UNIVERSIDADE ESTADUAL DE CAMPINAS FACULDADE DE ODONTOLOGIA DE PIRACICABA
Michele de Oliveira Lima
APLICAÇÃO DE POLYETHERETHERKETONE (PEEK) EM
RETENTOR INTRARRADICULAR: AVALIAÇÃO DA
RESISTÊNCIA À FRATURA E DISTRIBUIÇÃO DE TENSÕES
NA RAIZ.
APPLICATION OF POLYETHERETHERKETONE (PEEK)
POSTS: EVALUATION OF FRACTURE RESISTANCE AND
STRESS DISTRIBUTION IN THE ROOT.
Piracicaba 2019
Michele de Oliveira Lima
APLICAÇÃO DE POLYETHERETHERKETONE (PEEK) EM
RETENTOR INTRARRADICULAR: AVALIAÇÃO DA RESISTÊNCIA À
FRATURA E DISTRIBUIÇÃO DE TENSÕES NA RAIZ.
APPLICATION OF POLYETHERETHERKETONE (PEEK) POSTS:
EVALUATION OF FRACTURE RESISTANCE AND STRESS
DISTRIBUTION IN THE ROOT.
Tese apresentada à Faculdade de Odontologia de Piracicaba da Universidade Estadual de Campinas como parte dos requisitos exigidos para a obtenção do título de Doutora em Clínica Odontológica, na Área de 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 Dental Clinic, in Operative Dentistry area.
Orientador: Prof. Dr. Flávio Henrique Baggio Aguiar
Este exemplar corresponde à versão final da tese defendida pela aluna Michele de Oliveira Lima e orientada pelo Prof. Dr. Flávio Henrique Baggio Aguiar.
Piracicaba 2019
Identificação e informações acadêmicas e profissionais do(a) aluno(a) -ORCID: 0000-0002-2750-7392
Dedicatória
A Deus, por sempre ter demonstrado sua bondade e presença em minha vida. Agradeço pelo dom da vida, pelos obstáculos superados e pelos objetivos alcançados. Sou grata pelas pessoas maravilhosas que colocou em minha vida, certamente tornaram minha caminhada mais leve.
Aos meus pais, Hélio e Marlene, exemplos de amor, disciplina, carinho e respeito. Obrigada por todo o amor e conselhos dados nos momentos mais precisos e por nos proporcionarem o bem mais valioso que podiam nos dar, o estudo. Agradeço por me direcionarem no caminho correto. Vocês são meu exemplo de vida e perseverança, cuja sabedoria e integridade em tudo o que realizam, moldaram-me como sou.
À minha irmã Érika, pela amizade, apoio e companheirismo desde sempre. Obrigada por se fazer presente nas mensagens e conselhos, entendido minha ausência e apoiado minhas escolhas. Sou grata pelo incentivo e por sempre torcer pelas minhas vitórias.
Ao meu namorado Frederico, que me incentivou e me encorajou tantas vezes. Obrigada por toda a paciência, companheirismo e amor. Sou grata pela compreensão nos momentos de choro, estresse e ausência. Saiba que seu apoio foi essencial para a concretização deste título de doutorado.
Agradecimento Especial
Ao meu orientador, professor doutor Flávio Henrique Baggio Aguiar, que desde a iniciação científica acreditou que eu podia ir mais além. Minha eterna gratidão pela orientação e confiança na minha capacidade de realização. Obrigada por sempre ter dado apoio quando necessário, por ter acreditado neste trabalho e por me acolher como uma de suas joaninhas. Muito obrigada por me proporcionar um crescimento profissional tão rico e por todos os ensinamentos transmitidos.
Agradecimentos
À direção da Faculdade de Odontologia de Piracicaba da Universidade Estadual de Campinas, na pessoa do Diretor Prof. Dr. Francisco Haiter Neto e do diretor associado Prof. Dr. Flávio Henrique Baggio Aguiar.
À Profª. Dra. Karina Gonzales Silvério Ruiz, coordenadora dos cursos de Pós-Graduação e ao Prof. Dr. Valentim Adelino Ricardo Barão, coordenador do Programa de Pós-Graduação em Clínica Odontológica.
Aos professores da Área de Dentística, Flávio Henrique Baggio Aguiar, Giselle Maria Marchi Baron, Luis Roberto Marcondes Martins, Marcelo Giannini, Luis Alexandre Maffei Sartini Paulillo, Débora Alves Nunes Leite Lima e Vanessa Cavalli Gobbo, pela convivência diária e pelo conhecimento transmitido.
Ao professor Anderson Catelan, por toda a paciência e atenção. Saiba que tenho imensa gratidão e admiração pelo seu trabalho.
Ao professor Ricardo Armini Caldas, agradeço por me orientar e auxiliar com os dados de elementos finitos.
À banca examinadora da qualificação, Profª. Vanessa Cavalli Gobbo, Prof. Waldemir Francisco Vieira-Junior e Prof. Ricardo Armini Caldas e à suplente Profª. Lúcia Trazzi Prieto, por deixarem seus afazeres para correção do meu trabalho. Obrigada por todas as considerações e correções.
Aos professores da banca de defesa da tese, Profª. Thatiana de Vicente Leite, Profª. Fabiana Mantovani Gomes França, Profª. Giselle Maria Marchi Baron, Prof. Luís Roberto Marcondes Martins, Prof. Flávio Henrique Baggio Aguiar, e aos suplentes Prof. Anderson Catelan, Prof. Waldemir Francisco Vieira-Junior e Profª. Lúcia Trazzi Prieto por aceitarem meu convite.
A todos os familiares, que na ausência dos meus pais, não mediram esforços para me ajudar. Divido os méritos desta conquista, porque ela também pertence a vocês.
Aos colegas que compartilharam a casa e a rotina comigo, Thayla, Jéssica, Rafaela, Talita e Gui, agradeço pela amizade, carinho e respeito. Por todo o apoio e palavras de conforto nos momentos mais necessários, por não me deixarem desanimar.
Aos colegas de turma do mestrado e doutorado, Mari, Jéssica, Waldemir, Cris, Thayla, Suelen, Marília, Isabel e Diogo, pela amizade conquistada e por todo apoio e incentivo de vocês na pós graduação. Agradeço a cada um de vocês por todo
carinho e por tornarem os dias em Piracicaba mais leves e divertidos. Que as experiências compartilhadas até aqui nos guiem para alcançarmos a alegria de chegar ao destino projetado.
Às joaninhas, irmãs de orientação, Jéssica, Mari, Maria, Renata, Marcela e Joyce, obrigada por todo o apoio, pela amizade que compartilhamos e principalmente, pelo respeito mútuo.
