UNIVERSIDADE FEDERAL FLUMINENSE FACULDADE DE ODONTOLOGIA
ESTABILIDADE DE COR DE RESINAS BISACRÍLICAS
Niterói
UNIVERSIDADE FEDERAL FLUMINENSE FACULDADE DE ODONTOLOGIA
ESTABILIDADE DE COR DE RESINAS BISACRÍLICAS
KARIN EGGER
Dissertação apresentada à Faculdade de Odontologia da Universidade Federal Fluminense, como parte dos requisitos para obtenção do título de Mestre, pelo Programa de Pós-Graduação em Odontologia.
Área de Concentração: Clínica Odontológica
Orientador: Prof. Dr. Raphael Vieira Monte Alto
Niterói 2017
FICHA CATALOGRÁFICA
E28 Egger, Karin
Estabilidade de cor de resinas bisacrílicas / Karin Egger; orientador: Prof. Raphael Vieira Monte Alto. – Niterói: [s.n.], 2017. 34 f.: il.
Dissertação (Mestrado em Clínica Odontológica) – Universidade Federal Fluminense, 2017.
Bibliografia: f. 32 -33.
1. Restaurações provisórias. 2. Resina bisacrílica. 3. Estabilidade de cor. I. Alto, Raphael Vieira Monte [orient.] II. Título.
BANCA EXAMINADORA
Prof. Dr. Raphael Vieira Monte Alto
Instituição: Faculdade de Odontologia da Universidade Federal Fluminense Decisão: _________________________
Assinatura: ________________________________________________________ Prof. Dr. Gustavo Oliveira dos Santos
Instituição: Faculdade de Odontologia da Universidade Federal Fluminense Decisão: _________________________
Assinatura: ________________________________________________________
Prof. Dr. Leandro de Moura Martins
Instituição: Faculdade de Odontologia da Universidade Federal do Amazonas Decisão: _________________________
DEDICATÓRIA
Aos meus pais, Annick e Gerhard, por serem aqueles que sempre estiveram ao meu lado em todos os momentos me apoiando e incentivando a seguir sempre em frente.
A minha Zu, pelo amor e amizade mais sinceros que conheci na vida. Aos meus amigos, e aos meus professores, pelo apoio, confiança e motivação.
AGRADECIMENTOS
A Deus, por estar presente a todo momento guiando meus passos; Aos meus pais e a Zuleide, por todo incentivo e por me proporcionarem absolutamente tudo que precisei durante esse projeto; Ao meu Orientador prof. Raphael Vieira Monte Alto, pela confiança e por todo
suporte; Ao professor Gustavo Oliveira dos Santos, pela amizade e pelos ensinamentos compartilhados até hoje. Ao professor Leandro de Moura Martins pela paciência, por me ajudar em todos os momentos que precisei e pela estatística realizada; A Fernanda Hang e toda equipe do laboratório de qualidade da Coltene, em especial ao João de Souza Nascimento, por todo suporte para execução da pesquisa; Ao Mario Groisman e toda equipe da Mario Groisman Odontologia por entenderem
as minhas ausências durante este período; A Helda Barcellos, por toda amizade e suporte; A Renata Paranhos Millioni e Monique Solon de Mello pelos momentos de
descontração, de trabalho e de desafios, que dividimos; Ao Wagner Neves, por todo amor, paciência e dedicação, estando ao meu lado em
todos os momentos; Por fim, mas não menos importante, ao amigo Raphael Vieira Monte Alto, que antes de orientador, foi o amigo mais dedicado, maior incentivador e o grande responsável por todo o meu amor pela vida acadêmica. Muito obrigada.
RESUMO
Egger K. ESTABILIDADE DE COR DAS RESINAS BISACRÍLICAS. [dissertação]. Niterói: Universidade Federal Fluminense, Faculdade de Odontologia; 2017.
