Influence of resin cement thickness and temperature variation on mechanical behavior of dental ceramic fragment restoration.

To evaluate the stress behavior of ceramic fragment restoration, varying the thickness of the cement layer and intraoral temperature variation. A solid model of a upper lateral incisor was obtained and a defect at enamel distal/incisal edge was restored with a ceramic fragment. Based on this initial model, 4 different models (M) were built: M1 - absence of cement layer (CL) (0 µm of thickness); M2 - CL with an uniform thickness of 50 µm; M3 - CL with 50 µm at the margin of ceramics and 100 µm in the inner area far from margins; M4 - CL with 50 µm at the margin of ceramics and 200 µm in the inner area far from margins. The environment temperature changed from 5 °C to 50 °C in 4 increments. The finite element analysis was performed. Increase the cement layer thickness generated higher stress levels on ceramic surface in all temperatures, as well as on cement interface. In general hot temperature was the worst scenario for ceramic fragments integrity, since tensile and compressive stress were more intense. The maximum principal stress on ceramic fragment was found 90 MPa for M4 at 50 °C, followed for M3 (87 Mpa). For CL, the peak of stress was found for M3 at 5 °C (47 MPa). Is it possible to conclude that thick resin cement layer contribute to higher stress concentration on ceramic fragment, and extremely hot temperatures increase the risk of structural failure, since both ceramic and \cl are exposed to higher compressive and tensile stresses.

Influência do tipo de conexão (quadrado ou hexagonal) na resistência a deformação do conjunto chave-parafuso de retenção de prótese sobre o implante / Influence of joint design (square or hexagonal) on resistance to deformation of driver-screw retention assembly on implant-supported prosthesis

O tratamento reabilitador com próteses implantossuportadas tem alcançado elevados índices de sucesso. No entanto, falhas mecânicas ainda podem ocorrer, especialmente, nos parafusos de retenção dos pilares protéticos de restaurações unitárias sobre implante, sendo esses desenhados para ser o elo mais fraco na estrutura e ser o primeiro elemento a falhar em situações de sobrecarga. Nesse contexto, o objetivo deste trabalho foi avaliar in vitro a influência de diferentes tipos de conexões (quadrado ou hexagonal) na resistência à deformação do conjunto chave-parafuso de retenção de três diferentes marcas comercias (Neodent, Singular e Sin). Foram utilizados quarenta e dois (42) parafusos de retenção, de três (3) diferentes marcas comerciais. Esses foram divididos em dois grandes grupos de conexão, quadrada (QUA) e hexagonal (HEX) e separados por marcas comerciais. Foram utilizados vários componentes (implantes e pilares protéticos) que apresentavam plataforma regular padrão (4.1 mm de diâmetro). Para medir a força da resistência à deformação do conjunto chave- -parafuso de retenção, utilizou-se um torquímetro digital de alta precisão, para cada uma das três (3) diferentes marcas comerciais - Neodent (NEO), Singular (SGL) e Sin (SIN) - variando a geometria do sistema de conexão (quadrado ou hexagonal). Observou-se ausência de diferença estatisticamente significante (p<0,05) entre as três marcas comerciais analisadas. Por outro lado, independente da marca comercial, dentre os parafusos examinados, os parafusos quadrados apresentaram maior resistência à torção do que os parafusos hexagonais (AU).

Rehabilitation with implant-supported prostheses has reached high success rates. However, mechanical failures may still occur mainly in retention screws of abutments in single implant-supported crowns, which are designed to be the weakest structure and the first component to fail under overloading. In this context, the aim of this in vitro study was to evaluate the influence of different joint designs (square or hexagonal) on resistance to deformation of driver-screw retention assembly of three commercial brands (Neodent, Singular and Sin). A total of forty-two retention screws from three commercial brands were used. The samples were divided into two joint groups, square (SQU) and hexagonal (HEX) and separated by commercial brands. Several components (implants and abutments) with standard regular platform (4.1 mm diameter) were used. The resistance to deformation of the driver-retention screw assembly was measured using an accurate digital torque wrench for all commercial brands - Neodent (NEO), Singular (SGL) and Sin (SIN) - varying the joint designs (square or hexagonal). No statistically significant difference (p<0.05) among the brands evaluated was found. On the other hand, square screws showed higher resistance to torsion than hexagonal screws regardless the commercial brand (AU).

Pesquisa estatística sobre os tipos de conexões implante/componentes protéticos mais utilizados no Brasil / Statistical survey of types of connections implant/prosthetic component most used in the Brazil

Atualmente encontra-se disponível no mercado de Implantodontia uma grande variedade de desenhos de implante e de componentes protéticos, propiciando os mais diversos tipos de designs de restauração sobre implante. O objetivo deste trabalho foi avaliar o design da restauração (plataforma regular ou reduzida) e o tipo de conexão do implante (hexágono externo, hexágono interno e cone morse) preferencialmente usados no Brasil e os motivos que justificaram essa escolha pelos profissionais. Para isso, foram entrevistados 216 profissionais durante o 31º Congresso Internacional de Odontologia de São Paulo (CIOSP), realizado no ano de 2013. A maioria dos entrevistados foi do gênero masculino (67,7%), especialistas (59,2%) e com até cinco anos de graduado (25,0%). Observou-se que a maioria dos profissionais entrevistados utiliza hexágono externo (52,8%), seguido por hexágono interno (22,2%), cone morse (24,0%) e replace select (0,9%). Em relação aodesignda interface pilar implante, observou-se que a maioria prefere plataforma regular (58,4%) em relação à plataforma reduzida (41,6%). Concluiu-se que a maioria dos profissionais que atua na área de Implantodontia no Brasil opta pela utilização de restaurações sobre implante com hexágono externo e plataforma regular principalmente devido à conveniência de uso...

