UNIVERSIDADE FEDERAL FLUMINENSE FACULDADE DE ODONTOLOGIA
ANÁLISE NORMATIZADA DOS PARAFUSOS RETENTORES DAS PRÓTESES PARAFUSADAS SOBRE COMPONENTES CÔNICOS SUBMETIDOS À FADIGA
Niterói 2017
FACULDADE DE ODONTOLOGIA
ANÁLISE NORMATIZADA DOS PARAFUSOS RETENTORES DAS PRÓTESES PARAFUSADAS SOBRE COMPONENTES CÔNICOS SUBMETIDOS À FADIGA
ALDIR NASCIMENTO MACHADO
Tese apresentada à Faculdade de Odontologia da Universidade Federal Fluminense, como parte dos requisitos para obtenção do título de Doutor, pelo P r o g r a m a d e P ó s - G r a d u a ç ã o e m Odontologia.
Á r e a d e C o n c e n t r a ç ã o : C l í n i c a Odontológica
Orientador: Prof. Dr. Cresus Vinicius Depes de Gouvêa
Niterói 2017
M149 Machado, Aldir Nascimento
Análise normatizada dos parafusos retentores das próteses
parafusadas sobre componentes cônicos submetidos à fadiga /
Aldir Nascimento Machado; orientador: Prof. Dr. Cresus Vinicius
Depes de Gouvea. – Niterói: [s.n.], 2017.
42 il.
Inclui gráficos e tabelas.
Tese (Doutorado em Odontologia) – Universidade Federal
Fluminense, 2017. Bibliografia: f. 33-39.
1. Esteticone . 2. Prótese dentária. 3. Micro-unit. 4. Abutment-cônicos.5. Materiais dentários. I. Gouvea, Cresus Vinicius Depes de [orien.]. II.Título
Prof. Dr. Cresus Vinicius Depes de Gouvêa
Instituição: Faculdade de Odontologia da Universidade Federal Fluminense
Decisão: _________________________Assinatura: ________________________ Prof. Dr. Raul Feres Monte Alto Filho
Instituição: Faculdade de Odontologia da Universidade Federal Fluminense
Decisão: _________________________Assinatura: ________________________
Prof. Dr. Gustavo Oliveira dos Santos
Instituição: Faculdade de Odontologia da Universidade Federal Fluminense
Decisão: _________________________Assinatura: ________________________
Prof. Dr. Eduardo Veras Lourenço
Instituição: Faculdade de Odontologia da Universidade Estadual do Rio de Janeiro Decisão: _________________________Assinatura: ________________________
Prof. Dr. Gustavo Vicentis de Oliveira Fernandes
Instituição: Faculdade de Odontologia da Universidade Salgado de Oliveira
.
Dedico este trabalho à minha mãe, Leda, eterna
incentivadora da minha formação acadêmica, à minha
mulher, Izabelly e meus filhos, Fernanda, Arthur e Théo,
companheiros inseparáveis, que colocam meus pés no chão
Ao meu Orientador, Professor Cresus Vinícius Depes de Gouvêa, que me abriu as portas para um novo campo, sempre me incentivando e me dando asas para desenvolver novos conhecimentos. Sempre com muita compreensão, e amizade.
Ao Professor Aristides da Rosa Pinheiro, pela amizade, confiança, parceria, incentivo e apoio.
Ao Professor Carlos Nelson Elias, pelo interesse e empenho na realização do presente trabalho, assim como pela amizade e incentivo constantes.
Aos Professores Angela Scarparo e Flavio Warol, pelo auxilio luxuoso na finalização deste trabalho e pela grande amizade que une nossas famílias.
Aos Professores Raul Feres Filho, Jose Jorge Schoichet e Monica
Calazans companheiros, incentivadores, exemplos de profissional que servem de
inspiração para todos que amam a Odontologia.
Ao Professor Waldimir Rocha Carvalho, pelo companheirismo e colaboração. Aos amigos Professores do curso de Especialização de Implantodontia da UFF, Cleonício Cordeiro, Alexandre Cardozo, Flávio Merly, Raphael Monte Alto,
Bruno Rangel, Sueli Pimentel e Priscila Casado, pela amizade e parceria.
Aos Técnicos do LABA-UFF, Marco Gomes, Hugo Igreja, Wellington
Casemiro e ao Sr. Leonardo do IME-RJ, pelo interesse e colaboração.
Às amigas Ana Cristina Portela e Bárbara Ignez Machado da Costa, pelo carinho, paciência e deliciosa convivência nestes quatro anos.
Agradeço ao pessoal do PPGO – UFF, João e Lucy pela atenção e toda a ajuda prestada.