Objetivo: Avaliar a estabilidade de cor de cinco resinas bisacrílicas
autopolimerizáveis após 24 horas de imersão em café e manchamento nestas superfícies. Metodologia: Cem espécimes (19,85mm x 1,0 mm) de cinco resinas bisacrílicas autopolimerizáveis comerciais foram divididas em dois grupos. Controle: 10 espécimes de cada marca comercial foram confeccionados e armazenados individualmente por 24 horas em água destilada a 37º C. Café: 10 espécimes de cada marca comercial foram confeccionados e armazenados, individualmente, no café por 24 horas a 37ºC. Após a confecção de cada espécime, cada um foi
numerado e a cor foi avaliada num espectrofotômetro pelo método CIELab antes da imersão nas soluções de cada grupo. 24 horas após imersão todos os espécimes foram novamente avaliados e a mudança de cor (ΔE) foi calculada. Resultados: Os dados de alteração de cor mostraram que, quando armazenados em água,
Luxatemp, Structor e Protemp sofreram uma mudança de cor discreta, sendo Structor 3 estatisticamente igual ao Cooltemp que junto com Yprov obtiveram a maior alteração de cor. Quando armazenados em café Luxatemp e Structor 3 foram estatisticamente semelhantes e obtiveram as menores médias, bem como Protemp embora também tenha sido estatisticamente igual ao Yprov que junto com Cooltemp sofreram maior alteração de cor. Conclusão: O presente estudo demonstrou que todas as marcas comerciais testadas sofreram grande alteração de cor e se demonstraram clinicamente insatisfatórias quanto a estabilidade de cor, embora estatisticamente tenham obtido resultados diferentes entre si.
ABSTRACT
Egger K. COLOR STABILITY OF BIS-ACRYL RESINS [dissertation]. Niterói: Universidade Federal Fluminense, Faculdade de Odontologia; 2017.
Purpose: To evaluate the color stability of five self-cured bis-acryl resins after 24 hours of coffee immersion and staining on these surfaces. Material and methods: One hundred specimens (19.85mm x 1.0mm) of five commercial self-curing bisacrylic resins were divided into two groups. Control: 10 specimens of each trademark were prepared and stored individually for 24 hours in distilled water at 37º C. Coffee: 10 specimens of each commercial brand were prepared and stored individually in the coffee for 24 hours at 37ºC. After making each specimen, each was numbered and the color was evaluated in a spectrophotometer by the CIELab system before immersion in the solutions of each group. 24 hours after immersion all specimens were retested and the color change (ΔE) was calculated. Results: The color change data showed that when stored in water, Luxatemp, Structor and Protemp underwent a discrete color change, with Structor 3 being statistically equal to Cooltemp, which together with Yprov obtained the higher color changes. When stored in coffee
Luxatemp and Structor 3 were statistically similar and obtained the lowest averages, as well as Protemp although it was also statistically equal to Yprov that along with Cooltemp suffered higher color changes.
Conclusion: The present study demonstrated that all of the trademarks tested have undergone major color changes and have shown to be clinically unsatisfactory as to color stability, although statistically different results were obtained.
1 - INTRODUÇÃO
A evolução da odontologia reabilitadora tem caminhado para tratamentos cada vez mais conservadores e materiais que possibilitam ser minimamente invasivo quando falamos em reabilitação estética. A escolha de um tratamento reabilitador estético com restaurações cerâmicas envolvem várias etapas, entre elas a fase de restauração provisória, que deverá desempenhar importantes funções para manutenção das características biológicas, estéticas e funcionais prévias à instalação da prótese definitiva.
É muito importante que as restaurações temporárias desempenhem funções básicas como proteção pulpar, restabelecimento da oclusão, preservação do preparo dental e das estruturas periodontais, estética, fonética, bem como fornecer informações diagnósticas e servir de guia para a restauração definitiva. O material ideal para confecção das restaurações temporárias deve ser facilmente manipulado, não tóxico, com pouca contração de polimerização e esteticamente aceitável. Bem como apresentar propriedades mecânicas como resistência ao desgaste, dureza superficial, adaptação marginal, possibilidade de reparo e polimento.1,2
Atualmente, com os avanços tecnológicos e desenvolvimento de novos materiais odontológicos bem como com a necessidade de menor desgaste das estruturas dentárias, as resinas bisacrílicas ganharam espaço e assumiram vantagens em relação a outros materiais restauradores provisórios já consagrados na clínica diária, em função da sua facilidade de manipulação, por serem autopolimerizáveis de presa rápida e principalmente por sua estética superior. 3,4
As resinas bisacrílicas foram introduzidas no mercado odontológico com a intenção de complementar algumas características das resinas acrílicas, principalmente as de PMMA, apresentando características superiores incluindo dureza, resistência à flexão e módulo de elasticidade.5 No entanto, uma vez que são
feitos de monômeros de dimetacrilato, as resinas compostas bisacrílicas são altamente reticuladas e tendem a ser mais frágeis do que as resinas de PMMA com base em monometacrilato, que compreendem moléculas lineares de cadeia longa com propriedades de reticulação intermoleculares mínimas. Sua composição de
resina orgânica, cargas inorgânicas e monômeros, confere as características de resistência e estética semelhantes às resinas compostas.6,7,8,9
A alteração de cor de restaurações provisórias pode ser um problema estético, especialmente quando é necessário um tempo maior de utilização dessas restaurações. Embora o uso de estabilizadores tenha diminuído quimicamente tais alterações, essas restaurações são propensas à absorção de líquidos, de modo que os pigmentos contidos neles podem produzir facilmente alterações de cor.10
Assim, o presente estudo se deu para avaliar a estabilidade de cor de cinco diferentes marcas comerciais de resinas bisacrílicas quando armazenadas em café após 24 horas.
