Lucas de Oliveira Tomaselli
Influência da temperatura e do conteúdo de carga na espessura de
película, resistência de união, mudança de cor e grau de conversão
de compósitos resinosos sob facetas cerâmicas com diferentes
espessuras
Influence of the temperature and filler content on film thickness,
bond strength, color changing and degree of conversion of resin
composite under ceramic veneers with different thicknesses
Piracicaba 2018
FACULDADE DE ODONTOLOGIA DE PIRACICABA
UNIVERSIDADE ESTADUAL DE CAMPINAS
LUCAS DE OLIVEIRA TOMASELLI
Influência da temperatura e do conteúdo de carga na espessura de
película, resistência de união, mudança de cor e grau de conversão
de compósitos resinosos sob facetas cerâmicas com diferentes
espessuras
Influence of the temperature and filler content on film thickness,
bond strength, color changing and degree of conversion of resin
composite under ceramic veneers with different thicknesses
Dissertação apresentada à Faculdade de Odontologia de Piracicaba da Universidade Estadual de Campinas como parte dos requisitos exigidos para a obtenção do título de Mestre em Materiais Dentários.
Dissertation presented to the Piracicaba Dental School of the University of Campinas in partial fulfillment of the requirements for the degree of Master of Science in Dental Materials.
Orientador: Prof. Dr. Mário Alexandre Coelho Sinhoreti
ESTE EXEMPLAR CORRESPONDE À VERSÃO FINAL DADISSERTAÇÃO DEFENDIDA PELO ALUNO LUCAS DE OLIVEIRA TOMASELLI E ORIENTADA PELO PROF. DR. MÁRIO ALEXANDRE COELHO SINHORETI.
Piracicaba 2018
Resumo
O objetivo neste estudo foi avaliar o efeito do aumento da temperatura e do conteúdo de carga na espessura de película, resistência de união, alteração de cor e grau de conversão de compósitos resinosos experimentais fotoativados através de facetas cerâmicas com diferentes espessuras. Foram preparados dois compósitos com composições monoméricas idênticas (29% em peso de Bis-GMA, 32,5% em peso de UDMA, 32,5% em peso de BisEMA e 6% em peso de TEGDMA), porém com quantidades de partículas de carga (20% de sílica pirogênica - 0,05 μm e 80% de vidro de BaBSiO2 – 0,7 μm) diferentes (65%
ou 50% em peso). Foram confeccionadas 93 facetas cerâmicas cilíndricas com 7,5 mm de diâmetro e diferentes espessuras (0,4 mm; 0,8 mm ou 1,5 mm). O compósito contendo 65% de carga foi utilizado em duas temperaturas distintas (ambiente - 25ºC e aquecido - 60ºC). Para o teste de espessura de película (n=10), 0,1 mL de cada compósito foi dispensado entre duas placas de vidro e pressionado com uma carga de 150N para a formação de um filme, seguindo-se a norma ISO 4049 – 2009. Para o teste de resistência de união, foram utilizados dentes incisivos bovinos que tiveram sua superfície desgastada até expor área plana de esmalte. Os corpos-de-prova de microcisalhamento (n=10) foram confeccionados por meio de tubos de Tygon (TGY-030) com diâmetro interno de 0,9mm e altura de 0,5mm no qual foram inseridos compósitos experimentais, fotoativados (Bluephase G2, 1200 mW/cm2) através de uma das facetas de cerâmica com diferentes espessuras por 20 segundos. O carregamento foi realizado com fio ortodôntico de 0,3mm de diâmetro que envolveu o cilindro de compósito próximo à área de união, à velocidade de 0,5mm/min (Instron, modelo 4411). A alteração de cor foi avaliada por um espectrofotômetro (Vita EasyShade Advanced), de acordo com os parâmetros CIEDE 2000. As mensurações foram feitas antes e após envelhecimento em UV (120 horas) de cada compósito aderido às facetas cerâmicas (n=10). O grau de conversão foi avaliado em amostras cilíndricas (6mm de diâmetro por 1,0mm de espessura, n=5) utilizando-se espectroscopia Raman. Os resultados obtidos em cada ensaio foram submetidos a 2-way ANOVA e as médias comparadas pelo teste de Tukey (α=5%), exceto para o teste de espessura de película, onde foi utilizado 1-way ANOVA. O aquecimento do compósito convencional produziu média de espessura de película comparável ao compósito flowable e ao compósito não aquecido, porém verificou-se diferença entre flowable e convencional não aquecido. Não houve diferença na resistência de união ao microcisalhamento entre os três
compósitos nem mesmo abaixo das diferentes facetas. O grau de conversão dos compósitos flowable foi estatisticamente superior ao dos demais compósitos. Também verificou-se maior grau de conversão sob facetas de 0,4 mm, quando comparado com o obtido abaixo de facetas de 1,5mm, verificou-se valor comparável a ambas abaixo de facetas de 0,8mm. A alteração de cor foi maior para compósitos convencionais não aquecidos, verificou-se também maior alteração de cor em compósitos abaixo de facetas de 0,4 mm quando comparadas com a alteração abaixo de facetas de 1,5mm, valor comparável a ambos foi obtido abaixo de facetas de 0,8mm. Pode-se concluir que os compósitos experimentais possuem potencial para bom desempenho clínico caso sejam utilizados para cimentação de facetas cerâmicas de até mesmo de 1,5 mm de espessura, quando utilizada a técnica de alteração de temperatura.