Ao Engenheiro Mecânico Marcos (Marcão) e à funcionária Selma, pela presença e presteza nas tarefas do laboratório de materiais dentários, onde realizei parte desta pesquisa.
À Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) pela concessão de bolsa de doutorado.
O presente trabalho foi realizado com apoio da Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Código de Financiamento 001
RESUMO
O objetivo deste estudo foi avaliar a resistência à fratura e distribuições de tensões na raiz do retentor intrarradicular confeccionado a partir de polímero polieteretercetona (PEEK) fresado em sistema de CAD/CAM. Sessenta raízes de incisivos bovinos foram tratadas endodonticamente e manipuladas segundo os fatores em estudo (n=10): tipo de retentor e remanescente. Retentores intrarradiculares foram cimentados, de acordo com os grupos experimentais: férula ausente e pino de fibra de vidro (f0FP); férula de 2 mm e pino de fibra de vidro (f2FP); férula ausente e pino de fibra de vidro anatomizado com resina composta (f0PR); férula de 2 mm e pino de fibra de vidro anatomizado com resina composta (f2PR); férula ausente e núcleo em PEEK (f0PPC) e férula de 2 mm e núcleo em PEEK (f2PPC). Após a cimentação dos retentores, foram confeccionadas e cimentadas coroas metálicas. Os espécimes foram embutidos em resina acrílica e o ligamento periodontal foi simulado utilizando poliéter. Cada amostra foi posicionada sobre dispositivo da máquina de ensaios universal, e uma força foi aplicada na porção palatina a 45° até que ocorresse a fratura. A resistência à fratura foi mensurada em Newton e os dados submetidos à análise estatística por meio de ANOVA dois fatores (α=0,05). A análise do padrão de fratura foi realizada visualmente, utilizando-se uma classificação de acordo com a extensão da fratura. Adicionalmente, foram desenvolvidos modelos digitais tridimensionais com capacidade de representar as tensões geradas na raiz por meio do método de elementos finitos. Foram avaliadas as situações de cimentação de pino de fibra de vidro e núcleo em PEEK, na presença ou ausência de férula. Os resultados foram analisados pelo critério de Mohr Coulomb. A resistência à fratura não foi influenciada pelo tipo de retentor intrarradicular, não havendo diferença estatística significativa entre os grupos analisados (p=0,243). Houve diferenças estatísticas significativas para o fator remanescente (p<0.0001), sendo observado que grupos com férula apresentaram maior resistência à fratura quando comparados aos grupos sem férula. Todos os espécimes apresentaram padrão de fratura irreparável. O padrão de fratura encontrado foi condizente com a análise de tensões demonstrada pelo estudo de elementos finitos. O modo de falha de dentes com férula apresentou-se mais catastrófico quando comparado ao modo de falha de dentes sem férula. Pode-se concluir que a prePode-sença de férula promove aumento da resistência à fratura de dentes tratados endodonticamente e restaurados com retentor intrarradicular e coroa; o modo de falha encontrado para dentes com presença de férula e com ausência de
férula obteve padrões distintos; o núcleo em PEEK não modificou a biomecânica de dentes tratados endodonticamente e assemelhou-se aos resultados encontrados para pinos de fibra de vidro.
Palavras-chave: Restauração dentária permanente. Raiz dentária. Técnica para retentor intrarradicular.
ABSTRACT
The aim of this study was to evaluate the fracture strength and stress distribution in the root of intraradicular retainer made of polyetheretherketone polymer (PEEK) milled in a CAD/CAM system. Sixty bovine incisors roots were endodontically treated and manipulated according to the factors under study: retainer type and remaining (presence or absence of ferrule). Intraradicular retainers were cemented according to the six experimental groups (n=10) : no-ferrule glass fiber post (f0FP); 2
mm-ferrule glass fiber post (f2FP); no-ferrule resized glass fiber post (f0PR); 2
mm-ferrule resized glass fiber post (f2PR); no-ferrule PEEK post and core (f0PPC), and
2-mm ferrule PEEK post and core (f2PPC). After the retainers were cemented, metallic
crowns were made and cemented. The specimens were embedded in acrylic resin and the periodontal ligament was simulated using polyether. Each sample was placed on a universal testing machine, and a force was applied to the palatine portion at 45° until fracture occurred. Fracture resistance was measured in Newton (N) and data were submitted to statistical analysis using two-way ANOVA (α=0.05). Fracture pattern was visually analyzed and classified according to the extent of the fracture. In addition, three-dimensional digital models representing the tensions generated in the root were developed using the finite element method. Cementation of glass fiber post or PEEK post and core was evaluated in the presence or absence of ferrule. The results were analyzed by the Mohr Coulomb criterion. The fracture strength was not influenced by the type of intraradicular retainer, and there was no statistically significant difference between the analyzed groups (p=0.243). There were significant statistical differences for the remaining factor (p <0.0001), and it was observed that groups with ferrule presented greater fracture resistance when compared to groups without ferrule. All specimens presented an irreparable fracture pattern, which was consistent with stress analysis demonstrated by the finite element study. The mode of failure of teeth with ferrule was more catastrophic when compared to that of teeth without ferrule. It can be concluded that the presence of ferrule promotes an increase in fracture resistance of teeth treated endodontically and restored with intraradicular retainer and crown; the presence or ferrule also influences failure mode; PEEK post and core did not modify the biomechanics of endodontically treated teeth, resembling the results found for fiber glass posts.
Keywords: Permanent dental restoration. Tooth root. Technique for intraradicular retainer.
SUMÁRIO
1 Introdução 14
2 Artigo: Application of polyetheretherketone (PEEK) posts: evaluation of fracture resistance and stress distribution in the root. 17
3 Conclusão 36
Referências 37
Apêndice 1: Metodologia ilustrada. 40
Anexo 1: Submissão do artigo. 46
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1 INTRODUÇÃO
O desafio da reabilitação de dentes tratados endodonticamente tem sido objeto de estudos que buscam identificar meios que tornem o complexo restaurador mais resistente às cargas mastigatórias. Dentes tratados endodonticamente são acometidos por alto risco de falha biomecânica (Llena-Puy et al., 2001) devido à significante diferença de propriedades mecânicas do complexo restaurador comparado ao dente hígido (Assif & Gorfil, 1994; Schwartz & Robbins, 2004).
