i
DIMORVAN BORDIN
“BIOFILME E SALIVA AFETAM O COMPORTAMENTO BIOMECÂNICO DOS IMPLANTES DENTÁRIOS"
“BIOFILM AND SALIVA AFFECT THE BIOMECHANICAL BEHAVIOR OF DENTAL IMPLANTS”
PIRACICABA 2014
iii
UNIVERSIDADE ESTADUALDE CAMPINAS FACULDADE DE ODONTOLOGIA DE PIRACICABA
DIMORVAN BORDIN
“BIOFILME E SALIVA AFETAM O COMPORTAMENTO BIOMECÂNICO DOS IMPLANTES DENTÁRIOS”
“BIOFILM AND SALIVA AFFECT THE BIOMECHANICAL BEHAVIOR OF DENTAL IMPLANTS”
Dissertação de Mestrado apresentada à Faculdade de Odontologia de Piracicaba da Universidade Estadual de Campinas para obtenção do título de Mestre em Clínica Odontológica na área de Prótese Dental.
Dissertation presented to the Piracicaba School of Dentistry of the University of Campinas in partial fulfillment of the requirements for the degree of Master in Dental Clinic in Dental Prosthesis area
Orientador: Prof. Dr. Wander José da Silva
Co-orientadora: Profª. Drª Altair Antoninha Del Bel Cury
Este exemplar corresponde à versão final da dissertação defendida pelo aluno Dimorvan Bordin orientado pela Prof. Dr. Wander José da Silva e co-orientado pela Prof. Drª Altair A. Del Bel Cury
______________________________________________ Assinatura da co-orientadora.
PIRACICABA 2014
vii RESUMO
O coeficiente de atrito entre implante-pilar-parafuso tem sido considerado o fator principal na manutenção da estabilidade do conjunto. Estudos prévios demonstram que a saliva e o biofilme interposto entre estas superfícies podem alterar o coeficiente de atrito, comprometendo o comportamento biomecânico do conjunto. Nesse estudo foi avaliado a influência da película de saliva (Pel) e do biofilme (Bf) no coeficiente de atrito (CA) entre materiais protéticos utilizados na fabricação de pilares de titânio (Ti) e zircônia (Zr), e a influência do CA no comportamento biomecânico de uma prótese unitária implanto suportada. Discos de Ti (12,5 X 2mm) (n=14) receberam acabamento com lixas e foram divididos aleatoriamente em seis grupos de acordo com o par tribológico (Ti-Ti e Ti-Zr) em três condições de superfície do disco: Controle (Ctrl) sem película de saliva ou biofilme, com película de saliva (Pel) ou com biofilme (Bf). Os grupos obtidos foram: Ti Ctrl; Ti-Ti Pel; Ti-Ti-Ti-Ti Bf; Ti-Ti-ZrCtrl; Ti-Ti-Zr Pel; Ti-Ti-Zr Bf. Discos de Ti-Ti e Zr foram submetidos à aferição da rugosidade de superfície por interferometria. Os discos foram imersos em saliva para a formação de uma película de saliva e sobre esta um biofilme multiespécie (64,5 horas) composto por cinco espécies bacterianas e uma fúngica, respectivamente
Actinomyces naeslundii, Streptococcus oralis, Streptococcus mutans, Veillonella dispar, Fusobacterium nucleatum, Candida albicans. O ensaio tribológico de atrito foi realizado
em um tribômetro, onde uma esfera de Ti ou Zr (5mm) foi utilizada como contraparte. Uma carga de 10N foi aplicada e mantida na contraparte durante o deslocamento horizontal do disco (1mm/segundo). Os dados de CA foram avaliados por análise da variância a dois critérios e teste post hoc de Tukey (α=5%). O padrão de desgaste da superfície foi observado por microscopia eletrônica de varredura (MEV). Posteriormente, foi construído um modelo tridimensional virtual para a análise das tensões por e elementos finitos representando uma reabilitação unitária implanto-suportada de um incisivo central superior. Uma coroa protética foi modelada e virtualmente cimentada sobre um pilar anatômico. O pilar foi parafusado à um implante cone morse (4,1 X 11mm). O conjunto foi posicionado no modelo ósseo virtual da maxila. Seis modelos foram obtidos de acordo com o material do pilar (Ti e Zr) e de acordo com o coeficiente de atrito obtido nas condições estudadas (Ctrl, Pel e Bf). O CA, previamente obtido no ensaio tribológico, foi simulado na superfície
viii
de contato entre: implante-pilar; implante-parafuso; pilar-parafuso. Após a geração da malha (0,50mm), uma carga de 49N foi aplicada em ângulo de 45 graus na superfície palatina da coroa. Os valores de tensão foram avaliados de acordo o critério de tensão máxima principal e tensão de cisalhamento para o tecido ósseo e a tensão de von Mises para o implante e componentes protéticos. Os dados foram avaliados por análise da variância a dois critérios e calculada a porcentagem de contribuição de cada parâmetro do estudo. A superfície do titânio apresentou rugosidade de 0,19 ±0,01µm e da zircônia 0,25 ±0,01µm. O CA Ti-Ti Pel e Ti-Ti-Bf diminuiu em relação à Ti-Ti Ctrl (p<0,05). O CA dos grupos Ti-Zr Ctrl e Ti-Zr Bf foram semelhantes entre si (p>0,05) e aumentaram no grupo Ti-Zr Pel (p<0,05). Na avaliação dos materiais, o comportamento do Ti e Zr foi semelhante na presença de Pel(p>0,05) e diferiu nas demais condições (p<0,05). No estudo in silico, o CA contribuiu com 89,83% para a tensão no parafuso, diminuindo quando o CA foi menor (p<0,05). A tensão máxima principal e cisalhamento no osso medular foram influenciadas pelo CA com 63,94% e 98,59% (p<0,05), respectivamente. Concluiu-se que a película de saliva e o biofilme interferem com o comportamento biomecânico de uma reabilitação unitária implanto-suportada.
Palavras-Chave: Implantes dentários. Osseointegração. Análise de elementos finitos. Biofilmes.
ix ABSTRACT
The friction coefficient between abutment-implant- screw has been considered as a key factor in retention joint stability. Previous studies shown that saliva and biofilm interfacing these surfaces may shift the friction coefficient, jeopardizing the joint biomechanical behavior. This study evaluated the influence of saliva (Pel) and biofilm (Bf) on friction coefficient (FC) between prosthetic materials used to manufacture abutments such as titanium (Ti) and zirconia (Zr) and the influence of the FC in the biomechanical behavior of single dental implant rehabilitation. Ti discs (12.5 x 2mm) (n=14) were polished with sandpaper and randomly into six groups according to the tribological couple (Ti and Ti-Zr) under three conditions: without biofilm or saliva pellicle as negative control (Ctrl); saliva pellicle (Pel) and biofilm (Bf). The obtained groups were: Ti-Ti Ctrl; Ti-Ti Pel; Ti-Ti Bf; Ti-Zr Ctrl; Ti-Zr Pel; Ti-Zr Bf. Discs of Ti and Zr underwent roughness measurements by interferometry. A saliva pellicle and a multispecies biofilm (64,5 hours) were developed onto the Ti discs. The biofilm was composed by 5 bacterial species and 1 fungal, respectively Actinomyces naeslundii, Streptococcus oralis, Streptococcus mutans,
Veillonella dispar, Fusobacterium nucleatum, Candida albicans. A tribological assay was
performed in a tribometer, where a sphere made of Ti or Zr (5mm) was used as counter part. A 10N of load was applied and maintained in the counter part during the horizontal displacement of the disc (1mm/sec). The FC data were evaluated by two-way Anova and Tukey post hoc test (α=5%).The surface wear patterns were observed by scanning electron microscopy (SEM). Subsequently, was built a virtual three-dimensional model representing a single dental implant rehabilitation for upper central incisor. A prosthetic crown was modeled and cemented onto an anatomic abutment. The abutment was screw-retained into the morse taper implant (4.1 X 11mm). The joint was positioned into a virtual bone model of maxilla. Six models were obtained according to the abutments material (Ti or Zr) in the friction coefficient under studied conditions (Ctrl, Pel and Bf). The previously FC obtained in the tribological assay was simulated in the contact surfaces between: implant-abutment; implant-screw; abutment-screw. After the mesh generation (0.50mm), a 49N of load was applied at 45 degree in the palatal surface of the crown. The stress data were evaluated according to the maximum principal and shear stress for the bone tissue and von Mises
x
stress for the implant and prosthetic components. Two-way Anova was used to calculate the percentage of contribution of each parameter. The surface roughness of Ti was 0.19 ±0.01µm and Zr 0.25 ±0.01µm. The FC of Ti-Ti Pel and Ti-Ti Bf decreased when compared to Ti-Ti ctrl (p<0.05). The FC of Ti-Zr Ctrl and Ti-Zr Bf were similar (p>0.05) and increased in the Ti-Zr Pel (p<0.05). In the in silico study, the FC contributed with 89.83% of the stress in the screw, decreasing the stress when the FC was lower (p<0.05). The maximum stress in the cortical bone was influenced by 59.78% of friction and increased when the FC was lower (p<0.05). The maximum and shear stress in the cancellous bone were influenced by the FC with 63.94% and 98.59% (p<0.05), respectively. It can be concluded that the biofilm jeopardize the biomechanical behavior of a implant-supported single crown restoration.