Machado AN. ANÁLISE NORMATIZADA DOS PARAFUSOS RETENTORES DAS PRÓTESES PARAFUSADAS SOBRE COMPONENTES CÔNICOS SUBMETIDOS À FADIGA [Tese]. Niterói: Universidade Federal Fluminense, Faculdade de Odontologia; 2017
Parafuso retentor de prótese parafusada, é a parte mais frágil do sistema biomecânico dos componentes cônicos, além da função básica de reter a prótese, apresenta a função de autoproteção, pois quando submetido a excesso de carga, após longos períodos de uso, ou retendo próteses desadaptadas tendem a afrouxar ou fraturar. Dois tipos de abutments, esteticone e micro-unit, tiveram seus parafusos retentores avaliados, tendo como base a Norma ABNT ISO 14801:2012, à fadiga revelou que o período necessário para afrouxamento do parafuso retentor do esteticone, é menor do que o parafuso retentor do micro-unit, em cargas compatíveis com 40%, 50%, 60% e 70% da carga máxima em compressão máxima que indicou que é necessário 30% a mais de carga para fraturar o parafuso retentor de um componente micro-unit em comparação com o de um esteticone. Estes parafusos quando em próteses múltiplas parafusadas não apresentam sinal de afrouxamento, somente sendo percebidos em consultas periódicas de manutenção, quando servem de alerta para alterações como, alteração de carga, desadaptações da estrutura metálica, desgaste do material alterando pontos de contato oclusal. Dados obtidos a partir desta Norma, embora simule o carregamento funcional do componente sobre implantes endósseos, na condição “mais crítica”, não são aplicáveis para prever desempenho in vivo de um implante endósseo ou componente protético, particularmente se mais de um implante for utilizado.
Machado AN. NORMATIZED ANALYSIS OF RETENTION SCREW OF SCREWED PROTHESIS OVER CONICAL ABUTMENTS SUBMITTED TO FADIGA [Thesis]. Niterói: Universidade Federal Fluminense, Faculdade de Odontologia; 2017
Retention screw in addition to the basic function of retaining the prosthesis, it is the most fragile part of the biomechanical system of the conical components. It has the function of self-protection, because when subjected to excessive load, after long periods of use, or by retaining prostheses maladjusted lean to loosen or fracture. Two types of abutments, esteticone and micro-unit, had their retainer screws evaluated, based on the ABNT NBR ISO 14801: 2012 Standard, on fatigue revealed that the period required for loosening of the esthetic retainer screw, is smaller than the retainer bolt of the micro-unit in loads compatible with 40%, 50%, 60% and 70% of the maximum compressive load which indicated that 30% more load is required to fracture the retaining bolt of a micro-unit component compared with that of an esteticone. These screws when in multiple screwed prosthesis do not present a loosening signal, only being noticed in periodic maintenance visits, when they serve as an alert for alterations such as, load change, misfits framework, material wear altering occlusal contact points. Data obtained from this standard, while simulating the functional loading of the component on endosteal implants, in the "most critical" condition, are not applicable to predict in vivo performance of an endosteal implant or prosthetic component, particularly if more than one implant is used.
1 - INTRODUÇÃO
Próteses sobre implantes são construídas sobre sistemas mecânicos com interfaces de componentes retidos por parafusos, em sua maioria, e suas finalizações cimentadas ou parafusadas sobre estes sistemas. Este trabalho laboratorial se destinou a avaliar os parafusos de retenção das próteses parafusadas que utilizam dois tipos componentes cônicos, como componentes transmucosos, a condição de fadiga. Foram analisados os parafusos de retenção de pilares esteticone 27,32, (Conexão Sistema de Próteses, Arujá – SP ; Brasil) e micro-unit, (Conexão Sistema de Próteses, Arujá – SP ; Brasil) procurando definir ordem de grandeza da diferença da longevidade de um componente em relação ao outro, conforme numero de ciclos necessários a falha, sob as mesmas condições.
Entende-se por falha o afrouxamento ou desaperto do parafuso de retenção, 47,52,58, problema que afeta diretamente a prótese sobreimplante, sobrecarregando os parafusos de retenção 33,42,50 remanescente, aumentando o cantilever e a carga sobre os implantes que ainda mantenham seus parafusos estáveis.
A osseointegração 4, descrita por Branemark, apresentava uma estabilidade do implante em relação ao osso circunjacente, com perda óssea inicial média de 1mm, no primeiro ano, e 0,1 mm a cada ano subsequente, Albrektsson 5,45,55 descreveu perda óssea periimplantar como um desequilíbrio do organismo a uma reação de corpo estranho, demandada por reações celulares, com ativação de osteoclastos deflagradas por três fatores distintos ou combinados que são: problemas sistêmicos do paciente, restos de cimento e alteração da carga sobre os implantes. Desgastes das próteses, afrouxamento e fraturas de parafusos de retenção, podem levar a alteração da carga sobre os implantes.
A despeito de parte da literatura não apresentar relação direta entre carga e perda óssea 36,39,40, em virtude de todos os trabalhos terem sido realizados em animais, há relatos de reabsorções ósseas periimplantares como resultado da adaptação biomecânica do osso ao estresse, e sua progressão crescente quando submetida a estresse sobre o osso medular e a carga lateral sobre o implante, que podem resultar na falência do implante 15,30,38,40.
A transmissão da carga oclusal para os implantes variam de acordo com o tipo de plataforma do sistema de implante utilizada11, do numero de implantes utilizados na reabilitação 15,56, da inclinação do implantes 46,52,56 e dos componentes 14,33,36, da passividade da infra estrutura, metálica ou não 1,2,11,21,41, da presença e da extensão dos cantilevers 18, e do tipo do componente 10,12,14,38,58 empregado na prótese.
O direcionamento das cargas oclusais sobre as próteses sobre implantes podem se alterar dependendo do material utilizado, nas próteses múltiplas totais principalmente preconizadas, para serem construídas em resina acrílica, o desgaste acontece em um espaço de tempo, de aproximadamente 5 anos 34,59, podendo levar a alterações no formato das próteses, dos pontos de contato oclusais, inclusive em cantileveres, que influenciam diretamente na transmissão das cargas oclusais transmitidas aos implantes.
