ALAN RODRIGO MUNIZ PALIALOL

INFLUÊNCIA DO PROTOCOLO ADESIVO NAS PROPRIEDADES FÍSICO-QUÍMICAS E RESISTÊNCIA DE UNIÃO À CERÂMICA DE CIMENTOS

RESINOSOS EXPERIMENTAIS CONTENDO SISTEMA FOTOINICIADOR TERNÁRIO

INFLUENCE OF ADHESIVE PROTOCOL ON PHYSICOCHEMICAL PROPERTIES AND CERAMIC BOND STRENGTH OF EXPERIMENTAL

RESIN CEMENTS CONTAINING TERNARY PHOTOINITIATOR SYSTEM

Piracicaba

2017

UNIVERSIDADE ESTADUAL DE CAMPINAS

FACULDADE DE ODONTOLOGIA DE PIRACICABA

INFLUÊNCIA DO PROTOCOLO ADESIVO NAS PROPRIEDADES FÍSICO-QUÍMICAS E RESISTÊNCIA DE UNIÃO À CERÂMICA DE CIMENTOS

RESINOSOS EXPERIMENTAIS CONTENDO SISTEMA FOTOINICIADOR TERNÁRIO

INFLUENCE OF ADHESIVE PROTOCOL ON PHYSICOCHEMICAL PROPERTIES AND CERAMIC BOND STRENGTH OF EXPERIMENTAL

RESIN CEMENTS CONTAINING TERNARY PHOTOINITIATOR SYSTEM

Tese apresentada à Faculdade de Odontologia de Piracicaba,

da Universidade Estadual de Campinas, como parte dos

requisitos exigidos para obtenção do Título de Doutor em

Clínica Odontológica, Área de Concentração em Dentística.

Thesis presented to the Piracicaba Dental School of the

University of Campinas in partial fulfillment of the

requirements for the degree of Doctor in Clinical Dentistry,

in Restorative Dentistry area.

Orientador: Profa. Dra. Giselle Maria Marchi Baron ESTE EXEMPLAR CORRESPONDE À VERSÃO

FINAL DA TESE DE DOUTORADO DEFENDIDA

PELO ALUNO ALAN RODRIGO MUNIZ PALIALOL,

ORIENTADO PELA PROFA. DRA. GISELLE MARIA

MARCHI BARON.

Piracicaba

2017

ALAN RODRIGO MUNIZ PALIALOL

Agência(s) de fomento e nº(s) de processo(s): FAPESP, 2014/02898-7

Ficha catalográficaUniversidade Estadual de Campinas

Biblioteca da Faculdade de Odontologia de PiracicabaMarilene Girello - CRB 8/6159

Palialol, Alan Rodrigo Muniz, 1984- P176i PalInfluência do protocolo adesivo nas propriedades físico-químicas e

resistência de união à cerâmica de cimentos resinosos experimentais contendosistema fotoiniciador ternário / Alan Rodrigo Muniz Palialol. – Piracicaba, SP :[s.n.], 2017.

PalOrientador: Giselle Maria Marchi Baron. PalTese (doutorado) – Universidade Estadual de Campinas, Faculdade de

Odontologia de Piracicaba.

Pal1. Cerâmica. 2. Cimentos de resina. 3. Adesivos. 4. Fotopolimerização. I.

Marchi, Giselle Maria,1970-. II. Universidade Estadual de Campinas. Faculdadede Odontologia de Piracicaba. III. Título.

Informações para Biblioteca Digital

Título em outro idioma: Influence of adhesive protocol on physicochemical properties andceramic bond strength of experimental resin cements containing ternary photoinitiatorsystemPalavras-chave em inglês:CeramicResin cementsAdhesivesPhotopolymerizationÁrea de concentração: DentísticaTitulação: Doutor em Clínica OdontológicaBanca examinadora:Giselle Maria Marchi Baron [Orientador]Rafael Pino VittiWilliam Cunha BrandtVanessa Cavalli GobboLuis Roberto Marcondes MartinsData de defesa: 23-02-2017Programa de Pós-Graduação: Clínica Odontológica

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DEDICATÓRIA

Dedico este trabalho ao meu pai Antônio, à minha mãe Rosimeiri, ao meu

irmão Thiago e à toda minha família pelo apoio, amor e compreensão durante toda esta

jornada.

AGRADECIMENTOS ESPECIAIS

A Deus, por estar sempre presente iluminando minha vida, guiando meus

passos e me dando força para seguir em frente.

Aos meus avós João, Maria, Antônio e Yolanda pela torcida, apoio, amor e

carinho mesmo estando ausente na maior parte do tempo.

A todos os familiares que sempre torceram e incentivaram minha caminhada

nessa jornada. Obrigado pelo apoio!

Ao irmão crossfitero que Piracicaba me deu, Diogo Dressano e sua família.

Só tenho a agradecer pela parceria e palavras de incentivo e apoio nos momentos bons e

ruins. Meu muito obrigado! Tamo junto mlk!

Aos amigos e parceiros de pesquisa Adriano Lima e Luciano Gonçalves,

pela parceria, paciência, ensinamentos e convivência que se estende até hoje! Muito

obrigado!

À minha orientadora Profa. Giselle Maria Marchi Baron, exemplo de

pessoa e profissional a ser seguido. Serei sempre grato pelas oportunidades, pela

confiança no meu trabalho, pelos ensinamentos acadêmicos e conselhos na vida pessoal.

Sinto orgulho de ter sido seu orientado! Muito obrigado!

AGRADECIMENTOS

À direção da Faculdade de Odontologia de Piracicaba da Universidade

Estadual de Campinas, na pessoa do Diretor Prof. Dr. Guilherme Elias Pessanha

Henriques e do Diretor Associado Prof. Dr. Francisco Haiter Neto.

Ao Conselho Nacional de Desenvolvimento Científico e Tecnológico

(CNPq), pelo auxílio financeiro na concessão de bolsa e à Fundação de Amparo à

Pesquisa do Estado de São Paulo (FAPESP), pela concessão de bolsa de Doutorado

(2014/02898-7) e de Estágio e Pesquisa no Exterior (2014/23317-2) que possibilitaram a

realização desse trabalho.

À Coordenadoria Geral da Pós-Graduação da FOP/UNICAMP, em

nome da Profa. Dra. Cinthia Correia Machado Tabchoury, do secretário Leandro

Viganó e da secretária Alessandra Pinho Sinhoreti, por toda atenção.

À minha Supervisora durante estágio de pesquisa no exterior (2015) na

Oregon Health and Science University, Profa. Dra. Carmem Silvia Pfeifer, uma pessoa

ímpar, outro exemplo a ser seguido! Obrigado pelos desafios que me fizeram crescer, por

toda atenção, paciência e ensinamentos transmitidos com a maior boa vontade e

dedicação.

Aos professores da Oregon Health and Science University, Prof. Dr. Jack

Ferracane e Prof. Dr. Luiz E. Bertassoni pelos ensinamentos e convivência durante o

estágio de pesquisa no exterior.

Aos Profs. Flavio Henrique Baggio Aguiar, Fernanda Miori Pascon e

Anderson Catelan pelas sugestões e idéias que colaboraram para o enriquecimento desse

trabalho no exame de qualificação.

Aos Profs. Luis Roberto Marcondes Martins, Vanessa Cavalli, Rafael

Pino Vitti e William Cunha Brandt pelas correções, sugestões e idéias que colaboraram

para o enriquecimento desse trabalho na defesa de Tese.

Aos Profs. Luis Roberto Marcondes Martins, Flávio Henrique Baggio

Aguiar, Larissa Sgarbosa de Araújo Matuda e Anderson Catelan pelo aceite do

convite para membro suplente durante os exames de qualificação e defesa de tese.

Aos Profs. Da Área de Dentística, Profa. Dra. Giselle Maria Marchi Baron,

Profa. Dra. Débora Alves Nunes Leite Lima, Profa. Dra. Vanessa Cavalli, Prof. Dr.

Flávio Henrique Baggio Aguiar, Prof. Dr. Marcelo Giannini, Prof. Dr. Luis

Alexandre Maffei Sartini Paulillo, Prof. Dr. Luis Roberto Marcondes Martins, Prof.

Dr. José Roberto Lovadino, pelos conhecimentos transmitidos na área clínica e

acadêmica que contribuíram para o meu crescimento profissional.