It is currently available in the Implantology market a wide variety of implant designs and abutments, providing many types of designs for implant-supported restorations. The aim of this study was to evaluate the restoration design (regular or reduced platform) and the type of implant connection (external hexagon, internal hexagon, and morse-tape connection) preferably used in Brazil and the reasons for that choice. For this, 216 professionals were interviewed during the 31st International Dental Congress of São Paulo (CIOSP), in 2013. The respondents were mostly men (67.7%), specialists in Implantology (59.2%), and up to five years of graduation (25%). Among the types of the implant connections selected, most of respondents used external hexagon (52.8%), followed by internal hexagon (22.2%), morse-tape connection (24.0%), replace select system (0.9%). Regarding the design of implant-abutment interface, it was observed that most of the respondents used regular platform (58.4%), followed by reduced platform (41.6%). It was concluded that most of the professionals working with dental implants in Brazil prefer external hexagon and regular platform due convenience of use...

Stress distribution on dentin-cement-post interface varying root canal and glass fiber post diameters. A three-dimensional finite element analysis based on micro-CT data

Objective: The aim of the present study was to analyze the influence of root canal and glass fiber post diameters on the biomechanical behavior of the dentin/cement/post interface of a root-filled tooth using 3D finite element analysis. Material and Methods: Six models were built using micro-CT imaging data and SolidWorks 2007 software, varying the root canal (C) and the glass fiber post (P) diameters: C1P1-C=1 mm and P=1 mm; C2P1-C=2 mm and P=1 mm; C2P2-C=2 mm and P=2 mm; C3P1-C=3 mm and P=1 mm; C3P2-C=3 mm and P=2 mm; and C3P3-C=3 mm and P=3 mm. The numerical analysis was conducted with ANSYS Workbench 10.0. An oblique force (180 N at 45º) was applied to the palatal surface of the central incisor. The periodontal ligament surface was constrained on the three axes (x=y=z=0). Maximum principal stress (σmax) values were evaluated for the root dentin, cement layer, and glass fiber post. Results: The most evident stress was observed in the glass fiber post at C3P1 (323 MPa), and the maximum stress in the cement layer occurred at C1P1 (43.2 MPa). The stress on the root dentin was almost constant in all models with a peak in tension at C2P1 (64.5 MPa). CONCLUSION: The greatest discrepancy between root canal and post diameters is favorable for stress concentration at the post surface. The dentin remaining after the various root canal preparations did not increase the stress levels on the root. .

Stress distribution on dentin-cement-post interface varying root canal and glass fiber post diameters. A three-dimensional finite element analysis based on micro-CT data.

OBJECTIVE: The aim of the present study was to analyze the influence of root canal and glass fiber post diameters on the biomechanical behavior of the dentin/cement/post interface of a root-filled tooth using 3D finite element analysis. MATERIAL AND METHODS: Six models were built using micro-CT imaging data and SolidWorks 2007 software, varying the root canal (C) and the glass fiber post (P) diameters: C1P1-C=1 mm and P=1 mm; C2P1-C=2 mm and P=1 mm; C2P2-C=2 mm and P=2 mm; C3P1-C=3 mm and P=1 mm; C3P2-C=3 mm and P=2 mm; and C3P3-C=3 mm and P=3 mm. The numerical analysis was conducted with ANSYS Workbench 10.0. An oblique force (180 N at 45º) was applied to the palatal surface of the central incisor. The periodontal ligament surface was constrained on the three axes (x=y=z=0). Maximum principal stress (σ(max)) values were evaluated for the root dentin, cement layer, and glass fiber post. RESULTS: The most evident stress was observed in the glass fiber post at C3P1 (323 MPa), and the maximum stress in the cement layer occurred at C1P1 (43.2 MPa). The stress on the root dentin was almost constant in all models with a peak in tension at C2P1 (64.5 MPa). CONCLUSION: The greatest discrepancy between root canal and post diameters is favorable for stress concentration at the post surface. The dentin remaining after the various root canal preparations did not increase the stress levels on the root.

Periodontal ligament influence on the stress distribution in a removable partial denture supported by implant: a finite element analysis.