2 - METODOLOGIA
2.1 Material
Cinco marcas comerciais de resinas bisacrílicas, na cor A2, foram selecionadas para esse estudo in vitro (Tabela 1).
Tabela 1
Produto Marca Comercial Lote
Luxatemp Star DMG 740693
Protemp 4 3MESPE 635117
CoolTemp Coltene H11305
Structor 3 Voco 1622243
Yprov Bisacryl Yller 2324
Para a confecção dos espécimes foi utilizada uma matriz esférica em aço inoxidável medindo 19,85mm de diâmetro interno / 38,10mm de diâmetro externo / 1,0mm de altura (Figura 1) que é a espessura máxima obtida em preparos minimamente invasivos para facetas.1 Também foram utilizadas 2 placas de vidro retangulares para cada matriz (Figura 2), com diâmetro suficiente para cobrir a área das matrizes metálicas em seus dois lados; tiras de poliéster com espessura de até 50 30 μm (Figura 3).
Figura 1
Figura 2
2.2. Método
PREPARAÇÃO DOS ESPÉCIMES
Vinte espécimes foram confeccionados de cada uma das cinco marcas de resina bisacrílica totalizando cem discos. Então foram criados dois grupos, controle (n=10) e teste (n=10) para cada resina (Tabela 2).
Tabela 2
Produto Grupo Controle
– água destilada Grupo Teste - café Luxatemp Star 10 10 Protemp 4 10 10 CoolTemp 10 10 Structor 3 10 10 Yprov Bisacryl 10 10
Para confeccionar cada espécime, foram posicionados os materiais na seguinte ordem: placa de vidro, tira de poliéster, matriz metálica (seguido da inserção da resina bisacrilica na matriz), tira de poliéster, e a segunda placa de vidro para espalhar o material na matriz e planificar a superfície (Figura 4). Cada resina bisacrílica foi inserida na matriz com a sua ponta de automistura e utilizando uma pistola. Após a inserção do material na matriz, foi aguardado o tempo de presa do material de acordo com cada fabricante. Nenhum procedimento de polimento foi realizado sobre a superfície dos discos para simular os passos clínicos de uma técnica de fabricação direta de restaurações provisórias. Após a completa polimerização apenas os excessos de material que extravasaram para fora da matriz (Figura 5) foram removidos com auxilio de uma espátula.
AVALIAÇÃO DA COR
Todos os espécimes de cada grupo foram numerados de 1 a 10 e foram avaliados com um espectrofotômetro (X-rite sp60) pelo sistema CIELab. Após as medições de cor, cada disco foi armazenado individualmente em sacos plásticos (Figura 6), sendo identificados quanto ao produto e grupo, e cobertos com água destilada (grupo controle) ou café (grupo teste) e estocados numa estufa a 37ºC por 24 horas (Figura 7).2 O tempo médio de consumo de 1 xícara de café é de 15 minutos e o consumo médio de café é de 3,2 xícaras por dia. Portanto, o tempo de armazenamento de 24 horas simula o consumo da bebida em um mês.11 Após 24 horas nas soluções, os espécimes foram lavados com água destilada e secados com papel antes da medição de cor pelo mesmo operador. A diferença de cor total entre as 2 posições (após 24 horas de armazenamento nos dois grupos) no espaço de cores tridimensional (3D) L * a * b * foi calculada como um único número, ∆E. ΔE, conhecida como a distância euclidiana entre dois pontos num espaço de cores Figura 4
tridimensional, foi calculada a partir dos valores médios de ΔL *, Δa * e Δb * utilizando a seguinte fórmula:
∆E* = [(L1*−L0*)2 + (a1*−a0*)2 + (b1*−b0*)2]1/2
Os dados de alteração de cor foram avaliados estatisticamente pelo teste de normalidade Shapiro-Wilk. Após esta verificação foi aplicado o teste estatístico não-paramétrico Kruskal Wallis e teste de Dunn para comparação de médias, considerando os fatores sob estudo, com um nível de significância de 5%. A mudança de cor foi quantificada clinicamente pelo National Bureau of Standards (NBS), que avalia a maneira como o olho humano avalia uma mudança de cor
Figura 6
(Tabela 3). A fórmula utilizada para esta conversão é NBS unidade = × 0,92. Os valores médios de todos os espécimes foram convertidos em unidades NBS para revelar se as alterações de cor dos grupos estudados eram clinicamente detectáveis.