As próteses múltiplas parafusadas totais, conhecidas como protocolo Branemark, foram desenvolvidas sobre abutments transmucosos 4,59 do tipo standard, posteriormente por necessidades estéticas e com a intenção de aproximar a união prótese/abutment da interface abutment/implante, surgiu o transmucoso esteticone 27,32,33, que trata-se de um componente cônico, segmentado em duas partes distintas, com um pequeno parafuso retentor da prótese. Existem basicamente dois tipos de componentes transmucosos cônicos, os pilares cônicos aqui representado pelo esteticone sem antirrotacional e dos mini pilares conicos aqui representado pelo micro-unit, ambos destinados a próteses múltiplas parafusada. A diferença básica dos dois abutments está na altura, onde o esteticone possui 6.7mm de altura e o mini pilar cônico possui somente 4.5mm, quando utilizados com cinta de 1mm, na inclinação de suas paredes de 15o e 20o respectivamente, o que proporciona eixos de inserção distintos, mas ambos possuem parafusos de retenção com diâmetros similares, que acumulam a função de autoproteção do sistema, afrouxando ou fraturando quando submetidos a excesso de carga ou condições desfavoráveis, evitando a transmissão deste estresse mecânico ao osso periimplantar. A análise destes parafusos, em compressão máxima apresentou diferença de 30% de carga necessária para se fraturar um parafuso retentor de micro-unit em comparação a um de pilar tipo esteticone, fruto de sua macromorfologia 33. Submete-los ao teste de fadiga permitiu analisar a longevidade dos parafusos de um componente em relação ao outro.
O comportamento mecânico de um material reflete a relação entre a sua resposta ou deformação a uma carga ou força que esteja sendo aplicada 19. Algumas propriedades mecânicas importantes são a resistência, a dureza, a ductilidade e a rigidez. Estas propriedades são verificadas pela execução de experimentos de laboratório cuidadosamente programados, que reproduzem o mais fiel possível as condições de serviço. Se uma carga é estática ela se altera de uma maneira relativamente lenta dentro de um período de tempo e é aplicada sobre uma seção reta ou superfície de um membro 19 .O comportamento mecânico pode ser verificado mediante um simples ensaio de tensão-deformação Tais ensaios são comumente conduzidos para metais à temperatura ambiente. Os ensaios de compressão são usados quando se deseja conhecer o comportamento de um material submetido a grandes e permanentes deformações. Ensaios de fadiga definem a vida total de um material submetido à cargas cíclicas, é a combinação entre o numero de ciclos necessário à enucleação da trinca e o que corresponde à sua propagação até a falha final 19.
Com cargas oclusais, relatada sobre implantes em condições normais, com força total de 220N a 450N e em elementos isolados com 91N para anteriores e para posteriores com no máximo 314N 9.
A construção de um parâmetro destinado a alimentar um protocolo de manutenção 44, é necessário, para permitir intervenção, reacrilizações 34 e trocas periódicas de parafusos 20, na intenção de eliminar a possibilidade de sobrecargas que geram falhas e fraturas 39, a partir de condições normais do uso, em função dos desgaste, evitando aumento da carga e prevenindo uma possível reabsorção óssea.
2 - METODOLOGIA
Esse trabalho laboratorial, seguiu as recomendações da norma brasileira , ABNT NBR ISO 14801:2012, de ensaios dinâmicos de fadiga para implantes odontológicos endósseos, unitário do tipo transmucoso com seus components protéticos pré-fabricados, embora esta norma simule o carregamento functional do corpo de um implante odontológico endósseo e seu componente protético pré-fabricado em situação mais critica. Esta norma não é aplicável para prever o desempenho in vivo de um implante ou componente protético odontológico endósseo, particularmente se mais de um implante for utilizado para uma prótese.
O presente estudo foi conduzido no LABA –UFF ( Laboratório de Biomecânica Aplicada da Universidade Federal Fluminense), no período de outubro de 2016 a setembro de 2017.
Os corpos de prova (CP), consistem de um implante hexágono externo de plataforma regular de 4.1 mm de diâmetro, ( Master Easy – Conexão Sistemas de Prótese – São Paulo – Brasil) e componentes protéticos de um sistema que não inclui componentes pré-angulados, fixados em um dispositivo de fixação rígida . com módulo de elasticidade superior a 3 GPa (poliacetal, Caterplast – São Paulo. Brasil), concebidos de modo que não deformem a amostra durante o ensaio, e permita instalar a amostra , anteriormente à inserção do implante, foi aberto pré-furo no bloco, sem pré-rosqueamento, com diâmetro de 3,5 mm. Conforme orientação do fabricante, durante a inserção do implante no bloco o torque não excedeu 60 N.cm, com torquímetro digital, ( TORQUÍMETRO DIGITAL MODELO TQ-680; Instrutherm Instrumentos de Medição; São Paulo – SP – Brasil), e o pilar foi montado com torque de 20 N.cm, um componente hemisférico, utilizado para o contato com o aplicador de carga da máquina. Este componente possui raio esférico de 10 mm, atendendo a distância (A) de (11,00 ± 0,24) mm determinada pela norma técnica. O componente hemisférico foi fabricado em cromo cobalto.