Abstract
The aim of this study was to evaluate the effect of increasing temperature and filler content on film thickness, microshear bond strength, color change and degree of conversion of experimental resin composites photoactivated through ceramic veneers with different thicknesses. Two composites with identical monomeric compositions (29 wt.% Bis-GMA, 32.5 wt.% UDMA, 32.5 wt.% BisEMA and 6 wt.% TEGDMA) were prepared, but with different amounts of filler particles (20% pyrogenic silica - 0.05 μm and 80% BaBSiO2 -
0.7 μm glass) (65% or 50% by weight). A total of 93 cylindrical ceramic veneers with a diameter of 7.5 mm and different thicknesses (0.4 mm, 0.8 mm or 1.5 mm) were built. The composite containing 65% of filler was used at two different temperatures (ambient - 25 ° C and heated - 60 ° C). For the film thickness test (n = 10), 0.1 mL of each composite was dispensed between two glass plates and pressed with a 150N film loading, followed by ISO 4049 - 2009 For the microshear bond strength test, bovine incisor teeth were used that had their surface worned until exposed flat enamel area. The microshear specimens (n = 10) were built using Tygon tubes (TGY-030) with internal diameter of 0.9mm and height of 0.5mm in which experimental composites were photoactivated (Bluephase G2 , 1200 mW / cm2) through one of the ceramic veneers with different thicknesses for 20 seconds. The loading was performed with 0.3 mm diameter orthodontic wire that rounded the composite cylinder near the bonding area at a speed of 0.5 mm / min (Instron, model 4411). The color change was evaluated by a spectrophotometer (Vita EasyShade Advanced), according to CIEDE 2000 parameters. Measurements were made before and after aging in UV (120 hours) of each composite adhered to the ceramic veneers (n = 10). The degree of conversion was evaluated in cylindrical samples (6mm in diameter by 1.0mm in thickness, n = 5) using Raman spectroscopy. The results obtained in each test were submitted to 2-way ANOVA and the means compared by the Tukey test (α = 5%), except for the film thickness test, where 1-way ANOVA was used. Heating the conventional composite produced mean film thickness comparable to the flowable composite and to the conventional one, but there was difference between flowable and conventional. There was no difference in microshear bond strength between the three composites nor even below the different veneers. The degree of conversion of the flowable composites was statistically higher than the other composites. It was also
verified a higher degree of conversion under 0.4 mm veneers, when compared to that obtained under 1.5mm veneers, a value comparable to both below 0.8mm veneers was verified. The color change was higher for unheated conventional composites, and there was also a greater color change in composites below 0.4 mm veneers when compared to the 1.5 mm veneers alteration, a value comparable to both was obtained below veneers of 0,8mm. It can be concluded that the experimental composites have potential for good clinical performance if they are used for cementing ceramic veneers of up to 1.5 mm thick, when using the temperature alteration technique.
Sumário
1 INTRODUÇÃO ……….…….10
2 ARTIGO: Influence of the temperature and filler content on film thickness, bond strength, color changing and degree of conversion of resin composite under ceramic veneers with different thicknesses……….14
3 CONCLUSÃO ...33
REFERÊNCIAS ...33
1. INTRODUÇÃO
A busca por restaurações de coloração extremamente clara se tornou cotidiana na Odontologia (Gaengler et al., 2004). Os padrões utilizados pela mídia para definir o belo claramente influenciam a escolha dos pacientes sobre seu tratamento. O reflexo destes padrões na prática clínica se torna inevitável, o que eleva o desafio do clínico que necessita atender à exigência estética; porém, não podendo negligenciar fatores importantes como a resistência mecânica e adesiva da restauração, durabilidade e os impactos destes na saúde intermaxilar (Ilie et al., 2017).
No arsenal de possibilidades que o clínico tem para realizar as reabilitações bucais, se encontram as restaurações diretas, feitas diretamente na cavidade bucal e as indiretas, realizadas em laboratório de prótese ou no próprio consultório sobre modelos, sendo posteriormente cimentadas (Wakiaga et al., 2004). A Odontologia é uma ciência em constante aprimoramento e se em outros tempos, em nome da retenção de um material às estruturas dentais, desgastavam-se estruturas sadias, hoje em Odontologia permite-se preparos com menor desgaste, portanto menos invasivos (Magne e Belser, 2004). Tal feito só pôde ser alcançado graças a Odontologia Adesiva e ao constante desenvolvimento de materiais que, mesmo em mínimas espessuras, podem ser utilizados com segurança na prática clínica. O clínico possui uma vasta variedade de técnicas e materiais restauradores, além de diferentes substratos para se alcançar a união, do esmalte dental e dentina com compósitos, metais e materiais cerâmicos. Cabe a ele, junto ao paciente, escolher a melhor combinação de técnica e material para cada caso.
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É consenso entre especialistas que o tecido dental sadio deva ser protegido de desgastes desnecessários (Larson et al., 2003). Uma vez que um tecido desgastado jamais será reposto, as restaurações indiretas passaram, cada vez mais, perder espessura, tornando a coloração do substrato um objeto de suma importância junto com a coloração do agente de cimentação (Azer et al., 2011). Outro fator de extrema importância quando se trata de restaurações indiretas é a resistência de união, tanto do cimento ao substrato, quanto do cimento à peça protética.
Os compósitos resinosos formam a classe de materiais restauradores mais utilizada na Odontologia. Na sua forma mais habitual, encontram-se os compósitos indicados para restaurações diretas, os quais permitem esculpir a forma dental e ainda mimetizar as características ópticas das estruturas dentais (Ferracane, 2011). Ainda, os compósitos são utilizados na confecção de restaurações indiretas e também na fixação de restaurações indiretas de cerâmica, metal e compósito, sendo chamados nesse caso de cimentos resinosos.
A composição dos compósitos se baseia na tríade básica matriz orgânica (monômeros), partículas de carga (sílica, quartzo, vidros cerâmicos e outras) e um agente de união (silano). Se for comparada a composição dos compósitos restauradores com a dos cimentos resinosos, as diferenças se encontram no sistema iniciador, além da proporção dos monômeros utilizados e na quantidade de carga, conferindo ao cimento menor viscosidade e maior escoamento, porém, com propriedades mecânicas inferiores (Shinkai e Suzuki, 2014).
Assim, devido a grande versatilidade dos compósitos, surgiram técnicas de aplicação que tentam agregar as propriedades de escoamento dos cimentos resinosos com a resistência mecânica dos compósitos restauradores de consistência regular. A
técnica mais conhecida é chamada de técnica de termoplastificação, onde o compósito de consistência regular torna-se menos viscoso quando aquecido devido a maior agitação das moléculas (Lucey et al., 2010), proporcionando viscosidade suficiente para a fixação de peças protéticas, semelhantemente aos cimentos resinosos. Assim, espera-se que esespera-se compósito aquecido possa espera-ser utilizado como agente de cimentação, espera-sem perder suas propriedades de resistência mecânica.
Um compósito convencional não permitiria o assentamento correto de uma peça protética por sua alta viscosidade, o que acarretaria em aumento da espessura de película e consequentemente uma desadaptação. A técnica da termoplastificação consiste em diminuir a viscosidade de uma resina por meio do aumento de sua temperatura. Não se sabe, porém, se realmente utilizar um compósito convencional para cimentação aumentaria a resistência de união entre material restaurador e substrato ou afetaria suas propriedades mecânicas e reológicas. Outro fato desconhecido é se o fotoiniciador mais utilizado em resinas compostas, a canforquinona, junto ao seu co-iniciador, uma amina terciaria, não seriam afetados pelo aumento da temperatura. Com isso, a sua manutenção de cor poderia ser afetadas e interferir na cor das peças cerâmicas após sua fixação (Schneider et al., 2009).