Tabela 3
Unidade NBS Observações críticas de diferenças de
cor
0.0-0.5 Excessivamente pouca mudança
0.5-1.5 Pouca: pouca mudança
1.5-3 Perceptível: mudança perceptível
3-6 Apreciável: mudança proeminente
6-12 Muito: mudança excessivamente
acentuada
3 - ARTIGOS PRODUZIDOS
COLOR STABILITY OF BIS-ACRYL RESINS
Karin Egger,MSc student*
Raphael Vieira Monte Alto, Adjunct professor
*Corresponding author: Karin Egger – Rua Bandeira do Sul 67 anil - Rio de Janeiro – RJ – Brazil. Zip code: 22750-400 Phone: 55 21 24476971 - Mobile: 55 21 998145530 - e-mail: kaa.egger@gmail,.com
ABSTRACT
Egger K. COLOR STABILITY OF BIS-ACRYL RESINS [dissertation]. Niterói: Universidade Federal Fluminense, Faculdade de Odontologia; 2017.
Purpose: To evaluate the color stability of five self-cured bis-acryl resins after 24 hours of coffee immersion and staining on these surfaces. Material and methods: One hundred specimens (19.85mm x 1.0mm) of five commercial self-curing bisacrylic resins were divided into two groups. Control: 10 specimens of each trademark were prepared and stored individually for 24 hours in distilled water at 37º C. Coffee: 10 specimens of each commercial brand were prepared and stored individually in the coffee for 24 hours at 37ºC. After making each specimen, each was numbered and the color was evaluated in a spectrophotometer by the CIELab system before immersion in the solutions of each group. 24 hours after immersion all specimens were retested and the color change (ΔE) was calculated. Results: The color change data showed that when stored in water, Luxatemp, Structor and Protemp underwent a discrete color change, with Structor 3 being statistically equal to Cooltemp, which together with Yprov obtained the higher color changes. When stored in coffee
Luxatemp and Structor 3 were statistically similar and obtained the lowest averages, as well as Protemp although it was also statistically equal to Yprov that along with Cooltemp suffered higher color changes.
Conclusion: The present study demonstrated that all of the trademarks tested have undergone major color changes and have shown to be clinically unsatisfactory as to color stability, although statistically different results were obtained.
1 - INTRODUCTION
The evolution of rehabilitation dentistry has been moving towards increasingly conservative treatments and materials that make it possible to be minimally invasive when we talk about aesthetic rehabilitation. The choice of aesthetic restorative treatment with ceramic restorations involves several stages, among them the temporary restoration phase, which should perform important functions to maintain the biological, aesthetic and functional characteristics prior to the installation of the final prosthesis.