Aos amigos de pós-graduação Ailla Lancellotti, Maria Beatriz D’Arce,

Maria Humel, Ciça, Hugo, Anderson Catelan, Livia Aguilera, Larissa Sgarbosa,

Kamila Andrade, Juliana Públio, Felipe Nogueira Anacleto, Bruno Vilela Muniz,

Thais Mageste, pela convivência e por tornar os dias mais agradáveis.

Aos amigos de República durante a graduação, Guilherme Ramos Costa,

Vitor Hugo, Leonardo Filizzola, Anderson de Souza, Fernando Domingos, Rafael

Kinouti, Fabrício Fonseca, pela convivência, parceria e amizade acima de tudo!

Aos amigos de República durante a pós-graduação, Adriano Lima, Lucas

Moura, Armando Kaieda, Leonardo Santos e Anderson Catelan pela convivência nas

horas boas e difíceis e por tornar mais fácil a vida longe da minha família. Muito obrigado

pela parceria e amizade!

Aos amigos que a FOP me deu na graduação e continuam presentes até hoje

Thatiana de Vicente Leite, Daniel Sunfeld e Diogo Silva. Obrigado pela convivência e

amizade.

Aos colegas de mestrado e doutorado deste e de outros programas.

À funcionária da Área de Dentística Mônica, pela convivência e por se

mostrar sempre solícitas e prestativa quando precisei.

Ao Engenheiro Mecânico Marcos Blanco Cangiani, sempre solícito e pronto

para ajudar na hora do aperto.

Ao Biólogo e técnico do setor de Microscopia Eletrônica de Varredura

Adriano Martins pela ajuda e auxílio quando precisei.

Ao protético Carlos Donato pela comprometimento e colaboração com este

trabalho.

A todos os funcionários da limpeza por tornarem o ambiente de trabalho

limpo e agradável para todos.

À Suha (in memoriam) pelo companheirismo, fidelidade e proteção,

conquistados com muito esforço e persistência, devido o seu valor.

RESUMO

No presente estudo foi avaliado a influência do protocolo adesivo nas propriedades físico-

químicas e resistência de união (RU) à cerâmica de cimentos resinosos experimentais

(CREs) contendo um sistema fotoiniciador ternário. Foram preparados cinco formulações

de CREs contendo como base os monômeros Bis-GMA e TEGDMA (na proporção 1:1

em massa). O sistema fotoiniciador foi composto por 1 mol% de canforoquinona, 2 mol%

de amina terciária 2-(dimetilamino) etil metacrilato e diferentes concentrações do sal

hexafluorofosfato de difeniliodôno (DFI): 0; 0,25; 0,5; 1 e 2 mol%, definindo assim, cinco

formulações de CREs. Como inibidor, foi acrescido à mistura 0,1 mol% de hidroxitolueno

butilado e 60% em peso de partículas silanizadas de vidro de bário-alumínio-silicato

foram incorporadas como carga inorgânica. Diante disso, dez grupos foram estabelecidos

de modo que metade foi confeccionado sem a mistura com adesivo Adper Scotchbond

Multi-Purpose - bond (G1 – G5) e a outra metade com a mistura de 3 µl de adesivo (G6

- G10). A fotoativação, para todos os testes, foi realizada através de um bloco de cerâmica

IPS e.max com LED Bluephase G2 a 1265.5 mW/cm2 por 60 segundos. Para o teste de

RU foram confeccionados setenta espécimes de cerâmica IPS e.max (n=7; 10 mm x 10

mm x 3 mm). Os espécimes foram cimentados em blocos de resina fotopolimerizável

Filtek Z250 (10 mm x 10 mm x 5 mm). Após armazenamento em estufa por 24 horas a

37oC, as amostras foram seccionadas para obtenção de palitos (25 a 30 por bloco). Metade

dos palitos de cada bloco foram submetidos ao ensaio de microtração imediato em

máquina de ensaio universal EMIC (velocidade de 0,5 mm/min). A outra metade foi

separada para o teste de microtração após armazenamento em água destilada pelo período

de um ano. Foi realizado análise do padrão de fratura em lupa estereoscópica (Leica

MZ75). Adicionalmente, foi avaliado a resistência coesiva (RC) dos CREs (n=10),

cinética de polimerização e grau de conversão (GC) em espectrômetro de infravermelho

transformado de Fourier (FTIR) (n=5) e teste de sorção e solubilidade (SS) (n=5). Os

dados foram analisados através do teste de análise de variância (medidas repetidas para

RU e 2 fatores para os demais testes) e teste Tukey, a um nível de significância de 5%.

Para os valores de RU, não houve diferença estatísitca entre os grupos, tanto no tempo

imediato quanto após o armazenamento (p>0,05). Da mesma forma, não houve diferença

estatística entre os tempos imediato e após armazenamento (p>0,05). O grupo 0 mol%

DFI apresentou os maiores valores de solubilidade e os menores valores para GC e RC

(p<0,05). Os demais grupos apresentaram valores semelhantes entre si (p>0,05). A adição

do adesivo aumentou os valores de GC apenas para o grupo 0 mol% DFI (p<0,05). A

adição do sal DFI melhorou a reatividade e as propriedades físico-químicas dos CREs,

porém, não foi capaz de aumentar a RU à cerâmica. O uso do adesivo não exerceu

influência nas propriedades físico-químicas dos CREs contendo sal de DFI. O

armazenamento em água destilada por um ano não reduziu a RU à cerâmica.

Palavras-chave: Cerâmica. Cimento resinoso. Adesivo. Hexafluorofosfato de

difeniliodônio.

ABSTRACT

The present study evaluated the influence of an adhesive protocol on physicochemical

properties and ceramic bond strength (BS) of experimental resin cements (ERCs)

containing a ternary photoinitiator system. For this purpose, five ERCs were prepared

using a Bis-GMA/TEGDMA (1:1 molar ratio) base compound. The photoinitiator system

was composed by 1 mol% of camphorquinone, 2 mol% of dimethylaminoethil

methacrylate and different diphenyliodonium hexafluorophosphate (DPI) salt different

concentrations of 0, 0.25, 0.5, 1 or 2 mol%, resulting in five ERCs. As an inhibitor,

0.1mol% of hydroxyl butyl toluene was used and a 60% in weigth of silanated barium-

aluminum-silicate glass for fillers particles. Thus, ten groups were established so that one

half was performed without adhesive mixture (G1-G5) and the other half (G6-G10) with

adhesive mixture of 3 µl of Adper Scotchbond Multi-Purpose – Bond. For all laboratory

tests, the light curing was performed through an IPS e.max ceramic block with Bluephase

G2 light source at 1265.5 mW/cm2 for 60 seconds. Seventy IPS e.max Press ceramic

specimens (10 mm x 10 mm x 3 mm) were fabricated and randomly divided among the

ten groups (n=7) previously established. The specimens were fixed to light curing

composite resin Filtek Z250 blocks (10 mm x 10 mm x 5 mm). After storage for 24 hours

at 37oC, the specimens were sectioned perpendicular to the bond interface (25 to 30 beams

per block) and half of the beams of each block were submitted to immediate microtensile

bond strength test. The other half was separated for the microtensile test after storage in

distilled water for one year. The failure mode was analyzed by a stereomicroscope (Leica

MZ75) at 40x magnification. Additionally, it was evaluated the ultimate tensile strength

(UTS) of ERCs using hourglass shape specimens (n=10). Degree of conversion (DC) and

real-time polymerization kinetics were measured in disc shape specimens (n=5) using

near-infrared spectroscopy (NIRS). Water up take and solubility (WS) were assessed too

using disc shape specimens (n=5). Data were analyzed using analysis of variance

(repeated measures for BS test and two criteria for the other tests) and Tukey test at a

significance level of 5%. For immediate and after water storage BS values, there was no

statistical difference between groups (p>0,05). Similarly, there was no statistical

difference between immediate and after one year of water storage (p>0,05). The 0 mol%

DPI ERC showed the higher values of WS and the lower values for DC, maximum rate

of polymerization and UTS (p<0,05). The others ERCs presented similar values and were

not statistically different from each other (p>0,05). The addition of adhesive led to higher

DC values only for 0 mol% DPI ERC (p<0,05). The addition of DPI salt improve the

reactivity and physicochemical properties of ERCs. The adhesive had no influence on the

physicochemical properties of ERCs containing DPI salt. Addition of a DPI salt to light-

activated ERCs increased its DC, but was not able to increase the BS between the ceramic

and resin materials. For this study, one year of water storage was not capable of

jeopardizing ceramic BS.