OBJECTIVES: The non-homogenous aspect of periodontal ligament (PDL) has been examined using finite element analysis (FEA) to better simulate PDL behavior. The aim of this study was to assess, by 2-D FEA, the influence of non-homogenous PDL on the stress distribution when the free-end saddle removable partial denture (RPD) is partially supported by an osseointegrated implant. MATERIAL AND METHODS: Six finite element (FE) models of a partially edentulous mandible were created to represent two types of PDL (non-homogenous and homogenous) and two types of RPD (conventional RPD, supported by tooth and fibromucosa; and modified RPD, supported by tooth and implant [10.00x3.75 mm]). Two additional Fe models without RPD were used as control models. The non-homogenous PDL was modeled using beam elements to simulate the crest, horizontal, oblique and apical fibers. The load (50 N) was applied in each cusp simultaneously. Regarding boundary conditions the border of alveolar ridge was fixed along the x axis. The FE software (Ansys 10.0) was used to compute the stress fields, and the von Mises stress criterion (svM) was applied to analyze the results. RESULTS: The peak of svM in non-homogenous PDL was higher than that for the homogenous condition. The benefits of implants were enhanced for the non-homogenous PDL condition, with drastic svM reduction on the posterior half of the alveolar ridge. The implant did not reduce the stress on the support tooth for both PDL conditions. CONCLUSION: The PDL modeled in the non-homogeneous form increased the benefits of the osseointegrated implant in comparison with the homogeneous condition. Using the non-homogenous PDL, the presence of osseointegrated implant did not reduce the stress on the supporting tooth.

Periodontal ligament influence on the stress distribution in a removable partial denture supported by implant: a finite element analysis

OBJECTIVES: The non-homogenous aspect of periodontal ligament (PDL) has been examined using finite element analysis (FEA) to better simulate PDL behavior. The aim of this study was to assess, by 2-D FEA, the influence of non-homogenous PDL on the stress distribution when the free-end saddle removable partial denture (RPD) is partially supported by an osseointegrated implant. MATERIAL AND METHODS: Six finite element (FE) models of a partially edentulous mandible were created to represent two types of PDL (non-homogenous and homogenous) and two types of RPD (conventional RPD, supported by tooth and fibromucosa; and modified RPD, supported by tooth and implant [10.00x3.75 mm]). Two additional Fe models without RPD were used as control models. The non-homogenous PDL was modeled using beam elements to simulate the crest, horizontal, oblique and apical fibers. The load (50 N) was applied in each cusp simultaneously. Regarding boundary conditions the border of alveolar ridge was fixed along the x axis. The FE software (Ansys 10.0) was used to compute the stress fields, and the von Mises stress criterion (svM) was applied to analyze the results. RESULTS: The peak of svM in non-homogenous PDL was higher than that for the homogenous condition. The benefits of implants were enhanced for the non-homogenous PDL condition, with drastic svM reduction on the posterior half of the alveolar ridge. The implant did not reduce the stress on the support tooth for both PDL conditions. Conclusion: The PDL modeled in the non-homogeneous form increased the benefits of the osseointegrated implant in comparison with the homogeneous condition. Using the non-homogenous PDL, the presence of osseointegrated implant did not reduce the stress on the supporting tooth.

Plataforma regular versus switching: estudo mecânico por meio de testes laboratoriais de fadiga e análise de elementos finitos em implantes com hexágono externo e interno / Regular and switched-platform: fatigue and finite element analysis in implants with external and internal hexagon

Proposição. O objetivo do presente trabalho foi avaliar a influência do conceito de plataforma switching na confiabilidade e modo de falha de restaurações unitárias sobre implante com hexágono externo ou interno na região anterior da maxila. Adicionalmente, análises de elementos finitos foram realizadas para avaliar o padrão de distribuição de tensão dentro do complexo pilar-implante e no tecido ósseo peri-implantar. Materiais e Métodos. 84 implantes foram divididos em 4 grupos (n = 21) para realização dos testes de fadiga: SWT-EH e REG-EH (implantes de conexão externa com plataforma switching ou regular, respectivamente); SWT-IH e REG-IH (implantes de conexão interna com plataforma switching ou regular, respectivamente). Análises estatísticas de Weibull foram realizadas considerando as missões de 50.000 ciclos a 210N e 300N. Adicionalmente, foram construídos 4 modelos de elementos finitos considerando as mesmas variáveis para obtenção das tensões equivalentes de von Mises (σvM) no complexo pilar-implante e das máximas tensões principais (σmax) no osso peri-implantar. Resultados. Os valores de Beta para os grupos SWT-EH (1,31), REG-EH (1,55), SWT-IH (1,83) e REG-IH (1,82) indicaram que a fadiga acelerou a falha em todos os grupos. Os valores de confiabilidade calculados para os grupos SWT-EH, REG-EH, SWT-IH e REH-IH foram 0,53 (0,33 - 0,70), 0,93 (0,80 - 0,97), 0,99 (0,93 - 0,99) and 0,99 (0,99 -de tensão estiveram no pilar (SWT-IH = 186 MPa e REG-IH = 88.8 MPa). No osso cortical, os implantes com plataforma switching geraram menor tensão (σmax) tanto para conexão externa (SWT-EH = 49.0 MPa e REG-EH = 56.5 MPa) como para conexão interna (SWT-IH = 37.7 MPa e REG-IH = 45.5 MPa). Conclusões. Os maiores valores de σvM observados no complexo pilar-implante quando usados implantes com plataforma switching (grupos SWT-EH e SWT-IH) resultaram em menor confiabilidade do sistema restaurador apenas para implantes com conexão externa, mas não com conexão interna...