A uma distância de 3,0 mm ± 0,5 mm apical do osso nominal, simulando perda óssea, fixado de forma que seu eixo central esteja em un angulo (α) de 30o ± 2o de em relação à direção de carregamento do equipamento de ensaio, permitindo
movimento livre transversal a direção da carga . O método deve ter o seu centro de carregamento localizado na interseção do eixo longitudinal central da extremidade livre da parte da conexão com o plano normal ao eixo longitudinal do implante, atendendo a distância (A) de 11 mm ± 0,24mm a partir do nível de sustentação do implante, sendo assim o braço de alavanca (y) aplicado ao sistema pode ser calculado pela equação [sen(α).A] e resulta em 5.5 mm. A força de carregamento deve ser aplicada à superfície de de carregamento hemisférico por um dispositivo de força com uma superfície plana normal à direção de carregamento da máquina (EQUIPAMENTO DE DESGASTE TERMOMECÂNICO, MODELO ER 37000; ERIOS® Equipamentos Técnicos e Científicos LTDA; São Paulo – SP – Brasil) . Os
CP foram submetidos a carregamento cíclico senoidal com frequência de 5 Hz. Para cada valor de momento aplicado, o número de ciclos foi registrado até a ocorrência de falha do CP ou até o limite de ciclos para interrupção do ensaio ter sido alcançado. Os valores de força empregados corresponderam a 40%, 50%, 60% e 70% do valor médio de Força no limite de resistência, determinado no ensaio estático. O número de ciclos máximo considerado foi 5 000 000. Os ensaios foram realizados em meio seco com temperatura de (20,0 ± 5,0) o C.
Os componentes montados sobre os implantes dos CPs foram:, pilar cônico do tipo Estheticone (Conexão Sistemas de Prótese – São Paulo – Brasil) CPE, e mini pilar cônico, tipo micro-unit (Conexão Sistemas de Prótese – São Paulo – Brasil) CPM, o primeiro composto de duas partes, uma base cônica com cinta de 1mm de altura e um parafuso passante, destinado a reter na sua parte superior o parafuso retentor da prótese, que somado a cinta compõe o conjunto com 6,7mm de altura, medidos da plataforma do implante até o topo do componente, torqueados seguindo especificações do fabricante com 20Ncm, sobre este conjunto foi instalado cilindro provisório em titânio sem antirotacional na sua area interna só fazendo contato com o componente, na sua base e na area do parafuso de retenção, que sofreu torque de 10Ncm, seguindo especificações do fabricante, fixando o cilindro ao componente, sobre este conjunto cápsula de cromo cobalto em formato hemisférico, atendendo as determinações da ABNT NBR ISO 148013, o segundo, mini pilar cônico composto de duas partes, uma base cônica com cinta de 1mm de altura e um parafuso passante, destinado a reter na sua parte superior o parafuso retentor da prótese,
que somado a cinta compõe o conjunto com 4,5mm de altura, medidos da plataforma do implante até o topo do componente, torqueados seguindo especificações do fabricante com 20Ncm, sobre este conjunto foi instalado cilindro provisório em titânio sem antirotacional na sua area interna só fazendo contato com o componente, na sua base e na area do parafuso de retenção, que sofreu torque de 10Ncm, seguindo especificações do fabricante, fixando o cilindro ao componente, sobre este conjunto cápsula de cromo cobalto em formato hemisférico, atendendo as determinações da ABNT NBR ISO 148013. Figura 1
!
Figura 1. Esquema ilustrativo do ensaio mecânico realizado neste estudo (ISO 14801:2012)
O material normalizado na especificação ASTM F67-77 é considerado um material padrão de controle pela Norma ASTM F316-90, que controla os requisites de biocompatibilidade para materiais empregados em implantes. Esse fato indica que esse é um material que não causa reações adversas quando em contato com meio biológico humano. A especificação ASTM F136-79 normaliza a liga (Grau 5)
destinada a fabricação de implantes cirúrgicos
Os CPs (CPE e CPM), eram verificados a cada 1.000.000 ciclos ou quando do desligamento diário da máquina, portanto não há como determinar o ciclo exato da falha, o primeiro CPE a falhar ocorreu no quarto ciclo de milhão (3.999.998 ciclos), com carga de 330N, e Momento Máximo de 1,848 Nm, que para este CPE corresponde a 60% da carga maxima, não houve falha na mesma carga para CPM, correspondendo 50% da carga maxima para estes CPs.O tratamento dos corpos de prova seguiram o disposto na ABNT NBR ISO 14801-20123,
3 - ARTIGOS PRODUZIDOS
Standard analysis of screw-retaining of screwed prosthesis on conical rotational abutments subjected to fatigue
Aldir Nascimento Machado 1 Aristides da Rosa Pinheiro 2 Carlos Nelson Elias 3 Waldimir Carvalho 4 Cresus Vinicius Depes de Gouvêa5
1 Assistant Professor, Department of Clinic, Fluminense Federal University, (UFF), Niterói, Rio de Janeiro, Brazil.
2 Professor of Implantology, Fluminense Federal University (UFF), Niterói, Rio de Janeiro, Brazil.
3 Professor of the Department of Mechanical Engineering and Material Science, Military Engineering Institute (IME) Laboratory of Biomaterials, Rio de Janeiro, Brazil, 4 Professor of Department of Prosthodontics, Laboratory of Applied Biotechnology, Fluminense Federal University School of Dentistry Niterói, Brazil.
5 Chairman, Department of Prosthodontics, Laboratory of Applied Biotechnology, Fluminense Federal University School of Dentistry, Niteroi, Brazil.
