HV +2 (p>0.05) and among HV +2, HV +3 and LV -2 (p>0.05) in all conditions.
For all cements shades there was a significant increase in Knoop hardness after 24 h (p<0.05), for the same conditions of the direct and indirect curing methods, and for all cement depths.
In relation to mode of activation, all cements shades had a statistically significant difference in Knoop hardness between the direct and indirect mode. The direct mode showed higher hardness values than the indirect mode at 15 min and 24 h (p<0.05), independent irrespective of the depth.
When the depth was analyzed, the Knoop hardness at 100 µm was significantly higher than 700 µm (p<0.05), for the same conditions of the direct and indirect curing methods, and post-cured time.
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Table 1 - Knoop hardness means ± Standard Deviation for the different groups.
Depth MV 0 HV +1 LV -1 HV +2 LV -2 HV +3 LV -3
Direct 15 min 100 µm *$&46.2 ± 2.6A *$&37.6 ± 2.0B *$&34.5 ± 2.0C *$&33.0 ± 2.6 CD *$&32.9 ± 1.6CD *$&29.7 ± 1.0E *$&32.6 ± 1.5D
700 µm *&42.1 ± 2.3A *&35.1 ± 1.8 B *&31.7 ± 1.5C *&31.1 ± 2.4CD *&30.4 ± 1.4CD *&27.6 ± 1.8E *&30.8 ± 1.8D
Direct 24 h 100 µm *$53.3 ± 3.4A *$45.7 ± 1.7B *$41.2 ± 1.4C *$39.7 ± 1.2CD *$39.4 ± 1.6D *$36.6 ± 1.9E *$38.9 ± 2.0D
700 µm *51.7 ± 1.3A *43.5 ± 2.3B *39.7 ± 3.4C *37.4 ± 1.6CD *36.3 ± 2.1D *34.5 ± 2.2E *36.5 ± 1.7D
Indirect 15 min 100 µm $&44.9 ± 1.3ª $&35.3 ± 1.9B $&31.8 ± 2.0C $&30.1 ± 3.0CD $&31.4 ± 1.5CD &$28.3 ± 1.5E $&30.9 ± 1.5D
700 µm &40.3 ± 2.1ª &33.5 ± 1.9B &30.4 ± 2.4C &28.6 ± 1.3CD &28.2 ± 2.4CD &26.3 ± 0.8E &27.5 ± 1.2D
Indirect 24 h 100 µm $50.9 ± 2.6ª $41.9 ± 3.4B $37.5 ± 2.9C $36.8 ± 1.8CD $35.9 ± 1.3D $33.6 ± 1.5E $36.1 ± 1.6D
700 µm 48.6 ± 2.1ª 40.1 ± 1.2B 35.2 ± 2.6C 33.6 ± 2.7CD 32.8 ± 2.5D 31.4 ± 2.3E 33.1 ± 1.7D Means followed by different uppercase letters in the same row indicate significant differences for resin cement shades (p<0.05). *Differ of the indirect group for the same conditions of the post-cure time and depth (p<0.05). $Differ of the depth of 700 µm for the same conditions of the direct or indirect curing methods, and post-cure time (p<0.05) &Differ of the 24 h for the same conditions of the direct or indirect curing methods, and depth (p<0.05).
13 Discussion
The durability, quality and performance of the ceramic restoration in clinical situation depend on the adequate polymerization of the resin cement. Baynet et al. (1994)30 showed that it is necessary the adequate polymerization for maximizing the mechanical properties of the resin cement. Some factors can influence the polymerization degree of the resin cement, such as, shade of the ceramic, ceramic thickness, opacity, light-activation time, and intensity of the light-curing units.5,18,19,20,21,22,23 The polymerization of the resin cement depends on the light absorption and dispersion within the cement, the shade, opacity, chemical composition and filler particle.24,25,26
The resin cement selected for this study was the light-curing Variolink Veneer in seven shades. The shades are radiopaque Low Value (LV -1, -2, and -3), and High Value (HV +3) and shades are not radiopaque Medium Value (MV 0) and High Value (HV +1 and HV +2), according to manufacturer’s information. The colors High Value let the restoration appear brighter and white with HV+3 corresponding to an opaque with the lowest translucency (about 5%). MV0 is the most neutral and presents the highest translucency (about 50%). The colors Low Value presents a warm yellow reddish tinge and LV -3 with low translucency (about 9%).