Purpose. The aim of the present study was to evaluate the effect of platform switching concept on reliability and failure modes of anterior single-unit restorations for internal and external hex implants. Additionally, finite element analysis were performed to assess the stress distribution within implant-abutment complex and peri-implant bone. Materials and Methods. 84 implants were divided in 4 groups (n=21) for fatigue tests: REG-EH and SWT-EH (regular and switched-platform implants with external connection, respectively); REG-IH and SWT-IH (regular and switched-platform implants with internal connection, respectively). Weibull analysis for a mission of 50,000 cycles at 300N was performed. Additionally, 4 three-dimensional finite element models reproducing the characteristics of specimens used in mechanical tests were created to evaluate the equivalent von Mises stress (σvM) within implant-abutment complex and the maximum principal stress (σmax) in the peri-implant bone. Results. The Beta values for groups SWT-EH (1.31), REG-EH (1.55), SWT-IH (1.83) and REG-IH (1.82) indicated that fatigue accelerated the failure of all groups. The calculated reliability for groups SWT-EH, REG-EH, SWT-IH and REH-IH were 0.53(0.33-0.70), 0.93(0.80-0.97), 0.99(0.93-0.99) and 0.99(0.99-1.00), respectively. Failure modes (screw and/or abutment fracture) were similar for regular and switched-platform implants. Within implant-abutment complex, the higher peak of stress (σvM) was observed in fixation screw (SWT-EH = 190 MPa and REG-EH = 160 MPa) for groups with external hex implants; while for groups with internal hex implants was in abutment (SWT-IH = 186 MPa and REG-IH = 88.8 MPa). In the cortical bone, switched-platform implants generated lower peak of stress (σmax) for both external (SWT-EH = 49.0 MPa and REG-EH = 56.5 MPa) and internal (SWT-IH = 37.7 MPa and REG-IH = 45.5 MPa) connections. Conclusions. The higher levels of stress observed within implant-abutment complex when…

Plataforma regular versus switching: estudo mecânico por meio de testes laboratoriais de fadiga e análise de elementos finitos em implantes com hexágono externo e interno / Regular and switched-platform: fatigue and finite element analysis in implants with external and internal hexagon

Proposição. O objetivo do presente trabalho foi avaliar a influência do conceito de plataforma switching na confiabilidade e modo de falha de restaurações unitárias sobre implante com hexágono externo ou interno na região anterior da maxila. Adicionalmente, análises de elementos finitos foram realizadas para avaliar o padrão de distribuição de tensão dentro do complexo pilar-implante e no tecido ósseo peri-implantar. Materiais e Métodos. 84 implantes foram divididos em 4 grupos (n = 21) para realização dos testes de fadiga: SWT-EH e REG-EH (implantes de conexão externa com plataforma switching ou regular, respectivamente); SWT-IH e REG-IH (implantes de conexão interna com plataforma switching ou regular, respectivamente). Análises estatísticas de Weibull foram realizadas considerando as missões de 50.000 ciclos a 210N e 300N. Adicionalmente, foram construídos 4 modelos de elementos finitos considerando as mesmas variáveis para obtenção das tensões equivalentes de von Mises (σvM) no complexo pilar-implante e das máximas tensões principais (σmax) no osso peri-implantar. Resultados. Os valores de Beta para os grupos SWT-EH (1,31), REG-EH (1,55), SWT-IH (1,83) e REG-IH (1,82) indicaram que a fadiga acelerou a falha em todos os grupos. Os valores de confiabilidade calculados para os grupos SWT-EH, REG-EH, SWT-IH e REH-IH foram 0,53 (0,33 - 0,70), 0,93 (0,80 - 0,97), 0,99 (0,93 - 0,99) and 0,99 (0,99 -de tensão estiveram no pilar (SWT-IH = 186 MPa e REG-IH = 88.8 MPa). No osso cortical, os implantes com plataforma switching geraram menor tensão (σmax) tanto para conexão externa (SWT-EH = 49.0 MPa e REG-EH = 56.5 MPa) como para conexão interna (SWT-IH = 37.7 MPa e REG-IH = 45.5 MPa). Conclusões. Os maiores valores de σvM observados no complexo pilar-implante quando usados implantes com plataforma switching (grupos SWT-EH e SWT-IH) resultaram em menor confiabilidade do sistema restaurador apenas para implantes com conexão externa, mas não com conexão interna...