xi Sumário DEDICATÓRIA xiii AGRADECIMENTOS xv INTRODUÇÃO 1
CAPÍTULO 1: Biofilm and saliva affect the biomechanical behavior of dental implants 4
CONCLUSÃO 21
REFERÊNCIAS 22
APÊNDICE 25
xiii
DEDICATÓRIA
A Deus, aos meus pais Jair Bordin, Rosilene de Souza Bordin e à minha irmã Suelen
xv AGRADECIMENTOS
Ao meu orientador Prof. Dr. Wander José da Silva, obrigado primeiramente pelo meu aceite no programa de pós-graduação. Agradeço imensamente pela amizade, atenção e paciência despendida, dedicação e profissionalismo.
À minha co-orientadora Profª. Drª. Altair Antoninha Del Bel Cury pelo exemplo de disciplina e compromisso com o ensino. Sua dedicação e determinação servem como combustível para darmos sempre o nosso melhor. Agradeço imensamente por toda contribuição para a minha formação.
Ao Prof. Dr. Carlos Fortulan agradeço por toda atenção e dedicação durante a execução desse trabalho, em especial na assistência durantes os ensaios para aferição do coeficiente de atrito e interpretação dos dados. Sua participação foi essencial para a execução desse trabalho.
Ao Prof. Dr. Bruno Salles Sotto-Maior, obrigado pela assistência e pelas discussões muito contribuidoras na minha formação. Obrigado pelo compartilhamento do conhecimento.
À Profa. Dra. Fernanda Faot, agradeço pela sua disponibilidade e atenção tanto para o desenvolvimento desse trabalho quanto para a execução de trabalhos paralelos.
À Profa. Dr. Cecilia Turssi, agradeço pela sua contribuição nas discussões prévias ao desenvolvimento desse trabalho.
Aos meus pais Jair Bordin e Rosilene de Souza Bordin por todo o suporte que tive desde a decisão de seguir a profissão até esse momento. O estímulo para estudar e seguir em frente é a melhor herança que eu poderia ter recebido. Obrigado pela educação e pelos valores passados. Esse momento também é de vocês.
xvi
À minha irmã Suelen Bordin, pela amizade e companheirismo. Obrigado pelo apoio sempre.
À minha avó, Lorena Finatto de Souza e aos padrinhos Gisnei de Souza, Gláucia
Biazus, Sérgio Triches e Cleonice Trichese a Tia Adriana de Souza (in memoriam).
Aos amigos Leonardo Bridi, Davi Blum, Wendy Becker, Karla Becker, Silvia
Matte, Daniela Damman, Kelly Knack, Natália Eichemberg, Olivia Locatelli, Sabrina Guerra, Fernanda Camargo.
Especialmente aos meus eternos amigos Tiago Cezar e Betânia Bazzan por todo o suporte nesse tempo que estive longe de casa. Obrigado por poder contar com vocês nos momentos mais difíceis.
À Universidade Estadual de Campinas, na pessoa do seu Magnífico Reitor, Prof.
Dr. José Tadeu Jorge.
À Faculdade de Odontologia de Piracicaba da Universidade Estadual de Campinas, na pessoa do seu Diretor, Prof. Dr. Guilherme Elias Pessanha Henriques, e do Diretor Associado Prof. Dr. Francisco Haiter Neto.
À Coordenadora dos Cursos de Pós-Graduação da Faculdade de Odontologia de Piracicaba da Universidade Estadual de Campinas, Profa. Dra. Cinthia Pereira Machado
Tabchoury, a quem agradeço também pela disponibilidade em ajudar e pelos ensinamentos
que tanto contribuíram para meu crescimento profissional.
A Coordenadora do Programa de Pós-Graduação em Clínica Odontológica da Faculdade de Odontologia de Piracicaba da Universidade Estadual de Campinas, Profª Drª
xvii
Aos professores da área de Prótese Parcial Removível da FOP-Unicamp, Profa.
Dra. Altair Antoninha Del Bel Cury, Profa. Dra. Renata Cunha Matheus Rodrigues Garcia, Profa. Dra. Celia Barbosa Rizatti e Prof. Dr. Wander José da Silva
Aos demais professores do Departamento de Prótese com quais tive oportunidade de cursar as disciplinas.
Aos funcionários da faculdade de odontologia de Piracicaba, em especial ao
Adriano, obrigado por toda atenção durante o aprendizado no manuseio do microscópio
eletrônico de varredura e no micro tomógrafo.
Aos meus amigos gaúchos de Piracicaba, Ataís Bacchi, Bruna Fronza, Bruna
Corrêa e Salles Barbosa, obrigado pelos momentos de descontração.
Ao grupo de Elementos Finitos, Marco Aurélio de Carvalho, Priscilla Lazari,
Marcele Jardim, Germana Camargos, Livia Forster e Camila Lima.
Especialmente à Marcele Jardim, Priscilla Lazari e Marco Aurélio de Carvalho por todas as discussões, os trabalhos e por todo aprendizado. Obrigado por transmitirem seus conhecimentos na metodologia de elementos finitos.
À Martinna Bertolinni e Yuri Cavalcanti pelas discussões e pelo aprendizado sobre biofilmes. Agradeço especialmente à Indira Cavalcanti, amiga e co-autora desse trabalho que esteve ao meu lado durante toda a execução desse trabalho. Muito obrigado por tudo!
Aos companheiros do Laboratório de Prótese Parcial Removível e colegas dePós-Graduação, Andrea Araújo, Aline Sampaio, Ana Paula Martins, Antônio Pedro
xviii
Reinoldes, Moisés Nogueira, Bruno Zen, Júlia Campana, Cindy Dodo, Diego Nóbrega, Edmara Bergamo, Francisco Girundi, Fernando Rigolin, Germana Camargos, Giselle Ribeiro, Giancarlo Torre, Guilherme Oliveira, Indira Cavalcanti, Kelly Machado, Larissa Vilanova, Letícia Machado, Lívia Foster, Lis Meirelles, Luana Aquino, Luiz Carlos Filho, Marco Aurélio Carvalho, Marcele Pimentel, Martinna Bertolini, Ney Pacheco, Paula Furlan, Plínio Senna, Raissa Machado, Rafael Soares, Samilly Souza, Silvia Lucena, Sheila Porta, Victor Munõz e Yuri Cavalcanti. pela convivência sempre
agradável. Muito obrigado a cada um de vocês.