In this present study, the first hypothesis, which stated that the Knoop hardness is similar for different cement shade was rejected. The results showed that higher values for Knoop hardness were obtained for shade MV0 with a statistically significant difference when compared to other shades. The HV+3 shade showed lower hardness values. Comparisons for Knoop hardness among shades at 15 min and a 24 h showed that MV0 > HV+1 > LV-1 > LV-3 = HV+2 = LV -2 > HV+3 (p<0.05), regardless of the mode of activation, the post-cured time or cement depth. Then, each shade might require a specific activation strategy in order to maximize hardness. The polymerization depends on the light dispersion within of the material and an adequate amount of light is required to obtain high
14
polymerization.27 Reges et al. (2008)5 showed a relationship between depth of cure and translucency of resin cement. The opaque shades might not cure adequate, because of the increase the absorption of the light by the pigments and decreased capacity for light penetrate into the composite, decreasing the hardness of the cement.5,24,29,31 Ozturk et al. (2013)31 detected that the more translucent the resin cement, the higher the hardness. According to the author this can be explained by the fact that the transparent resin cements absorb more light and the depth of polymerization of these cements is higher than the opaque cements.
In the present study, two post-cure times, 15 min and 24 h were evaluated. The results indicated that the second hypothesis was not accepted. All resin cements shades showed a significant increase in Knoop hardness after 24 h, for the same conditions of the direct and indirect curing methods, and for all cement depths. Although, the polymerization of light-activated resin cement occurs within the first 10 to 15 minutes, it can continue until 24h after the activation.32,33,34 A significant amount of free radicals remains trapped within the matrix after the end of irradiation allowing formation of polymer chains, which increases the hardness values. The “post-activation” reaction can continue, until there are free radicals available and monomers present sufficient mobility.35,36 This is important once clinically, an adequate polymerization of the resin cement must be rapidly obtained for the material to withstand immediate loads as adjustments and occlusal forces and adequate biocompatibility.5
In relation to mode of activation, the direct mode showed higher hardness values than the indirect mode for the two post-cure times and all cements shades. The results indicated that the third hypothesis was rejected. This finding is due to the light attenuation promoted by the intervening of the ceramic material. Halvorson et al. (2002)38 showed that the lower energy might influence the polymer development primary by decreasing the double bond conversion, since the polymerization is dependent on the radiant exposure to specimens. Besides, indirect activation reduces the level of irradiance the luting material, the polymer
15
network development might be affected by decreasing the monomer conversion and also by interfering with the type and degree of cross-linking.39
These results agree with previous study, which found higher hardness values for direct mode activation in relation to the indirect mode. However, some studies have found no significant difference between direct and indirect activation modes with interposition of the ceramics with 0.7 mm thickness,21 1 mm thickness,37 and 2 mm thickness.8,22 According to Pazin et al. (2008)21 probable sufficient light energy was delivered to both surfaces of the specimens and, consequently no significant influence in hardness occurred or by additional chemical curing effect of the resin cement that compensates for the lower light energy the bottom layers. Dual-cured resin cements have been indicated to compensate the attenuation of the light by the interposition of the indirect restorative material, and to ensure adequate polymerization of the resin cement.40 The results of this study suggest that, for all shades, insufficient light energy for polymerization was delivered to the specimens, during indirect activation. Increasing the curing time of the resin cement may result in higher hardness values (AlShaafi et al., 2014; Lee et al., 2011).