A presença de uma quantidade mínima de remanescente dentinário na porção cervical do elemento dentário promove aumento na resistência à fratura e longevidade do dente tratado endodonticamente, tornando a férula o fator mecânico mais importante para promover resistência à raiz tratada endodonticamente (Zhi-Yue & Yu-Xing, 2003; Soares et al., 2012).
Em situações de grande perda de estrutura dental, pinos intrarradiculares podem ser utilizados a fim de proporcionar retenção à restauração. Tradicionalmente, retentores intrarradiculares eram feitos com metais, o que os torna menos estéticos, especialmente na região anterior. Além disso, possuem alto módulo de elasticidade quando comparado à dentina remanescente, o que pode levar a concentração de tensões, fraturas radiculares e perda do elemento dental ao longo do tempo (Assif & Gorfil, 1994; Gbadebo et al., 2014).
Os pinos de fibra de vidro foram introduzidos na Odontologia no início da década de 90 devido ao aumento na demanda por restaurações livres de metal. Além de serem mais estéticos, apresentam módulo de elasticidade semelhante ao da dentina e ao de compósitos e são passíveis de união à estrutura dental através da técnica adesiva (Ferrari et al., 2000; Pegoretti et al., 2002; Schwartz & Robbins, 2004). Porém, uma vez que os pinos de fibra de vidro possuem tamanho padronizado, sua geometria muitas vezes não corresponde ao formato do canal fragilizado, resultando em adaptação imprecisa e uma espessa camada de cimento durante sua cimentação. Nessa situação, considerando o conduto como uma caixa de cinco paredes, cujo preenchimento não pode ser realizado por incrementos, o fator-C interno seria muito alto, sem a possibilidade de liberação da tensão residual, prejudicando a resistência adesiva (Kina & Bruguera, 2008).
Diante dessa observação e sabendo-se que o seu principal motivo de falha é a perda de retenção (Ferrari et al., 2000), foram propostas técnicas para contornar essa desvantagem. Uma das técnicas propostas foi a anatomização dos pinos de fibra
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de vidro com resina composta (pinos anatômicos), ou seja, é realizada modelagem do conduto radicular com resina composta fotoativada, confeccionando pinos individualizados (Grandini et al., 2003; Grandini et al., 2005; Faria-e-Silva et al., 2009). As vantagens desta técnica incluem diminuição da linha de cimentação, tornando-a mais uniforme, diminuição da incidência de bolhas e falhas na camada de cimento e ainda preservação da estrutura dentária, pois o pino se adapta ao canal e não o contrário (Grandini et al., 2005). Os pinos anatômicos promovem melhor adaptação do retentor às paredes do conduto e tendem a apresentar maiores valores de resistência de união pelo aumento da resistência ao cisalhamento (Faria-e-Silva et al., 2009).
Porém, a utilização de pinos de fibra de vidro anatômicos, pode levar a maiores concentrações de tensões nas interfaces de materiais com diferentes módulos de elasticidade, como pino, cimento e resina composta (Assif & Gorfil, 1994; Pegoretti et al., 2002).
Nesse contexto seria interessante o desenvolvimento de um núcleo moldado no canal radicular que seja fabricado com um material com módulo de elasticidade mais baixo, a fim de se obter um corpo único no retentor intrarradicular. Recentemente inúmeras pesquisas estão voltadas ao desenvolvimento de próteses médicas e odontológicas usinadas com um polímero produzido a partir da resina de polieteretercetona (Stawarczyk et al., 2014; Liebermann et al., 2016; Najeeb et al., 2016).
O polieteretercetona (PEEK) representa um polímero termoplástico de alto desempenho, que consiste de moléculas aromáticas de benzeno ligadas alternadamente por grupos funcionais de éter ou cetona. Apresenta boa estabilidade dimensional, biocompatibilidade, facilidade de polimento, usinabilidade (Stawarczyk et al., 2014; Costa-Palau et al., 2014), alta resistência ao desgaste, à fadiga e ao calor (Zhou et al., 2014).
Sua utilização tem sido proposta em bases de próteses fixas e próteses parciais removíveis (Najeeb et al., 2016). Porém, a composição química e a baixa energia de superfície do PEEK poderia promover dificuldades de união com materiais resinosos. Nesse aspecto, o estudo deste material por meio de elementos finitos poderia representar as diferenças e mudanças na adesão e distribuição de tensões ao longo da raiz (Caldas et al., 2018). Uma vez que as condições adesivas são difíceis de analisar in vitro e especialmente in vivo, a análise em elementos finitos torna-se
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um método eminente para estudar o efeito da união e o processo de perda de adesão em condições de tensões internas (Caldas et al., 2018).
O polímero PEEK é passível de usinagem em CAD/CAM permitindo a confecção de peças a partir de modelos 3D criados pelo escaneamento de moldagens dentárias. Os fabricantes afirmam que os materiais utilizados como matéria-prima para a usinagem exibem propriedades mecânicas melhoradas quando comparados aos polímeros polimerizados manualmente, devido ao fato de que são confeccionados sob condições controladas de temperatura e pressão, melhorando a qualidade da restauração. Essa técnica pode requerer ajustes mínimos ou nulos, fazendo com que o tempo clínico do profissional seja diminuído (Stawarczyk et al., 2012; Liebermann et al., 2016; Rayyan et al., 2015).
Assim, a fabricação de núcleos a partir da usinagem em CAD/CAM de polímero PEEK, possibilitaria a confecção de um retentor intrarradicular previamente moldado e produzido em laboratório, com a vantagem de poder ser indicado em casos de grande perda de estrutura dentária. Por possuir módulo de elasticidade menor que ligas metálicas e a ausência de interfaces (como presente no pino de fibra de vidro anatomizado com resina composta) formaria um corpo único que poderia levar à maior resistência do conjunto restaurador, diminuindo falhas adesivas e evitando fratura prematura do pino/núcleo de preenchimento.
Desse modo, o objetivo do presente estudo foi comparar a resistência à fratura (in vitro) e distribuição de tensões na raiz (análise de elementos finitos) de núcleos confeccionados em polímero PEEK usinados no sistema CAD/CAM com retentores em fibra de vidro anatomizados ou não anatomizados, na presença ou ausência de férula. As hipóteses testadas foram: (1) a ausência de férula poderia ser compensada pelo uso de um retentor em corpo único, e (2) núcleos em PEEK poderiam aumentar a resistência à fratura de dentes tratados endodonticamente.
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2 ARTIGO
APPLICATION OF POLYETHERETHERKETONE (PEEK) POSTS: EVALUATION OF FRACTURE RESISTANCE AND STRESS DISTRIBUTION IN THE ROOT.