Purpose. The aim of the present study was to evaluate the effect of platform switching concept on reliability and failure modes of anterior single-unit restorations for internal and external hex implants. Additionally, finite element analysis were performed to assess the stress distribution within implant-abutment complex and peri-implant bone. Materials and Methods. 84 implants were divided in 4 groups (n=21) for fatigue tests: REG-EH and SWT-EH (regular and switched-platform implants with external connection, respectively); REG-IH and SWT-IH (regular and switched-platform implants with internal connection, respectively). Weibull analysis for a mission of 50,000 cycles at 300N was performed. Additionally, 4 three-dimensional finite element models reproducing the characteristics of specimens used in mechanical tests were created to evaluate the equivalent von Mises stress (σvM) within implant-abutment complex and the maximum principal stress (σmax) in the peri-implant bone. Results. The Beta values for groups SWT-EH (1.31), REG-EH (1.55), SWT-IH (1.83) and REG-IH (1.82) indicated that fatigue accelerated the failure of all groups. The calculated reliability for groups SWT-EH, REG-EH, SWT-IH and REH-IH were 0.53(0.33-0.70), 0.93(0.80-0.97), 0.99(0.93-0.99) and 0.99(0.99-1.00), respectively. Failure modes (screw and/or abutment fracture) were similar for regular and switched-platform implants. Within implant-abutment complex, the higher peak of stress (σvM) was observed in fixation screw (SWT-EH = 190 MPa and REG-EH = 160 MPa) for groups with external hex implants; while for groups with internal hex implants was in abutment (SWT-IH = 186 MPa and REG-IH = 88.8 MPa). In the cortical bone, switched-platform implants generated lower peak of stress (σmax) for both external (SWT-EH = 49.0 MPa and REG-EH = 56.5 MPa) and internal (SWT-IH = 37.7 MPa and REG-IH = 45.5 MPa) connections. Conclusions. The higher levels of stress observed within implant-abutment complex when…

Aesthetic approach in single immediate implant-supported restoration.

The aim of this study was to analyze the main aspects that influence the aesthetics of single immediate implant-supported restorations through a literature review on the MEDLINE database. It was observed that immediate implant-supported restorations present clinical success with aesthetic predictability demonstrated by the literature. Proper patient selection and diagnostic and multidisciplinary planning are essential and should be associated to technical ability of professional and knowledge concerning the biology of periimplant tissues. It is suggested that provisional restoration should be immediately inserted after implant fixation to guide healing of gingival tissues with a proper emergence profile besides psychologic comfort for a patient due to immediate aesthetic reestablishment.

Influence of high insertion torque on implant placement: an anisotropic bone stress analysis.

The aim of this study was to evaluate the influence of the high values of insertion torques on the stress and strain distribution in cortical and cancellous bones. Based on tomography imaging, a representative mathematical model of a partial maxilla was built using Mimics 11.11 and Solid Works 2010 softwares. Six models were built and each of them received an implant with one of the following insertion torques: 30, 40, 50, 60, 70 or 80 Ncm on the external hexagon. The cortical and cancellous bones were considered anisotropic. The bone/implant interface was considered perfectly bonded. The numerical analysis was carried out using Ansys Workbench 10.0. The convergence of analysis (6%) drove the mesh refinement. Maximum principal stress (δmax) and maximum principal strain (εmax) were obtained for cortical and cancellous bones around to implant. Pearson's correlation test was used to determine the correlation between insertion torque and stress concentration in the periimplant bone tissue, considering the significance level at 5%. The increase in the insertion torque generated an increase in the δmax and εmax values for cortical and cancellous bone. The δmax was smaller for the cancellous bone, with greater stress variation among the insertion torques. The εmax was higher in the cancellous bone in comparison to the cortical bone. According to the methodology used and the limits of this study, it can be concluded that higher insertion torques increased tensile and compressive stress concentrations in the periimplant bone tissue.

Overdentures sobreimplante à barra: aspectos biomecânicos / Bar-clip implant-retained overdentures: biomechanical aspects

As overdentures sobreimplantes apresentam comprovado índice de sucesso por estudos clínicos longitudinais. Porém, há controvérsias na literatura sobre o mecanismo de transmissão e distribuição das tensões decorrentes da função mastigatória sobre overdentures através dos sistemas de retenção e implantes aos tecidos ósseos e de suporte. Assim, ainda nos dias de hoje, os mecanismos responsáveis pelas falhas biomecânicas dos implantes não estão completamente definidos pela literatura e a influência dos diversos fatores biomecânicos não é conclusiva. O objetivo deste estudo foi realizar uma revisão da literatura sobre os aspectos biomecânicos que podem induzir a falhas das overdentures sobreimplante, enfatizando os trabalhos que avaliaram os sistemas de retenção do tipo barra-clipe. Baseado nos estudos até então realizados, pode-se relacionar o uso de implantes esplintados por meio de barras metálicas (sistema rígido) a uma maior concentração de tensão nos implantes e componentes protéticos e, simultaneamente, alívio das tensões nos tecidos de suporte adjacentes aos implantes quando comparado a implantes não-esplintados (sistemas esféricos e magnetos). Porém, as características clínicas de cada paciente devem ser consideradas no planejamento para que ocorra um correto comportamento biomecânico das overdentures sobreimplante, refletindo-se na longevidade do tratamento.

Implant-supported overdentures show high success according to longitudinal clinical studies. However, there are controversies in the scientific literature regarding stress transmission and distribution on the supporting tissues given by retention mechanisms and implants during masticatory function. Nowadays, the mechanisms responsible for biomechanical failures on implants are not well-defined and their influence is inconclusive. The aim of this study was to make a literature review about the biomechanical aspects related to failures in implant-supported overdentures, emphasizing the studies with bar-connecting devices. Based on the reviewed studies, the use of implants connected by metallic bars (rigid system) can be related to a higher stress concentration on the implants and prosthetic components and with a lower stress in the supporting tissues near to the implants compared to non-splinted implants (spherical and magnetic systems). However, the clinical characteristics of each patient must be considered in the treatment planning for adequate biomechanical behavior of implant-supported overdentures, allowing excellent treatment longevity.