When depth was analyzed, the Knoop hardness at 100 µm was significantly higher than 700 µm, rejected the fourth hypothesis. These findings are in agreement with those of previous studies, which also found higher hardness values on the top 100 µm than the bottom 700 µm.5,41 During photoactivation, the incident light is attenuated with increasing distance from de irradiated surface, as a result of absorption and scattered by the fillers and resin components, reducing the curing effectiveness and thus hardness values as the depth increases.35,42,43 Rueggeberg (1999)43 showed that only 25% of the light energy hitting the top surface of the composite is available at 1 mm depth, and the attenuation might be by the interposition of the indirect restorative material.10,13,17 Although film thickness of 700 µm might not be suitable for luting purposes, the depth of polymerization of resin cements may indicate their polymerization potential. In clinical situations, the light attenuation promoted by indirect restorative material could be worsened by
16
different irradiance levels of curing devices, shades, opacities, and thickness of the indirect restorations.5
In summary, the present results showed that resin cement shades, mode of activation, post-cure times and depth of polymerization have effect on mechanical properties of the resin cement. Adequate polymerization of the resin cement is crucial for obtaining optimal mechanical and biological properties and clinical performance. Thus, the using of the high-intensity light sources and increasing the light exposure time are adequate when light cured resin cement through ceramic restorations. Future studies should be carried out investigate other possible factors that affecting the clinical performance of the ceramic restorations.
Conclusions
Within the limitations of this study, the following conclusions can be made: 1 – The resin cement shade and indirect activation have a significant effect on the Knoop hardness;
2 - There was a significant increase in Knoop hardness after 24 h in all cements shades;
3 - The depth decreased significantly on the Knoop hardness values.
Acknowledgements
This study was supported by National Council for Scientific and Technological Development - CNPq (Grant 304493/2014-7).
References
1 Rosenstiel SF, Land MF & Crispin BJ (1998) Dental luting agents: A review of the current literature Journal of Prosthetic Dentistry 80(3) 280–301.
17
2 Lawn BR, Pajares A, Zhang Y, Deng Y, Polack MA, Lloyd IK, Rekow ED & Thompson VP (2004) Materials design in the performance of all-ceramic crowns
Biomaterials 25(14) 2885-2892.
3 Groten M & Pröbster L (1997) The influence of different cementation modes on the fracture resistance of feldspathic ceramic crowns International Journal of
Prosthodontics 10(2)169-177.
4 Fleming GJ, Maguire FR, Bhamra G, Burke FM & Marquis PM (2006) The strengthening mechanism of resin cements on porcelain surfaces Journal of Dental
Research 85(3) 272-276.
5 Reges RV, Moraes RR, Correr AB, Sinhoreti MAC, Correr-Sobrinho L, Piva E & Nouer PRA (2008) In-depth polymerization of dual-cured resin cement assessed by hardness Journal of Biomaterials Applications 23(1) 85-96.
6 Giráldez I, Ceballos L, Garrido MA & Rodríguez J (2011) Early hardness of self-adhesive resin cements cured under indirect resin composite restorations Journal
of Esthetic and Restorative Dentistry 23(2)116-125.
7 Pegoraro TA, Silva NRFA & Carvalho RM (2007) Cements for use in esthetic dentistry Dental Clinics of North America 51(2) 453-471.
8 Moraes RR, Correr-Sobrinho L, Sinhoreti MA, Puppin-Rontani RM, Ogliari FA & Piva E (2008) Light-activation of resin cement through ceramic: relationship between irradiance intensity and bond strength to dentin Journal of Biomedical
Materials Research Part B Applied Biomaterials 85(1) 160-165.
9 Danesh G, Davids H, Reinhardt KJ, Ott K & Schafer E (2004) Polymerisation characteristics of resin composites polymerised with different curing units Journal
of Dentistry 32(6) 479-488.
10 Rasetto FH, Driscoll CF, Prestipino V, Masri R, & von Franhofer JA (2004) Light transmission through all-ceramic dental materials: a pilot study Journal of
Prosthetic Dentistry 91(5) 441-446.
11 Janda R, Roulet JF, Latta M & Rüttermann S (2007) Water sorption and solubility of contemporary resin-based filling materials Journal of Biomedical
18
12 Dall’Magro E, Sinhoreti MA, Correr AB, Consani RL, Sicoli EA, Mendoça MJ & Correr-Sobrinho L (2008) Effect of different modes of light modulation on the bond strength and Knoop hardness of a dental composite Brazilian Dental Journal 19(4) 334-340.