Não foram encontrados estudos comparando a alteração de cor de compósitos quando são aquecidos e utilizados como agente de fixação de facetas cerâmicas, bem como o efeito da espessura dessas facetas na alteração de cor. Outro fator de grande importância é a espessura da película formada pelo compósito de consistência regular após o aquecimento, no sentido de obter escoamento necessário para o bom assentamento de uma faceta cerâmica sobre um substrato. Também se faz necessário verificar a influência da temperatura e da atenuação de luz no grau de conversão desses
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materiais usados para fixação e avaliar se ocorre melhoria nas propriedades mecânicas do agente de cimentação. Assim, os objetivos neste estudo foram: 1) avaliar a espessura de película de compósitos experimentais com diferentes viscosidades (flowable, convencional e convencional aquecido); 2) avaliar o grau de conversão, resistência de união e alteração de cor de cor de compósitos experimentais com diferentes viscosidades (flowable, convencional e convencional aquecido), fotoativados através de facetas cerâmicas com diferentes espessuras. As hipóteses testadas foram: 1) o conteúdo de carga e o aquecimento dos compósitos influenciariam na espessura de película; 2) o conteúdo de carga e o aquecimento dos compósitos influenciariam no grau de conversão; 3) o conteúdo de carga e o aquecimento dos compósitos influenciariam na resistência de união; 4) o conteúdo de carga e o aquecimento dos compósitos influenciariam na alteração de cor após envelhecimento artificial acelerado; 5) a espessura das facetas cerâmicas influenciaria no grau de conversão, resistência de união e alteração de cor de compósitos com diferentes viscosidades (flowable, convencional e convencional aquecido).
2 ARTIGO: Influence of the temperature and filler content on film
thickness, bond strength, color changing and degree of conversion of resin
composite under ceramic veneers with different thicknesses
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Abstract
The aim of this study was to evaluate the effect of increasing temperature and filler content on film thickness, microshear bond strength, color change and degree of conversion of experimental resin composites photoactivated through ceramic veneers with different thicknesses. Two composites with identical monomeric compositions (29 wt.% Bis-GMA, 32.5 wt.% UDMA, 32.5 wt.% BisEMA and 6 wt.% TEGDMA) were prepared, but with different amounts of filler particles (20% pyrogenic silica - 0.05 μm and 80% BaBSiO2 - 0.7 μm glass) (65% or 50% by weight). A total of 93 cylindrical
ceramic veneers with a diameter of 7.5 mm and different thicknesses (0.4 mm, 0.8 mm or 1.5 mm) were built. The composite containing 65% of filler was used at two different temperatures (ambient - 25 ° C and heated - 60 ° C). For the film thickness test (n = 10), 0.1 mL of each composite was dispensed between two glass plates and pressed with a 150N film loading, followed by ISO 4049 - 2009 For the microshear bond strength test, bovine incisor teeth were used that had their surface worned until exposed flat enamel area. The microshear specimens (n = 10) were built using Tygon tubes (TGY-030) with internal diameter of 0.9mm and height of 0.5mm in which experimental composites were photoactivated (Bluephase G2 , 1200 mW / cm2) through one of the ceramic veneers with different thicknesses for 20 seconds. The loading was performed with 0.3 mm diameter orthodontic wire that rounded the composite cylinder near the bonding area at a speed of 0.5 mm / min (Instron, model 4411). The color change was evaluated by a spectrophotometer (Vita EasyShade Advanced), according to CIEDE 2000 parameters. Measurements were made before and after aging in UV (120 hours) of each composite adhered to the ceramic veneers (n = 10). The degree of conversion was evaluated in cylindrical samples (6mm in diameter by 1.0mm in thickness, n = 5) using Raman spectroscopy. The results obtained in each test were submitted to 2-way ANOVA and the means compared by the Tukey test (α = 5%), except for the film thickness test, where 1-way ANOVA was used. Heating the conventional composite produced mean film thickness comparable to the flowable composite and to the conventional one, but there was difference between flowable and conventional. There was no difference in microshear bond strength between the three composites nor even
below the different veneers. The degree of conversion of the flowable composites was statistically higher than the other composites. It was also verified a higher degree of conversion under 0.4 mm veneers, when compared to that obtained under 1.5mm veneers, a value comparable to both below 0.8mm veneers was verified. The color change was higher for unheated conventional composites, and there was also a greater color change in composites below 0.4 mm veneers when compared to the 1.5 mm veneers alteration, a value comparable to both was obtained below veneers of 0,8mm. It can be concluded that the experimental composites have potential for good clinical performance if they are used for cementing ceramic veneers of up to 1.5 mm thick, when using the temperature alteration technique.
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1. INTRODUCTION
The pursuit for extremely light colored restorations has become routine in Dentistry (Gaengler et al. 2004). The patterns used by the media to define the beautiful, clearly influence the patients' choice about their treatment. The reflex of these patterns in clinical practice becomes unavoidable, which raises the challenge of the clinician who needs to meet the aesthetic requirement, but not neglecting important factors such as the mechanical resistance of the restoration, durability and their impact on intermaxillary health (Ilie et al. 2017).
In the arsenal of possibilities that the clinician have to operate his rehabilitations, there era direct restorations, made directly in the oral cavity, and indirect, realized in laboratory of prosthesis or in the own office on working casts, being later cemented (Wakiaga et al. 2004). The clinician has a wide variety of restorative materials, techniques to be used, as well as different substrates such as metal, dental structure, ceramic materials, among others. Therefore, the clinician and the patient could choose the best combination of technique and material for each case.
It is a consensus among experts that healthy dental tissue should be protected from unnecessary wear (Larson et al. 2003). Since a worned out dental tissue will never be recovered indirect restorations have increasingly lost thickness, making substrate color extremely important along with the fixation agent color (Azer et al. 2011).. Another factor of extreme importance when talking about indirect restorations is the bond strength, from resin cement to dental substrate or resin cement to restorative material.
Composite resins have become, with their improvements, one of the main materials used in Dentistry. In its most usual form, the composite resins are indicated to direct restorations, which allow us to sculpt the dental shape and still deliver optica characteristics very similar to dental structures. However, the composite can be used in indirect restorations and also in the fixation of indirect restorations of ceramic, metal or composite. In this case, they are called resin cements.