Michele O. Limaa, Ricardo A. Caldasb, Valentim A. R. Barãob, Fabiana M.G.
Françac, Gisele M. Marchia, Debora A.N.L. Limaa, Flávio H. B. Aguiara
a University of Campinas (UNICAMP), Piracicaba Dental School,
Department of Restorative Dentistry, Av. Limeira 901, Piracicaba, 13414-903, SP, Brazil.
b University of Campinas (UNICAMP), Piracicaba Dental School,
Department of Prosthodontics and Periodontology, Av. Limeira 901, Piracicaba, 13414-903, SP, Brazil.
C São Leopoldo Mandic Institute and Dental Research Center, Rua José
Rocha Junqueira 13, Bairro Swift, Campinas, CEP: 13045-755, São Paulo, Brazil.
Corresponding author
Department of Restorative Dentistry Flávio Henrique Baggio Aguiar
Piracicaba Dental School, University of Campinas, Av. Limeira, 901, P.O. BOX 52, Piracicaba, SP, 13414-903, Brazil
Phone number: +55 19 2106-5337/ + 55 19 34210144 E-mail: baguiar@unicamp.br
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Abstract
Objectives: to evaluate the feasibility of using milled PEEK post and core in
endodontically treated teeth. Methods: sixty bovine roots were treated endodontically and cemented with intraradicular retainers, according to each experimental group: no-ferrule glass fiber post (f0FP); 2 mm-ferrule glass fiber post (f2FP); no-ferrule resized
glass fiber post (f0PR); 2 mm-ferrule resized glass fiber post (f2PR); no-ferrule PEEK
post and core (f0PPC) and 2-mm ferrule PEEK post and core (f2PPC). Metallic crowns
were made and cemented. The periodontal ligament was simulated using polyether. A force was applied to the palatine portion of each sample at 45°, until fracture occurred. The fracture resistance was measured and data were submitted to two-way ANOVA (α=0.05). Failure mode was analyzed visually, and three-dimensional digital models were developed to calculate the tensions generated in the root using the finite element analysis. The models of fiber glass post and PEEK post and core were evaluated in the presence or absence of ferrule. Results were analyzed by the Mohr-Coulomb criterion. Results: Fracture resistance was not influenced by the type of intraradicular retainer (p=0.243), but ferrule factor provided higher fracture resistance (p<0.0001). All specimens presented irreparable failure mode. The failure mode of teeth with ferrule was more catastrophic than in the absence ferrule. Significance: PEEK post and core performed similarly to fiber glass posts. The use of PEEK might reduce laboratory and chair side time. Dental professionals can obtain a 3D virtual image by scanning the root space with CAD/CAM technology, and create a specifically fitted monolayer intraradicular retainer system.
Keywords: Intraradicular retainer; ferrule; PEEK; finite element analysis; fracture resistance.
1. Introduction
Roots with minimal or no coronal tooth structure have been commonly restored with cast post and core for the purpose of increasing retention of dental restoration [1]. The advantage of using cast post and core is reported in the absence of interfaces with materials of different elastic modulus, which could concentrate less tension in the root coronal third [2,3]. Furthermore, due to its high elastic modulus, metallic cast post and core is associated with more catastrophic failure compared to fiber post [4].
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In this context, it is interesting to develop an anatomical post and core that is made of a material with lower elasticity modulus, in order to form a single-piece intraradicular retainer, avoiding interfaces of different elasticities. Recently, several studies have focused on the development of medical and dental prostheses milled with a polymer produced from polyetheretherketone (PEEK) resin [5-7].
Polyetheretherketone consists of a thermoplastic polymer which exhibits good dimensional stability, biocompatibility, easy polishing and machinability [5,8]. Recently, its use has been proposed for fixed prosthesis and removable partial denture bases [7]. However, the chemical composition and the low surface energy of PEEK could lead to difficulties of union with resin materials [9]. In this aspect, the finite element analysis of this material could explain the differences and changes in adhesion and tension distribution along the root [10].
Manufacturing a PEEK polymer post and core using milling in CAD/CAM would make a laboratory-produced, previously molded intraradicular retainer, with the advantage of being indicatable in cases of great loss of tooth structure. The advantage stems from the fact that PEEK has a lower elasticity modulus than metal alloys, and can present a unique interface between the post and tooth, different from the ones present in relined fiber glass post with composite resin or the conventional fiber post technique.
The resulting single-piece structure could lead to greater resistance of the restorative system, reducing adhesive failures and preventing premature fracture of the post/core. In addition, the use of digital dentistry for manufacturing of intraradicular retainers could lead to a higher clinical success rate, reducing the failure rate of restorative complex due to operator failures.
Thus, the aim of the present study was to compare fracture resistance (in vitro) and root stress distribution (finite element analysis) of PEEK polymer post and core milled in CAD/CAM system with resized glass fiber post and non-resized glass fiber post, in roots with presence or absence of ferrule. The hypotheses tested were: (1) the absence of ferrule would be compensated by the use of a single-piece post and core, and (2) PEEK post and core would improve the fracture resistance of endodontically treated teeth.
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2. Materials and Methods
2.1 Sample preparation and laboratory analyses
Sixty mandibular bovine incisors were extracted and stored in 0.1 % thymol buffered solution. Teeth were decoronated at 13 mm or 15 mm from the apex, according to each experimental group. Each sample was examined and selected according to the following exclusion criteria: 1- root canal diameter, the canal space was the most circular and/or had a maximum diameter of 2 mm, measured with a digital caliper; 2- root curvature; 3- radicular apex diameter. Subsequently, the roots were separated into 6 groups: no-ferrule glass fiber post (f0FP); 2 mm-ferrule glass fiber post
(f2FP); no-ferrule resized glass fiber post (f0PR); 2 mm-ferrule resized glass fiber post
(f2PR); no-ferrule PEEK post and core (f0PPC) and 2 mm-ferrule PEEK post and core
(f2PPC).
All specimens were prepared by the same operator. Endodontic treatment was performed using K-files and Gates-Glidden #3 to #5 (Dentsply Maillefer, Ballaigues, Switzerland) according to step-back technique [11] under saline solution irrigation. After preparation, the root canals were irrigated with EDTA. Obturation was performed by the lateral condensation technique using medium large gutta-percha (Dentsply, Petrópolis, RJ, Brazil) and endodontic cement (Sealer 26, Dentsply, York, PA, USA).