13 El-Mowafy OM, Rubo MH & el-Badrawy WA (1999) Hardening of new resin cements cured through a ceramic inlay Operative Dentistry 24(1) 38–44.
14 Akgungor G, Akkayan B & Gaucher H (2005) Influence of ceramic thickness and polymerization mode of a resin luting agent on early bond strength and durability with a lithium disilicate-based ceramic system Journal of Prosthetic
Dentistry 94(3) 234–241.
15 Blackman R, Barghi N & Duke E (1990) Influence of ceramic thickness on the polymerization of light-cured resin cement Journal of Prosthetic Dentistry 63(3) 295–300.
16 Foxton RM, Pereira PN, Nakajima M, Tagami J & Miura H (2003) Effect of light source direction and restoration thickness on tensile strength of a dual-curable resin cement to copy-milled ceramic American Journal of Dentistry 16(2) 129–134. 17 Jung H, Friedl KH, Hiller KA, Haller A & Schmalz G (2001) Curing efficiency of different polymerization methods through ceramic restorations Clinical Oral
Investigations 5(3) 156-161.
18 Peixoto RT, Paulinelli VM, Sander HH, Lanza MD, Cury LA, Poletto & LT (2007) Light transmission through porcelain Dental Materials 23(11) 1363-1368.
19 Uctasli S, Hasanreisoglu U & Wilson HJ (1994) The attenuation of radiation by porcelain and its effect on polymerization of resin cements Journal of Oral
Rehabilitation 21(5) 565-575.
20 Soares CJ, da Silva NR & Fonseca RB (2006) Influence of the feldspathic ceramic thickness and shade on the microhardness of dual resin cement Operative
Dentistry 31(3) 384-389.
21 Pazin MC, Moraes RR, Gonçalves LS, Borges GA, Sinhoreti MAC & Correr-Sobrinho L (2008) Effects of ceramic thickness and curing unit on light
19
transmission through leucite-reinforced material and polymerization of dual-cured luting agent Journal of Oral Science 50(2) 131-136.
22 Kilinc E, Antonson SA, Hardigan PC & Kesercioglu A (2011) The effect of ceramic restoration shade and thickness on the polymerization of light- and dual-cure resin cements Operative Dentistry 36(6) 661-669.
23 Passos SP, Kimpara ET, Bottino MA, Rizkalla AS & Santos Jr GC (2014) Effect of ceramic thickness and shade on mechanical properties of a resin luting agent
Journal of Prosthodontics 23(6) 462-466.
24 Shortall AC (2005) How light source and product shade influence cure depth for a contemporary composite Journal of Oral Rehabilitation 32(12) 906-911.
25 Musanje L & Darvell BW (2006) Curing-light attenuation in filled-resin restorative materials Dental Materials 22(9) 804-817.
26 Reges RV, Costa AR, Correr AB, Piva E, Puppin-Rontani RM, Sinhoreti MAC & Correr-Sobrinho L (2009) Effect of light-curing units, post-cured time and shade of resin cement on knoop hardness Brazilian Dental Journal 20(5) 410-413.
27 Leloup G, Holvoet PE, Bebelman S & Devaux J (2002) Raman scattering determination of the depth of cure of light-activated composites: influence of different clinically relevant parameters Journal of Oral Rehabilitation 29(6) 510-515. 28 Öztürk E, Hickel R, Bolay S & Ilie N (2012) Micromechanical properties of veneer luting resins after curing through ceramics Clinial Oral Investigations 16(1) 139-146.
29 Öztürk E, Chiang YC, Cosgun E, Bolay S, Hickel R & Ilie N (2013) Effect of resin shades on opacity of ceramic veneers and polymerization efficiency through ceramics Journal of Dentistry 41(5) 8-14.
30 Bayne SC, Heymann HO & Swift EJ Jr (1994) Update on dental composite restorations Journal of the American Dental Association 125(6) 687-701.