Influence of high insertion torque on implant placement: an anisotropic bone stress analysis

The aim of this study was to evaluate the influence of the high values of insertion torques on the stress and strain distribution in cortical and cancellous bones. Based on tomography imaging, a representative mathematical model of a partial maxilla was built using Mimics 11.11 and Solid Works 2010 softwares. Six models were built and each of them received an implant with one of the following insertion torques: 30, 40, 50, 60, 70 or 80 Ncm on the external hexagon. The cortical and cancellous bones were considered anisotropic. The bone/implant interface was considered perfectly bonded. The numerical analysis was carried out using Ansys Workbench 10.0. The convergence of analysis (6 percent) drove the mesh refinement. Maximum principal stress (σmax) and maximum principal strain (εmax) were obtained for cortical and cancellous bones around to implant. Pearson's correlation test was used to determine the correlation between insertion torque and stress concentration in the periimplant bone tissue, considering the significance level at 5 percent. The increase in the insertion torque generated an increase in the σmax and εmax values for cortical and cancellous bone. The σmax was smaller for the cancellous bone, with greater stress variation among the insertion torques. The εmax was higher in the cancellous bone in comparison to the cortical bone. According to the methodology used and the limits of this study, it can be concluded that higher insertion torques increased tensile and compressive stress concentrations in the periimplant bone tissue.

O objetivo deste estudo foi avaliar a influência dos altos valores de torque de inserção na distribuição de tensões e deformações no osso cortical e medular. Com base em imagens de tomografia computadorizada, um modelo matemático representativo de um segmento da maxila foi construído utilizando os programas Mimics 11.11 e Solid Works 2010. Seis modelos foram construídos e cada um recebeu um implante com os seguintes torques de inserção no hexágono externo: 30, 40, 50, 60, 70 ou 80 Ncm. O osso cortical e medular foi considerado anisotrópico. A interface osso/implante foi considerada perfeitamente unida. A análise numérica foi realizada através do Ansys Workbench 10.0. A convergência de análise (6 por cento) determinou o refinamento da malha. A tensão máxima principal (σmax) e a deformação máxima principal (εmax) foram obtidos para o osso cortical e medular ao redor do implante. O teste de correlação de Pearson foi utilizado para determinar a correlação entre torque de inserção e de concentração de tensões e deformações no tecido ósseo peri-implantar, considerando o nível de significância de 5 por cento. O aumento no torque de inserção gerou um aumento nos valores σmax e εmax para o osso cortical e medular. O σmax foi menor para o osso medular, com maior variação de tensão entre os torques de inserção. O εmax foi maior no osso medular em relação ao osso cortical. De acordo com a metodologia utilizada e com os limites do estudo, pode-se concluir que torques alto de inserção aumentou as concentrações de tensões de tração e compressão no tecido ósseo peri-implantar.

Factores que influencian la selección del color en prótesis fija: Revisión de literatura

El valor estético de una restauración cerámica es parcialmente influenciado por múltiples factores. Muchos de estos factores son conocidos por el odontólogo, sin embargo, existen otros , tales como: grosor de la cerámica, color del agente cementante, color de la estructura dental subyacente, limitaciones de las guías de colores disponibles, composición de los materiales cerámicos, etc. que pueden interferir en la correcta selección del color, siendo un problema clínico muy común. El propósito de este trabajo fue hacer una revisión bibliográfica sobre la influencia de los factores físicos y sensoriales y como estos pueden afectar en la selección del color de las restauraciones protésicas con el fin de evitarlos o disminuirlos.

The esthetic value of dental ceramic restorations is influenced by several factors. Many factors is know by the dentist , however, others factors like: ceramic thickness, luting agent, shade guides, color of dental substrate, the limited range of available ceramic shades, varying compositions of ceramic materials, is a common clinical problem. The aim of this study was made a literature review of the influence of physical and sensorial factors on the shade selection in ceramics restorations for avoid or minimize these factors.

Fatores biomecânicos relevantes na seleção dos grampos em próteses parciais removíveis com extremo livre: estudo clínico / Biomechanical factors outstandings in the clasps selection in free-end removable partial dentures: a clinical study