The composition of composite resins is based on the triad organic matrix (monomers), fillers (silica, quartz or ceramic glass) and photoinitiator for initiate the polymerization reaction (camphorquinone, TPO, BAPO and others). Compared with the
resin cements composition, the major difference is found in the type of monomers (less viscous) and in the amount of filler, giving to the resin cement less viscosity, better flow, but lower mechanical properties. Thus, due to this great versatility of the composites, application techniques appeared that could try to aggregate the flow properties of the resin cements with the mechanical properties of the restorative composites. The most known technique is called thermoplastic technique, where the regular-consistency composite becomes less viscous when heated due to increased agitation of the molecules, providing sufficient viscosity for the fixation of indirect restorations, similarly to the resin cements. Thus, it is expected that this heated composite can be used as a cementing agent without losing its mechanical strength properties (Magne et al. 2011).
A conventional composite would not allow the correct seating of an indirect restoration, leading to a very thick film of material and, consequent misadaptation. Then, the thermoplastic technique would reduce the viscosity of composite by increasing its temperature (Lucey et al. 2010). It is not known, however, whether using a conventional composite for cementation would increase the bond strength between restorative material and substrate or would affect its mechanical and rheological properties. Another unknown fact is that if the photoinitiator most used in composite resins, camphorquinone, along with its co-initiator, a tertiary amine, would not be affected by the increase in temperature. Therewith, their maintenance of color could be affected and interfere in the color of the indirect restorations after their fixation (Schneider et al. 2009).
There are no studies comparing the color changing of composite resins when they are heated and used as a fixation agent of ceramic veneers, as well as, the influence of the ceramic veneer thickness on the color changing. Another point of great importance is to determine the film thickness of regular composite after heating in order to verify if there is change in the flow to permit the correct setting of ceramic veneers. It is also necessary to verify the influence of temperature and light attenuation on the degree of conversion and to evaluate if there is an improvement in the mechanical properties of the fixation agent. Thus, the objectives of this study were: 1) to evaluate the film thickness of experimental composites with different viscosities (flowable, conventional and conventional pre-heated); 2) to evaluate the degree of conversion,
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bond strength and color change of experimental composites with different viscosities (flowable, conventional and conventional pre-heated), photoactivated trough ceramic veneers with different thicknesses. The hypotheses tested were: 1) the filler content and composite heating would influence the film thickness; 2) the filler content and the composite heating would influence the degree of conversion; 3) the filler content and the composite heating would influence the bond strength to enamel; 4) the filler content and the composite heating would influence color change after accelerated artificial aging; 5) the thickness of ceramic veneers would influence the degree of conversion, bond strength and color change of composites with different viscosities (flowable, conventional and conventional pre-heated).
2. MATERIAL AND METHODS
2.1 Material
Experimental composite resins:
All composite resins were prepared with the same monomeric matrix: Bis-GMA (29%wt - Sigma Aldrich, St. Louis, MO, USA), UDMA (32.5wt% - Sigma Aldrich), Bis-EMA (32.5wt% - Sigma Aldrich) and TEGDMA (6wt% - Sigma Aldrich). The amount of filler particle was different; 65wt% in conventional composite (20wt% fumed silica – 0.05 μm [Nippon Aerosil Co. Ltd., Yokkaichi, Tokyo, Japan] and 80wt% of BaBSiO2 glass - 0.7 μm [Esstech Inc., Essington, PA, USA]) and 50wt% in flowable
composite (20wt% of fumed silica – 0.05 μm [Nippon Aerosil] and 80wt% of BaBSiO2 glass - 0.7 μm [Esstech Inc]). Camphorquinone (0.25wt% - Sigma Aldrich) and ethyl-4-dimethylamino benzoate (0.50wt% - Sigma Aldrich) were used as the photo-initiator system and 2,6-bis(1,1-dimethylethyl)-4-methylphenol (0.01wt%- Sigma Aldrich) as the photo-polymerization inhibitor. The composite resins were divided into 3 groups, according to the consistency at the moment of use: C-Conventional, CPH-Conventional Pre-Heated and, F-flowable. In conventional and flowable consistency, the composites were used at environment temperature and, in conventional pre-heated consistency the composite was heated at 60ºC for viscosity reduction. All experimental composite resins
were packaged in plastic container wrapped in black insulation tape to protect the material from light. All samples preparation and testing procedures were carried out at controlled temperature (25 ± 2 °C) and humidity (50 ± 5%). The heating of the conventional composite was done in an apparatus (ThermoSmart, AstoriLab, Poncarale, BS, Italy) suitable for composite resins and placed in dosing syringes.
Ceramic veneers preparation.
Ninety three ceramic disc-shaped specimens with 7.5 mm in diameter (31 with 0.4 mm, 31 with 0.8 mm and 31 with 1.5 mm in thickness) were prepared using IPS e.max Press ceramic system (Ivoclar Vivadent, Schaan, Liechtenstein), shade HT A1, following the manufacturer’s instructions. These 31 ceramic discs-shaped simulating veneers restorations in each group were divided into 3 subgroups (n = 10), according to the composite resin used (C, CPH and F). One surface of these discs was polished and other etched with 10% hydrofluoric acid to simulate the clinical conditions.
2.2 - Film thickness (FT).
The film thickness (n=10) was performed according to ISO 4049-2009 specification, where the thickness of 2 overlapping glass plates is measured four times before the insertion of the composite resin between the glass plates. The temperature of the glass plates was standardized at 37 °C to simulate the oral conditions. A standardized volume of each composite (0.10 mL) was placed between the two glass plates and a load of 150N was applied on the top plate for 90 sec. The photo-activation was done through the glass plate (Bluephase G2, Ivoclar-Vivadent – 1,200 mW/cm2) for 20 sec. Four measurements of the new thickness (lower plate + composite resin + upper plate) was done. The difference between the average of these measurements and the initial one was considered the film thickness achieved by each material.
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Ninety enamel blocks (10x10mm) from bovine incisors were embedded in acrylic resin (Classico, Sao Paulo, SP, Brazil) into polyvinyl chloride tubes and wet-polished with 400- and 600-grit silicon carbide abrasive papers (Buehler, Lake Buff, IL, USA) to obtain flat enamel surfaces. The embedded enamel specimens were divided in 9 groups (n=10), according the composite resin and ceramic veneer thickness used. For all groups, the enamel surface was etched with 35% phosphoric acid gel (3M/ESPE, St.Paul, MN, USA), rinsed, dried and one coat of Scotchbond Multipurpose adhesive (3M/ESPE) was applied following the manufacturer’s instructions. Before the light-activation, translucent Tygon tubings (0.9 mm internal diameter x 0.5 mm in height) – three per each enamel block specimen – were positioned onto the enamel surface and used as molds (Figure 1-A). The adhesive material was light-cured for 10 seconds using a curing unit (Bluephase G2, Ivoclar-Vivadent, Liechtenstein – 1,200 mW/cm2) and the respective experimental composite resin was carefully inserted with a snap-fit syringe and 20-gauge needle tubes (Centrix Corp, Shelton, CT, USA) into the Tygon tubes lumen. After filling all three Tygon tubing molds, the experimental composite resins were light-cured for 20 s, through the respective ceramic veneer disc (0.4, 0.8 or 1.5 mm in thickness) fixed on the output region of the curing light tip (Fig. 1-B).