31 Guiraldo RD, Consani S, Consani RLX, Berger SB, Mendes WB & Sinhoreti MAC (2009) Light energy transmission through composite influenced by material shades Bulletin of Tokyo Dental College 50(4) 183-190.
20
32 Leung RL, Fan PL & Johnston WM (1983) Post-irradiation polymerization of visible light-activated composite resin Journal of Dental Research 62(3) 363-365. 33 Ciccone-Nogueira JC, Borsatto MC, de Souza-Zaron WC, Ramos RP & Palma-Dibb RG (2007) Microhardness of composite resins at different depths varying the post-irradiation time Journal of Applied Oral Science 15(4) 305-309.
34 Yan YL, Kim YK, Kim K-H & Kwon T-Y (2010) Changes in degree of conversion and microhardness of dental resin cements Operative Dentistry 35(2) 203-210. 35 Watts DC, McNaughton V & Grant AA (1986) The development of surface hardness in visible light-cured posterior composites Journal of Dentistry 14(4) 169-174.
36 Burtscher P (1993) Stability of radicals in cured composite materials Dental
Materials 9(4) 218-221.
37 Runnacles P, Correr GM, Baratto Filho F, Gonzaga CC & Furuse AY (2014) Degree of conversion of a resin cement light-cured through ceramic veneers of different thicknesses and types Brazilian Dental Journal 25(1) 38-42.
38 Halvorson RH, Erickson RL & Davdson CL (2002) Energy dependent polymerization of resin-based composite Dental Materials 18(6) 463-469.
39 Schneider FL, Moraes RR, Cavalcante LM, Sinhoreti MA & Correr-Sobrinho L (2008) Cross-link density evaluation through softening tests: effect of ethanol concentrations Dental Materials 24(2) 199–203.
40 Lee IB & Um CM (2001) Thermal analysis on the cure speed of dual cured resin cements under porcelain inlays Journal of Oral Rehabiltation 28(2) 186-197.
41 Puppin-Rontani RM, Dinelli RG, de Paula AB, Fucio SB, Ambrosano GM & Pascon FM (2012) In-depth polymerization of a self-adhesive dual-cured resin cement Operative Dentistry 37(2) 188-194.
42 Borges GA, Agarwal P, Miranzi BA, Platt JA, Valentino TA & dos Santos PH (2008) Influence of different ceramics on resin cement Knoop Hardness Number
Operative Dentistry 33(6) 622-628.
43 Rueggeberg F (1999) Contemporary Issues in Photocuring Compendium of
21
CONCLUSÃO
Dentro das limitações deste estudo, as seguintes conclusões podem ser feitas:
1 - A cor do cimento resinoso e ativação indireta teve significante efeito na dureza Knoop;
2 - Houve um significante aumento na dureza Knoop, após 24 horas em todas as cores do cimento resinoso;
3 - A profundidade diminuiu significantemente os valores de dureza Knoop.
22
REFERÊNCIAS
Bagis B, Turgut S. Optical properties of current ceramics systems for laminate veneers. J Dent. 2013; 41: 24-30.
Castro HL, Passos SP, Zogheib LV, Bona AD. Effect of cement shade and light-curing unit on bond strength of a ceramic cemented to dentin. J Adhes Dent. 2012; 14: 155-60.
Caughman WF, Chan DCN, Rueggeberg FA. Curing potential of dual-polymerizable resin cements in simulated clinical situations. J Prosthet Dent. 2001; 85(5): 479-84.
Dias MC, Piva E, Moraes RR, Ambrosano GMB, Sinhoreti MAC, Correr-Sobrinho L. UV-Vis spectrophotometric analysis and light irradiance through hot-pressed and hot-pressed-veneered glass ceramics. Braz Dent J. 2008; 19(3): 197-203.
El-Mowafy OM, Rubo MH, El-Badrawy WA. Hardening of New Resin Cements Cured through a Ceramic Inlay. Oper Dent.1999; 24(1): 38–44.