Keywords: Ceramics. Resin cement. Adhesive system. Diphenyliodonium

hexafluorophosphate.

SUMÁRIO

1 INTRODUÇÃO 15

2 ARTIGO: Influence of adhesive protocol on physicochemical properties and ceramic

bond strength of experimental resin cements containing ternary photoinitiator system 18

3 CONCLUSÃO 39

REFERÊNCIAS 40

APÊNDICE 1 – Detalhamento das metodologias 45

ANEXO 1 – Comprovante de submissão do artigo 52

151 INTRODUÇÃO

As cerâmicas são materiais utilizados rotineiramente em procedimentos

restauradores estéticos na odontologia devido as suas excelentes propriedades como alta

resistência à compressão, estabilidade química, baixa condutibilidade elétrica,

difusibilidade térmica, alta translucidez, alta fluorescência, biocompatibilidade, estética

favorável e coeficiente de expansão térmica similar ao da estrutura dental (Anusavice,

1996; Borges, et al., 2003). De acordo com sua composição química, tais cerâmicas

podem ser classificadas em: cerâmicas com óxidos metálicos e cerâmicas vítreas (Tian et

al., 2014). As cerâmicas com óxidos metálicos são constituídas em maior parte pela sua

fase cristalina (cristais de alumina ou zircônia), não apresentando mais do que 15% de

matriz vítrea, ou praticamente sem matriz vítrea (Kern, 2009). Já as cerâmicas vítreas

(feldspática, leucita, dissilicato de lítio) são compostas por uma matriz de vidro reforçada

por cristais dispersos na sua estrutura (Hölland, 2000; Conrad et al., 2007; Sundfeld Neto

et al., 2015).

A alteração da superfície de cerâmicas vítreas pelo condicionamento com

ácido fluorídrico, resulta no aumento da área de superfície de contato proporcionando

melhor interação entre cerâmica e agente cimentante (Kukiattrakoon & Thammasitboon,

2007; Zogheib et al., 2011). Para melhor aproveitamento do aumento da área de

superfície, o cimento deve apresentar uma capacidade de molhamento da superfície

adequada que consiga infiltrar nas irregularidades promovidas pelo condicionamento

ácido (Oh et al., 2002). Apesar do uso do silano na união à cerâmica ser bem consolidado

na literatura (Guarda et al., 2013; Yavuz et al., 2012), ainda existem poucos estudos

avaliando a necessidade de aplicação do adesivo antes do uso do cimento resinoso (Oh et

al., 2002; Naves et al., 2010) e muitos fabricantes recomendam a aplicação do cimento

resinoso diretamente sobre a superfície silanizada da cerâmica. No entanto, é questionável

se a combinação entre apenas agente silano e cimento resinoso seria capaz de promover

a melhor combinação entre o cimento e as irregularidades promovidas pelo

condicionamento ácido da cerâmica.

Devido à natureza frágil das cerâmicas, indica-se preferencialmente o uso da

16técnica adesiva de cimentação. Cimentos resinosos são eleitos como primeira escolha no

procedimento de cimentação de restaurações em cerâmica pura, pois proporcionam

vantagens como maior qualidade do selamento marginal, boa retenção, menor

solubilidade e aumento da resistência à fratura da cerâmica (Burke et al., 2002; Guazzato

et al., 2004a). Quanto ao modo de ativação, os cimentos resinosos podem ser classificados

como quimicamente ativados, fotoativados e de dupla ativação (Pedreira et al., 2009;

Baena et al., 2012). Dentre as principais características, os cimentos fotoativados

apresentam algumas vantagens frente aos cimentos com ativação química, como maior

controle do tempo de trabalho e melhor estabilidade de cor (Hekimoglu et al., 2000; Good

et al., 2008). Entretanto, diante do efeito de atenuação da luz ativadora promovido pela

cerâmica (Moraes et al., 2008; Arrais et al., 2009; Pick et al., 2010), a polimerização

adequada deste tipo de cimento torna-se mais difícil. Sabe-se que as propriedades

mecânicas de um compósito dependem da estrutura polimérica formada (smussen &

Peutzfeldt, 2001) e do grau de conversão (Lovell et al., 2001), que estão estritamente

relacionados com uma polimerização eficaz (Elliott et al., 2001). Sendo assim, a

polimerização inadequada do material de cimentação pode resultar em propriedades

mecânicas deficientes, maior sorção de água, maior solubilidade e menor estabilidade de

cor (Watts, 2005; Ferracane, 2006; Ruttermann, et al., 2010).

Outra opção para este tipo de procedimento seria a utilização de cimentos de

dupla ativação, uma vez que possuem o auxílio da ativação química para obtenção de

adequada conversão, mesmo com menor incidência de luz (Prieto et al., 2013). Porém, os

sistemas de dupla ativação possuem maior quantidade de amina terciária, molécula que

sofre oxidação ao longo do tempo acarretando em alteração da cor do cimento, fator que

pode comprometer a estética obtida inicialmente em restaurações anteriores de cerâmica

pura (Lu & Powers, 2004; Ghavam et al., 2010; Kilinc et al., 2011).

Encontra-se, na literatura, uma possibilidade para melhorar a polimerização

de compósitos fotoativados através do aumento de sua reatividade por meio da utilização

de sistemas fotoiniciadores mais eficazes. Ogliari e colaboradores (2007) observaram a

efetividade da adição de diferentes concentrações de um sal de ônio (hexaflurfosfato de

difeniliodônio) na cinética de polimerização de adesivos dentinários. O estudo

17demonstrou que a utilização conjunta com canforquinona, o fotoiniciador mais

comumente utilizado em compósitos odontológicos, pode promover a decomposição de

sais de ônio, permitindo que o mesmo atue na geração de radicais livres e,

consequentemente, no aumento da reatividade de polimerização de metacrilatos.

Baseado nos resultados obtidos, Gonçalves e colaboradores (2013),

avaliaram a influência da incorporação do sal de hexafluorfosfato de difeniliodônio na

reatividade de cimentos resinosos experimentais fotoativados. A adição do sal nos

cimentos resinosos elevou os valores das propriedades mecânicas do material, além de

aumentar a reatividade e melhorar os valores de conversão monomérica dos cimentos em

questão.

Entretanto, sabe-se que durante o procedimento de cimentação de facetas ou

laminados cerâmicos é comum a fotoativação da camada de adesivo (aplicada no dente e

na peça) e cimento resinoso ao mesmo tempo (Gresnigt & Özcan, 2011; Rigolin et al.,

2014) e não se sabe qual seria o efeito dessa combinação/mistura nas propriedades do

compósito formado na interface dente/cerâmica.

Sendo assim, o objetivo do presente estudo foi analisar a resistência de união

a longo prazo destes cimentos experimentais com e sem adesivo, sob desafio de

degradação hidrolítica, bem como o estudo de suas propriedades físico-químicas nas

condições de cimentação adesiva.

182 ARTIGO: Influence of adhesive protocol on physicochemical properties and

ceramic bond strength of experimental resin cements containing ternary

photoinitiator system

Artigo submetido ao periódico The Journal of Prosthetic Dentistry (Anexo)

Alan R. M. Palialol, Flávio H. B. Aguiar, Hugo F. do Vale, Diogo Dressano, Luciano

S. Gonçalves, Adriano F. Lima, Giselle M. Marchi

Abstract

The aim of this study was to evaluate the effect of an adhesive on ceramic bond strength

and physicochemical properties of experimental resin cements (ERCs) containing a

ternary photoinitiator system. ERCs were prepared using a Bis-GMA/TEGDMA (1:1

molar ratio) base monomers with silanated glass fillers (60% wt). The photoinitiator

system used was camphorquinone (CQ-1mol%), dimethylaminoethyl methacrylate

(DMAEMA-2mol%) and different DPI concentrations (0, 0.25, 0.5, 1 or 2 mol%). Ten

groups were established so that one half was performed with addition of 3 µl of adhesive

(G6-G10) and the other half with no adhesive addition (G1-G5). Light curing was

performed through an IPS e.max ceramic block with Bluephase G2 light source at 1200

mW/cm2 for 60 seconds. Seventy IPS e.max Press ceramic specimens (10 mm x 10 mm

x 3 mm) were fabricated for the ceramic bond strength (BS) test. The specimens were

fixed to light curing composite resin Filtek Z250 blocks (10 mm x 10 mm x 5 mm).