Reprint requests and correspondence to: Aldir Nascimento Machado, CD, MScD, Rua Morais e Silva 139 c 01, Maracanã, Rio de Janeiro, Brazil 20271-031, Phone: 55 (021) 981871372, E-mail: aldirmachado@gmail.com Standard analysis of screw-retaining of screwed prosthesis on conical rotational abutments subjected to fatigue
ABSTRACT
Retention screw in addition to the basic function of retaining the prosthesis, it is the most fragile part of the biomechanical system of the conical components. It has the function of self-protection, because when subjected to excessive load, after long periods of use, or by retaining prostheses maladjusted to loosen or fracture. Two types of abutments, esthetic and micro-unit, had their retainer screws evaluated, based on the ABNT ISO 14801: 2012 Standard, on fatigue revealed that the period required for loosening of the esthetic retainer screw, is smaller than the retainer bolt of the micro-unit in loads compatible with 40%, 50%, 60% and 70% of the maximum compressive load which indicated that 30% more load is required to fracture the retaining bolt of a micro-unit component compared to that of an esthetic . These screws when in multiple screwed prosthesis do not present a loosening signal, only being noticed in periodic maintenance visits, when they serve as an alert for alterations such as, load change, misfits framework, material wear altering occlusal contact points. Data obtained from this standard, while simulating the functional loading of endosteal implants, in the "most critical" condition, are not applicable to predicted in vivo performance of an endosteal implant or prosthetic component, particularly if more than one implant is used .
INTRODUCTION
Implant prostheses are built on mechanical systems with mostly screw-retained component interfaces, and their cemented or screwed finalizations on these systems. The aim of this study was to evaluate the screw retention of screwed prostheses using two types of conical abutments, such as transmucosal components, on fatigue condition. The retention screws of estheticone 26,31, (Conexão Sistemas de Prótese, Arujá - SP, Brazil) and micro - unit, (Conexão Sistemas de Prótese, Arujá - SP, Brazil) were analyzed, looking for to define the magnitude of the longevity difference of one component relative to the other, according to the number of cycles required for failure, under the same condittions.
Failure to loosen or loosen the retaining screw 46,51,57 a problem that directly affects the implant prosthesis, overloading the remaining retention screws41,49, increasing the cantilever and load on the implants that still keep their screws stable. Osseointegration 4, described by Branemark, presented stability of the implant relative to the surrounding bone, with mean initial bone loss of 1mm in the first year and 0.1mm in each subsequent year, Albrektsson 5,45,55 described peri-implant bone loss as an disturbance of balance of to a foreign body reaction, demanded by cellular reactions, with activation of osteoclasts triggered by three distinct or combined factors: systemic patient problems, cement remnants and load changes on the implants. Prosthetic wear, loosening, and retention screw fractures can lead to a change in load on implants.
Although part of the literature does not present a direct relationship between overload and boné loss 36,39,40, because all the work has been performed on animals, there are reports of peri-implant bone resorption as a result of the bone biomechanical adaptation to stress, and its increased progression when subjected to
stress on the medullary bone and lateral loading on the implant, which may result in implant failure 15,30,38,40.
The transmission of the occlusal load to the implants varies according to the type of platform of the implant system used 11, the number of implants used in rehabilitation 15,56, the inclination of the implants 46,52,56 and the componentes 14,33,36, of the passivity of the infrastructure, metallic or not 1,2,11,21,41, of the presence and extension of the cantilevers 18, and the type of componente 10,12,14,38,58 used in the prosthesis.
The orientation of the occlusal loads on the prostheses on implants can change depending on the material used, in the total multiple prosthesis mainly recommended, to be built in acrylic resin, wear occurs in a period of time, approximately 5 years, 34,59 and can lead to changes in the shape of the prosthesis, occlusal contact points, including cantilevers, that directly influence the transmission of the occlusal loads transmitted to the implants.
The total screwed multiple prostheses, known as the Branemark protocol, were developed on transmucosal abutments 4,59 of the standard type, later by aesthetic needs and with the intention of approaching the prosthesis / abutment union of the abutment / implant interface, the transmucosal aestheticone 27,32,33 it is a conical component, segmented into two distinct parts, with a small screw retaining the prosthesis. There are basically two types of conical transmucosal components, the conical abutments represented here by the non-anti-rotational aesthetic and the mini conical abutments represented here by the micro-unit, both intended for multiple prostheses screwed. The basic difference of the two abutments is at the height where the aesthetic is 6.7mm high and the mini conical abutment has only 4.5mm, when used with 1mm strap, in the slope of its walls of 15o and 20o respectively, which
provides insertion, but both have retention screws, which accumulate the self-protection function of the system, loosening or fracturing when subjected to excessive load or unfavorable conditions, avoiding the transmission of this mechanical stress to the peri-implantar bone.The analysis of these screws, at maximum compression, presented a difference of 30% of the load necessary to fracture a micro-unit retainer screw compared to an aesthetic-type pillar, due to its macromorphology 33. Undergoing the fatigue test allowed to analyze the longevity of the screws of one component with respect to the other.
The mechanical behavior of a material reflects the relationship between its response or deformation to a load or force being applied 19. Some important mechanical properties are strength, hardness, ductility and stiffness. These properties are verified by the execution of carefully programmed laboratory experiments, which reproduce as faithful as possible the conditions of service. If a load is static it changes relatively slowly over a period of time and is applied over a straight section or surface of a member. 19 The mechanical behavior can be verified by a simple stress-strain test Such tests are commonly metals at room temperature. The compression tests are used when it is desired to know the behavior of a material subjected to large and permanent deformations. Fatigue tests define the total life of a material subjected to cyclic loads, it is the combination between the number of cycles necessary for the enucleation of crack and what corresponds to its propagation until the final failure 19.