Figure 1 – A – Schematic illustration of specimen´s preparation and; B – photoactivation through ceramic disc; C - Steel wire looped around the composite resin cylinder for µSBS test.
A B C
A B C
Ligth curing tip
Ceramic disc (0.4, 0.8 or 1.5mm) Tygon tube
Composite resin Enamel block
The specimens were stored in distilled water for 24 h at 37oC and the three Tygon tubes of each specimen were removed using a scalpel blade to expose the composite resin. Stereomicroscope (model SMZ-1B, Nikon, Japan) at 30x magnification was used to confirm that none of the cylinders presented defects or flaws at the bonding area. The PVC tube was positioned in a µSBS device and was properly fixed to a mechanical testing machine (Instron, model 4411, Canton, MA, USA) and a thin steel wire (0.3 mm in diameter) was looped around the base of each cylinder and aligned with the bonding interface (Fig. 1- C). Each cylinder was submitted to a crosshead speed of 0.5 mm/min until failure. The mean of three cylinders of each specimen was considered as the mean of each specimen (n=10) for statistical analysis. The debonded interfaces were examined under stereomicroscope (model SMZ-1B, Nikon) at 30x magnification and the failures were classified as: adhesive, cohesive within enamel, cohesive within resin and mixed (involving enamel/adhesive/Resin).
2.4 – Degree of conversion (DC).
For the degree of conversion (DC) analysis of the experimental resin composite, 5 circular specimens per group, with 6 mm diameter x 1,0 mm thickness, were made in rubber molds and photo-activated for 20s. This light-curing was done using a ceramic disc with each thickness (0.4, 0.8 and 1.5 mm) fixed on the output region of the curing light tip. After polymerization, the specimens were removed from the molds and dry stored in light-proof containers at 37ºC, for 72 h. DC was measured on the top surface of each specimen using RAMAN spectroscopy (XploRA , Horiba, Kyoto, Japan) The absorption spectra of non-polymerized and polymerized composites were obtained from the region between 4000 and 650 cm−1 with 32 scans at 4 cm−1. The aliphatic carbon-carbon double-bond absorbance peak intensity (located at 1638 cm–1) and that of the aromatic (C–C) (located at 1608 cm–1; reference peak) were collected. The DC was calculated using the following equation: DC = 100 × [1 − (R polymerized/R non-polymerized)], where R represents the ratio between the absorbance peak at 1638 cm−1 and 1608 cm−1.
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To measure color change, 10 specimens from each group were made. Placing 0.05 mL of resin on polyester strip and inserting the ceramic veneer on the cement with the treated face facing the cement, 150 N of pressure were applied, excess removed and photoactivated (Bluephase G2, Ivoclar-Vivadent - 1,200 mW / cm2) through the outer face. The surface in contact to ceramic veneer was etched with 10% hydrofluoric acid (Dentsply Industria e Comercio Ltda., Petropolis, RJ, Brazil) for 20 sec, washed, dried and a silane (Prosil, FGM, Brazil) layer was applied. CIELab co-ordinates (L, a, b) were recorded for each experimental composite pre- and immediately post- UV-light aging by means of a spectrophotometer (Vita EasyShade Advanced, VITA Zahnfabrik, Bad Säckingen, Baden-Württemberg, Germany) with a D65 illuminant. A white (L=14.9; a=2.1; b=9.0) paper was used as background for the color analysis. After the initial color measurements, all samples were UV-light aged for 120 hours using only the UV-B cycle exposure at 37oC, similar to that proposed in ISO 7491 (2000). To standardize the UV-light exposure, the specimens were placed at 10cm distance from the UV-light (UV-B 313, Equilam, Diadema, SP, Brazil).4
To evaluate color change, ΔE00 of each specimen was calculated using the
following CIEDE2000 formula17: ∆𝐸00= [( ∆𝐿 𝑘𝐿𝑆𝑆𝐿) 2 + ( ∆𝐶 𝑘𝐶𝑆𝐶) 2 + ( ∆𝐻 𝑘𝐻𝑆𝐻) 2 + 𝑅𝑇( ∆𝐶 𝑘𝐶𝑆𝐶) ( ∆𝐻 𝑘𝐻𝑆𝐻)] 0.5
, where ∆L, ∆C and ∆H are the differences in lightness, chroma and hue, and RT is a
function (the so-called rotation function) that accounts for the interaction between chroma and hue differences in the blue region. The weighting functions, SL, SC, and SH
are used to adjust the total color difference for variation in the location of the color difference pair in the L, a and b coordinates. The parametric factors KL, KC, and KH, are
correction terms for the experimental conditions, which were set to 1.
2.6 - Statistical analysis.
Power analysis was conducted to determine sample size for each experiment to provide a power of at least 0.8 at a significance level of 0.5 (=0.2). The FT data for each experimental composite resin were analyzed by one-way ANOVA and Tukey’s test for pairwise comparisons. The factor considered was composite in three levels (C,
CPH and F). The DC, µSBS and CC data were analyzed by two-way ANOVA and Tukey’s test for multiple comparisons. The two factors analyzed were composite in three levels (C, CPH, and F) and the ceramic thickness in three levels (0.4 mm, 0.8 mm and 1.5 mm).
3.0 - RESULTS
3.1 - Film Thickness
The one-way ANOVA showed significant effect of the experimental resin composites on the film thickness (p=0.00163). The results for the Tukey’s test and the means of film thickness are shown in Table 1. C showed film thickness significantly higher than F composite. There was no difference between conventional pre-heated and flowable composites.
Table 1. Film thickness (mm ± standard deviation) of the experimental resin composites.
Composite Thickness (mm)
C 0.056 ±0.009 a
CPH 0.053 ±0.007 ab
F 0.047 ±0.006 b
Means followed by same small letter in the column are not statistically different at 5%, by Tukey’s test. 3.2 – Micro-shear bond strength
Table 2 shows the microshear bond strength (µSBS) means and standard deviations for all experimental resin composites photoactivated through ceramic veneers with different thicknesses. The two-way ANOVA demonstrated that composite (p=0.24560) and ceramic thickness (p=0.09855) factors were not significant, as well as the interaction between these factors (p=0.97403). The thickness of the ceramic discs did not reduce the uSBS means regardless of the composite used. The experimental composites did not differ from themselves, regardless of ceramic veneer thickness.