It is very important that temporary restorations perform basic functions such as pulp protection, restoration of occlusion, preservation of dental preparation and periodontal structures, aesthetics, phonetics, as well as provide diagnostic information and guide the final restoration. The ideal material for making the temporary restorations should be easily manipulated, non-toxic, with little contraction of polymerization and aesthetically acceptable. As well as presenting mechanical properties such as wear resistance, surface hardness, marginal adaptation, possibility of repair and polishing.1,2
Nowadays, with the technological advances and development of new dental materials as well as the need for less wear and tear of the dental structures, the bis-acryl resins have gained space and have taken advantages over other temporary restorative materials already consecrated in the daily clinic, due to their ease use because they are self-cured fast prey and mainly because of their superior aesthetics. 3,4
The bisacrylic resins were introduced in the dental market with the intention of complementing some characteristics of the acrylic resins, especially those of PMMA, presenting superior characteristics including hardness, flexural strength and modulus of elasticity.5 However, since they are made of monomers of Dimethacrylate, bis-acrylic resins are highly crosslinked and tend to be more brittle than monomethacrylate based PMMA resins which comprise long chain linear molecules with minimal intermolecular crosslinking properties. Its composition of organic resin, inorganic loads and monomers, confers the characteristics of resistance and esthetics similar to the composite resins.6,7,8,9
Changing the color of temporary restorations can be an aesthetic problem, especially when a longer time of use of these restorations is required. Although the use of stabilizers has chemically reduced such changes, such restorations are prone to absorption of liquids, so that the pigments contained therein can easily produce color changes.10
The present study was conducted to evaluate the color stability of five different brands of bisacryl resins when stored in coffee after 24 hours.
2 - MATERIALS AND METHODS 2.1 Material
Five commercial brands of bis-acrylic resins, in color A2, were selected for this in vitro study (Table 1).
Table 1
Product Manufacturer Batch No.
Luxatemp Star DMG 740693
Protemp 4 3MESPE 635117
CoolTemp Coltene H11305
Structor 3 Voco 1622243
Yprov Bisacryl Yller 2324
For the preparation of the specimens a spherical matrix was made in stainless steel measuring 19.85 mm internal diameter / 38.10 mm external diameter / 1.0 mm high (Figure 1) which is the maximum thickness obtained in minimally invasive preparations for facets. 1 Two rectangular glass plates were also used for each matrix (Figure 2), with a diameter sufficient to cover the area of the metal matrices on its two sides; Polyester strips of the same diameter as the glass plate up to (50 30) μm (Figure 3).
Figure 2
2.2. Method
PREPARATION OF SPECIMENS
Twenty specimens were made from each of the five brands of bisacrylic resin totaling one hundred disks. Two groups were created, control (n = 10) and test (n = 10) for each resin (Table 2).
Figure 1
Table 2
Product Control Group
– distilled water Test Group - coffee Luxatemp Star 10 10 Protemp 4 10 10 CoolTemp 10 10 Structor 3 10 10 Yprov Bisacryl 10 10
To make each specimen, the materials were positioned in the following order: glass plate, polyester strip, metal matrix (followed by the insertion of the bisacrylic resin in the matrix), polyester strip, and the second glass plate to spread the material in the matrix and plan the surface (Figure 4). Each bisacrylic resin was inserted into the matrix with its self-mixing tip and using a gun. After insertion of the material, the holding time of curing of the material was expected according to each manufacturer‘s recomendation. No polishing procedure was performed on the surface of the disks to simulate the clinical steps of a direct fabrication technique of temporary restorations. Only the excesses of material that had leaked out of the matrix were removed with the aid of a spatula.
COLOR ASSESSMENT
All specimens from each group were numbered from 1 to 10 and evaluated using a spectrophotometer (X-rite sp60) by the CIELab system. After color measurements, each disk was stored individually in plastic bags and covered with distilled water (control group) or coffee (test group) and stored in an oven at 37 ° C for 24 hours.2 After 24 hours in the solutions, the specimens were washed with distilled water for 5 minutes and dried with paper before the color measurement by the same operator. The total color difference between the 2 positions (after 24 hours storage in the two groups) in the three-dimensional (3D) color space L * a * b * was calculated as a single number, ΔE. ∆E, known as the Euclidean distance between two points in a three-dimensional color space, was calculated from the mean values of ∆L*, ∆a*, and ∆b* using the following formula:
∆E* = [(L1*−L0*)2 + (a1*−a0*)2 + (b1*−b0*)2]1/2
Figure 6 Figure 5
The color change data were statistically evaluated using the Shapiro-Wilk normality test. After this verification, Kruskal Wallis non-parametric statistical test and Dunn's test for comparison of means were applied, considering the factors under study, with a significance level of 5%. The color change was quantified by the National Bureau of Standards (NBS), which rates the way the human eye evaluates a color change (Table 3). The formula used for this conversion is NBS unit = × 0.92. The mean values of all specimens were converted to NBS units to reveal whether the color changes of the studied groups were clinically detectable.