As próteses parciais removíveis com extremo livre (PPREL) apresentam comportamento biomecânico complexo e peculiar que impõe maiores esforços mastigatórios aos dentes suportes. Este trabalho objetiva estudar as diversas variáveis clínicas que influenciam na indicação de grampos para PPREL. Para isso, foram analisados 84 modelos de estudo delineados e planejados de 71 pacientes, totalizando 130 grampos vizinhos ao extremo livre; acompanhados dos dados clínicos e radiográficos. Observou-se que foram utilizados grampos por ação de ponta (“T”, “Tmod”, “i”) em 88,46% dos pilares. Nos demais (11,55%), utilizou-se grampos circunferenciais simples, combinado ou em anel, e MDL. Em pilares com equador protético alto, prevaleceu o uso de grampos a barra em “i”(48,48%). Já os grampos “Tmod” predominaram em pilares com equador baixo (50%) ou no 1/3 médio (51,35%) e os grampos “T” preponderaram em equadores inclinados com áreas retentivas por mésio-vestibular (56,52%) ou disto-vestibular (66,66%). Nos pilares posteriores, foi comum o uso do apoio por distal (63,52%) e esplintagem ao dente adjacente. Alguns fatores como coroa clínica longa (5,38%), má posição do pilar (4,61%), estética (3,07%), retentividade do rebordo (2,3%), fragilidade do suporte (1,53%), coroa clínica curta (0,76%) e espaço reduzido para o grampo (0,76%) influenciaram diretamente na escolha dos grampos. Já fatores como mobilidade dos pilares, altura das inserções musculares, profundidade do fórnix vestibular e arco antagonista atuaram apenas de forma coadjuvante. Após a análise dos dados coletados concluiu-se que os grampos por ação de ponta com apoio por distal associados à esplintagem do dente adjacente foram os mais indicados para PPREL

The free-end removable partial dentures (RPD) shows a complicated and peculiar biomechanical behavior that impose high occlusion forces to the abutment teeth. By this way, the aim of this study was to evaluate the several factors that influence the clasps indication to free-end RPD. It was analysed 84 designed and planned study models of 71 patients, involving 130 clasps near-by a free-end; followed by clinical and radiographical informations. It was observed that bar clasps (“T”, “Tmod”, “i”) were used in 88.46% of abutment teeth. In the others (11.55%), it was used simple, combinated or ring circumferential clasps, and MDL. In abutment teeth with high equator line the “i” clasps were predominant (48.48%). The “Tmod” clasps were predominant in abutment teeth with low equator line (50%) or in middle third (51.35%) and “T” clasps were predominant in inclined equators with mesio-buccal (56.52%) or disto-buccal (66.66%) retention. In the posterior abutment teeth, it was prevalent the distal rest (63.52%) and embracing to the adjacent tooth. Some others factors like long clinical crown (5.38%), wrong position of abutment teeth (4.61%), aesthetics (3.07%), retention in alveolar ridge (2.3%), fragility of abutment teeth (1.53%), short clinical crown (0.76%) and short space to the clasp (0.76%) influenced directly during the clasps selection. Factors like mobility of abutment teeth, height of muscular insertions, depth of buccal fornix and antagonist arch acted like secondary factors. After the informations analysis it may be concluded that the bar clasps with distal rest and embracing to the adjacent tooth were the most indicated to free-end RPD

Influence of voids in the hybrid layer based on self-etching adhesive systems: a 3-D FE analysis.

UNLABELLED: The presence of porosities at the dentin/adhesive interface has been observed with the use of new generation dentin bonding systems. These porosities tend to contradict the concept that etching and hybridization processes occur equally and simultaneously. Therefore, the aim of this study was to evaluate the micromechanical behavior of the hybrid layer (HL) with voids based on a self-etching adhesive system using 3-D finite element (FE) analysis. MATERIAL AND METHODS: Three FE models (Mr) were built: Mr, dentin specimen (41x41x82 µm) with a regular and perfect (i.e. pore-free) HL based on a self-etching adhesive system, restored with composite resin; Mp, similar to M, but containing 25% (v/v) voids in the HL; Mpp, similar to Mr, but containing 50% (v/v) voids in the HL. A tensile load (0.03N) was applied on top of the composite resin. The stress field was obtained by using Ansys Workbench 10.0. The nodes of the base of the specimen were constrained in the x, y and z axes. The maximum principal stress (σmax) was obtained for all structures at the dentin/adhesive interface. RESULTS: The Mpp showed the highest peak of σmax in the HL (32.2 MPa), followed by Mp (30 MPa) and Mr (28.4 MPa). The stress concentration in the peritubular dentin was high in all models (120 MPa). All other structures positioned far from voids showed similar increase of stress. CONCLUSION: Voids incorporated into the HL raised the σmax in this region by 13.5%. This behavior might be responsible for lower bond strengths of self-etching and single-bottle adhesives, as reported in the literature.

Influence of voids in the hybrid layer based on self-etching adhesive systems: a 3-D FE analysis

The presence of porosities at the dentin/adhesive interface has been observed with the use of new generation dentin bonding systems. These porosities tend to contradict the concept that etching and hybridization processes occur equally and simultaneously. Therefore, the aim of this study was to evaluate the micromechanical behavior of the hybrid layer (HL) with voids based on a self-etching adhesive system using 3-D finite element (FE) analysis. MATERIAL AND METHODS: Three FE models (Mr) were built: Mr, dentin specimen (41x41x82 μm) with a regular and perfect (i.e. pore-free) HL based on a self-etching adhesive system, restored with composite resin; Mp, similar to M, but containing 25 percent (v/v) voids in the HL; Mpp, similar to Mr, but containing 50 percent (v/v) voids in the HL. A tensile load (0.03N) was applied on top of the composite resin. The stress field was obtained by using Ansys Workbench 10.0. The nodes of the base of the specimen were constrained in the x, y and z axes. The maximum principal stress (σmax) was obtained for all structures at the dentin/adhesive interface. RESULTS: The Mpp showed the highest peak of σmax in the HL (32.2 MPa), followed by Mp (30 MPa) and Mr (28.4 MPa). The stress concentration in the peritubular dentin was high in all models (120 MPa). All other structures positioned far from voids showed similar increase of stress. CONCLUSION: Voids incorporated into the HL raised the σmax in this region by 13.5 percent. This behavior might be responsible for lower bond strengths of self-etching and single-bottle adhesives, as reported in the literature.