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Table 2. Microshear bond strength means (MPa ± standard deviation) for experimental resin composites light-cured through ceramic veneers with different thicknesses. Composite Ceramic veneer thickness
0.4mm 0.8mm 1.5mm Pooling mean
F 35.64 ± 6.88 32.92 ± 7.39 32.01 ± 8.40 33.52 ± 7.48 a
C 37.05 ± 11.24 34.76 ± 11.63 31.64 ± 10.89 34.48 ± 11.09 a
CPH 41.28 ± 5.80 35.81 ± 9.47 35.09 ± 8.22 37.39 ± 8.19 a
Pooling mean 37.99 ± 8.38 A 34.50 ± 9.39 A 32.91 ± 9.06 A
Means followed by same small letter in the same column and capital letter in row, are not statistically different at 5%, by Tukey´s test.
Figure 2 shows that for all groups with flowable composites (0.4 mm, 0.7 mm and 1.5 mm thickness ceramic veneers) the mixed failures were prevalent. For conventional composites groups (heated or not and with 0.4 mm, 0.7 mm or 1.5 mm thickness ceramic veneers), there were similar percentages of adhesive and mixed failures.
Figure 2. Failure pattern analysis of the debonded specimens (%).
3.3 – Degree of conversion 0 20 40 60 80 100 F/1,5 F/0,8 F/0,4 CPH/1,5 CPH8 CPH/0,4 C/1,5 C/0,8 C/0,4
Failure classification (%)
Table 3 shows the degree of conversion (%) means and standard deviations for all experimental resin composites photoactivated through ceramic veneers with different thicknesses. The two-way ANOVA demonstrated that composite (p=0.00075) and ceramic thickness (p=0.00019) factors were significant, but not the interaction between them (p=0.26510). The experimental composite photo-activated througth 0.4mm ceramic veneers showed higher degree of conversion when compared to 1.5mm veneers. The composite photo-activated throught 0.8mm ceramic veneers presented intermidiate mean and did not differ from the others ceramic thicknesses. The F composite presented the best degree of conversion when compared to C and CPH.
Table 3. Conversion of degree means (% ± standard deviation) for experimental resin composites light-cured through ceramic veneers with different thicknesses.
Composite Ceramic veneer thickness Pooling mean
0.4mm 0.8mm 1.5mm
F 82.99 ± 2.22 80.43 ± 1.60 77.88 ± 2.98 80.43 ± 3.06 a
C 78.66 ± 1.11 78.13 ± 1.67 76.97 ± 3.16 77.92 ± 2.13 b
CPH 80.11 ± 1.44 76.23 ± 1.24 75.55 ± 2.31 77.29 ± 2.62 b
Pooling mean 80.59 ± 2.41 A 78.26 ± 0.58 AB 76.80 ± 2.81 B
Means followed by same small letter in the column and capital letter in row, are not statistically different at 5%, by Tukey’s test.
3.4 – Color changing
Table 4 shows the color changing (∆E00) means and standard deviations for all
experimental resin composites photoactivated through ceramic veneers with different thicknesses. The two-way ANOVA demonstrated that composite (p=0.00001) and ceramic thickness (p=0.02642) factors were significant, but not the interaction between them (p=0.63675). The experimental composite photo-activated througth 0.4mm ceramic veneers showed the highest ∆E00 mean and differed from 1.5mm ceramic
veneers. The composite photo-activated throught 0.8mm ceramic veneers presented intermidiate ∆E00 mean and did not differ from the others ceramic thicknesses. The C
composite presented the highest ∆E00 and differed from C and CPH, that did not differ
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Table 4. Color changing means (∆E00 ± standard deviation) for experimental resin
composites light-cured through ceramic veneers with different thicknesses.
Material Ceramic veneer thickness
0.4mm 0.8mm 1.5mm Pooling mean
F 1.19 ± 0.80 1.16 ± 0.11 1.13 ± 0.15 1.16 ± 0.46 b
C 2.33 ± 0.70 1.98 ± 0.75 1.82 ± 0.12 2.04 ± 0.61 a
CPH 1.80 ± 0.71 1.46 ± 0.43 1.28 ± 0.15 1.51 ± 0.52 b
Pooling mean 1.77 ± 0.85 A 1.53 ± 0.59 AB 1.41 ± 0.33 B
Means followed by same small letter in the column and capital letter in row, are not statistically different at 5%, by Tukey’s test.
DISCUSSION.
The first hypothesis that the filler content and composite heating would affect the film thickness was rejected. The film thickness formed in this study was not affected by the composite heating, but the filler content affected the film thickness. This result corroborates with those obtained by Blalock et al. (2006) who observed that heating did not produce a reduction in film thickness (Blalock et al. 2006). However, in this study the heating gave the conventional composite similar film thickness to the flowable composite. Film thickness is an important factor when cementing indirect restorations. Higher film thicknesses may lead to the maladaptation of these restorations and also, due to the greater amount of material to be polymerized, greater volumetric contraction would make the cementation more susceptible to failure (Sampaio et al. 2017). The lower film thickness in a conventional composite that has been heated probably occurs by the increased agitation of molecules and mass plasticization of unpolymerized material, which increases flow (Lucey et al. 2010). The influence of the filler content was evidenced because there was a significant difference between the conventional and flowable composites film thicknesses. Since the composites had the same polymer matrix, the higher amount of fillers in the conventional composite gave higher viscosity and, consequently, higher film thickness.
Regarding the degree of conversion analysis, the second hypothesis that the filler content and the composite heating would influence the degree of conversion was
rejected. There was a statistical difference between the conventional composites with higher filler content and the flowable composite. The higher content of filler particles in the composites of conventional consistency may have reflected part of the incident light and, consequently, less degree of conversion. In addition, the higher molecular mobility in the early stages of the polymerization reaction in the flowable composite may have also contributed favorable to the conversion of the polymer network into formation. However, the heating of the conventional composite did not produce statistical difference in comparison to the conventional composite that was not heated. This result does not corroborate with the results of Daronch et al., who demonstrated that there was a higher degree of conversion for preheated composites. They stated that when the composite is preheated, there is a greater shock of molecules coming from the greater molecular agitation (Daronch et al. 2005). However, Lohbauer et al., promoted a similar study where they measured the degree of conversion at different times (5 minutes after photoactivation and 24 hours after photoactivation) and the results affirm that after 24 hours this difference between degree of conversion tends to fall and potentially become null over time (Lohbauer et al. 2009). In this study, an interval of 72 hours was waited between the time of photoactivation and measurement of the degree of conversion. Thus, perhaps this explains the fact that there was no difference between heated and unheated composites.