Table 3
NBS Units Critical Remarks of Color Differences
0.0-0.5 Excessively mere change
0.5-1.5 Mere: Mere change
1.5-3 Noticeable: Perceivable change
3-6 Appreciable: Prominent change
6-12 Much: Excessively marked change
12 or more Very much: Change to other color
3 - RESULTS
The color change data presented a non-normal distribution in the Shapiro-Wilk test and after the application of the Kruskal Wallis non-parametric statistical test and the Dunn test for comparison of means, considering the factors under study, with a significance level of 5 %, it was possible to understand that by evaluating the 5 different materials, when stored in water, they underwent a discrete color change, where Luxatemp, Structor and Protemp were the ones that less altered their color and were statistically the same, despite numerically the structural resin 3 bisacrylic resin (Voco - Germany) have a value of almost double the value of the other two resins becoming, according to the standard deviation, statistically equal to Cooltemp.
The two resins that had the most color change when kept in distilled water for 24 hours were Cooltemp and Yprov, which were statistically the same (Table 1).
Water Group Mean (SD) Luxatemp Star 0,429 (0,164) a Protemp 4 0,432 (0,343) a Structor 3 0,852 (0,229) ab Cooltemp 1,778 (0,450) bc Yprov 3,190 (0,383) c Table 1
In the materials that were stored in coffee we found the following color changes: Luxatemp and Structor 3 were statistically similar and obtained the lowest means of color change, as well as Protemp which obtained a mean similar to these 2 groups although based on a high standard deviation, which shows a great variation among the specimens, was also statistically equal to Yprov, which was considered along with Cooltemp the materials that suffered the greatest color change (Table 2).
Coffee Group Mean (SD) Luxatemp Star 10,645 (1,016) a Structor 3 12,403 (2,688) a Protemp 4 14,684 (3,079) ac Yprov 23,169 (5,738) bc Cooltemp 25,808 (0,721) b Table 2
The color change was quantified by the National Bureau of Standards (NBS), which assesses how the human eye evaluates a color change (Table 3). The formula used for this conversion is the unit NBS = × 0.92. The mean values of all specimens were converted to NBS units to reveal whether the color changes of the groups studied were clinically detectable.
NBS Unit Critical Remarks of Color Differences
0.0-0.5 Excessively mere change
0.5-1.5 Mere: Mere change
1.5-3 Noticeable: Perceivable change
3-6 Appreciable: Prominent change
6-12 Much: Excessively marked change
12 ou mais Very much: Change to other color
Table 3
In this way it was possible to observe that, clinically, the Luxatemp and Protemp resins underwent a very subtle color change when stored in distilled water, whereas Structor 3 was classified a level above the scale but still with little color change, with the three resins still no clinical perception of change. The Cooltemp and Yprov resins, even when stored in water, already presented a clinically visible color change (Table 4).
Water Group NBS Unit Luxatemp Star 0,394 Protemp 4 0,397 Structor 3 0,783 Cooltemp 1,635 Yprov 2,934 Table 4
The groups that were stored in coffee, obviously presented greater color changes in relation to the control groups, where Luxatemp and Structor 3 were the ones that underwent the least changes and were classified as excessively marked change, whereas Cooltemp Yprov and Protemp obtained the worst performances and the its clinically visible color changes may be classified as having changed to another color on the scale (Table 5).
Coffee Group NBS Uit Luxatemp Star 9,793 Structor 3 11,410 Protemp 4 13,509 Yprov 23,743 Cooltemp 21,316 Table 5
4 - DISCUSSION
The perception of color by the visual evaluation of objects is a subjective, physiological and psychological process that varies from person to person. This variability is the result of several factors, including the observed object and the position of the enlightenment in relation to the observer and between them, color characteristics of the light emitted on the object, metamerism as well as factors inherent to the observer such as fatigue, aging and emotional state. Instrumental colorimetry could potentially eliminate the subjective errors of color evaluation since trichromatic colorimeters are accurate for the in vitro measurement of color and color differences.10 In this way, the use of spectrophotometers and colorimeters that have
standardized illumination integrated and supposedly unaffected by ambient light allow a non-subjective assessment of color variations.12,13
The standardization of the choice of a single color, A2, for each sample of the respective trade marks was due to the fact that in natural teeth, possibly the A2 color of the Vita scale would be the most prevalent in the population and the most used. Once the specimens of each resin were made, although all were of the A2 color, it is possible that we perceive a color difference between them both in the visual method and through the use of the spectrophotometer found by obtaining the values of L * a * b *.