Root surfaces were dipped into melted wax (New Wax, Technew, Rio de Janeiro, RJ, Brazil), and specimens were fixed with acrylic resin (Classico, Campo Limpo Paulista, SP, Brazil) using a polyvinyl chloride pipe (Tigre S/A, Joinville, SC, Brazil) and embedding 11.5 mm of the root. The root was removed along its long axis, and the wax was removed. Between the root and the resin block, a polyether-based material (Impregum Soft, 3M ESPE, St. Paul, MN, USA) was inserted, forming a layer that simulated the periodontal ligament.
The root specimens were prepared with Largo drills #5 (Dentsply Maillefer, Ballaigus, Switzerland), compatible with the thickness of n°3 glass fiber post (Exacto, Ângelus, Londrina, PR, Brazil), leaving 3 mm of endodontic material from the apex. Specimens with 2 mm-ferrule were prepared by the same operator using diamond drills (4072- KG Sorensen, Cotia, SP, Brazil).
Root specimens in PEEK post and core groups were previously lubricated with hydrosoluble gel and molded with acrylic resin (Duralay- Reliance Dental Manufacturing, Chicago, IL, USA). Standardization of the coronary portion was
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achieved using core of NucleoJet (NucleoJet, Ângelus, Londrina, PR, Brazil). The intraradicular impression was sent to the prosthetic laboratory and scanned by Cerec inLab (Sirona-Bensheim, Germany) CAD/CAM software. From the digital models created, a PEEK polymer block (PEEK OPTIMA- Juvora, Lancashire, UK) was milled to produce a post and core.
The canal walls of the f0PR and f2PR groups were lubricated with a
hydrosoluble gel and molded with bulk fill composite resin (Filtek Bulk Fill, 3M ESPE, St. Paul, MN, USA). This composite resin and the fiber post were positioned inside the root canal and photoactivated with light emitting diode (Valo, Ultradent Products, Inc., South Jordan-UT, USA) in High Power mode for 5 s. Resized posts were removed from the canal and complete polymerization was performed for 15 s.
For all specimens, the dentin was etched with 35 % phosphoric acid (Ultra-Etch; Ultradent Products Inc, Salt Lake City, UT, USA) for 15 s, then rinsed for 20 s, and gently dried with paper points (Endopoints, Manacapuru, Brazil), followed by application of the adhesive system Adper Scotchbond Multi-purpose Plus (3M ESPE, St. Paul, MN, USA) with activator, primer, catalyst steps, according to manufacturer's recommendations.
Prior to the luting procedure, all fiber posts were cleaned with alcohol, air-dried, and received a silane layer (RelyX Ceramic Primer, 3M ESPE), whereas PEEK posts and cores were etched with 98 % sulfuric acid for 60 s, then rinsed for 60 s and air-dried [9,12]. A layer of Visio.link (Bredent, Senden, Germany) was applied on PEEK surface, followed by photoactivation for 90 s, according to Uhrenbacher et al., 2014 [12].
All posts were cemented to the root with RelyX ARC luting agent (3M ESPE, St. Paul, MN, USA). Groups receiving fiber posts had the core foundation restorations made with bulk fill composite resin, followed by the same procedure used for the preparation of the coronary portion in PEEK post and core groups, as described above. Acrylic crowns previously obtained from a mold (5.0 mm mesio-distal width and 9.0 mm cervical-incisal width) of upper central incisor shape and including a point in the palatal used to define the force application of the universal testing machine. The acrylic crowns were relined on the cores, numerated, and casted with nickel-chromium alloy (Durabond, São Paulo, SP, Brazil). Metal crowns adaptation was verified on the cores and cemented with zinc phosphate luting agent (SS White, Philadelphia,
22
Pennsylvania, USA) according to manufacturer's instructions. Excess material was removed and the specimens were stored at 37 °C for 48 h.
The fracture resistance (N) was evaluated in a Universal Testing Machine (Instron 1144, Instron Corporation, Canton, MA, USA) with load applied on the palatal portion of the crown specimens at a 45º angle to the horizontal plane, at a speed of 1 mm/min, until fracture. The fracture strength (N) value of each sample was defined as the highest point observed in the represented load x displacement curve.
2.2 Failure mode
After evaluating the fracture resistance, all samples were visually analyzed to detect the type of failure. A visual distinction was made among 4 fracture modes, using a classification system modified from Rippe et al., 2014 [13], considering the location as follows: (Type 1) radicular fracture up to 1 mm below the simulated bone level; (Type 2) radicular fracture up to 2 mm below the simulated bone level; (Type 3) radicular fracture up to 3 mm below the simulated bone level; and (Type 4) radicular fracture more than 4 mm below the simulated bone level.
2.3 Finite Element Analysis
A three-dimensional (3D) human incisor tooth model was obtained from an open-access online database [10,14]. The tooth model was resized to compatible dimensions used in the laboratory study. According to cervical conditions used in the experiments, two dental preparations were modeled: no ferrule (f0) and 2 mm-ferrule
(f2). Dimensions of Largo drills #5 (Dentsply Maillefer, Ballaigus, Switzerland) were
taken into account to model the endodontic treatment. Three-dimensional geometries and assemblies were created with a computer-aided design (CAD) software (SolidWorks 2010, Concord, MA, USA). Intraradicular retainers were created representing the experimental groups: glass fiber post and PEEK post and core. A total of four 3D models were created including periodontal ligament, acrylic resin cylinder, tooth root, dental coronal remnants, and prosthetic crown.
The 3D models were imported to a computer-aided engineering software (ANSYS Workbench 11, Ansys Inc, Pittsburg, PA, USA). Meshes were composed by 10-nodes tetrahedrons checked for element quality and refined in areas of interest. Elements were assigned material properties. All materials were considered linear elastic, isotropic, and homogeneous, except the orthotropic glass-fiber posts (Table 1).
23
The applied material properties were obtained from published data as presented in Table 1.
A simulated total load of 100 N was applied in cingulum at 45° to the long axis of the tooth. Model movements were restricted by fixing all six degrees of freedom at the bottom and lateral surface of the base nodes of acrylic resin cylinders. Complete bond failure was simulated between tooth and restorative materials, following a previously described protocol [10], in order to achieve better correlation for finite element analysis and in vitro studies.
Mohr–Coulomb failure theory was used to analyze the stress ratio in dentin, according to a previous study [10], considering the dentin ultimate tensile strength and ultimate compressive strength of 96 MPa [15] and 295 MPa [16], respectively. Maximum and minimum principal stress are presented and compared.
Table 1- Material properties used in finite element analysis.