In this study, the bond strength of the experimental composites to the micro-shear on the bovine enamel was not affected neither by the composite heating nor by the amount of filler. Then, the third hypothesis that the filler content and the composite heating would influence the bond strength to enamel was rejected. Demirbuga et al. found different results from this study when they checked the bond strength of heated composites. They used commercial composites based on silorane and methacrylate, in addition to having used dentin as a dental substrate. In this case, they found a significant improvement in bond strength when the composites were heated to 68°C. They credited this improvement to the greater flow and adaptation of the composite to the dental surface (Demirbuga et al.). In this study, neither the effect of heating nor the filler content on the experimental composites were evident. This may be due to the good adaptation achieved with the experimental composites, since most of the failures were of the mixed type or there was a balance between adhesive and mixed.
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Both the heating and the filler particle content influenced the color change of the experimental composites. Therefore, the fourth hypothesis that the filler content and the composite heating would influence color change after accelerated artificial aging was accepted. Conventional composite pre-heating decreased both ΔE00 when
compared to the non-heated composite. The explanation for this may be related to the initial degradation of the tertiary amine by heating, thus creating higher energy states. These molecules with a high degree of excitation can react with oxygen, other aromatic groups or small organic molecules, which can be incorporated during the manipulation of the material (Stansbury 2000). From these reactions, color centers are formed, also called chromophores, which increase the absorption of visible light, particularly in the blue region of the electromagnetic spectrum, causing the yellowing of the material (Cheung e Darvell 2002).
On the other hand, the amount of fillers also changed the color stability of the composites. The highest color change was observed for the conventional composite with more filler particles in comparison to the flowable composite. Studies published by De Oliveira et al. (2006) and Fróes-Salgado et al. (2010) also observed that the higher the amount of filler, the greater the color change of the composites. The greater the amount of filler in a composite, the greater the light reflection and the greater its attenuation during photoactivation (de Oliveira et al. 2016)(Fróes-Salgado et al. 2010). This was observed in this study where the degree of conversion was lower in the composites with greater amount of filler. Accordingly, the greater the amount of unreacted monomers and amines, which will be degraded after UV accelerated artificial aging. In addition, in the composites with greater amount of filler, the photons from the aging in UV would have greater effect on the polymeric matrix of the composites, since the surface area of the specimens was the same.
Regarding the effect of ceramic venner thickness, it was observed that the thickness influenced the degree of conversion and the ΔE00 but did not influence the
bond strength. Then, the fifth hypothesis that the ceramic veneers thickness would influence the degree of conversion, bond strength and color change of the composites was partially rejected. Probably, the progressive attenuation of the light between the different ceramic thicknesses was responsible for the greater degree of conversion of the composites polymerized under the veneers of 0.4mm thickness in relation to the
composites polymerized under veneers of 1.5mm thickness. However, the 0.8mm thick veneers did not influence the degree of composite conversion. However, the reduction in the degree of conversion did not reflect the results of the bond strength test, where there was no difference between the thicknesses of the ceramic veneers. Probably, in the composite groups where the thickness of the ceramics was 1.5mm, the lower degree of conversion did not influence its adhesive properties.
Regarding the color change of the composites, the veneers thickness influenced the ΔE00. This result can be related to the greater thickness of the ceramic
veneer, which makes it more difficult to observe the color change of the composites. However, for the overall color change (ΔE00), it was possible to observe that for the
ceramic veneers of 0.4mm thick, the color change was higher than ceramic veneers of 1.5mm thick.
In view of all the hypotheses, it seems evident that there are advantages and disadvantages of using the thermoplastic technique. For clinical implications, it is up to the clinic dentist to choose the way to perform his rehabilitations taking into account factors not applicable in laboratory tests such as technical skill, clinical experience and availability of material and equipment.
CONCLUSION
The composite resins presented similar values for the evaluated parameters, except for the higher degree of conversion seen in the flowable composite resin; however, this higher degree of conversion did not result in an improvement in microshear bond strength. Thus, composite resins confirm their versatility with potential for good clinical performance if used for ceramic veneers fixatation, even with 1.5 mm thick, when the thermoplastic technique is used.
31
REFERENCES
Azer SS, Rosenstiel SF, Seghi RR, Johnston WM. Effect of substrate shades on the color of ceramic laminate veneers. J. Prosthet. Dent. 2011;106(3):179–83.
Blalock JS, Holmes RG, Rueggeberg FA. Effect of temperature on unpolymerized composite resin film thickness. J. Prosthet. Dent. 2006;96(6):424–32.
Cheung KC, Darvell BW. Sintering of dental porcelain: effect of time and temperature on appearance and porosity. Dent. Mater. 2002;18(2):163–73.
Daronch M, Rueggeberg FA, De Goes MF. Monomer conversion of pre-heated composite. J. Dent. Res. 2005;84(7):663–7.
Demirbuga S, Ucar FI, Cayabatmaz M, Zorba YO, Cantekin K, Topçuoğlu HS, et al. Microshear bond strength of preheated silorane- and methacrylate-based composite resins to dentin. Scanning. 38(1):63–9.
Fróes-Salgado NR, Silva LM, Kawano Y, Francci C, Reis A, Loguercio AD. Composite pre-heating: Effects on marginal adaptation, degree of conversion and mechanical properties. Dent. Mater. 2010;26(9):908–14.
Gaengler P, Hoyer I, Montag R, Gaebler P. Micromorphological evaluation of posterior composite restorations - a 10-year report. J. Oral Rehabil. 2004;31(10):991–1000. Ilie N, Hilton TJ, Heintze SD, Hickel R, Watts DC, Silikas N, et al. Academy of Dental Materials guidance-Resin composites: Part I-Mechanical properties. Dent. Mater. 2017;33(8):880–94.
Larson TD. 25 years of veneering: what have we learned? Northwest Dent. 82(4):35–9. Lohbauer U, Zinelis S, Rahiotis C, Petschelt A, Eliades G. The effect of resin composite pre-heating on monomer conversion and polymerization shrinkage. Dent. Mater. 2009;25(4):514–9.