À técnica Sra. Gislaine Piton do Laboratório de Prótese Parcial Removível, obrigado pelo bom convívio.
Aos funcionários do laboratório de produção de prótese Reinaldo, Márcia e Neide obrigado por serem tão atenciosos e gentis.
Aos professores da Universidade de Passo Fundo (UPF) Bruno Carlini, João
Paulo de Carli, Soluete Oliveira, João Vicente Barbizam, Doglas Cecchin e Ana Paula Farina, obrigado por me apresentarem à pesquisa odontológica e por todo incentivo desde
a graduação até o presente momento.
Às Sras.Érica Alessandra Pinho Sinhoreti e Raquel Q. Marcondes Cesar
Sacchi, secretárias da Coordenadoria Geral dos Programas de Pós-Graduação da Faculdade
de Odontologia de Piracicaba; e à Eliete Aparecida Ferreira Marim secretária do Departamento de Prótese e Periodontia da Faculdade de Odontologia de Piracicaba, pela atenção e disponibilidade.
A todos que em algum momento estiveram ao meu lado nesta jornada, meus sinceros agradecimentos.
1 INTRODUÇÃO
Os implantes dentários vêm sendo utilizados com sucesso na reabilitação de desdentados totais e parciais e apresentam taxas de sobrevivência em torno de 88,6% em período de 10 anos de acompanhamento (Mangano et al., 2014). Embora com alta taxa de sucesso, fatores como ancoragem óssea, componentes retidos por parafusos, desajuste entre os componentes e o uso de materiais que possuem propriedades distintas, possibilitam falhas mecânicas quando submetidos às cargas dinâmicas durante a mastigação (Mangano et al., 2014). Dessa forma, a escolha do material de confecção do pilar pode exercer importante influência no comportamento biomecânico da prótese (Stimmelmayr et al., 2012; Carvalho et al., 2014).
Os pilares de ligas de titânio têm sido utilizados como intermediários entre o implante e a coroa protética apresentando excelente desempenho (Carrillo de Albornoz et al., 2014). No entanto, com avanço da odontologia estética, os pilares fabricados em zircônia têm sido largamente indicados como alternativa aos pilares de titânio. Apresentam a vantagem de não causar o escurecimento da margem gengival, em especial na região anterior da maxila onde o fator estético é mais requisitado (Carrillo de Albornoz et al., 2014). Além disso, a zircônia possui elevada dureza, alta tenacidade à fratura, alto módulo de elasticidade e resistência ao desgaste, que são propriedades desejáveis no contexto clínico (Andersson et al., 2003; Garine et al., 2007). Estudos clínicos demonstram que os pilares cerâmicos possuem altas taxas de sobrevida (97,5%) em 5 anos de acompanhamento (Andersson et al., 2003).
Estudos têm sido conduzidos para a avaliação do desgaste dos materiais utilizados para confecção de pilares (Klotz et a., 2011; Stimmelmayr et al., 2012). Klotz et al. (2011) verificou a ocorrência de desgaste da superfície dos implantes de titânio quando foram utilizados pilares de zircônia sob carregamento. O desgaste na interface implante-pilar é esperado devido à significativa diferença entre as propriedades de cada material. A zircônia possui dureza Knoop, aproximadamente dez vezes superior à do titânio, além de apresentar o dobro de resistência à fratura (Brodbeck et al., 2003). Portanto, a energia proveniente do carregamento é dissipada, ocorrendo a deformação do titânio que possui menor módulo de
2
elasticidade (Stimmelmayr et al., 2012). Após o carregamento dinâmico, os implantes de titânio que receberam pilares de zircônia apresentaram desgaste 68,6% maior quando comparados aos pilares de titânio (Stimmelmayr et al., 2012). Esses estudos indicam que a adaptação entre implante-pilar pode ser comprometida pelo desgaste da superfície do titânio (Klotz et a., 2011; Stimmelmayr et al., 2012).
Tanto a fixação do pilar de titânio quanto do pilar de zircônia ao implante é realizada pelo parafuso, o qual representa a peça mais fraca do sistema. A fratura e o afrouxamento do parafuso são complicações recorrentes e ocorrem em 3,3% das reabilitações de conexão interna unitárias (Calderon et al., 2014). Esse fenômeno pode contribuir para o aumento da micromovimentação do conjunto, prejudicando a distribuição de tensões nos componentes protéticos e tecido ósseo peri-implantar. Sendo assim, diversos fatores têm sido associados à perda da estabilidade de união entre implante-pilar. Entre eles incluem a perda da pré-carga, o desajuste entre as peças, a rugosidade de superfície, a sobrecarga oclusal, o desgaste das interfaces causado pela micromovimentação ou atrito insuficiente entre o implante, o pilar e o parafuso (Breeding, et al., 1993; Gratton et al., 2001; Guzaitis et al., 2011; Jorn et al., 2014).
Para manter o conjunto estável, o atrito entre as superfícies é essencial, uma vez que após o travamento do parafuso, apenas algumas regiões dos picos das roscas ficam em íntimo contato com a superfície interna do implante (Breeding et al., 1993). Estudos anteriores relataram que a presença de micro-organismos provenientes da microinfiltração na interface implante-pilar podem formar biofilmes, contribuindo para diminuir o coeficiente de atrito entre as superfícies (Souza et al., 2010a; Souza et al., 2010b). Além disso, a presença de componentes constituintes da parede celular como lipídios ou produtos provenientes do metabolismo microbiano como polissacarídeos podem causar corrosão de superfície devido ao pH baixo, podendo comprometer o comportamento e a integridade desses materiais (Souza et al., 2010a; Souza et al., 2010b, Barao et al., 2011; Barao et al., 2012).
Diversos estudos que utilizam a metodologia de elementos finitos têm sido conduzidos com o objetivo de compreender o comportamento biomecânico das
3
reabilitações implanto-suportadas (Quaresma et al., 2008; Schrotenboer et al., 2009; Rungsiyakull et al., 2011; Hanaoka et al., 2014). No entanto, a condição de contato friccional entre os componentes protéticos é comumente desconsiderada, limitando o estudo à avaliação do comportamento da prótese em uma condição de união perfeita entre as peças. Não encontramos estudos disponíveis na literatura, no qual foi avaliada a influência de condições biológicas nos valores de coeficiente de atrito e desgaste entre os materiais protéticos, bem como, sua influência na distribuição de tensões em próteses sobre implante. Portanto, a avaliação do comportamento entre esses materiais pode auxiliar na compreensão das falhas em reabilitações unitárias implanto-suportadas.
Dessa forma, questiona-se o desempenho biomecânico de materiais que possuem propriedades distintas quando submetidos às condições de carregamento na presença de fatores biológicos como saliva e biofilme. Além disso, estudos que avaliam o comportamento da zircônia em contato com o titânio nas condições propostas são necessários. Assim, o objetivo do presente estudo foi avaliar a influência da saliva e do biofilme microbiológico no coeficiente de atrito entre materiais utilizados para a confecção de pilares e usar os dados dos coeficientes de atrito obtidos para a avaliação do comportamento biomecânico de uma prótese unitária implanto suportada por meio da análise do método de elementos finitos.