With occlusal loads, reported on implants under normal conditions, with total force of 220N to 450N and in isolated elements with 91N for anterior and posterior with a maximum of 314N 9.
The construction of a parameter to feed a maintenance protocol 42 requires, in order to allow intervention, 44 and periodic screw changes 20, in the intention of eliminating the possibility of overloads that generate failures and fractures 39, from normal conditions of use, due to wear, avoiding an increase of the load and preventing a possible bone resorption.
METHODOLOGY
This laboratory work, followed the recommendations of the Brazilian standard, ABNT NBR ISO 14801: 2012, of dynamic fatigue tests for endosteal dental implants, transmucosal type unit with its prefabricated prosthetic components, although this standard simulates the funconial loading of the body of an endosteal dental implant and its prefabricated prosthetic component in a more critical situation. This standard is not applicable to predict the in vivo performance of an endosteal implant or dental prosthetic component, particularly if more than one implant is used for a prosthesis. The present study was conducted at the LABA -UFF (Laboratory of Applied Biomechanics of the Fluminense Federal University), and, the materials used in the study are described below, in Table 1.
The specimens (CP) consist of a regular external hexagon implant of 4.1 mm in diameter (Conexão Sistemas de Prótese, Arujá - SP, Brazil) and prosthetic components of a system that does not include pre-angled components , fixed in a rigid fixation device. with a modulus of elasticity greater than 3 GPa (polyacetal, Caterpast - São Paulo, Brazil), designed so that they do not deform the sample during the test, and allow to install the sample, before insertion of the implant, was opened pre-drilled in the block , without threading, with a diameter of 3.5 mm.
According to the manufacturer's instructions, during the insertion of the implant in the block, the torque did not exceed 60 N.cm, with a digital torque wrench, and the abutment was mounted with a torque of 20 N.cm, a hemispherical component, used for contact with the load applicator of the machine. This component has a spherical radius of 10 mm, taking into account the distance (A) of (11.00 ± 0,24) mm determined by the technical standard. The hemispherical component was made of cobalt chromium.
At a distance of 3.0 mm ± 0.5 mm apical from the nominal bone, simulating bone loss, fixed so that its central axis is at an angle (α) of 30o ± 2o in relation to the direction of loading of the test, allowing free movement transverse to the load direction. The method shall have its loading center located at the intersection of the central longitudinal axis of the free end of the part of the connection with the plane normal to the longitudinal axis of the implant, taking the distance (A) from 11 mm ± 0,24 mm from the level (y) applied to the system can be calculated by the equation [sin (α) .A] and results in 5.5 mm. The loading force shall be applied to the hemispherical loading surface by a force device with a flat surface normal to the direction of loading of the machine (THERMOMECHANICAL WEAR EQUIPMENT, MODEL ER 37000, ERIOS, Equipamentos Técnicos e Científicos LTDA; SP - Brazil). The CPs, Figure1, were submitted to sinusoidal cyclic loading with a frequency of 5 Hz. For each moment value applied, the number of cycles was recorded until the CP failure occurred or until the cycle limit for interruption of the test was reached. The force values corresponded to 40%, 50%, 60% and 70% of the average value of Strength at the limit of resistance determined in the static test. The maximum number of cycles considered was 5,000,000. The tests were performed on a dry medium with a temperature of (20.0 ± 5 ° C), considering the values described in Table 2.
The components assembled on the implants of the CPs were: Conical pillar of the Estheticone type (Conexão Sistemas de Prótese, Arujá - SP, Brazi) CPE, and mini conical abutment, type micro-unit (Conexão Sistemas de Prótese, Arujá - SP, Brazi) CPM , the first compound of two parts, a conical base with a 1mm high strap and a through screw, intended to retain the prosthesis retainer on its upper part, which, together with the strap, makes up the assembly with a height of 6.7mm, measured from the implant platform to the top of the component, torque tested following manufacturer's specifications with 20Ncm, on this set was installed titanium cylinder without anti-rotation in its internal area only making contact with the component, at its base and the area of the retaining screw , which underwent torque of 10Ncm, following manufacturer's specifications, fixing the cylinder to the component, on this set cobalt chromium capsule in hemispherical format, meeting the determinated at ABNT NBR ISO 148013, the second, a conical mini-pillar composed of two parts, a tapered base with 1 mm high strap and a through screw, intended to retain the upper part of the prosthesis retainer screw, which together with the strap the set with 4.5mm height, measured from the platform of the implant to the top of the component, torque following the manufacturer's specifications with 20Ncm, on this set was installed titanium cylinder without anti-rotation in its internal area only making contact with the component, at its base and in the area of the retaining screw, which has undergone a torque of 10Ncm, according to the manufacturer's specifications, fixing the cylinder to the component, on this cobalt chromium capsule set in hemispherical format, meeting the requirements of ABNT NBR ISO 148013. The material standardized in the ASTM F67-77 specification is considered a standard control material by ASTM Standard F316-90, which controls the biocompatibility requirements for materials used in implants. This fact indicates that
this is a material that does not cause adverse reactions when in contact with human biological environment. The ASTM F136-79 specification normalizes the alloy (Grade 5) for the manufacture of surgical implants.Table 1
RESULTS
Data obtained after mechanical testing are set forth in Table 4, and statistical analysis can be seen in Table 5, the reported expanded measurement uncertainty is stated as the standard uncertainty of the measurement multiplied by the coverage factor, which for a distribution with effective degrees of freedom corresponds to a coverage probability of approximately 95%. The standard uncertainty of measurement was determined according to publication EA-4/02.