Lucey S, Lynch CD, Ray NJ, Burke FM, Hannigan A. Effect of pre-heating on the viscosity and microhardness of a resin composite. J. Oral Rehabil. 2010;37(4):278–82. Magne P, Paranhos MPG, Burnett LH, Magne M, Belser UC. Fatigue resistance and failure mode of novel-design anterior single-tooth implant restorations: influence of material selection for type III veneers bonded to zirconia abutments. Clin. Oral Implants Res. 2011;22(2):195–200.
de Oliveira DCRS, de Menezes LR, Gatti A, Correr Sobrinho L, Ferracane JL, Sinhoreti MAC. Effect of Nanofiller Loading on Cure Efficiency and Potential Color Change of Model Composites. J. Esthet. Restor. Dent. 2016;28(3):171–7.
Sampaio CS, Barbosa JM, Cáceres E, Rigo LC, Coelho PG, Bonfante EA, et al. Volumetric shrinkage and film thickness of cementation materials for veneers: An in vitro 3D microcomputed tomography analysis. J. Prosthet. Dent. 2017;117(6):784–91. Schneider LFJ, Cavalcante LM, Consani S, Ferracane JL. Effect of co-initiator ratio on the polymer properties of experimental resin composites formulated with camphorquinone and phenyl-propanedione. Dent. Mater. 2009;25(3):369–75.
Stansbury JW. Curing dental resins and composites by photopolymerization. J. Esthet. Dent. 2000;12(6):300–8.
Wakiaga J, Brunton P, Silikas N, Glenny AM. Direct versus indirect veneer restorations for intrinsic dental stains. Cochrane database Syst. Rev. 2004;(1):CD004347.
33
3 CONCLUSÃO
As resinas compostas experimentais apresentaram valores similares para os parâmetros avaliados, com exceção do grau de conversão que foi superior nas resinas compostas flowable; no entanto, este maior grau de conversão não resultou em melhora na resistência ao microcisalhamento do compósito. Assim, as resinas compostas confirmaram sua versatilidade com potencial para bom desempenho clínico caso sejam utilizadas para cimentação de peças protéticas de até mesmo 1,5 mm de espessura, quando utilizada a técnica de termoplastificação.
REFERÊNCIAS*
Azer SS, Rosenstiel SF, Seghi RR, Johnston WM. Effect of substrate shades on the color of ceramic laminate veneers. J. Prosthet. Dent. 2011;106(3):179–83.
Blalock JS, Holmes RG, Rueggeberg FA. Effect of temperature on unpolymerized composite resin film thickness. J. Prosthet. Dent. 2006;96(6):424–32.
Cheung KC, Darvell BW. Sintering of dental porcelain: effect of time and temperature on appearance and porosity. Dent. Mater. 2002;18(2):163–73.
Daronch M, Rueggeberg FA, De Goes MF. Monomer conversion of pre-heated composite. J. Dent. Res. 2005;84(7):663–7.
Demirbuga S, Ucar FI, Cayabatmaz M, Zorba YO, Cantekin K, Topçuoğlu HS, et al. Microshear bond strength of preheated silorane- and methacrylate-based composite resins to dentin. Scanning. 38(1):63–9.
Fróes-Salgado NR, Silva LM, Kawano Y, Francci C, Reis A, Loguercio AD. Composite pre-heating: Effects on marginal adaptation, degree of conversion and mechanical properties. Dent. Mater. 2010;26(9):908–14.
Gaengler P, Hoyer I, Montag R, Gaebler P. Micromorphological evaluation of posterior composite restorations - a 10-year report. J. Oral Rehabil. 2004;31(10):991–1000. Ilie N, Hilton TJ, Heintze SD, Hickel R, Watts DC, Silikas N, et al. Academy of Dental Materials guidance-Resin composites: Part I-Mechanical properties. Dent. Mater. 2017;33(8):880–94.
Larson TD. 25 years of veneering: what have we learned? Northwest Dent. 82(4):35–9.
* De acordo com as normas da UNICAMP/FOP, baseadas na padronização do
International Committee of Medical Journal Editors - Vancouver Group. Abreviatura dos periódicos em conformidade com o PubMed.
35
Lohbauer U, Zinelis S, Rahiotis C, Petschelt A, Eliades G. The effect of resin composite pre-heating on monomer conversion and polymerization shrinkage. Dent. Mater. 2009;25(4):514–9.
Lucey S, Lynch CD, Ray NJ, Burke FM, Hannigan A. Effect of pre-heating on the viscosity and microhardness of a resin composite. J. Oral Rehabil. 2010;37(4):278–82. Magne P, Paranhos MPG, Burnett LH, Magne M, Belser UC. Fatigue resistance and failure mode of novel-design anterior single-tooth implant restorations: influence of material selection for type III veneers bonded to zirconia abutments. Clin. Oral Implants Res. 2011;22(2):195–200.
de Oliveira DCRS, de Menezes LR, Gatti A, Correr Sobrinho L, Ferracane JL, Sinhoreti MAC. Effect of Nanofiller Loading on Cure Efficiency and Potential Color Change of Model Composites. J. Esthet. Restor. Dent. 2016;28(3):171–7.
Sampaio CS, Barbosa JM, Cáceres E, Rigo LC, Coelho PG, Bonfante EA, et al. Volumetric shrinkage and film thickness of cementation materials for veneers: An in vitro 3D microcomputed tomography analysis. J. Prosthet. Dent. 2017;117(6):784–91. Schneider LFJ, Cavalcante LM, Consani S, Ferracane JL. Effect of co-initiator ratio on the polymer properties of experimental resin composites formulated with camphorquinone and phenyl-propanedione. Dent. Mater. 2009;25(3):369–75.
Stansbury JW. Curing dental resins and composites by photopolymerization. J. Esthet. Dent. 2000;12(6):300–8.
Wakiaga J, Brunton P, Silikas N, Glenny AM. Direct versus indirect veneer restorations for intrinsic dental stains. Cochrane database Syst. Rev. 2004;(1):CD004347.
APÊNDICE 1
Metodologia ilustrada.
Figura 1. Frasco contendo o material experimental envolto com fita isolante para evitar contato de luz.
Figura 2. ThermoSmart- Aquecedor de resina composta termo-ajustável.
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Figura 4. Fita adesiva utilizada para fixar a faceta cerâmica na ponta ativa do fotopolimerizador.
Figura 5. Ponta ativa do fotopolimerizador com a faceta cerâmica fixada.
Figura 7. Esquema ilustrativo de microcisalhamento por fio ortodôntico.
Figura 8. Desenho esquemático do aparato usado no ensaio de espessura de película (ISO 4049-2009).
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Figura 10. Aparelho Easyshade (Vita). )
Figura 11. Ponta do aparelho Easyshade tocando a faceta para mensuração de cor.