4
CAPÍTULO 1: Biofilm and saliva affect the biomechanical behavior of dental implants
Abstract
The frictional contact between screw-abutment-implant surface is a key point to preserve the stability of the system and has been considered an important factor in the long-term clinical success of dental implants rehabilitation. However, previous studies showed that oral biofilms decrease the friction coefficient (FC) between prosthetic surfaces and it could compromise the biomechanical behavior of a rehabilitation supported by dental implant. Therefore, this study quantified the FC between prosthetic materials, used as abutments, and implants in the presence of saliva film and biofilm. Also, this FC was used to evaluate the biomechanical behavior of a implant-supported single crown restoration. Friction coefficient (FC) was obtained between titanium-titanium Ti) and titanium-zirconia (Ti-Zr) with or without the presence of a multispecies biofilm (Bf) or salivary pellicle (Pel). The interface between Ti-Ti, Ti-Zr without salivary pellicle or biofilm was used as control (Ctrl). The friction coefficients obtained were transposed to a finite element model of a single dental crown implant-supported restoration. Six models were obtained according to the abutments materials (Ti and Zr) and the FC previously recorded (Bf, Pel,Ctrl). A load of 49N was applied on the crown. The quantitative stress was calculated using the maximum stress and shear stress criteria for cortical and cancellous bone and equivalent von Misses criteria for implant, abutment and screw. The recorded FC were: Ti-Ti Ctrl 0.23; Ti-Ti Pel 0.19; Ti-Ti Bf 0.16; Ti-Zr Ctrl 0.14; Ti-Zr Pel 0.19; Ti-Zr 0.13. The results of finite element analysis showed that FC contributed with 89.83% of the stress in the screw of abutment screw (p<0.05), decreasing the stress when the FC decreased. The change in the FC resulted in the significant increase of 59.78% (p<0.05) of maximum stress in cortical bone. It can be concluded that the shift of the FC due to the presence of salivary pellicle or biofilm are able to jeopardize the biomechanical behavior of an implant-supported single crown restoration.
5 Introduction
To better understand the complexity of the mechanics involved in the oral rehabilitation, especially in the screw-abutment-implant system and the maintenance of its stability, computer based simulation such as the Finite Elements Analysis (FEA) is used as a fast, predictor and harmless tool (Caglar et al., 2011; Chun et al., 2006; Guda et al., 2008; Hanaoka et al., 2014; Khraisat, 2012; Lang et al., 2003). Most FEA studies consider the contact between the materials surfaces as a key point to preserve the stability of the screw-abutment-implants system in the long-term clinical success of dental implants rehabilitation (Gratton et al., 2001; Henry et al., 1996). Therefore, the friction and consequent wear between the materials could be influenced by parameters such as the roughness, young’s modulus, surface treatment and the presence of lubricate solution (Jorn et al., 2014; Souza et al., 2010a; b). The absence of these specific parameters, may not properly code FEA studies, remains as shortage in this methodology.
Although some factors may be associated to the instability of the screw-abutment-implant system, the preload loss can be considered the most important one (Calderon et al., 2014; Jorn et al., 2014). Defined as the force responsible to keep the joint implant-abutment continuously tight during the chewing, the preload is generated after the screws placement. Factors such as the friction coefficient (FC) between the prosthetic contact surfaces (implant, abutment and screw), may contribute to achieving and maintaining the adequate preload (Burguete et al., 1994; Gratton et al., 2001; Jorn et al., 2014) and system locking.
Therefore, the quantification of the friction between the prosthetic contact surfaces submitted to different situations presented in the oral environment may increase the complexity of the simulations resulting in a more accurate finite element analysis. In an attempt to achieve this, the lubrication role of the infiltrated saliva in the implant-abutment connection was object of a previous study (Jorn et al., 2014). Although the authors concluded that the saliva could harm the stress distribution of the dental implants, the arbitrarily selection of the friction coefficients by the authors does not allow an inference based on such results. Further, the role of oral biofilms, commonly presented in the oral environment, is not totally recognized on the performance of dental implant systems.
6
Previous studies already showed that bacterial can colonize the inner surface of implant surfaces (Ricomini Filho et al., 2010; Koutozis et al., 2014), and some studies showed that this microbiological entity is able to reduce the friction coefficient when interposed between an alumina and titanium surfaces (Souza et al., 2010a,b). In this way, a lower FC could contribute to increase the micromotion in the implant-abutment joint that could be transferred to prosthetic components and bone tissue (Gratton et al., 2001).
Concerning the absence of parameters to be used in the FEA and the potential influence of saliva and oral biofilms, the aim of this study was quantify the FC between prosthetic materials used as abutments and implants manufacturing in the presence of salivary pellicle and biofilm, and evaluate this FC in the biomechanical behavior of dental implants rehabilitation.
Material and Methods
Experimental design
Eighty-four titanium (Ti) discs surfaces were standardized and randomly allocated for trials according to the tribological couple. Titanium-titanium (Ti-Ti) and titanium-zirconia (Ti-Zr) in three different conditions: titanium surface as control without saliva pellicle and biofilm (Ti-Ti Ctrl and Ti-Zr Ctrl), Saliva-pellicle-coated discs (Ti-Ti Pel and Ti-Zr Pel) and multispecies biofilm (Ti-Ti Bf and Ti-Zr Bf) obtaining six groups (n=14). Next, the friction coefficient (FC) was analyzed using a tribometer with a Ti or Zr ball as counter body, followed by a SEM (scanning electron microscopy) analysis. Additionally, Ti an Zr surface discs were evaluated for roughness parameters (n=4). After the FC was obtained virtual models were built to evaluate the biomechanical behavior of an implant-supported single crown restoration using a finite element analysis. Six models were obtained according to the abutments material (Ti and Zr) and the FC condition previously recorded (Ctrl, Pel, Bf). The FC was simulated in the contact surfaces between implant-abutment, implant-screw, screw-abutment from a morse taper implant (4.1 x11 mm) in the upper incisive region. A load of 49N (45 degree) was applied and the quantitative stress
7
was calculated using the maximum stress and shear stress criteria for cortical and cancellous bone and equivalent von Misses criteria for implant, abutment and screw. This study was previously approved by the Local Research and Ethics Committee (117/2013).
Sample preparation
Titanium grade IV discs (12.5 x 2 mm) (Sandinox®; Sorocaba, SP, Brazil) were ground progressively with smoother aluminum oxide papers with 200, 320, 400, 600 and 1200 μm grid (Carbimet; Buehler, Lake Bluff, IL, USA) in a horizontal polisher (model APL-4; Arotec, Cotia, SP, Brazil). The discs were ultrasonically cleaned with ethanol and purificated water and finally dried for autoclave sterilization at 121ºC for 15 min (Souza et al., 2010). The zirconia Y-TPZ discs were obtained commercially by CAD-CAM manufacturing (US Dental Depot®, Fort Lauderdale, Florida, USA). The discs preparation protocol was defined taking into account the surface roughness of commercial abutments during the pilot tests.
Surface roughness
The surface roughness of titanium and zirconia discs (n=4) was measured by a white light optical interferometer (New View 7300; Zygo Corp®., CT, USA). The roughness
parameters were obtained: Sa- average roughness (µm); Spk-reduced peak height (µm) and Svk-reduced valley depth (µm); Sds - summit density (represented by the number of peaks divided by the area - 1/µm2).
Salivary pellicle formation
For salivary pellicle formation, the Ti discs were positioned individually into a 24-well plate filled with 2 mL of a saliva solution (50% of non-stimulated and pasteurized saliva, 37.5% of deionized water and 12.5% of saline solution). The salivary pellicle was formed for 4 hours at 37 ºC under shaker (Guggenheim et al., 2001).
8 Biofilm development
A multispecies biofilm composed by the following strains: Actinomyces naeslundii OMZ 745, Streptococcus oralis OMZ 607, Streptococcus mutans OMZ 918, Veillonella
dispar OMZ 493, Fusobacterium nucleatum OMZ 598 and Candida albicans OMZ 110.
The biofilm was developed on salivary pellicle coated-discs (Guggenheim et al., 2001; Shapiro et al., 2002). Briefly, each strain was optically adjusted to 1.0 at 550 nm and a mixed-species inoculum was prepared with equal volumes of each strain. The biofilm was developed in a 24-well plate with modified fluid universal medium (mFUM) supplemented with glucose (0.15%) and sucrose (0.15%) (70% saliva and 30% mFUM). The plates were incubated anaerobically at 37 °C. The discs were washed in saline solution three times per day. Fresh medium was replaced at 16.5 h and 40.5 h. After 64.5 h the discs were submitted to the friction coefficient assays.