Ultimate tensile strength (UTS) was performed using hourglass specimens (n=10).

Degree of conversion (DC) and real-time polymerization kinetics were carried out using

near-infrared (NIR) spectroscopy in disc shape specimens (n=5). Water sorption and

19solubility (WS) test were performed using disc shape specimens (n=5). Data were

analyzed using analysis of variance (two criteria and repeated measures) and Tukey test

(α=0.05). All groups presented similar BS to the ceramic. Similarly, there was no

statistical difference between immediate BS and after one year of water storage. The 0

mol% DPI ERC showed higher values of WS and lower values of DC, maximum rate of

polymerization and UTS. The others ERCs presented similar values and were not

statistically different from each other. The addition of adhesive led to higher DC values

only for 0 mol% DPI ERC. The addition of DPI salt improves the reactivity and

physicochemical properties of ERCs. The adhesive had no influence on the

physicochemical properties of ERCs containing DPI salt. Addition of a DPI salt to light

curing ERCs increased its DC, but was not able to increase the BS between the ceramic

and resin composite materials. For this study, one year of water storage was not capable

of jeopardizing ceramic BS.

Key Words: Diphenyliodonium hexafluorophosphate. Resin Cement. Ceramics. Dental

Adhesive.

Introduction

Dental ceramics are used for aesthetic restorative procedures due to excellent

properties, such as a similar coefficient of thermal expansion to the tooth structure,

chemical stability, low electrical conductivity, high compressive strength, thermal

diffusivity, translucence and fluorescence1. For effective adhesion, the surface of glassy

dental ceramics must be effectively etched using a strong acid, e.g. hydrofluoric, which

increases surface free energy and contact area, improving the interaction between the

20resin cement and ceramic2, 3. However, resinous material must present suitable wettability

to infiltrate the ceramic surface irregularities promoted by the etching procedure4. It has

been questioned if only resin cement is sufficient to promote suitable adhesion, due to

relatively high viscosity that restricts adequate flow properties, and previous studies have

demonstrated the positive influence of resin cement to ceramic adhesion following the

additional application of an adhesive layer4, 5.

Resin cements are the first choice for cementation of all-ceramic restorations

due to good marginal sealing, retention and increase of fracture strength of ceramic6-10.

Regarding the curing mode, resin cements can be classified as self curing, light curing,

and dual curing11, 12. Light-cured resin cements exhibit more control of working and

setting time and improved color stability compared with self-cured types13, 14.

Previous studies have reported the effect of thickness, crystalline structure,

and general opacity on light absorption through ceramics15-17 and it is well known that

non-optimal polymerization of the resin cement can result in inferior mechanical

properties, reduced color stability and greater water sorption and solubility18-20.

Therefore, dual curing cements are considered the most appropriate for all-ceramic

restorations, since a maximum degree of conversion is more likely to be achieved, even

under lower light exposure21. However, dual curing systems present high concentrations

of tertiary amine compared with entirely photoactivated materials, since it must have

sufficient quantity to react with the chemical initiator (usually, benzoyl peroxide).

Nevertheless, the high amount and type of tertiary amine (aromatic) leads to oxidation of

this molecule over time, resulting in color change of resin cement, compromising

aesthetic quality, mainly in anterior full ceramic restorations22-24. Other negative aspects

21presented by the dual resin cements are the requirement for mechanically mixing, which

may increase air inclusions and decrease mechanical properties25, as well as reduced

working time due and less temporal control of the setting reaction, critical for cementation

procedures.

A possibility to improve cure and potentially the effectiveness of resin cement

may be realized by the use of alternative, or modified photoinitiator systems that improve

polymerization efficiency in low light situations. The use of iodonium salts in resinous

materials containing camphorquinone (CQ) has been previously reported to improve

degree of conversion, flexural strength and flexural modulus, due to increased reactivity

of adhesive systems and resin cements26, 27. It follows that a more reactive system with

higher quantum yield may assist in providing adequate degree of conversion in lower

light conditions through opaque ceramics.

The use of iodonium salts such as diphenyliodonium hexafluorphosphate

(DPI) in combination with conventional binary CQ-amine photoinitiator systems

increases the degree and rate of polymerization of dental resins by facilitating an

increased free radical concentration compared with the binary system alone26, 27. Despite

the maximum absorption of DPI at ~200-250 nm, its interaction with the ketone radical

formed by activation of CQ-amine system, generates additional active phenyl radicals

improving the efficiency of the reaction. The influence of the DPI on mechanical

properties of experimental resin cements were demonstrated in previous investigations28-

30.

Moreover, it is known that during veneering cementation procedure, it is

22common to light cure the adhesive layer (applied to the tooth and ceramic) and resin

cement at the same time40,41. However, it is not known what would be the effect of this

combination/mixture of adhesive and cement on the properties of the composite formed

at the tooth/ceramic interface.

Therefore, the aim of this study was to evaluate the influence of an adhesive

and different DPI concentrations on the long-term ceramic bond strength of light curing

experimental cements under hydrolytic degradation challenge, as well as their

physicochemical properties. Study hypotheses were: 1) Water storage will decrease

ceramic bond strength. 2) Addition of an adhesive to experimental resin cement will not

improve physicochemical properties of experimental resin cements. 3) DPI salt will

improve ceramic bond strength and physicochemical properties of experimental resin

cements.

Material and methods

Transmission of light through ceramic

In order to evaluate the attenuation of light transmitted through ceramic, the

irradiance of the LED source (Bluephase G2, Ivoclar-Vivadent, Schaan, Liechtenstein)

on ‘High Power’ mode was measured with the calibrated spectrometer (MARC® Resin

Calibrator, BlueLight analytics Inc., Halifax, Canada). Three measurements were

performed using the bottom surface sensor either without the ceramic at a distance of 0

mm or beneath the ceramic block (3 mm).

Preparation of experimental resin cements

23A monomer blend with 1:1 mass ratio of 2,2-bis[4-(2-hydroxy-3-

methacryloxypropoxy) phenyl] propane (Bis-GMA) and triethyleneglycol dimethacrylate

(TEGDMA) (Esstech Inc., Essington, PA, USA) was prepared. Camphorquinone

(1mol%) (Esstech) and 2-(dimethylamino) ethyl methacrylate (2mol%) (Sigma–Aldrich,

St. Louis, MO, USA) were added as the photoinitiator system. For the model blends, five

experimental resin cement (ERC)s were prepared by incorporation of 0 (control), 0.25,

0.5, 1 or 2 mol% of a diphenyliodonium hexafluorophosphate (DPI) salt (Sigma–

Aldrich). The monomers were mixed with 60% mass fraction of silanated barium-

aluminum-silicate glass fillers (Esstech Inc., 0.7 µm average size). All the compounds

were blended using a centrifugal mixing device (SpeedMixer, DAC 150.1 FVZ-K,

Hauschild Engineer- ing, Hamm, North Rhine-Westphalia, Germany).

Microtensile bond strength and failure pattern analysis

For the bond strength test, 70 lithium disilicate reinforced ceramic blocks (10

mm length, 10 mm width, 3 mm thickness) (IPS E.max Press, Ivoclar Vivadent, Schaan,

Liechtenstein) shade MO1 and 70 microhybrid composite resin blocks (Filtek Z250, 3M

ESPE, St. Paul, MN, USA) shade A2 (10 mm length, 10 mm width, 5 mm thickness) were

fabricated (n=7). Resin composite blocks were made with an elastomer mold (Express,

3M ESPE, St. Paul, MN, USA) filled with 2 layers, each one light cured for 20 s each

using a third generation LED source (Bluephase G2, Ivoclar Vivadent, Schaan,

Liechtenstein) with an irradiance of 1266 mW/cm2, measured using a calibrated

spectrometer (MARC® Resin Calibrator, BlueLight analytics Inc., Halifax, Canada).