Statistical analysis applies when the given data can be reasonably assumed to be a random sample of (or representation of) some specific defined population or universe of material of interest (under specific test conditions), and it is desired either to characterize the material or to predict the performance of future random samples of the material (under similar test conditions), or both, ASTM E739-10 2015. Table 5
The specimens (CPE and CPM) were checked every 1000,000 cycles or when the machine is daily slammed, so there is no way to determine the exact cycle of the failure, the first CPE to fail occurred in the fourth million cycle (3,999,998 cycles), with load of 330N, and Maximum Moment of 1,848 Nm, which for this CPE corresponds to 60% of the maximum load, there was no failure in the same load for CPM, corresponding to 50% of the maximum load for these specimens, of proof followed the provisions of ABNT NBR ISO 14801-20123
Statistical analysis
A Shapiro-wilk test was performed to evaluate the normality of the tests (Table
6). The null hypothesis about the difference between the cycle mean of the groups is
equal to zero was rejected (p=0.0334).
DISCUSSION
This study evaluated prosthesis retention screws made on two types of tapered components, under fatigue, with different behaviors due to their macromorphology, where those using antistatic components loosened with a smaller number of cycles than those using micro- unit. The success of endosteal implants devised by Adell 4 is directly related to the longevity of osseointegration. After 35 years, the paradigm of osseointegration is questioned by Trindade 55, which refers to a foreign body reaction in equilibrium, which can be altered from three factors that trigger this equilibrium, change in load, systemic problems and remains of cement. This load change can be promoted by the loosening of the screws that support the prosthesis especially the multiple bolted ones 48 and that use conical components. According to the literature, when the function is compromised by mismatches in the infrastructure (Sahin 47), with inadequate torques (Bruna 13, Farina 17, Guzaitis 20, Neto 42, Sella 50, Theoharidou 52, Kim 28), structures with inadequate designs are affected by biomechanical sequelae (Abduo 1, Abduo 2, Ehrenkranz 16, Goiato 18).
Biomechanical risks have been reported in case of implant prostheses (Sanz 49 Hernandez-Rodriguez 22 and Watanabe 57). Among the factors involved, the literature reports as triggers or potentiators: maladaptive prostheses due to the type of cylinder
used in the construction of the infrastructure (Bhering 11, Moraes 37) heights of inadequate abutments (Moreno 38 and Siadat, 51), abutments with exaggerated angulations (Watanabe 56 , Tian 53, Lavendiatis 31), in the process of casting the infrastructure (Baggi 8), with biomechanical consequences that alter the transmission of the occlusal load to the implants and peri-implant bone (Balik 10, Natali 41).
The selection of the components described Camargo 14 and Mesquita 35 is of particular importance in the transmission of the occlusal load to the implants. Kastenbaum 27 and Lewis 32, point to the east as a conic component with a design that allows adequate transmission of forces.
Machado 33 observed that the retentive screw that would loosen in situations of excessive load, in the esthetic one in comparison to the micro-unit component, needs a smaller load to loosen the analysis of these screws, in the maximum compression presented difference of 30% of load necessary to fracture a micro-unit retainer screw compared to an aesthetic-type abutment, as a result of its macromorphology 33. Undergoing the fatigue test allowed to analyze the longevity of the screws of one component with respect to the other.
According to Sananez 48 This load, which is more than one component in relation to the other, is transmitted to the perimplantar bone, Duyck 15 reports that by loosening a prosthesis retainer screw, the load on the next implant is increased due to a change in the length of the prosthesis supported by the abutments base, ie by increasing its cantilever 18,57.
This study observed that the retaining screws of the aesthetic abutments loosened with a smaller number of cycles in relation to the micro-unit abutments, demonstrating a shorter survival period, which although laboratory tests are not conclusive, in relation to the clinic, show different biomechanical behavior .
The influence of biomechanics was described by Renouard 46, Hobkirk 23 and Kitamura 29 and the action on the peri-implant bone by Isidor 25 in relation to occlusal overloads were reported by Miyata 36, Torcato 54, Naert 39 and Kozlovsky 30, lead to peri-implant bone resorption, putting the integrity of the implants at risk , being more frequent in tissues with inflammatory processes, already established, but they are categorical to affirm that the studies to be performed in animals, are not conclusive, even when they present bone loss as described by Nagasawa 40, Hof 24, Naert 39, Moreno 38 and Qian 45 , these overloads can be produced by loosening screws in multiple prostheses, overloading the remaining screws, and in prostheses using micro-unit components, the overload diagnosis may be slower.
The way to avoid biomechanical unfavorable situations, reported by Zarb 59, Ziztmann 60, as the loss of the screw According to Yeo 58, it is through periodic maintenance visit, where the integrity of the prosthesis is evaluated Noda43, Pjetursson 44, McCool 34, Sella 50 and Jung 26 pointed out that periodic appointments due to wear of dentures mainly with occlusal surfaces in acrylic resin, which has, with the use, natural wear and tear, altering the occlusion load transmission described by Duyck 15 and Bakke 9. Overloading the retaining screws According to Sella 50, re-tightening and replacing screws when necessary should be carried out. Gouvêa 19 and Hecker 21, Ayllón 7 describes that one of the most effective mechanical tests to measure the behavior of a material is when we submit to fatigue, second. ABNT NBR ISO 14801: 2012 3, standardizes fatigue tests on endosteal implants.