According to the CIE-Lab system recommended by the American Dental Association, all colors in nature are obtained by mixing three basic colors: red, blue and green. The photometric and colorimetric instruments measure the color that the values are expressed in three coordinates (L *, a *, b *) where L * represents the brightness of the object, varying between black (0) and white (100), a * varies between red and green chrome and b * for yellow or blue chroma. Using the spectrophotometer to evaluate such co-ordinates of each of the specimens of the respective trade marks, it was possible to evaluate that each of them has very different proportions of L * a * b * for the same color A2, which may be an important factor to different color change results.14
Coincidentally, the resins that suffered the greatest coffee staining were those that had a higher L * value in the control group, and it is important to note that the L * coordinate, which represents the luminosity, is the one that the human eye perceives most clearly. that the amount of cells (rods) responsible for black and white vision is much larger than that of the cells responsible for color vision (cones). 15 Thus, there was a clinically perception of greater luminosity, that is, the value of L * was closer to 100, while the less pigmented resins, Luxatemp and Structor 3, had a lower L * value
in the control group. All resins had their L * values decreased after exposure to coffee, but Protemp, Cooltemp and Yprov had a greater difference in relation to the control.
Furthermore, in this study it was possible to notice that the bisacrylic resins with lower color stability were the Yprov and Cooltemp resins both when stored in water and in coffee. Both had statistically and clinically inferior results in relation to the other resins in both groups, although the Structor resin showed a statistically similar result when stored in water but better when stored in coffee. The Protemp resin also showed a lower result similar to the first two when stored in the coffee although it was satisfactory when stored in water.
Although statistically Protemp, Cooltemp and Yprov showed worse performance with regard to staining and color stability than the others, all resins had clinically unsatisfactory results. In the present study, coffee was used due to its high potential for staining.16 Coffee pigmentation may have occurred through the absorption and adsorption of polar dyes on the organic phase of the resins.10,17,18
The chemical properties of the materials, the stability of the pigments, the polarity of the monomers, the effectiveness of the initiator system, the amount of filler and the amount of crosslinked structure are important factors in the degree of polymerization, water sorption and color stability. Most of the bisacrylic polymers are more polar because they have a greater affinity for water and other polar liquids. Thus, differences in the amount of charge, amount of crosslinked structure and thus sorption of water were the unknown parameters that may have affected the color results of the bisacryl resins.11,19
There is controversy in the literature on the effect of water absorption on the color stability of the bisacrylic resins. Sham et al20 described bisacrylic resins as more color stable compared to methyl / ethyl methacrylate resins as a result of lower water absorption when temporary restorations were used for long periods. Additional studies were recommended to validate this result, as the water absorption capacity of the acrylic resins increases due to the presence of unreacted monomers by the inclusion of air during the manual manipulation of the material. The bisacrylic resins are compounds that have the advantage of self-mixing through the use of a compatible gun and mixing tips, recommended by each manufacturer, which in
theory minimizes air entrainment and should decrease porosities by also decreasing the amount of unpolymerized monomers. Such a characteristic would be responsible for the decrease of the amount of sorption of water and thus increasing the color stability.21
In this study the hypothesis was raised of the possibility of the base / catalyst ratio having influenced the result of the variations of, although it was not conclusive. The Luxatemp and Protemp resins have a 10: 1 self-mixing ratio while Structor 3, Cooltemp and Yprov have this ratio of 2: 1. Based on the result obtained there is a tendency that the 2: 1 ratio may interfere with color stability, since 2 of the 3 materials that had the worst result, Cooltemp and Yprov, have this mixing ratio. In order to guarantee a greater certainty of this data, it is necessary to study more about this characteristic as well as to know more specifically the proportions of the chemical components present in the base and catalyst pulps, in order to better correlate if there is relation of the composition of the material with the proportions of self-mixing. In addition, the early pigmentation of the materials is known to be associated with the finishing, polishing and hence the roughness of the surfaces.19,22,23,24,25 In this study, no additional procedure was performed after the complete polymerization of the material . Some studies have reported that resin matrices with larger filler particles would result in surface irregularities, causing a color difference.24,25 Possibly, there is a difference in the size and quantity of these particles in each of the different trademarks, which may justify the different values of, and a new study finishing and polishing after the polymerization of these materials can present better results regarding color stability.