Ceramic blocks were etched with 10% hydrofluoric acid (Dentsply, Petrópolis, Brazil)

for 20 s, rinsed with air/water spray and air-dried. Then, a silane-coupling agent (RelyX

24Ceramic Primer, 3M ESPE, St. Paul, MN, USA) was applied on the ceramic surface and

air-dried for 1 min. In groups G6 to G10, a coat of adhesive (Adper Scotchbond Multi-

Purpose -Bond, 3M ESPE, St. Paul, MN, USA) was applied after the silane and light

cured together with the cement. A Microman 25 M pipette (Gilson, Villiers-le-Bel,

France) was used to standardize the amount of cement (10 µl) and adhesive (3 µl). ERCs

were applied on the ceramic surface, and bonded to the composite block. Light-curing

was performed through the ceramic for 60 s using the LED source (Bluephase G2) with

an irradiance of 1266 mW/cm2. After light curing procedure, the specimens were storage

in distilled water at 37°C for 24 h. Following 24 h storage, the specimens were cross-

sectioned perpendicularly to the ceramic-composite interface with a low-speed saw

(Isomet, Buehler Ltd., Lake Bluff, IL, USA) under water-cooling, to obtain beams (25 to

30 peer block). Half of beams of each block were submitted to immediate microtensile

bond test performed in an universal testing machine (EMIC DL 2000, São José dos

Pinhais, PR, Brazil) at a crosshead speed of 0.5 mm/min. The other half was submitted

for the storage in distilled water (changed every 15 days) for one year and subsequent

microtensile test.

After the microtensile bond-strength test, the fractured interfaces were

analyzed under a stereomicroscope (Leica MZ75, Heerbrugg, Switzerland) at 40x

magnification and the failure modes were classified into four types: adhesive failure,

cohesive failure in ceramic, cohesive failure in composite and mixed failure involving

ceramic, cement and composite.

Polymerization kinetics and degree of conversion

25Real-time polymerization was analyzed using a Fourier Transform near

infrared spectroscopy (FT-NIRS; Nicolet 6700, Thermo Scientific, Hemel Hemstead,

UK) monitoring the peak at 6164 cm-1, which corresponded with the vinyl bond -CH2

absorbance. Specimens (6 mm diameter x 0.8 mm thick, n=5) were prepared in a disc

shape rubber mold using only the ERCs (G1-G5) or mixing the ERCs with 3 µl of

adhesive (Adper Scotchbond Multipurpose Bond, 3M ESPE) (G6-G10). A Microman 25

M pipette (Gilson, Villiers-le-Bel, France) was used to standardize the amount of cement

(10 µl) and adhesive (3 µl). Light curing of the ERC specimens was performed using the

same LED unit and time of curing used for bond strength test, beneath a IPS E.max Press

ceramic block, to simulate the attenuation of light during the cementation procedure. Rate

of polymerization was obtained by taking the first derivative between time (s) and

conversion (%).

Ultimate tensile strength

Hourglass shape specimens (3 mm base, 0.8 mm thick and constricted area

of 1mm2, n=10) were prepared using an elastomer mold (Express, 3M ESPE, St. Paul,

MN, USA). For standardize the cement (10 µl) and adhesive (3 µl) quantity, it was used

a Microman 25 M pipette (Gilson, Villiers-le-Bel, France). Specimens were light cured

using the same Bluephase G2 LED source (Ivoclar Vivadent, Schaan, Liechtenstein) for

60s through an IPS E.max Press ceramic block (Ivoclar Vivadent, Schaan, Liechtenstein)

measuring 10 mm in length x10 mm in wide x 3 mm in thickness. After light curing, all

specimens were storage in distilled water at 37°C for 24 h and submitted to ultimate tensile

strength test in an universal testing machine (EMIC DL 2000) at a crosshead speed of 0.5

mm/min. The crosssectional area of the fractured zone of each specimen was measured

26using a digital caliper (Mitutoyo Corporation, Tokyo, Japan) and the ultimate tensile

strength (UTS, MPa) of each specimen was calculated as the maximum force at tensile

failure, divided by the cross-sectional area of the specimen.

Water sorption and solubility

The water sorption and solubility test was carried out according to Gonçalves

et al., 2013, but with changes in the specimens dimension of specimen and light curing

process. Disc shape specimens (n=5) measuring 6 mm of diameter and 0,5 mm of

thickness were made using an elastomer mold (Express, 3M ESPE, St. Paul, MN, USA).

The light curing was performed using the same LED source Bluephase G2 (Ivoclar

vivadent, Lichtenstein) for 60 s and through an IPS E.max Press ceramic block (10 mm

in length x10 mm in wide x 3 mm in thickness), as described before. Afterward, the

specimens were dry-stored at 37°C for 24h and repeatedly weighed using an analytical

balance (Discovery DV215CD; Ohaus Corporation, Pine Brook, NJ, USA) accurate to

0.01mg until achieving a constant mass (m1). Specimens were then individually placed

in sealed vials, immersed in distilled water (changed every period of 7 days), and stored

at 37°C. After 21 days, the surface water of the specimens was removed by blotting with

absorbent paper, and the weighing process was repeated to obtain a new mass (m2). The

specimens were then dry-stored again at 37°C and reweighed after 24h intervals until the

obtainment of a constant final dry mass (m3). Water sorption and solubility were

calculated in µg/mm3 from the percentage differences in mass gain or loss during the

sorption and desorption cycles by the formulas; sorption = m2-m3(µg) / V(mm3);

solubility = m1-m3(µg) / V(mm3).

27Statistical analysis

For the bond strength test, the experimental unit considered was the

ceramic/composite blocks, not the sticks. Normality and homoscedasticity of data were

evaluated using Shapiro Wilk test. Bond strength values were submitted to repeated

measures 3-way ANOVA and Tukey’s test (α=0.05). The other tests results were

submitted to 2-way ANOVA and Tukey’s test (α=0.05).

Results

Atenuation of light promoted by ceramic

Table 1 shows the irradiance of the light source (1265.6 mW/cm2) that was

reduced to 62 mW/cm2 when the exposure was performed through the ceramic block. This

reduction lead to a reduction of 95.1% of the energy delivered to ERCs (75.9 J/ cm2 to

3.7 J/ cm2 after 60s).

Table 1. Irradiance values in different light-curing modes.

Irradiance (mW/cm2)

Radiant exposure after

60s (J/ cm2)

Loss of energy/irradiance

(%)

Without ceramic 1265.6 75.9 -

Beneath ceramic 62 3.7 95.1

Microtensile bond strength and failure pattern

Values for ceramic bond strength are described on table 2. According to

values, addition of DPI salt to ERCs did not improve the bond strength values (p>0,05).

28Groups with and without adhesive addition were not statistically different (p>0,05).

Similarly, there was no statistical difference between immediate bond strength and after

one year of water storage (p>0,05).

Table 2. Microtensile bond strength means and standard deviations (MPa) for all groups

according to time, use of adhesive and DPI concentration.

Time Adhesive DPI salt (mol%) 0 0.25 0.5 1 2

immediate with 32.30 (6.11) 36.00 (5.14) 36.24 (8.36) 37.22 (8.74) 34.19 (6.19)

without 37.50 (7.92) 39.04 (4.09) 33.88 (7.82) 39.32 (8.31) 34.33 (6.03)

after 1 year with 31.62 (3.86) 32.09 (4.95) 36.46 (6.66) 34.55 (5.26) 31.38 (1.99) without 37.64 (3.31) 32.36 (3.52) 32.39 (4.65) 38.06 (6.14) 35.36 (4.58)

All groups were statistically similar. ANOVA repeated measures (α=0.05).

Failure pattern evaluation was performed for both times of microtensile bond

strength test (immediate and after 1 year of storage). In both times, predominantly, it can

be observed mixed failure (Figure 1 and 2) and almost none adhesive failure. Still, it can

be noticed similar performance of ERCs comparing both times.

Figure 1. Distribution (%) of failure pattern observed for ERCs after immediate microtensile bond strength.

29

Figure 2. Distribution (%) of failure pattern observed for ERCs after 1 year of water

storage.

Ultimate tensile strength

Values for UTS are described on table 3. There was no statistical difference

between groups with and without adhesive (p>0,05). The 0 mol% DPI ERC showed the

lowest values (p<0,05) and the others cements were not statistically different between

them (p>0,05).