Frictional coefficient assay
Ti discs of each group (Pel, Bf and Ctrl n = 14) were fixed in a tribometer support (pin against disc) (Faculty of Mechanic Engineering – USP, São Carlos, SP, Brazil). The sliding test was performed in a vertical normal load of 10N applied to each disc with a counter body of Ti or Zr ball (Y-TPZ) with 5 mm of diameter. The test was carried out with a stroke length of 10 mm at 1 mm/sec. These parameters were selected in a pilot study. The dynamic friction coefficient was evaluated with LabView® software (National Instruments®, São Paulo, SP, Brazil). After checking whether data were distributed normally with the Shapiro-Wilks test, the results were statistically analyzed by two-way ANOVA and Tukey post-hoc test (α=5%).
Scanning electron microscopy (SEM)
The discs covered with biofilm were fixed overnight in Karnovsky Fixative (2.5% glutaraldehyde, 2% formaldehyde, 0.1M sodium phosphate buffer, pH 7.2) followed by dehydration in a series of ethanol washes (60%, 70%, 80%, 90% (5 minutes) and 100% (10 minutes) and allowed to dry under aseptic conditions. The discs were mounted on stubs, sputter-coated with gold and observed by SEM (JEOL JSM-5600LV; Peabody, MA, USA)
9
at an accelerating voltage at 15 kV and angled in an inclination of 60 degrees to evaluate the wear patterns..
Finite elements assay
Model preparation
The anterior portion of edentulous maxilla was reconstructed using a medical tomography in the InVesalius® software (CTI®, Campinas, SP, Brazil). The STL images (stereolithography) were exported to the Solidworks software 2013® (Dassault Systèmes Solidworks®, Waltham, MA, USA) to the bone model construction. The model was composed of cancellous bone surrounded by 1.5 mm of cortical bone corresponding to type III bone quality. Single crown rehabilitation was simulated in anterior region of maxillary and was supported by a morse taper implant (4.1 x 11mm). The CAD model of an anatomic abutment (through-bolt) and a screw model were provided by the manufacture (Neodent®,
Curitiba, PR, Brazil). All anatomic references of the crown were based on micro tomography images. The crown was considered cemented-retained represented by a 0.50 µm of the cement thick layer. After the implants placement 1mm bellow the bone, the prosthetic crown of an upper middle incisor was constructed. The virtual models were exported to Ansys Workbench 14.0 software® (Swanson Analysis Inc®, Canonsburg, PA,
USA) for the mathematical analysis.
The Young's modulus and Poison ratio used were, respectively: Cortical bone (13.6 GPa, 0.26) (Cruz et al., 2009); Trabecular bone (1.36 GPa, 0.31) (Cruz et al., 2009); Titanium for implant, abutment and screw (110 GPa 0.35) (Cruz et al., 2009); Zirconia (Y-TPZ) for the abutment (205 GPa, 0.22) (Coelho et al., 2009). The prosthetic crown was considered as lithium dissilicate (96 GPa, 0.23) (Albakry et al., 2003) luted by a resin cement (18.3 GPa, 0.30) (Li et al., 2006). Convergence analysis with 5% of tolerance was achieving using a tetrahedral mesh with 0.50 mm of elements size. All models were considered homogeneous, isotropic and linear elastics, except the prosthetic components contacts that were considered non-linearly elastics. The means frictions coefficients obtained in the in vitro study were used in the contact prosthetic surfaces, between screws
10
head to abutment; screws thread to implants thread and the morse taper abutments to implant internal surfaces. Six tridimensional models were obtained according to the abutments material: Ti (titanium abutment); Zr (zirconia abutment) and the FC between the surfaces: Pel (saliva pellicle), Bf (biofilm) and Ctrl (control).
Regarding the boundary condition, it was defined by fixing the mesial and distal external bones surfaces. A 49N of load was applied with an inclination of 45 degrees at the palatal surface of the prosthetic crown (Att et al 2012; Carvalho et al., 2014). The maximum principal and shear stress were calculated for bone and an equivalent von Misses stress was obtained for the prosthetic components and implant. The percentage of contribution (% total sum of squares [%TSS] of each evaluated condition (material and friction coefficient) and the influence of the interactions were calculated (Sotto-Maior et al., 2012).
Results
The interferometer parameters showed that Zr presented higher average roughness (Sa: Ti=0.19 ±0.01; Zr=0.25 ±0.01 µm) with predominant extreme peaks (Spk: Ti=0.42 ±0.02; Zr=0.58 ±0.08 µm) and valleys when compared to Ti (Svk: Ti=0.30 ±0.02; Zr= 0.42 ±0.04 µm). The Summit density (1/µm2) for Ti and Zr were 0.01 ±0.00 and 0.00 ±0.00
respectively.
The FC records are shown in table 1.The Ti-Ti couple without Pel or Bf (Ctr) showed the highest FC and presented an adhesive wear pattern (Fig. 1, A). The presence of Pel or Bf decreases the FC and the pattern of surface wear (Fig.1, B and C). The FC between Ti-Zr was similar between the Ctrl and Bf group, showing a similar cutting wear patterns in the Ti surface (Fig.1, D and F). The Pel increase the FC among Ti-Zr, followed by a higher cutting surface wear pattern of Ti disc. (fig. 1, E).
11
Table 1- Friction coefficient (means and standard deviation) according to the tribological couple (Ti-Ti and Ti-Zr) and condition (control, saliva pellicle and biofilm.
Control Saliva Pellicle Biofilm
Ti-Ti 0,23 ±0,03 (A,a) 0,19 ±0,03 (A,b) 0,16 ±0,01 (A,c)
Ti-Zr 0,14 ±0,01(B,a) 0,19 ±0,02 (A,b) 0,13 ±0,00 (B,a)
Means followed by distinct letters indicate statistical significance difference (p<0.0001; Tukey test.) Uppercase distinct letter indicate difference between materials. Lowercase distinct letters indicate difference between the evaluated conditions within each material.
Fig.1- SEM observations of titanium discs after the FC measurements: A Ti ctrl); B (Ti-Ti Pel); C ((Ti-Ti-(Ti-Ti Bf); D ((Ti-Ti-Zr Ctrl); E ((Ti-Ti-Zr Pel); F ((Ti-Ti-Zr Bf). Arrows shows surface wear patterns in titanium disc surface due the contact with the counter body.
12
A representative image of the stress distribution pattern obtained in the FEA is showed in the Fig. 2. Results regarding all the evaluated condition are shown in Fig. 3.
Fig. 2 – Representative image (titanium abutment and control condition) showing the finite element model used in the simulation and the stress distribution. A: von Mises Stress (MPa) in the screw. B: Maximum principal stress (MPa) in the cortical cancellous bone.
Fig. 3-Stress distribution in the prosthetic components and bone tissue according to the abutments material: titanium (Ti) and zirconia (Zr) and friction coefficient: control (Ctrl), salivary pellicle (Pel) and biofilm (Bf)
13
The %TSS of each evaluated condition in the computer analysis is shown in Table 2.