Ferracane JL, Aday P, Matsumoto H, Marker VA. Relationship between shade and depth of cure for light-activated dental composite resins. Dent Mater. 1986; 2: 80-4. Fleming GJP, Maguire FR, Bhamra G, Burke FM & Marquis PM. The strengthening mechanism of resin cements on porcelain surfaces. J Dent Res. 2006; 85(3): 272– 6.
Giráldez I, Ceballos L, Garrido MA, Rodríguez J. Early hardness of self-adhesive resin cements cured under indirect resin composite restorations. J Esthet Restor Dent. 2011; 23: 116-25.
Guiraldo RD, Consani S, Consani RLX, Berger SB, Mendes WB, Sinhoreti MAC. Light energy transmission through composite influenced by material shades. Bull Tokyo Dent Coll. 2009; 50(4): 183-90.
Hofmann N, Papsthart G, Hugo B, Klaiber B. Comparison of photo-activation versus chemical or dual-curing of resin-based luting cements regarding flexural strength, modulus and surface hardness. J Oral Rehabil. 2001; 28(11): 1022-8.
De acordo com as normas da UNICAMP/FOP, baseadas na padronização do International Committee of Medical Journal Editors. Abreviatura dos periódicos em conformidade com o Medline
23
Inokoshi S, Willems G, Van Meerbeek B, Lambrechts P, Braem M, Vanherle G. Dual-cure luting composites. Part I: filler particle distribution. J Oral Rehabil. 1993; 20(2): 133-46.
Jeong TS, Kang HS, Kim SK, Kim S, Kim HI, Kwon YH. The effect of resin shades on microhardness, polymerization shrinkage, and color change of dental composite resins. Dent Mater J. 2009; 28(4): 438–45.
Karaagaclioglu L, Yilmaz B. Influence of cement shade and water storage on the final color of leucite-reinforced ceramics. Oper Dent. 2008; 33(4): 386-91.
Kesrak P, Leevailoj C. Surface hardness of resin cement polymerized under different ceramic materials. Int J of Dent. 2012.
Kilinc E, Antonson SA, Hardigan PC, Kesercioglu A. The effect of ceramic restoration shade and thickness on the polymerization of light- and dual-cure resin cements. Oper Dent. 2011; 36(6): 661-9.
Lawn BR, Pajares A, Zhang Y, Deng Y, Polack MA, Lloyd IK, Rekow ED, Thompson VP. Materials design in the performance of all-ceramic crowns. Biomaterials. 2004; 25(14): 2885-92.
Leloup G, Holvoet PE, Bebelman S, Devaux J. Raman scattering determination of the depth of cure of light-activated composites: influence of different clinically relevant parameters. J Oral Rehabi. 2002; 29: 510–5.
Leung RL, Fan PL, Johnston WM. Post-irradiation polymerization of visible light-activated composite resin. J Dent Res. 1983; 62(3): 363-5.
Lührs AK, De Munck J, Geurtsen W, Van Meerbeek, B. Composite cements benefit from light-curing. Dent Mater. 2014; 30: 292-301.
Musanje L, Darvell BW. Curing-light attenuation in filled-resin restorative materials. Dent Mater. 2006; 22: 804–17.
Onose H, Sano H, Kanto H, Ando S, Hasuike T. Selected curing characteristics of light-activated composite resins. Dent Mater. 1985, 1: 48-54.
Oréfice RL, Discacciati JAC, Neves AD, Mansur HS, Jansen WC. In situ evaluation of the polymerization kinetics and corresponding evolution of the mechanical properties of dental composites. Polymer Testing. 2003; 22: 77–81.
Öztürk E, Chiang YC, Cosgun E, Bolay S, Hickel R, Ilie N. Effect of resin shades on opacity of ceramic veneers and polymerization efficiency through ceramics. J Dent. 2013; 41: 8-14.
24
Öztürk E, Hickel R, Bolay S, Ilie N. Micromechanical properties of veneer luting resins after curing through ceramics. Clin Oral Invest. 2012; 16: 139-46.