Material Elastic modulus (GPa) Poisson's ratio Shear modulus (GPa) References
Dentin 18 0.31 Santos Filho (2014)
Polyether 0.05 0.45 Santos Filho (2014)
Acrylic resin 13.5 0.31 Santos Filho (2014)
Composite resin 15.8 0.24 Santos Filho (2014
Resin cement 8.3 0.24 Oyar (2014)
NiCr alloy 205 0.33 Oyar (2014)
PEEK 4 0.25 Kim (2012)
Glass fiber post ª
x=37 xy=0.34 xy=3.54
Caldas (2018)
y=9.5 yz=0.27 yz=14.57
z=9.5 xz=0.34 xz=3.54
ª x- Axis in the glass fiber post long axis
2.4 Statistical Analysis
The exploratory analysis indicated a logarithmic transformation for the data to satisfy assumptions for analysis of variance (ANOVA). Two-way ANOVA was applied after the transformation. The analysis was performed in program R, considering the level of significance of 5 %.
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3. Results
3.1 Fracture resistance
The results of fracture resistance analysis are presented in table 2. Fracture resistance was significantly higher in the presence of ferrule (p<0.0001). There was no significant difference between the types of intraradicular retainer (p=0.2432).
Table 2- Mean (standard deviation) of fracture resistance (N) according to the type of intraradicular retainer and clinical situation of coronary remnant (ferrule).
Type of retainer Remaining coronary
Ferrule No-ferrule
Glass fiber post 720,44 (190,29) Aa 426,95 (55,61) Ba Resized glass fiber post 849,06 (98,44) Aa 449,26 (92,06) Ba PEEK post and core 820,66 (240,17) Aa 439,47 (80,93) Ba
Different letters (uppercase in the horizontal and lowercase in the column) are statistically different (p≤0.05).
3.2 Failure mode
According to our experimental designer, 100 % of catastrophic failures (crack propagated vertically in the middle and apical root thirds) were expected, in consequence of use of metallic crowns in order to avoid any fracture interference of the crown material in the results.
However, the presence of ferrule led to a more catastrophic fracture mode (type 3 and type 4) than in groups without ferrule (figure 1), with mesio-distal fracture and detachment of the root and crown fragment (figure 2).
The crack originated in different regions, depending on the presence or absence of ferrule. For groups with ferrule, the fracture started closer to the lingual face, whereas in the absence ferrule, crack propagated in the medial region of the proximal faces (figure 2).
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Figure 1- Fracture mode distribution. Captions: f0FP - no-ferrule glass fiber post; f2FP - 2 mm ferrule glass fiber post; f0PR - no-ferrule resized glass fiber post; f2PR - 2 mm ferrule resized glass fiber post; f0PPC - no-ferrule PEEK post and core; f2PPC - 2 mm ferrule PEEK post and core.
Type 1 - radicular fracture up to 1 mm below the simulated bone level; Type 2 - radicular fracture up to 2 mm below the simulated bone level; Type 3 - radicular fracture up to 3 mm below the simulated bone level; and Type 4 - radicular fracture more than 4 mm below the simulated bone level.
Figure 2- Specimens classified with catastrophic failure mode. A: Failure mode in roots with absence of ferrule. B: failure mode in roots with ferrule.
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% f0FP f2FP f0PR f2PR f0PPC f2PPC
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3.3 Finite element analysis (FEA)
The maximum principal stress, minimum principal stress, and Mohr-Coulomb stress ratio were evaluated when a load was applied to the tooth lingual cingulum. For clarity of representation, figures 3, 4, and 5 demonstrate the effects on root surface caused by the applied load.
For all analyzed parameters (maximum principal stress, minimum principal stress and Mohr-Coulomb stress ratio) the tensions generated in the root were similar among the groups of different posts, although PEEK post and core has shown higher stress values when compared to fiber glass post.
The absence of ferrule led to a higher concentration of compressive and tensile stresses in a cervical area. The presence of ferrule caused a more pronounced effect on FEA fracture resistance than the type of restorative material, corroborating the laboratory results of this research.
Stress vectors generated in FEA simulations with or without ferrule demonstrated that the origin of the crack is located in different regions, depending on the presence or absence of dental coronal remnants. The crack occurs perpendicularly to maximum principal vectors (red vectors indicate the maximum principal stress). In the presence of ferrule, fracture started at the region closer to the lingual face, whereas in the absence of ferrule, FEA figures indicate that the crack started at the medial region of the proximal faces (figures 6 and 2). Vectors size is proportional to its value. Biggest vectors are in agreement with the site and direction of initial crack.
27
Figure 3- Maximum Principal Stress data demonstrating the effects on root
surface caused by loading. Captions: f0FP - no-ferrule glass fiber post; f2FP - 2 mm ferrule glass fiber post; f0PPC - no-ferrule PEEK post and core; f2PPC - 2 mm ferrule PEEK post and core.
Figure 4- Minimum Principal Stress data demonstrating the effects on root surface caused by loading. Captions: f0FP - no-ferrule glass fiber post; f2FP - 2 mm ferrule glass fiber post; f0PPC - no-ferrule PEEK post and core; f2PPC - 2 mm ferrule PEEK post and core.
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Figure 5- Mohr-Coulomb Stress Ratio data demonstrating the effects on root surface caused by loading. Captions: f0FP - no-ferrule glass fiber post; f2FP - 2 mm ferrule glass fiber post; f0PPC - no-ferrule PEEK post and core; f2PPC - 2 mm ferrule PEEK post and core.
Figure 6- Stress vectors generated in FEA simulations with absence of ferrule and with presence of ferrule demonstrate the origin of the crack. Red vectors: indicates the maximum principal stress (the crack occurs perpendicularly to maximum principal vectors).
29
4. Discussion
The purpose of using posts is to provide retention to definitive restoration when endodontically treated teeth have lost much dental structure and there is insufficient remaining clinical crown [20,21]. The space preparation and the quantity of coronal and root dentin remaining after root canal treatment are important factors in the performance and longevity of the tooth and restoration [22].
The amount of remaining dentin after preparation is a more relevant factor in influencing longevity than the type of post and core [23]. A minimum of 1.5 - 2 mm ferrule of dentin provides higher fracture resistance than in the absence of ferrule, and enhances longevity of endodontically treated teeth restored with post and crown [22,24].
This occurs because fracture resistance will be increased by any mechanism that increases the amount of energy required to propagate the primary crack [25]. The ferrule acts as an additional barrier that holds the crack propagation and consequently increases the intrinsic resistance of the core [26]. Thus, the first hypothesis was rejected.