Table 2- Percentage of contribution (%TSS) for von-Mises stress for the prosthetic components (implant, abutment and screw) and maximum and shear stress for cortical and cancellous bone
The FC influenced the stress concentration in the cancellous bone with 98.59% to the shear stress (p<0.05) and 63.94% to the maximum stress (p<0.05), (Table 2). A lower FC induced by the Pel or Bf was responsible for increasing the stress concentration in cortical bone (p>0.05).The abutments materials (Ti or Zi) were responsible for 36.62% of the maximum stress in the cortical bone, where the Ti resulted in the highest stress (p<0.05). The von Mises stress in the abutment was influenced (93.86%) by the abutments material, where the Zr abutments showed the highest stress. The FC contribution showed no difference for the von Mises stress distribution in the abutment or implant (p>0.05) (Table 2). Assessing the prosthetic components, only the screw was influenced by the FC (89.83%) (p<0.05), induced by the Pel or Bf that contributed to decrease the stress
Discussion
The present study simulates the shifts in the FC between the prosthetic surfaces based on the results from the in vitro experiment with the presence of saliva or biofilm, simulating what usually occurs in oral environment. According to the results, shifts in the FC due to the presence of saliva or biofilm are able to change the biomechanical behavior
Prosthetic components Cortical bone Cancellous bone
Implant Abutment Screw Maximum
Stress Shear Stress
Maximum
Stress Shear Stress Source P %TSS P %TSS P %TSS P %TSS P %TSS P %TSS P %TSS Material 0.03 75.63 0.01 93.86 0.08 8.49 0.04 36.62 0.05 78.95 0.02 34.62 0.12 1.07
Friction 0.25 18.10 0.44 3.44 0.01 89.83 0.05 59.78 0.44 11.76 0.02 63.94 0.00 98.59 Error 6.27 2.70 1.68 3.60 9.29 1.44 0.34 Total 100 100 100 100 100 100 100 %TSS = total sum of squares. Significance adjusted to P<0.05.
14
of implants, changing the stress distribution that suggest the use of such coefficients became an important upgrade to finite element analysis.
The surface roughness of the materials seems to have a crucial role in FC determination. Two opposite surface with higher surface roughness will determine less friction, once the friction occurs only between the peaks of the materials. However, this can be changed according to the load and the materials properties (Stimmelmayr et al., 2012). Considering the oral environment, the pellicle of saliva has been claimed to be able to promote a uniform role to the Ti surface (Cavalcanti et al., 2014). Thus the friction that previously occurred only between the peaks now occurs in a large contact area, generating higher friction values and consequently greater wear of the titanium surface. Our results showed that FC and “cutting” wear increased when the saliva was interposed between Ti-Zr surfaces. This can be attributed to saliva composition, that is predominantly composed by water (~95%), corroborating with a previous study by Turssi et al., 2006 (Turssi et al., 2006), which demonstrated the water inability to decrease the wear rate between dental materials. The present study used a saliva solution composed by non-stimulated saliva, and distillated water and saline solution in order to promote a salivary pellicle onto titanium discs. The published protocol was used in attempt to reproduce a condition that usually occurs in the oral environment. Furthermore, it has been previously demonstrated the presence of the most abundant proteins as isoform 1 of serum albumin, prolactin-inducible protein, filaggrin and desmoglein-1 (Cavalcanti et al., 2014).
The presence of biofilm reduces the FC between Ti-Ti when compared to Pel and Ctrl (p<0.05) showing a similar behavior of lubricant solutions (Souza et al., 2010). This behavior has been attributed to the polysaccharide chains of α1,3 and 1,6 glucan from the exopolimeric matrix. These polysaccharides are responsible for the good viscoelastic properties, providing to the biofilm the ability to support a certain level of strain, decreasing the contact pressure between the surfaces (Vinogradov et al., 2004; Cense et al., 2006). In addition, an adhesive wear behavior was observed in the titanium surface with plastic deformation, which usually occurs when both metallic surfaces contact each other under load.
15
Although the biofilm decrease the FC among Ti-Ti, the same was not observed to Ti-Zr. The ways in which the roughness peaks become deformed elastically or plastically under load are related to the Sds roughness parameter. Both Ti and Zr showed low "Sds" parameters, which may result in higher localized stress contact, and higher wear. Furthermore, the Zr has higher young's modulus than the Ti (210Gpa (Dittmer et al., 2010) and 110 GPa (Huang et al., 2008; Rubo and Capello Souza, 2010) respectively). Thus, the strain energy obtained during the sliding test was dissipated into the material of lower young modulus. During the friction assay, the Zr removed the biofilm and the Ti discs surface exposing the oxide film. A similar behavior was previously observed by Souza et al., 2010a when a higher load was applied to an alumina ball in contact with titanium disc, resulting in a higher wear. Further, the higher wear rates of with Ti produce debris called "rolls" that were involved in the friction measurements and were observed by other studies (Le Mogne et al., 1992; Zanoria et al., 1995).
Moreover, based on our results, the presence of saliva or biofilm between abutment-screw-implant in an implant-supported single crown restoration lead to a shift in the FC between the surfaces contributing significantly to the decrease of the stress in the screw. In this context, insufficient stress in the screw can be associated with the preload loss, since a proper tensile force its desirable to maintain a joint stable during chewing. An insufficient tensile force in the screw can result in abutment screw loosening, considered the most commonly prosthetic failure in single dental implant rehabilitations (Goodacre et al., 1999; Gratton et al., 2001). Further, the decreased friction may contribute to the increase of the micromotion of the implant-abutment interface (Gratton et al., 2001) which can be easily transferred to the periimplant bone area. In addition, the cortical bone overloading can be responsible for the marginal bone loss and consequently failure in the long-term follow up (Duyck et al., 2001; Isidor, 1996).
The oral microbiota, and consequently oral biofilms, have an extremely complex composition and it would be not possible to reproduce this complexity in an in vitro model. Respecting this limitation, the present study considered that this model is one of the most complete multispecies biofilm model in literature. It has been validated, and represents a
16
general oral biofilm, composed of microorganisms that are commonly found in oral cavity (Guggenheim et al., 2001; Shapiro et al., 2002). It is important to point that all microorganisms present in this model have been previously isolated from dental implants and were used by other studies (Dhir et al., 2013; Sanchez et al., 2014). Although the present study was limited to static loading, the finite element analysis confirmed that saliva pellicle and biofilm might decrease the FC between prosthetic materials, contributing to change the biomechanical behavior of screw and peri-implantar bone tissue.
Concerning the influence of frictional properties under loading in oral conditions, the results obtained by the FEA provides important data to better understand the biomechanical behavior of dental implants. However, the number of virtual, mechanical, and clinical studies of single dental implant-supported rehabilitation is still limited. Therefore, further trials with multiple combinations of oral conditions in the biomechanical context are required to better understand the long-term failure of an implant-supported single crown restoration.
Conclusion
It was concluded that both saliva pellicle and multispecies biofilm shift the biomechanical behavior of the single dental implants supported rehabilitation.
References
Albakry M, Guazzato M, Swain MV (2003). Biaxial flexural strength, elastic moduli, and x-ray diffraction characterization of three pressable all-ceramic materials. The Journal of
prosthetic dentistry 89(4):374-380.
Att W, Yajima ND, Wolkewitz M, Witkowski S, Strub JR (2012). Influence of preparation and wall thickness on the resistance to fracture of zirconia implant abutments. Clinical
17
Burguete RL, Johns RB, King T, Patterson EA (1994). Tightening characteristics for screwed joints in osseointegrated dental implants. The Journal of prosthetic dentistry 71(6):592-599.
Caglar A, Bal BT, Karakoca S, Aydin C, Yilmaz H, Sarisoy S (2011). Three-dimensional finite element analysis of titanium and yttrium-stabilized zirconium dioxide abutments and implants. The International journal of oral & maxillofacial implants 26(5):961-969.
Calderon PS, Dantas PM, Montenegro SC, Carreiro AF, Oliveira AG, Dantas EM et al. (2014). Technical complications with implant-supported dental prostheses. Journal of oral
science 56 (2):179-184.
Carvalho MA, Sotto-Maior BS, Del Bel Cury AA, Pessanha Henriques GE (2014). Effect of platform connection and abutment material on stress distribution in single anterior implant-supported restorations: A nonlinear 3-dimensional finite element analysis. The
Journal of prosthetic dentistry. 112 (1):1096-1102.