Passos SP, Kimpara ET, Bottino MA, Rizkalla AS, Santos Jr GC. Effect of ceramic thickness and shade on mechanical properties of a resin luting agent. J Prosthodont. 2014; 23: 462–6.
Pazin MC, Moraes RR, Gonçalves LS, Borges GA, Sinhoreti MAC, Correr-Sobrinho L. Effects of ceramic thickness and curing unit on light transmission through leucite-reinforced material and polymerization of dual-cured luting agent. J Oral Sci. 2008; 50(2): 131-6.
Peixoto RTRC, Paulinelli VMF, Sander HH, Lanza MD, Cury LA, Poletto, LTA. Light transmission through porcelain. Dent Mater. 2007; 23: 1363–8.
Rasetto FH, Driscoll CF, Prestipino V, Masri R, von Franhofer JÁ. Light transmission through all-ceramic dental materials: a pilot study. J Prosthet Dent. 2004; 91(5): 441-6.
Reges RV, Costa AR, Correr AB, Piva E, Puppin-Rontani RM, Sinhoreti MAC, Correr-Sobrinho L. Effect of light-curing units, post-cured time and shade of resin cement on knoop hardness. Braz Dent J. 2009; 20(5): 410-3.
Reges RV, Moraes RR, Correr AB, Sinhoreti MAC, Correr-Sobrinho L, Piva E, Nouer PRA. In-depth polymerization of dual-cured resin cement assessed by hardness. J Biomater Appl. 2008; 23: 85-96.
Rueggeberg FA, Craig RG. Correlation of parameters used to estimate monomer conversion in a light-cured composite. J Dent Res. 1988; 67(6): 932-7.
Shortall AC. How light source and product shade influence cure depth for a contemporary composite. J Oral Rehabil. 2005; 32: 906-11.
Tango RN, Sinhoreti MAC, Correr AB, Correr-Sobrinho L, Consani RLX. Effect of veneering materials and curing methods on resin cement Knoop hardness. Bras Dent J. 2007; 18(3): 235-9.
Wu X, Nakagawa M, Teraoka F. Failure morphology of all-ceramic prostheses. Dent Mater J. 2012; 31(3): 494–8.
Yan YL, Kim YK, Kim KH, Kwon TY. Changes in degree of conversion and microhardness of dental resin cements. Oper Dent. 2010; 35(2): 203-10.
25 APÊNDICE
Metodologia
1 - Confecção do disco de cerâmica
Para confecção do disco da cerâmica reforçada por di-silicato de lítio (IPS e.max Press, Ivoclar-Vivadent, Schaan, Liechtestein) com espessura de 0,7 mm por 10 mm de diâmetro, cera tipo II (Thowax) liquefeita (Bredent, Tipo 55) foi inserida na parte interna de uma matriz metálica com 10 mm de diâmetro por 0,9 mm de espessura para obtenção do padrão em cera (Figura 1). O mesmo foi incluído com revestimento à base de fosfato IPS Empress Esthetic Speed (Ivoclar vivadent) (Figuras 2 e 3). Após a eliminação da cera, o bloco de revestimento foi retirado do forno e uma pastilha de cerâmica (IPS e.max Press, Ivoclar-Vivadent), cor HT A1, foi posicionada no conduto, juntamente com o êmbolo (Figura 4), e levado ao forno EP600 (Ivoclar Vivadent) mantido por 20 minutos a 1075 °C, seguido de pressão de 5 bar por 15 minutos.
26 Figura 2 – Inclusão com
revestimento
Figura 3 – Inclusão com revestimento
Figura 4 – Posicionamento do êmbolo
27
Posteriormente, o disco de cerâmica foi removido do revestimento com jateamento de partículas de óxido de alumínio (100 m) usando o aparelho (Oxyker Dry; Flli Manfredi) com pressão de 4 bar, seguido pela limpeza Invex (Ivoclar Vivadent) por 10 minutos, lavagem em água corrente e secagem com jato de ar (Figura 5). Em seguida, o disco foi submetido ao acabamento e polimento com lixas de carbeto de silício com granulação decrescente 320, 400, 600 e 1200 (Norton, São Paulo, SP, Brasil) sob refrigeração constante em água, a fim de obter as dimensões de 10 mm de diâmetro por 0,7 mm de espessura aferidas com paquímetro digital (Mitutoyo Corporation, Tokyo, Japan). Posteriormente, o disco foi submetido a limpeza em ultrassom por 10 minutos.