El sistema masticatorio y las alteraciones funcionales consecuentes a la pérdida dentaria / The masticatory system and functional alterations consequent to tooth loss

A pesar de las mejoras ocurridas en las condiciones de salud general de la población, aún es frecuente, con el proceso de envejecimiento, la de pérdida de piezas dentarias, acarreando disturbios en el sistema masticatorio y reflejándose en todo el organismo del anciano. De esta forma, este trabajo realizó una revisión de literatura al respecto de este sistema, sus funciones, peculiaridades y alteraciones especialmente relacionadas a la pérdida dentaria, enfatizando la importancia de las rehabilitaciones protésicas para restaurar la función y los cuidados necesarios en el planeamiento, instalación y manutención de las prótesis en los pacientes de la tercera edad. Fue posible concluir que, debido a la complejidad del sistema masticatorio y de todas las estructuras relacionadas, la reunión del mayor número posible de informaciones durante la anamnesis, examen clínico, radiográfico y de modelos de estudio montados en el articulador son de mucha importancia para el éxito de cualquier tratamiento que envuelve pacientes ancianos. Estos tratamientos, deben someterse a un planeamiento multidisciplinar donde cada especialidad siga una secuencia lógica e integrada de ejecución, para que sean alcanzados los resultados anhelados

Despite of the improvements happened in the general conditions of population health, it's frequent the occurrence of teeth loss with the aging. This phenomenon cause masticatory system disturbance and can be observed in all the elderly organism. By this way, this study realized a literature review about this system, its functions, peculiarities and alterations related to the loss of tooth, emphasizing the importance of prosthetic rehabilitations to restore the functions and the necessary care on treatment planning, installation and prosthesis maintenance in elderly people. In virtue of masticatory system complexity and its related structures, it can be concluded that the reunion of a great data number during the anamnesis, clinical and radiographic examination, and the mounting of diagnostic casts in semi-adjustable articulator are very important for a successful treatment involving elderly people. These treatments may involve a multidisciplinary planning where each involved specialty follow a logic and integrated sequence of execution to reach the desired results

Envelhecimento do aparelho estomatognático: alterações fisiológicas e anatômicas / Ageing of the stomatognathic system: physiologic and anatomical alterations

Com o aumento da expectativa de vida da população em todo o planeta, o número de idosos tem crescido proporcionalmente, mas sem que haja um acompanhamento das condições de saúde para esta faixa etária da população. Em virtude da heterogeneidade de condições físicas, psíquicas e sociais apresentadas por esse grupo, nem todos os profissionais apresentam-se habilitados para entender e solucionar problemas relacionados ao envelhecimento. Dessa forma, este trabalho tem por objetivo esclarecer as modificações decorrentes do envelhecimento em âmbito fisiológico e anatômico das principais estruturas do Aparelho Estomatognático associando as suas causas, efeitos e formas de prevenção, a fim de auxiliar os profissionais da Odontologia na distinção das verdadeiras alterações da idade daquelas relacionadas a patologias, para que possam estabelecer condutas terapêuticas adequadas. Assim, foram estudados a estrutura óssea, o sistema neuromuscular, a articulação temporomandibular, glândulas salivares, mucosa oral, o periodonto, o tecido conjuntivo, o epitélio juncional, o cemento, o osso alveolar, o dente (esmalte, dentina, polpa) e a formação de placa bacteriana nos indivíduos idosos. Observou-se que mais informações e pesquisas são necessárias, em função do conhecimento de conceitos atuais, para possibilitar firmar dados conclusivos e sólidos a respeito do envelhecimento do Aparelho Estomatognático

With the increase of the life expectation around the world, the number of elderly people has been enlarged proportionally, but it can’t be observed on health care conditions for these people. By virtue of the heterogeneity of physical, psychic and social conditions presented by this group, nor all the professionals are able to understand and solve problems related with ageing. In that way, this work has for objective to explain the consequent modifications of the aging in the main structures on physiologic and anatomical extent of the Stomatognathic’s System, associating their causes, effects and prevention forms, in order to aid the professionals in the distinction of the true alterations of the age of those related to pathologies, so that they can establish appropriate therapeutic conducts. Like this, the bone structure, the system neuromuscular, the temporomandibular joint, salivary glands, oral mucosa, the periodontium, the conjunctive tissue, the junctional epithelium, the cementum, the alveolar bone, the tooth (enamels, dentine, pulp) and the formation of bacterial plaque in the elderly people. It was observed that more information and researches are necessary in function on the current concepts, to make possible to firm conclusive and solids data regarding the ageing of Stomatognathic’s System