The crack starts in the region of highest stress concentration (tensile stress), which probably resulted in root fractures, as can be seen in figures 3, 4, 5, and 6. In figure 6, it is evident that stress vectors are dissipated throughout the inner dentine and are impossible to detect clinically. Moreover, the inner dentinal matrix adjacent to the root canal is less mineralized and presents high density of dentinal tubules [25]. This fact could lead to a higher susceptibility of the inner dentine as a crack starting-point.
Furthermore, another important aspect reported is the primary adhesion failures, causing a gap and separation between crown and root [10,26] (figure 2). An abrupt adhesion failure at the lingual margin was accompanied by the opening of a gap starting between the root and the crown, which intensified and was followed by total failure [26].
After the initial adhesive gap, the fracture started according to the resulting stress vectors shown in figure 6. In teeth where a ferrule was present, the fracture began and propagated in a region nearest to lingual face, in contrast to teeth without ferrule, where the fracture began and propagated in the central region of proximal faces (figure 2).
30
The present study observed 100 % of catastrophic failures (fractures reaching the middle and apical root thirds), regardless of the material of the post. These results were expected due to our experimental design, which used metallic crowns in order to avoid any fracture interference of the crown material in the results.
In view of the present results, the presence of ferrule led to a more catastrophic fracture mode than observed in the absence of ferrule (figure 1), although the fracture resistance was higher in teeth with ferrule. Thus, groups with ferrule presented greater fracture resistance, and delayed onset of fracture, but the final resulting crack was more catastrophic. These findings are in accordance with a previous study [27], in which detected failure modes tended to be more favorable when short or no core buildup was used.
Although PEEK post and core presented higher stress values in FEA when compared to glass fiber post, no relevant statistical differences were observed among the retainer materials (table 2) in this in vitro study. This may be related to the high resistance properties of PEEK [9,28], though presenting lower elasticity modulus than glass fiber posts. Thus, the second hypothesis was rejected.
The elastic modulus of intraradicular posts is associated to the stress transmitted to the root, reported as being one of the most important factors in the fracture mechanism [29,30]. Materials of lower elastic modulus decrease stress in the interfaces, minimizing the transmission of stresses on the root walls, and allowing the restored system to mimic the mechanical behavior of a natural tooth [31,32]. The elastic limit of post can be influenced by many factors, such as composition of the material and diameter [33], modifying stress distribution and fracture resistance.
In this study, the increase in the intraradicular diameter of the glass fiber posts relined with resin composite did not significantly influence the fracture resistance of endodontically treated teeth. This is in accordance to a study by Farina et al. 2015 [32], which described dentinal wall thickness as an important factor for fracture resistance, but with no significant influence in relined posts.
Whereas there are several studies [11,34,35] indicating that the anatomical post has great influence on the retention and push-out bond strength, not much is known on the fracture resistance of relined or non-relined posts. The lack of statistical differences between relined and non-relined groups in fracture resistance tests reported here can be attributed to the similar elastic modulus between resin cement and resin composite.
31
Relining procedure increases post adaptation to the root walls and decreases the amount and thickness of resin cement around the fiber post, improving the frictional retention and reducing blister formation [32,36]. However, these techniques are not easy to perform, and require more clinical time when compared to the use of conventional fiber post cementation.
Thus, experimental milled materials might reduce the laboratory and chair side time. With the development of scanning technology dental professionals would obtain 3D virtual images by rapidly scanning the root space, and produce an intraradicular post and core using CAD/CAM. With the aid of CAD/CAM technology, a post and core system can be created as a one-piece structure that fits any tooth. In addition, the possibility of milling both the post and core would simplify the technique by eliminating the need for a composite resin to build-up a resin core [21,37].
Therefore, application of CAD/CAM technology to produce anatomic prefabricated custom intraradicular retainers seems a viable option. This technique allows for a cement layer of minimum thickness, and eliminates the necessity to adhesively bind a composite resin to build up an adequate core for assisting restoration retaining, creating a monolayer intraradicular retainer system [37], it may lead to a greater longevity of the rehabilitation procedure, due to the absence of interfaces.
Thus, the use of intraradicular PEEK post and core led to similar results of fracture resistance when compared to the fiber glass post. However, more laboratory and clinical research is necessary to validate conclusions on the use of intraradicular PEEK post and core.
5. Conclusion
A ferrule provides higher fracture resistance to endodontically treated teeth restored with post and crown.
Teeth with a ferrule presented higher fracture resistance and failure mode more catastrophic than teeth with absence of ferrule.
PEEK post and core retainer did not modify the fracture resistance of endodontically treated teeth.
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Acknowledgment
Acknowledgments to financial support providing a PhD scholarship by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001.
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[20] Santos-Filho PC, Castro CG, Silva GR, Campos RE, Soares CJ. Effects of post system and length on the strain and fracture resistance of root filled bovine teeth. Int Endod J. 2008;41:493-501. doi:10.1111/j.1365-2591.2008.01383.x. [21] Ruschel GH, Gomes ÉA, Silva-Sousa YT, Pinelli RGP, Sousa-Neto MD, Pereira
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[30] Wandscher VF, Bergoli CD, de Oliveira AF, Kaizer OB, Souto Borges AL, Limberguer Ida F, Valandro LF. Fatigue surviving, fracture resistance, shear stress and finite element analysis of glass fiber posts with different diameters. J Mech Behav Biomed Mater. 2015;43:69-77. doi:10.1016/j.jmbbm.2014.11.016. [31] Zarone F, Sorrentino R, Apicella D, Valentino B, Ferrari M, Aversa R, Apicella A. Evaluation of the biomechanical behavior of maxillary central incisors restored by means of endocrowns compared to a natural tooth: a 3D static linear finite elements analysis. Dent Mater. 2006;22:1035-44.
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[33] Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit, and strength of newer types of endodontic posts. J Dent. 1999;27:275-8.
[34] Grandini S, Goracci C, Monticelli F, Borracchini A, Ferrari M. SEM evaluation of the cement layer thickness after luting two different posts. J Adhes Dent. 2005;7:235-40.
[35] Faria-e-Silva AL, Pedrosa-Filho Cde F, Menezes Mde S, Silveira DM, Martins LR. Effect of relining on fiber post retention to root canal. J Appl Oral Sci. 2009;17:600-4.
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3 CONCLUSÃO
De acordo com os resultados obtidos, foi possível concluir que:
A presença de férula promove aumento da resistência a fratura de dentes tratados endodonticamente e restaurados com retentor intrarradicular e coroa.
Dentes com férula apresentaram maiores valores de resistência à fratura e obtiveram padrões mais catastróficos de falha quando comparado a dentes sem férula.