Cavalcanti IM, Ricomini Filho AP, Lucena-Ferreira SC, da Silva WJ, Paes Leme AF, Senna PM et al. (2014). Salivary pellicle composition and multispecies biofilm developed on titanium nitrided by cold plasma. Archives of oral biology 59(7):695-703.
Chun HJ, Shin HS, Han CH, Lee SH (2006). Influence of implant abutment type on stress distribution in bone under various loading conditions using finite element analysis. The
International journal of oral & maxillofacial implants 21(2):195-202.
Coelho PG, Bonfante EA, Silva NR, Rekow ED, Thompson VP (2009). Laboratory simulation of Y-TZP all-ceramic crown clinical failures. Journal of dental research 88(4):382-386.
Cruz M, Wassall T, Toledo EM, da Silva Barra LP, Cruz S (2009). Finite element stress analysis of dental prostheses supported by straight and angled implants. The International
journal of oral & maxillofacial implants 24(3):391-403.
Dhir S (2013). Biofilm and dental implant: The microbial link. Journal of Indian Society of
18
Dittmer MP, Kohorst P, Borchers L, Stiesch M (2010). Influence of the supporting structure on stress distribution in all-ceramic FPDs. The International journal of
prosthodontics 23(1):63-68.
Duyck J, Ronold HJ, Van Oosterwyck H, Naert I, Vander Sloten J, Ellingsen JE (2001). The influence of static and dynamic loading on marginal bone reactions around osseointegrated implants: an animal experimental study. Clinical oral implants research 12(3):207-218.
Goodacre CJ, Kan JY, Rungcharassaeng K (1999). Clinical complications of osseointegrated implants. The Journal of prosthetic dentistry 81(5):537-552.
Gratton DG, Aquilino SA, Stanford CM (2001). Micromotion and dynamic fatigue properties of the dental implant-abutment interface. The Journal of prosthetic dentistry 85(1):47-52.
Guda T, Ross TA, Lang LA, Millwater HR (2008). Probabilistic analysis of preload in the abutment screw of a dental implant complex. The Journal of prosthetic dentistry 100(3):183-193.
Guggenheim B, Giertsen E, Schupbach P, Shapiro S (2001). Validation of an in vitro biofilm model of supragingival plaque. Journal of dental research 80(1):363-370.
Gunne J, Jemt T, Linden B (1994). Implant treatment in partially edentulous patients: a report on prostheses after 3 years. The International journal of prosthodontics 7(2):143-148.
Hanaoka M, Gehrke SA, Mardegan F, Gennari CR, Taschieri S, Del Fabbro M et al. (2014). Influence of Implant/Abutment Connection on Stress Distribution to Implant-Surrounding Bone: A Finite Element Analysis. Journal of prosthodontics 23 (7): 565-71. Henry PJ, Laney WR, Jemt T, Harris D, Krogh PH, Polizzi G et al. (1996). Osseointegrated implants for single-tooth replacement: a prospective 5-year multicenter study. The
19
Huang HL, Hsu JT, Fuh LJ, Tu MG, Ko CC, Shen YW (2008). Bone stress and interfacial sliding analysis of implant designs on an immediately loaded maxillary implant: a non-linear finite element study. Journal of dentistry 36(6):409-417.
Isidor F (1996). Loss of osseointegration caused by occlusal load of oral implants. A clinical and radiographic study in monkeys. Clinical oral implants research 7(2):143-152. Jorn D, Kohorst P, Besdo S, Rucker M, Stiesch M, Borchers L (2014). Influence of lubricant on screw preload and stresses in a finite element model for a dental implant. The
Journal of prosthetic dentistry 112 (2): 340-8.
Khraisat A (2012). Influence of abutment screw preload on stress distribution in marginal bone. The International journal of oral & maxillofacial implants 27(2):303-307.
Laney WR, Jemt T, Harris D, Henry PJ, Krogh PH, Polizzi G et al. (1994). Osseointegrated implants for single-tooth replacement: progress report from a multicenter prospective study after 3 years. The International journal of oral & maxillofacial implants 9(1):49-54.
Lang LA, Kang B, Wang RF, Lang BR (2003). Finite element analysis to determine implant preload. The Journal of prosthetic dentistry 90(6):539-546.
Le Mogne T, Martin JM, Platon F, Berthier Y (1992). Rolls formation with triboceramics: which parameters and what mechanisms? Wear 21: 285-292.
Li LL, Wang ZY, Bai ZC, Mao Y, Gao B, Xin HT et al. (2006). Three-dimensional finite element analysis of weakened roots restored with different cements in combination with titanium alloy posts. Chinese medical journal 119(4):305-311.
Ricomini Filho AP, Fernandes FS, Straioto FG, da Silva WJ, Del Bel Cury AA (2010). Preload loss and bacterial penetration on different implant-abutment connection systems.
Brazilian dental journal 21(2):123-129.
Rubo JH, Capello Souza EA (2010). Finite-element analysis of stress on dental implant prosthesis. Clinical implant dentistry and related research 12(2):105-113.
20
Sanchez MC, Llama-Palacios A, Fernandez E, Figuero E, Marin MJ, Leon R et al. (2014). An in vitro biofilm model associated to dental implants: Structural and quantitative analysis of in vitro biofilm formation on different dental implant surfaces. Dental materials 30(10):1161-1171.
Shapiro S, Giertsen E, Guggenheim B (2002). An in vitro oral biofilm model for comparing the efficacy of antimicrobial mouthrinses. Caries research 36(2):93-100.
Sotto-Maior BS, Senna PM, da Silva WJ, Rocha EP, Del Bel Cury AA (2012). Influence of crown-to-implant ratio, retention system, restorative material, and occlusal loading on stress concentrations in single short implants. The International journal of oral &
maxillofacial implants 27(3):e13-18.
Souza JC, Henriques M, Oliveira R, Teughels W, Celis JP, Rocha LA (2010a). Biofilms inducing ultra-low friction on titanium. Journal of dental research 89(12):1470-1475. Souza JC, Henriques M, Oliveira R, Teughels W, Celis JP, Rocha LA (2010b). Do oral biofilms influence the wear and corrosion behavior of titanium? Biofouling 26(4):471-478. Stimmelmayr M, Edelhoff D, Guth JF, Erdelt K, Happe A, Beuer F (2012). Wear at the titanium-titanium and the titanium-zirconia implant-abutment interface: a comparative in vitro study. Dental materials 28(12):1215-1220.
Turssi CP, Faraoni JJ, de Menezes M, Serra MC (2006). Analysis of potential lubricants for in vitro wear testing. Dental materials 22(1):77-83.
Zanoria E, Danyluk S, McNallan M (1995). Effects of length, diameter and population density of tribological rolls on friction between self-mated silicon. Wear 181:784-789.
21 CONCLUSÃO
A presença de saliva e biofilme interposta entre superfícies protéticas interferem no comportamento biomecânico de próteses unitárias implanto-suportadas.
* De acordo com as normas da UNICAMP/FOP, baseadas na padronização do International Committee of Medical Journal Editors. Abreviatura dos periódicos em conformidade com o Medline.
22
REFERÊNCIAS*
Andersson B, Glauser R, Maglione M, Taylor A. Ceramic implant abutments for short-span FPDs: a prospective 5-year multicenter study. Int J Prosthodont. 2003;16(6):640-6.
Barao VA, Mathew MT, Assuncao WG, Yuan JC, Wimmer MA, Sukotjo C. The role of lipopolysaccharide on the electrochemical behavior of titanium. J Dent Res. 2011;90(5):613-8.
Barao VA, Mathew MT, Assuncao WG, Yuan JC, Wimmer MA, Sukotjo C. Stability of cp-Ti and Ti-6Al-4V alloy for dental implants as a function of saliva pH - an electrochemical study. Clin Oral Implats Res. 2012;23(9):1055-62.