Table 3. Ultimate tensile strength (UTS) of ERCs according to adhesive use and DPI concentrations.

Lower case letters compare rows (ERCs). There was no significant interaction between the factors regarding adhesive application.

30

Polymerization kinetics and Degree of conversion

Degree of conversion was significantly lower for ERCs without DPI

(p<0.0001; Table 4). The mixing of adhesive with the ERC without DPI promoted an

increase in DC values, statistically higher compared to ERC (0%DPI) without adhesive

addition (p<0.0001). For other ERCs, the adhesive did not influence DC values (p>0.05).

Observing the rate of polymerization (Figure 3), it could be noted that the ERC without

DPI presented inferior results, with best values observed when the adhesive was mixed

with cement. The cements containing DPI presented similar rate of polymerization

regardless the addition of adhesive.

Figure 3. Real time polymerization kinetics and rate of polymerization beneath a lithium disilicate ceramic (3mm thickness, MO1 shade) of the experimental groups.

31 Table 4. Degree of conversion of ERCs according to adhesive use and DPI concentrations.

Capital letters compare columns (addition of adhesive). Lower case letters compare rows (ERCs).

Water Sorption and Solubility

Table 5 shows the means and standard deviations of the water sorption and

solubility data obtained in this study. The 0 mol% DPI ERC showed higher values of

water sorption. The addition of adhesive improved only the solubility values for the 0

mol% DPI ERC. The others ERCs presented similar values between them.

Table 5. Water sorption and solubility of ERCs according to adhesive use and DPI concentrations.

Solubility Sorption ERCs without adhesive with adhesive without adhesive with adhesive

0 mol% 77.06 (4.76) Aa 56.12 (4.69) Ba 40.36 (3.44) Aa 50.36 (6.82) Aa 0.25 mol% 20.92 (2.71) Ac 20.36 (1.68) Ab 31.36 (2.71) Aa 36.68 (1.27) Ab 0.5 mol% 25.52 (3.56) Abc 24.10 (2.85) Ab 36.65 (4.53) Aa 43.05 (6.18) Aab 1 mol% 27.50 (2.65) Abc 21.17 (3.01) Ab 40.83 (9.13) Aa 35.94 (3.03) Ab 2 mol% 30.03 (3.17) Ab 24.03 (1.57) Ab 33.05 (4.24) Aa 40.97 (4.14) Aab

Capital letters compare columns (addition of adhesive). Lower case letters compare rows (ERCs).

Discussion

The present study used a lithium disilicate ceramic with a thickness of 3 mm

and medium opacity shade, which can be considered a counterindication for a light curing

cement due to light attenuation effects. The intention was precisely to challenge the

32ternary photoinitiator system in adverse conditions of low light. Moreover, the idea of an

exclusively light curing material that performs well in all different clinical situations from

pin to metal free crowns cementation would be interesting and would eliminate the issue

of working and setting time control of dual cure cements.

The first hypothesis of the study was rejected since there was no difference

in bond strength among immediate and after one year of water storage. One might say

that the ceramic bond strength should be jeopardized by water storage. Indeed, the

hydrolytic degradation is a point to be considered regarding resin composites, specially

when a long time of storage is applied. But, the substrate (resin composite block) that

ceramic was bonded to is another important factor that should be considered. One of the

big issues in dentin bonding that compromises the durability of adhesion is the

enzymatic/hydrolytic degradation38,39. The lack of tooth tissue as a substrate for bonding

excludes the enzymatic issue, leaving only the hydrolytic degradation which was not

capable of reducing the bond strength. Maybe more time of water storage should be

necessary to jeopardize the ceramic bonding.

Due to light attenuation through the ceramic blocks, the radiant exposure used

was considerably reduced (table 1). A previous study reported a 58% decrease in light

irradiance through IPS Empress Esthetic ceramic discs (shade A3, 2 mm thick)32.

However, in the present study, the ceramic thickness (3mm) and shade (MO1-Medium

Opacity) resulted in 95% loss in irradiance resulting in a radiant exposure of 3.7 J/cm2

that reached the resin cement after 60 s light exposure. Considering that 6-24 J/cm2 is an

adequate range to promote a suitable polymerization in clinical conditions33-35, maybe the

radiant exposure obtained could not properly excite CQ, jeopardizing not only the amount

33of photons reaching the composite but also the supply of electrons needed to interact with

DPI and create the additional free radicals. However, if we consider the size of a cement

film between 50-100 µm42, it might be considered that the low radiant exposure (3.7

J/cm2) was sufficient to polymerize the composite and allow suitable bond strength, even

in the control group (0 mol% DPI).

It is known that adequate polymerization and degree of conversion are

required to obtain good mechanical properties43. However, there are no reports in the

literature showing a linear correlation between degree of conversion and ceramic bond

strength, or minimum values of degree of conversion required to obtain suitable bond

strength. This is due to the fact that ceramic bonding depends not only on degree of

conversion but also on other factors such as surface treatment, cementation protocol and

chemical composition of ceramics44,45. Moreover, some studies have shown that,

depending on the material and condition, surface treatment of ceramic plays a more

important role than the chemical composition of resin cement46,47. According to the

results of the present study, it is possible to obtain a stable ceramic/resin composite

bonding against hydrolytic degradation challenge, even with a low conversion degree

(46% of the control group).

Further, the distribution of failure modes suggests similar bond quality even

without the use of adhesive, which was not able to improve the bond strength values. The

results of bond strength test corroborate with the values of failure pattern analysis, where

all groups showed similar performance regarding the amount and type of failure in both

times (immediate and after one year of storage). The same can be considered for groups

without adhesive (G1-G5) and with adhesive (G6-G10), where there was no difference in

34performance either, leading to believe that use of the adhesive was not able to promote

better wettabilty of ceramic surface, nor better bond strength values. Probably the

monomeric composition (BisGMA / TEGDMA ratio 1: 1) added to the amount of

inorganic filler (60% by mass) gave the CREs a viscosity capable of promoting good

surface wetting. Addition of an adhesive was able to improve DC only for the control

group (0mol% DPI), while for the other cements (containing DPI salt) it had no effect.

This result leads to rejection of our second hypothesis. Possibly the adhesive reduced the

viscosity of the system (adhesive + resin cement), resulting in higher mobility of the

reacting chains, increasing DC of the cement. This effect was not observed in the ERCs

containing DPI, possibly due to the higher reactivity already established of this system.

The third hypothesis was also rejected once DPI salt improved

physicochemical properties of ERCs, but it did not improve ceramic bond strength.

Physicochemical properties of ERCs with same composition of materials tested in the

present study were demonstrated in previous studies26,28. The addition of DPI salt was

able to reduce the sorption and solubility of the cements, as well as increase the flexural

strength and modulus of experimental materials tested26. The same effect of DPI salt on

the physicochemical properties could be observed in this study. The DC for all ERCs

containing DPI were similar and significantly higher compared with the control (without

DPI). Increased reactivity and improved polymerization of methacrylate-based dental

materials as consequence of DPI addition associated to camphorquinone has been

reported in previous studies26, 27. The salt intercepts the ketone radical anion, preventing

back electron transfer from occurring and then irreversibly decomposes to an aryl radical

and an aryl iodide, providing more free radicals and improving the curing of the

35CQ/amine system27, 31. If the DC of ERCs improve, the others properties will also get

better as a consequence, once physical/mechanical properties depends directly on DC of

composites18-20,36,37. This could be observed in this study for water sorption and solubility

and ultimate tensile strength.

It was obtained no difference on bond strength values of light cured ERCs to

overlying ceramic, despite low irradiance, low radiant exposure, ceramic opacity and

thickness, and water storage. It is important to highlight that the present results were

obtained “in vitro” and using experimental materials, which might not be fully

extrapolated to the clinical situation. Further aspects such as more time of water storage,

different concentration and composition of initiator systems as well as use of dentin as a

substrate for bonding warrant future investigation in order to improve the properties of

resin cement materials.

Conclusion

According to obtained results, it can be concluded that:

• One year of water storage was not sufficient to decrease ceramic bond strength of light

curing ERCs.

• Adhesive addition did not influence bond strength to ceramic, neither physicochemical

properties for ERCs with DPI salt, but it was able to increase DC only for no DPI ERC.