O núcleo em PEEK avaliado não modificou a biomecânica de dentes tratados endodonticamente, e assemelhou-se aos resultados encontrados para pinos de fibra de vidro.
37
REFERÊNCIAS
Assif D, Gorfil C. Biomechanical considerations in restoring endodontically treated teeth. J Prosthet Dent. 1994;71(6):565-7.
Caldas RA, Bacchi A, Barão VAR, Versluis A. Should adhesive debonding be simulated for intra-radicular post stress analyses? Dent Mater. 2018;34(9):1331-1341.
Costa-Palau S, Torrents-Nicolas J, Brufau-de Barberà M, Cabratosa-Termes J. Use of polyetheretherketone in the fabrication of a maxillary obturator prosthesis: a clinical report. J Prosthet Dent. 2014;112(3):680-2.
Faria-e-Silva AL, Pedrosa-Filho Cde F, Menezes Mde S, Silveira DM, Martins LR. Effect of relining on fiber post retention to root canal. J Appl Oral Sci. 2009;17(6):600-4.
Ferrari M, Vichi A, Mannocci F, Mason PN. Retrospective study of the clinical performance of fiber posts. Am J Dent. 2000;13:9B-13B.
Gbadebo OS, Ajayi DM, Oyekunle OO, Shaba PO. Randomized clinical study comparing metallic and glass fiber post in restoration of endodontically treated teeth. Indian J Dent Res. 2014;25(1):58-63.
Grandini S, Sapio S, Simonetti M. Use of anatomic post and core for reconstructing an endodontically treated tooth: a case report. J Adhes Dent. 2003;5(3):243-7.
Grandini S, Goracci C, Monticelli F, Borracchini A, Ferrari M. SEM evaluation of the cement layer thickness after luting two different posts. J Adhes Dent. 2005;7:235-40.
De acordo com as normas da UNICAMP/FOP, baseadas na padronização do International Committee of
38
Kina S, Bruguera A. Invisível: restaurações estéticas cerâmicas. Maringá: Dental Press Editora; 2008.
Liebermann A, Wimmer T, Schmidlin PR, Scherer H, Löffler P, Roos M, Stawarczyk B. Physicomechanical characterization of polyetheretherketone and current esthetic dental CAD/CAM polymers after aging in different storage media. J Prosthet Dent. 2016;115(3):321-8.
Llena-Puy MC, Forner-Navarro L, Barbero-Navarro I. Vertical root fracture in endodontically treated teeth: a review of 25 cases. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2001;92(5):553-5.
Najeeb S, Zafar MS, Khurshid Z, Siddiqui F. Applications of
polyetheretherketone (PEEK) in oral implantology and prosthodontics. J Prosthodont Res. 2016;60(1):12-9.
Pegoretti A, Fambri L, Zappini G, Bianchetti M. Finite element analysis of a glass fibre reinforced composite endodontic post. Biomaterials. 2002;23(13):2667-82.
Rayyan MM, Aboushelib M, Sayed NM, Ibrahim A, Jimbo R. Comparison of interim restorations fabricated by CAD/CAM with those fabricated manually. J Prosthet Dent. 2015;114(3):414-9.
Schwartz RS, Robbins JW. Post placement and restoration of endodontically treated teeth: a literature review. J Endod. 2004;30(5):289-301.
Soares CJ, Valdivia AD, da Silva GR, Santana FR, Menezes Mde S. Longitudinal clinical evaluation of post systems: a literature review. Braz Dent J. 2012;23(2):135-740.
Stawarczyk B, Ender A, Trottmann A, Özcan M, Fischer J, Hämmerle CH. Load-bearing capacity of CAD/CAM milled polymeric three-unit fixed dental
39
Stawarczyk B, Jordan P, Schmidlin PR, Roos M, Eichberger M, Gernet W, Keul C. PEEK surface treatment effects on tensile bond strength to veneering resins. J Prosthet Dent. 2014;112(5):1278-88.
Zhi-Yue L, Yu-Xing Z. Effects of post-core design and ferrule on fracture resistance of endodontically treated maxillary central incisors. J Prosthet Dent. 2003;89(4):368–73.
Zhou L, Qian Y, Zhu Y, Liu H, Gan K, Guo J. The effect of different surface treatments on the bond strength of PEEK composite materials. Dent Mater.
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APÊNDICE 1
METODOLOGIA ILUSTRADA
Delineamento experimental
Os fatores em estudo estão descritos a seguir:
Tipo de retentor intrarradicular: Pino de fibra de vidro, pino de fibra de vidro anatomizado com resina composta e núcleo em PEEK.
Férula: presença de férula de 2mm e ausência de férula.
As variáveis de resposta foram: resistência a fratura, padrão de fratura e tensões na raiz calculadas por elementos finitos.
Tabela 1- Descrição dos modelos computacionais e grupos experimentais.
Tipo de retentor Férula Grupo
Pino de fibra de vidro Presente f2FP
Pino de fibra de vidro Ausente f0FP
Pino de fibra de vidro anatomizado Presente f2PR Pino de fibra de vidro anatomizado Ausente f0PR
Núcleo em PEEk Presente f2PPC
Núcleo em PEEk Ausente f0PPC
Figura 1- Esquema representativo do tipo de retentor intrarradicular: núcleo em PEEK, pino de fibra de vidro não anatomizado e pino de fibra de vidro anatomizado com resina composta.
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Figura 2- Quantidade de remanescente coronário (presença ou ausência de férula).
Figura 3- Representação da desobturação e dimensões de preparo, tamanho de férula e altura do núcleo de preenchimento.
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Figura 5- Confecção do núcleo em PEEK e tratamento de superfície A: representação de padrão em duralay e núcleo em PEEK; B: fresagem do PEEK; C: tratamento de superfífie com ácido sulfúrico 98% e enxágue com água destilada; D: tratamento final de superfície com uma camada fina de visio.link.
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Figura 8- Cimentação de coroas metálicas. A: cimento de fosfato de zinco e manipulação de acordo com recomendações do fabricante; B: cimentação de coroas metálicas; C: remoção de excessos do cimento.
Figura 9- Simulação de ligamento periodontal.
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Figura 11. Modelos 3D do estudo de elementos finitos. A: pino de fibra de vidro não anatomizado com férula. B: núcleo em PEEK com férula. C: pino de fibra de vidro não anatomizado sem férula. D: núcleo em PEEK sem férula.
Figura 12. Representação da aplicação da carga no cíngulo (45° do longo eixo do dente) no estudo de elementos finitos.
A B A C A D A
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ANEXO 1
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ANEXO 2