It is important to emphasize the impossibility of establishing the exact correlation between the in vitro and in vivo tests, since the oral environment can not be reproduced in the laboratory, and the restorative materials are never subjected to the pigments for such a long period of time, taking into account that patients are advised to maintain good oral hygiene, to remove bacterial plaque and also to remove extrinsic stains from food. Despite this, according to the present study, moderation is recommended when eating foods that are very colored during the provisional stage, since all the resins tested had clinically unsatisfactory results.
5- CONCLUSIONS
Based on the methodology applied, on the conditions of experience and in accordance with the proposal, it is concluded that:
1) When stored in water, Luxatemp and Protemp4 have little color change and are almost imperceptible clinically. Followed by Structor 3 which also has little variation. Cooltemp and Yprov vary more and have noticeable variation.
2) When stored in the coffee, Luxatemp and Structor 3 showed a little better, although they change excessively marked. Protemp 4, Cooltemp and Yprov presents, inferior result to the others having, clinically, greater instability of color.
3) All of the trademarks tested underwent major color changes and were clinically unsatisfactory as to color stability, although statistically different results were obtained.
ACKNOWLEDGMENTS
6- REFERENCES
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MA. Flexural strength of interim crown and fixed partial denture resins. J Prosthet Dent 2002;87:225-8.
8) Lang R, Rosentritt M, Behr M, Handel G. Fracture resistance of PMMA and resin matrix composite-based interim FPD materials. Int J Prosthodont 2003;16:381-4. 9) Kerby, Ronald E. ; Knobloch, Lisa A. ; Sharples, Stanley ; Peregrina, Alejandro. Mechanical properties of urethane and bis-acryl interim resin materials. The Journal of Prosthetic Dentistry, July 2013, Vol.110(1)
10) Yannikakis SA, Zissis AJ, Polyzois GL, Caroni C. Color stability of provisional resin restorative materials. J Prosthet Dent 1998;80:533-9.
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12)Paul SJ, Peter A, Rodoni L, Pietrobon N. Conventional visual vs spectrophotometric shade taking for porcelain-fused- to-metal crowns: a clinical comparison. Int J Periodontics Restorative Dent 2004; 24: 222-231.
13) Horn DJ, Bulan-Brady J, Hicks ML. Sphere spectrophotometer versus human evaluation of tooth shade. J Endod 1998; 24: 786-790.
14) Okubo, Scott R. ; Kanawati, Ali ; Richards, Mark W. ; Childress, Steve. Evaluation of visual and instrument shade matching. The Journal of Prosthetic Dentistry, December 1998, Vol.80(6), pp.642-648
15) Samra APB, Pereia SK, Delgado LC, Borges CP. Color stability evaluation of aesthetic restorative materials. Braz Oral Res 2008;22:205-10.
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17) Bayindir F, Kürklü D, Yanikog!lu ND. The effect of staining solutions on the color stability of provisional prosthodontic materials. J Dent 2012;40:41-6. 18) Doray PG, Li D, Powers J. Color stability of provisional restorative materials after accelerated aging. J Prosthodont 2001;10:212-6.
19) Köroğlu, Aysegül ; Sahin, Onur ; Dede, Doğu Ömür ; Yilmaz, Burak. Effect of different surface treatment methods on the surface roughness and color stability of interim prosthodontic materials. The Journal of Prosthetic Dentistry, April 2016, Vol.115(4), pp.447-455
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4 - CONCLUSÕES
Com base na metodologia aplicada, nas condições experimentais e em conformidade com a proposição, conclui-se que:
1) Quando armazenadas em água, Luxatemp e Protemp4 possuem pouca alteração de cor , sendo quase que imperceptível clinicamente. Seguida por Structor 3 que também tem pouca variação. Cooltemp e Yprov variam mais e possuem variação perceptível.
2) Quando armazenadas em café, Luxatemp e Structor 3 se mostraram um pouco melhores, embora apresentem mudança excessivamente acentuada. Protemp 4, Cooltemp e Yprov apresenta, resultado inferior as demais tendo, clinicamente, maior instabilidade de cor.
3) Todas as marcas comerciais testadas sofreram grande alteração de cor e se demonstraram clinicamente insatisfatórias quanto a estabilidade de cor, embora estatisticamente tenham obtido resultados diferentes entre si.