• DPI salt is capable of increasing rate of polymerization and DC of light curing ERCs even

when cured beneath thick lithium disilicate ceramic, although it did not affect ceramic

bond strength.

36Acknowledgments

The authors are grateful for grants (2014/02898-7) provided by FAPESP. It was used by

the corresponding author in partial fulfillment of the requirements to obtain the degree of

Doctor in Clinical Dentistry (PhD) and as part of his PhD thesis.

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38cements containing different concentrations of ethyl 4-(dimethylamino)benzoate and 2-(dimethylamino)ethyl methacrylate as co-initiators. Dent Mater. 2016 Jun; 32(6):749-55. 29. Dressano D, Palialol AR, Xavier TA, Braga RR, Oxman JD, Watts DC, et al. Effect of diphenyliodonium hexafluorophosphate on the physical and chemical properties of ethanolic solvated resins containing camphorquinone and 1-phenyl-1,2-propanedione sensitizers as initiators. Dent Mater. 2016 Jun; 32(6):756-64. 30. Song L, Ye Q, Ge X, Misra A, Spencer P. Tris(trimethylsilyl)silane as a co-initiator for dental adhesive: Photo-polymerization kinetics and dynamic mechanical property. Dent Mater. 2016 Jan; 32(1):102-13. 31. Guo X, Wang Y, Spencer P, Ye Q, Yao X. Effects of water content and initiator composition on photopolymerization of a model BisGMA/HEMA resin. Dent Mater. 2008 Jun; 24(6):824-31. 32. Moraes RR, Correr-Sobrinho L, Sinhoreti MA, Puppin-Rontani RM, Ogliari FA, Piva E. Light-activation of resin cement through ceramic: relationship between irradiance intensity and bond strength to dentin. J Biomed Mater Res B Appl Biomater. 2008 Apr; 85(1):160-5. 33. Cunha LG, Alonso RC, Correr GM, Brandt WC, Correr-Sobrinho L, Sinhoreti MA. Effect of different photoactivation methods on the bond strength of composite resin restorations by push-out test. Quintessence Int. 2008 Mar; 39(3):243-9. 34. Lohbauer U, Rahiotis C, Kramer N, Petschelt A, Eliades G. The effect of different light-curing units on fatigue behavior and degree of conversion of a resin composite. Dent Mater. 2005 Jul; 21(7):608-15. 35. Seth S, Lee CJ, Ayer CD. Effect of instruction on dental students&#8217; ability to light-cure a simulated restoration. J Can Dent Assoc. 2012 78:c123. 36. Lovell LG, Lu H, Elliott JE, et al: The effect of cure rate on the mechanical properties of dental resins. Dent Mater. 2001; 17(6): 504-11. 37. Elliott JE, Lovell LG, Bowman CN: Primary cyclization in the polymerization of bis-GMA and TEGDMA: a modeling approach to understanding the cure of dental resins. Dent Mater. 2001;17(3): 221-29. 38. Liu R, Fang M, Xiao Y, Li F, Yu L, Zhao S, Shen L, Chen J. The effect of transient proanthocyanidins preconditioning on the cross-linking and mechanical properties of demineralized dentin. J Mater Sci Mater Med 2011 Nov;22(11): 2403-1.

39. Hashimoto M, Ohno H, Sano H, Kaga M, Oguchi H. In vitro degradation of resin-dentin bonds analyzed by microtensile bond test, scanning and transmission electron microscopy. Biomaterials. 2003 Sep;24(21):3795-803.

40. Gresnigt M, Ozcan M. Esthetic rehabilitation of anterior teeth with porcelain laminates and sectional veneers. J Can Dent Assoc. 2011;77: b143. 41. Rigolin FJ, Miranda ME, Flório FM, Basting RT. Evaluation of bond strength between leucite-based and lithium disilicate-based ceramics to dentin after cementation with conventional and self-adhesive resin agents. Acta Odontol Latinoam. 2014;27(1):16-24. 42. Cekik-Nagas I, Canay S, Sahin E. Bonding of resin core materials to lithium disilicate ceramics: The effect of resin cement film thickness. Int J Prosthodontics.

392010; 23(5): 469-471. 43. Calheiros FC, Kawano Y, Stansbury JW, Braga RR. Influence of radiant exposure on contraction stress, degree of conversion and mechanical properties of resin composites; Dent Mater, 22 (2006), pp. 799–803. 44. Guarda GB, Correr AB, Gonçalves LS, Costa AR, Borges GA, Sinhoreti MAC, Correr-Sobrinho L. Effects of surface treatments, thermocycling, and cyclic loading on the bond strength of a resin cement bonded to a lithium disilicate glass ceramic. Oper Dent. 2013; 38(2): 208-17. 45. Sundfeld Neto D, Naves LZ, Costa AR, Correr AB, Consani S, Borges GA, et al. The Effect of Hydrofluoric Acid Concentration on the Bond Strength and Morphology of the Surface and Interface of Glass Ceramics to a Resin Cement. Oper Dent. 2015; 40(5): 470-479. 46. Aboushelib MN, Sleem D. Microtensile bond strength of lithium disilicate ceramics to resin adhesives. J Adhes Dent. 2014; 16(6): 547-52. 47. Lise DP, Perdigão J, Van Ende A, Zidan O, Lopes GC. Microshear bond strength of resin cements to lithium disilicate substrates as a function of surface preparation. Oper Dent. 2015; 40(5): 524-32.

3 CONCLUSÃO

De acordo com os resultados obtidos, pode-se concluir que:

• O tempo de armazenamento de um ano em água destilada não foi capaz de reduzir os

valores de resistência de união à cerâmica dos CREs fotoativados.

• O adesivo não exerceu influência na resistência de união à cerâmica, tampouco nas

propriedades físico-químicas dos CREs contendo sal de DFI, mas foi capaz de aumentar

o grau de conversão apenas para o CRE sem o sal de DFI.

• O sal de DFI foi capaz de aumentar a taxa de polimerização e o grau de conversão dos

CREs fotoativados, mesmo utilizando uma cerâmica vítrea de grande espessura como

barreira para luz. Porém, nenhuma concentração do sal exerceu efeito na resistência de

união à cerâmica, tanto imediata quanto após armazenamento em água.

* 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.

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42Kern M. Resin bonding to oxide ceramics for dental restorations. J Adhes Sci

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Lee JH, Um CM, Lee IB. Rheological properties of resin composites according to

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Moraes RR, Correr-Sobrinho L, Sinhoreti MA, Puppin-Rontani RM, Ogliari FA,

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Naves LZ, Soares CJ, Moraes RR, Gonçalves LS, Sinhoreti MAC, Correr-

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45APÊNDICE – METODOLOGIA ILUSTRADA

1 Preparo dos cimentos resinsos experimentias

Inicialmente, foi obtido um composto base a partir da mistura dos monômeros

2,2 - bis [4 - (2 – hidróxi - 3 - metilacriloxipropoxi) fenil] - propano (Bis-GMA) (Sigma-

Aldrich, Millwaukee, WI, EUA) e dimetacrilato de trietilenoglicol (TEGDMA) (Sigma-

Aldrich) na proporção 1:1 em massa (Figura 1, A e B). Ao composto base foi adicionado

como sistema fotoiniciador 1 mol% de canforoquinona (CQ) (Esstech Inc., Essington,

PA, EUA) e 2 mol% de metacrilato de dimetilaminoetil (DMAEMA) (Sigma-Aldrich)

(Figura 1 D). Como inibidor, foi acrescido à mistura uma quantidade de 0,1 mol% de

hidroxitolueno butilado (BHT) (Sigma-Aldrich). A partir do composto base, foram

preparados cinco cimentos experimentais, contendo crescentes concentrações de

hexafluorfosfato de difeniliodônio (DPIHFP - Sigma-Aldrich) (0; 0,25; 0,5; 1 e 2 mol%).

Posteriormente, foram adicionados 60% em peso de partículas silanizadas de vidro bário-

alumínio-silicato com diâmetro médio de 0,7 µm (Esstech Inc., Essington, Pensilvânia,

USA) (Figura 1, C e E).

D E

CBA

46Figura 1. Reagentes utilizados para confecção dos cimentos resinosos: (A) Bis-GMA;

(B) TEGDMA; (C) Sal de hexafluorofosfato de difeniliodônio; (D) DMAEMA; (E) Carga

de vidro de bário alumínio silicato.