Figura 5 - Discos após remoção do revestimento 2 - Obtenção dos espécimes dos cimentos resinosos
O cimento resinoso Variolink Veneer (Ivoclar Vivadent AG, Shann Liechtenstein) nas cores Hight Value +1 (HV +1), Hight Value +2 (HV +2), Hight Value +3 (HV +3), Low Value 1 (LV 1), Low Value 2 (LV 2), Low Value 3 (LV -3) e Medium Value 0 (MV 0) foi inserido num molde de silicone com 5 mm de diâmetro por 1 mm de espessura (Figuras 6 e 7). Uma tira de poliéster foi adaptada sobre o molde e o disco de cerâmica posicionado sobre o cimento resinoso. A fotoativação da metade das amostras foi realizada através da cerâmica (modo indireto) (Figura 8) e as demais sem interposição da cerâmica
28
(modo direto) (Figura 9) por 20 segundos com o aparelho fotoativador Radii cal (SDI Limited Bayswater, Austrália), com intensidade de luz de 1200 mW/cm2.
Figura 6 – Molde de silicone (5x1mm) Figura 7 – Preenchimento do molde com cimento Variolink Veneer
Figura 8 – Fotoativação (modo indireto) Figura 9 – Fotoativação (modo indireto)
Quarenta amostras foram confeccionadas para cada cor do cimento resinoso e dois períodos de armazenagem foram avaliados: metade das amostras foi avaliada após 15 minutos, e as demais amostras após armazenagem por 24 horas em ambiente escuro e seco numa estufa a 37o C
29 3 - Determinação da dureza Knoop
Após os períodos de armazenagem (15 minutos e 24 horas), os espécimes foram adaptados numa matriz pré-moldada em resina acrílica incluída em tubo de PVC para o teste de dureza Knoop. Os discos foram adaptados nos espaços com adição de cera pegajosa plastificada (Figura 10). Após a fixação dos discos, o conjunto foi levado a uma politriz metalográfica para acabamento e polimento com lixas de granulação decrescente 320, 400, 600 e 1200 (Norton S/A, São Paulo, SP, Brasil) até a obtenção de polimento satisfatório para as leituras de microdureza (Figura 11 e 12).
Figura 10 – Fixação da amostra na Figura 11 – Acabamento e polimento matriz das amostras
Figura 12 – Amostra após acabamento e polimento
O ensaio de dureza Knoop foi efetuado no aparelho HMV – 2 (Shimadzu Corp.,Tokyo, Japan), calibrado com carga de 50 gramas, atuando por 15 segundos (Figura 13). Cinco indentações foram feitas na área da secção
30
transversal para duas diferentes profundidades no cimento: 100 e 700 μm da região de superfície do topo. O valor médio das cinco leituras foi registrado como número de dureza Knoop (KHN) para cada profundidade.
Figura 13 – Ensaio de dureza
4 – Análise estatística
Após a análise exploratória, os dados foram submetidos à análise de variância (ANOVA) em esquema de parcelas subdivididas, sendo as parcelas representadas pelos fatores cor, tempo pós-polimerização e modo de ativação com as respectivas interações duplas e triplas e a subparcela representada pelo fator profundidade e todas as interações de profundidade com os demais fatores. As interações significativas foram desdobradas e aplicado o teste de Tukey considerando o nível de significância de 5%.
31 14-Jan-2015
Dear Prof. Sobrinho:
Your manuscript entitled "Influence of shades and post-activation times of resin cement on Knoop Hardness" has been successfully submitted online and is presently being given full consideration for publication in the Brazilian Dental Journal.
Your manuscript ID is BDJ-2015-0026.
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Thank you for submitting your manuscript to the Brazilian Dental Journal. Sincerely,