Breeding LC, Dixon DL, Nelson EW, Tietge JD. Torque required to loosen single-tooth implant abutment screws before and after simulated function. In J Prosthodont. 1993;6(5):435-9.
Brodbeck U. The ZiReal Post: A new ceramic implant abutment. J Esthet Restor Dent. 2003;15(1):10-23; discussion 4.
Calderon PS, Dantas PM, Montenegro SC, Carreiro AF, Oliveira AG, Dantas EM, et al. Technical complications with implant-supported dental prostheses. J Oral Sci. 2014;56(2):179-84.
Carrillo de Albornoz A1, Vignoletti F, Ferrantino L, Cárdenas E, De Sanctis M, Sanz M. A randomized trial on the aesthetic outcomes of implant-supported restorations with zirconia or titanium abutments. J Clin Periodontol. 2014. [Epub ahead of print]
Cense AW, Peeters EA, Gottenbos B, Baaijens FP, Nuijs AM, van Dongen ME. Mechanical properties and failure of Streptococcus mutans biofilms, studied using a microindentation device. J Microbiol Methods. 2006 67:463-472.
* De acordo com as normas da UNICAMP/FOP, baseadas na padronização do International Committee of Medical Journal Editors. Abreviatura dos periódicos em conformidade com o Medline.
23
Garine WN, Funkenbusch PD, Ercoli C, Wodenscheck J, Murphy WC. Measurement of the rotational misfit and implant-abutment gap of all-ceramic abutments. Int J Oral Maxillofac Implants. 2007;22(6):928-38.
Gratton DG, Aquilino SA, Stanford CM. Micromotion and dynamic fatigue properties of the dental implant-abutment interface. J Prosthet Dent. 2001;85(1):47-52.
Guzaitis KL, Knoernschild KL, Viana MA. Effect of repeated screw joint closing and opening cycles on implant prosthetic screw reverse torque and implant and screw thread morphology. J Prosthet Dent.. 2011;106(3):159-69.
Hanaoka M, Gehrke SA, Mardegan F, Gennari CR, Taschieri S, Del Fabbro M, et al. Influence of Implant/Abutment Connection on Stress Distribution to Implant-Surrounding Bone: A Finite Element Analysis. J Prosthodont . 2014 [Epud ahead to print].
Jorn D, Kohorst P, Besdo S, Rucker M, Stiesch M, Borchers L. Influence of lubricant on screw preload and stresses in a finite element model for a dental implant. J Prosthet Dent. 2014; 112 (2):340-8.
Klotz MW, Taylor TD, Goldberg AJ. Wear at the titanium-zirconia implant-abutment interface: a pilot study. Int J Oral Maxillofac Implants. 2011;26(5):970-5.
Koutouzis T, Mesias R, Calderon N, Wong F, Wallet S. The effect of dynamic loading on bacterial colonization of the dental implant fixture-abutment interface: an in vitro study. J Oral Implantol. 2014; 40(4): 432-7.
Mangano F, Macchi A, Caprioglio A, Sammons RL, Piattelli A, Mangano C. Survival and complication rates of fixed restorations supported by locking-taper implants: a prospective study with 1 to 10 years of follow-up. J Prosthodont 2014;23(6):434-44.
* De acordo com as normas da UNICAMP/FOP, baseadas na padronização do International Committee of Medical Journal Editors. Abreviatura dos periódicos em conformidade com o Medline.
24
Quaresma SE, Cury PR, Sendyk WR, Sendyk C. A finite element analysis of two different dental implants: stress distribution in the prosthesis, abutment, implant, and supporting bone. J Oral Implantol. 2008;34(1):1-6.
Rungsiyakull C, Rungsiyakull P, Li Q, Li W, Swain M. Effects of occlusal inclination and loading on mandibular bone remodeling: a finite element study. Int J Oral Maxillofac Implants. 2011;26(3):527-37.
Schrotenboer J, Tsao YP, Kinariwala V, Wang HL. Effect of platform switching on implant crest bone stress: a finite element analysis. Implant Dent. 2009;18(3):260-9.
Souza JC, Henriques M, Oliveira R, Teughels W, Celis JP, Rocha LA. Biofilms inducing ultra-low friction on titanium. J Dent Res. 2010a;89(12):1470-5.
Souza JC, Henriques M, Oliveira R, Teughels W, Celis JP, Rocha LA. Do oral biofilms influence the wear and corrosion behavior of titanium? Biofouling. 2010;26(4):471-8.
Stimmelmayr M, Edelhoff D, Guth JF, Erdelt K, Happe A, Beuer F. Wear at the titanium-titanium and the titanium-titanium-zirconia implant-abutment interface: a comparative in vitro study. Dent Mater. 2012;28(12):1215-20.
Vinogradov AM, Winston M, Rupp CJ, Stoodley P. Rheology of biofilms formed from the dental plaque pathogen Streptococcus mutans. Biofilms. 2004; 1:49-56.
25 APÊNDICE
Tabela 1- Média, desvio-padrão e intervalo de confiança dos modelos de elementos finitos de acordo com o material do pilar e as condições avaliadas.
Parameters Implante (MPa) Pilar Parafuso Osso Cortical Osso Medular
Máxima Cisalhamento Máxima Cisalhamento
Material do pilar Titânio 181.18 ±3.33 (172.92-189.44) 188.53 ±4.60 (177.10-199.95) 144.72 ±0.38 (143.78- 145.66) 9.95 ±0.45 (8.83-11.08) 10.97 ±0.08 (10.76-11.17) 1.74 ±0.08 (1.56-1.93) 1.40±0.10 (1.14-1.66) Zircônia 167.26 ±5.98 (152.41-182.12) 232.92 ±8.70 (211.32-254.52) 145.55 ±0.31 (143.77-145.33) 9.49 ±0.28 (8.79-10.18) 10.61 ±0.13 (10.28-10.95) 1.66 ±0.06 (1.52-1.81) 1.38 ±0.09 (1.15-1.61) Condição Controle 175.64 ±6.07 (121.06-230.21) 211.95 ±38.34 (-132.52-556.42) 144.97 ±0.20 (143.19-146.75) 9.31±0.18 (7.66-10.96) 10.81 ±0.13 (9.60-12.01) 1.78 ±0.07 (1.14-2.42) 1.51 ±0.02 (1.31-1.70) Película de saliva 169.53 ±12.91 (53.52-285.54) 205.02 ±25.39 (-23.12-433.15) 144.65 ±0.07 (144.01-145.29) 9.84 ±0.41 (6.16-13.52) 10.70 ±0.34 (7.65-13.75) 1.67 ±0.04 (1.29-2.05) 1.34 ±0.01 (1.27-1.40) Biofilme 177.50 ±10.54 (82.84-272.16) 215.21 ±30.44 (-58.30-488.71) 144.28 ±0.10 (143.39-145.17) 10.01 ±0.40 (6.45-13.57) 10.87 ±0.28 (8.39-13.34) 1.66 ±0.06 (1.15-2.17) 1.34 ±0.01 (1.27-1.40)
26
Figura 1- Segmentação do osso cortical a partir de imagem tomográfica de uma maxila (Software Invesalius®).
27
Figura 3- Microtomografia de um incisivo central superior e posterior reconstrução tridimensional.
28
Figura 5- Camada de cimento (espessura 0,50mm) interposta entre a coroa cerâmica e o pilar.
29
Figura 7- Pilar do tipo munhão anatômico (parafuso passante) para incisivo central superior.
30
Figura 9-A: Montagem dos componentes em vista explodida. B: Modelo com abutment de titânio; C: Modelo com abutment em zircônia
Figura 10- Reconstrução tridimensional da superfície dos discos realizada por interferometria. A) Titânio. B) Zircônia
Figura 11- A) Tensão máxima principal no osso cortical. B) Tensão de von Mises no parafuso
31 ANEXOS
32