The conical abutments replaced the standard abutments and, on the grounds of the need for a smaller interocclusal space, the conical minipillars, such as micro-units, became widely used instead of the aesthetic-type conical abutments, but
according to this study , the response to the load on the prostheses is slower. The micro-unit will only fail with a larger number of cycles or at loads greater than that exerted on the aesthetics, which although positive may conceal overloads or variations thereof.
CONCLUSION
Although the results of laboratory tests can not be transported to in vivo situations due to innumerable variables, it is permissible to conclude the difference in behavior between the two retaining screws, which, although the same diameter, under the same conditions had different biomechanical behavior, due to the different macromorphology of the components.
The data found however suggest that a periodic maintenance protocol should be established, and in cases where space is not a limiting, esteticone pillars should be selected with the intention of a feed back, of the action of the loads that act on the prostheses and are usually transferred to the peri-implant bone.
Table 1. Materials used in the study execution
SPECIMENS
N Abutments Register
Code Batch feedstock
12 Abutment
Esteticone 02202199 161617 ASTMF-136 Grau 5 12 Provisional
Cylinder Esteticone
11200499 157629 ASTMF-136 Grau 5
12 Retention screw
Esteticone 01100499 162617 ASTMF-136 Grau 5 12 Abutment Micro
Unit 13202199 163310 ASTMF-136 Grau 5 12 Provisional
Cylinder Micro Unit
15900499 163817 ASTMF-136 Grau 5
12 Retention screw
Micro Unit 15700499 163132 ASTMF-136 Grau 5 24 Implant Easy
Grip HE 52271199
Table 2. Maximum load percentage used in this study MAXIMUM LOAD PERCENTAGE CPM CPE 40 % 264 N 224 N 50 % 330 N 280 N 60% 396 N 336 N 70% 462 N 392 N
!
Figure 1. Illustrative scheme of the mechanical test performed in this study (ISO 14801: 2012)
Table 3. Data obtained after mechanical fatigue test. Number of CPs CPs Maximum load (N) Maximum Moment (Nm)
Stopping Criterion Number of Cycles
01 CPEI 1 224 1,232 Number of Cycles 5 X 106 01 CPEI 2 224 1,232 Number of Cycles 5 X 106 01 CPEI 3 224 1,232 Number of Cycles 5 X 106
01 CPEII 1 280 1,540 loosening 3.999.998
01 CPEII 2 280 1,540 Number of Cycles 5 X 106 01 CPEII 3 280 1,540 Number of Cycles 5 X 106 01 CPEIII1 336 1,848 Number of Cycles 5 X 106 01 CPEIII2 336 1,848 Number of Cycles 5 X 106
01 CPEIII3 336 1,848 loosening 3.857.545
01 CPEIV1 392 2,156 loosening 2.859.983
01 CPEIV2 392 2,156 loosening 2.859.983
01 CPEIV3 392 2,156 loosening 2.859.983
01 CPMI 1 264 1,456 Number of Cycles 5 X 106 01 CPMI 2 264 1,456 Number of Cycles 5 X 106 01 CPMI 3 264 1,456 Number of Cycles 5 X 106 01 CPMII 1 330 1,815 Number of Cycles 5 X 106 01 CPMII 2 330 1,815 Number of Cycles 5 X 106 01 CPMII 3 330 1,815 Number of Cycles 5 X 106 01 CPMIII1 396 2,178 Number of Cycles 5 X 106 01 CPMIII2 396 2,178 Number of Cycles 5 X 106 01 CPMIII3 396 2,178 Number of Cycles 5 X 106 01 CPMIV1 462 2,541 Number of Cycles 3.999.998 01 CPMIV2 462 2,541 Number of Cycles 5 X 106 01 CPMIV3 462 2,541 Number of Cycles 3.999.998
Table 4. Number of cycles and specimens failure
Table 5. Number of cycles and loads percentage failure
ESTETICONE no cycles ( no specimens failure) MICRO-UNIT no cycles ( no specimens failure) GRUPO I 5 X106 5 X106 GRUPO II 3.999.998 5 X 106 GRUPO III 3.857.545 (1) 5 X 106 GRUPO IV 2.859.983 (3) 3.999.998 (2)
Table 6. Shapiro-Wilk W test for normal data: Paired test Variable | Obs Mean Std.
Std Dev. [95% Conf. Interval]
Estethicone 12 4119791 334245,2 1157859 3384122 4855460 micro-unit 12 4833333 112367 389250.6 4586015 5080651 diff 12 -713541.8 293547.4 1016878 -1359635 -67448.4
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CONCLUSÃO
Apesar do resultado de ensaios laboratoriais não poderem ser transportados para situações in vivo, devido a inúmeras variáveis, é lícito concluir a diferença de comportamento entre os dois parafusos retentores que apesar de possuirem diâmetros iguais, sob as mesmas condições tiveram comportamento biomecânico diferentes, em virtude da distinta macromorfologia dos componentes transmucosos.
Os dados encontrados no entanto sugerem, que um protocolo de manutenção periódica, deve ser estabelecido, e em casos onde o espaço não seja um limitante, pilares do tipo esteticone, devem ser selecionados com a intenção de um feed back , da ação das cargas que atuam sobre as próteses e são normalmente transferidas para o osso do periimplantar.