2 Confecção dos espécimes de cerâmica

Setenta blocos da cerâmica vítrea IPS e.max Press (Ivoclar Vivadent, Schaan,

Liechtenstein) com dimensões de 10 mm x 10 mm x 3mm foram utilizados neste estudo.

Após o processo de fabricação das amostras segundo o fabricante, o revestimento

aglutinado por fosfato foi removido com auxílio de jato de óxido de alumínio de 50 µm

(Oxyker Dry; F.lli Manfredi, Sofia, Itália), sob pressão inicial de 4 bar, e posteriormente,

2 bar para remoção do revestimento próximo das amostras da cerâmica. O conduto de

alimentação foi removido com um disco diamantado (KG Sorensen, Cotia, SP, Brasil)

acoplado em peça reta em baixa rotação e os espécimes submetidos a acabamento com

ponta cilíndrica de diamante. (Figura 2).

Figura 2. (A) Jateamento com óxido de alumínio; (B) Remoção dos espécimes de

cerâmica; (C) Aspecto dos espécimes após acabamento.

473 Resistência de união

Para o ensaio de resistência de ligação, os blocos cerâmicos reforçados com

disilicato de lítio (10 mm de comprimento, 10 mm de largura, 3 mm de espessura, cor

MO1) foram condicionados com ácido fluorídrico a 10% (Dentsply, Petrópolis, Brasil)

durante 20 s, lavados com jato de ar/água e secos. Em seguida, foi aplicado agente silano

(RelyX Ceramic Primer, 3M ESPE, St. Paul, MN, EUA) sobre a superfície cerâmica e

deixado em repouso por 1 min. Nos grupos G6 a G10, foi aplicado adesivo (Adper

Scotchbond Multi-Purpose-Bond, 3M ESPE, St. Paul, MN, EUA) após o silano e

fotoativado juntamente com o cimento. Os blocos cerâmicos foram cimentados aos

blocos de resina composta. A fotoativação foi realizada através da cerâmica durante 60 s

usando LED Bluephase G2 com irradiância de 1266 mW/cm2. Após a cimentação, os

espécimes foram armazenados em água destilada a 37 ° C durante 24 h. Feito isso, os

blocos foram seccionados perpendicularmente à interface de união cerâmica/cimento com

disco diamantado em baixa velocidade (Isomet, Buehler Ltd., Lake Bluff, IL, EUA)

(figura 3, A e B). Metade dos palitos obtidos de cada bloco foram submetidos ao ensaio

imediato de microtração realizada em máquina de ensaio universal (EMIC DL 2000, São

José dos Pinhais, PR, Brasil) com velocidade de 0,5 mm/min (figura 4, A e B). A outra

metade foi submetida ao processo de armazenamento em água destilada por um ano e

subsequente teste de microtração.

Figura 3. (A) Amostra fixada em placa de acrílico para realização dos cortes na máquina

ISOMET; (B) Cortes realizados perpendicularmente à interface de união para obtenção de palitos.

48

Figura 4. (A) Palito posicionado no dispositivo de microtração acoplado à máquina de ensaio

universal EMIC DL 2000; (B) Palito logo após a fratura com a interface de união livre de

cianoacrilato.

4 Cinética e polimerização e grau de conversão

A cinética de polimerização polimerização e grau de conversão final foram

realizados em espectrômetro de infravermelho transformação de Fourier (FT-NIRS,

Nicolet 6700, Thermo Scientific, Hemel Hemstead, UK) (figura 5, A). Os espécimes (6

mm de diâmetro x 0,8 mm de espessura, n=5) foram preparados em molde de borracha

com formato de disco utilizando apenas os cimentos (G1-G5) ou misturando-os com 3 µl

de adesivo (Adper Scotchbond Multipurpose Bond, 3M ESPE) (G6-G10). Utilizou-se

uma pipeta Microman 25 M (Gilson, Villiers-le-Bel, França) para padronizar a

quantidade de cimento (10 µl) e adesivo (3 µl). Para reproduzir a atenuação da luz durante

o processo de cimentação, foi realizado a fotopolimerização dos espécimes utilizando a

mesma fonte de LED e tempo de fotoativação utilizados para o teste de resistência de

união, através de um bloco de cerâmica IPS E.max Press (figura 5, B).

49

Figura 5. (A) Espectrômetro (FT-NIRS; Nicolet 6700, Thermo Scientific, Hemel Hemstead, UK) (B)

Mesa óptica equipada com suportes, LED Bluephase G2 e cabos de fibras ópticas conectadas ao FT-

NIR.

5 Resistência coesiva

Amostras em formato de ampulheta (n=10) foram confeccionadas utilizando

um molde de silicone por adição (Express, 3M ESPE, St. Paul, MN, EUA). Para

padronizar a quantidade de cimento (10 µl) e adesivo (3 µl), utilizou-se uma pipeta

Microman 25 M (Gilson, Villiers-le-Bel, França). Os espécimes foram fotoativados

utilizando a mesma fonte de LED Bluephase G2 (Ivoclar Vivadent, Schaan,

Liechtenstein) durante 60s através de um bloco de cerâmica IPS E.max Press (Ivoclar

Vivadent, Schaan, Liechtenstein) com 10 mm de comprimento x 10 mm de largura x 3

mm de espessura. Após fotoativação, todos os espécimes foram armazenados em água

destilada a 37°C por 24 h e submetidos ao ensaio de resistência coesiva em máquina de

ensaio universal (EMIC DL 2000) com velocidade de 0,5 mm/min. A área da zona

fraturada de cada amostra foi medida utilizando um paquímetro digital (Mitutoyo

Corporation, Tóquio, Japão) e a resistência coesiva (UTS, MPa) de cada amostra foi

calculada como a força máxima à falha de tensão, dividida pela área da secção transversal

da amostra.

50

Figura 6. (A) Moldes de silicone por adição das amostras em formato de ampulheta;

(B) Amostra posicionada na máquina de ensaio para realização do teste de resistência

coesiva; (C) Amostra logo após falha de tensão reproduzida pelo teste.

6 Sorção e solubilidade em água

O teste de sorção e solubilidade foi realizado de acordo com o estudo de

Gonçalves e colaboradores (2013), exceto pelas dimensões das amostras e procedimento

de fotoativação. Foram confeccionadas, a partir de matrizes de silicone por adição,

amostras em forma de disco (n=5) medindo 6 mm de diâmetro e 0,5 mm de espessura.

Após fotoativadas durante 60s através de um bloco de cerâmica IPS E.max

Press (Ivoclar Vivadent, Schaan, Liechtenstein), as amostras foram armazenados em

tubos de plástico secos por 24 h a 37°C. Em seguida, foram submetidas ao dessecador

(figura 7 C) contendo sílica gel e pesadas diariamente em balança analítica digital

(Discovery DV215CD; Ohaus Corporation, Pine Brook, NJ, USA) (figura 7 B) com

precisão de 0,01 mg até a obtenção de massa constante (m1). A espessura e o diâmetro

iniciais foram medidos em quatro pontos equidistantes utilizando um paquímetro digital

(Mitutoyo, Tóquio, Japão) para o cálculo do volume das amostras em mm3 no final do

teste. Após a estabilização da massa m1, as amostras foram imersas em 1,5 ml de água

destilada (figura 7 A) e armazenadas em estufa a 37°C por 21 dias, sendo a água trocada

a a cada quinze dias. Após 21 dias, as amostras foram levemente secadas com papel

absorvente e foram pesadas para obtenção da massa após imersão em água (m2). Em

seguida, as amostras foram novamente levadas ao dessecador, a 37°C, para novo processo

de pesagens consecutivas até se obter o valor da massa constante final (m3). Os valores

51de sorção e solubilidade foram calculados em µg/mm3, através das seguintes fórmulas:

sorção = m2-m3(µg) / V(mm3); solubilidade = m1-m3(µg) / V(mm3).

Figura 7. (A) Amostra em forma de disco inserida em água destilada; (B) Balança

analítica digital utilizada durante as três fases de pesagem das amostras; (C) Dessecador

contendo sílica gel para remoção da umidade das amostras.

A B C

52ANEXO

Comprovante de submissão do artigo

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Dear Mr. Alan Palialol,

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