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.

Evaluation of Surface Roughness of Monolithic Zirconia after Using Different Polishing Kits

Objective: To evaluate the effect of different kits to polish monolithic zirconia on its surface roughness. Material and Methods: Five samples were fabricated using zirconia blocks. Each sintered block was divided into four areas of equal size and each area was subjected to a specific surface treatment according to the four groups of the study: GC: no surface treatment, GG: unidirectional grinding with high speed tapered bur under refrigeration, GP1: wear similar to GG followed by polishing with zirconia polishing kit Kenda at the same wear direction, and GP2: wear similar to GG followed by polishing with zirconia polishing kit Diacera at the same wear direction. Qualitative and quantitative analyses of ceramic topography and roughness were performed using a digital optical profilometer, and Roughness measurements were performed using two parameters (Ra and Rz: arithmetical mean of the absolute values of the surface departures and of the five highest peaks and valleys, respectively). Scanning electron micrographs of each ceramic surface were obtained to illustrate sample roughness. The means of each group were analyzed by 1-way ANOVA followed by Tukey's test. Results: Morphological analysis showed that polishing kits provided the same pattern of a smooth surface. To statistical analysis, this study showed that different polishing kits influenced zirconia roughness for both Ra and Rz after surface wear (p < 0.05) with both situations improved the surface roughness observed immediately after zirconia sintering. Conclusion: According to the results, both polish kits resulted in a surface texture within acceptable clinical parameters.

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...

Tilted and short implants supporting fixed prosthesis in an atrophic maxilla: a 3D-FEA biomechanical evaluation.

PURPOSE: This study compared the biomechanical behavior of tilted long implant and vertical short implants to support fixed prosthesis in an atrophic maxilla. MATERIALS AND METHODS: The maxilla model was built based on a tomographic image of the patient. Implant models were based on micro-computer tomography imaging of implants. The different configurations considered were M4S, four vertical anterior implants; M4T, two mesial vertical implants and two distal tilted (45°) implants in the anterior region of the maxilla; and M6S, four vertical anterior implants and two vertical posterior implants. Numerical simulation was carried out under bilateral 150 N loads applied in the cantilever region in axial (L1) and oblique (45°) (L2) direction. Bone was analyzed using the maximum and minimum principal stress (σmax and σmin ), and von Mises stress (σvM ) assessments. Implants were analyzed using the σvM . RESULTS: The higher σmax was observed at: M4T, followed by M6S/L1, M6S/L2, M4S/L2, and M4S/L1 and the higher σvM : M4T/L1, M4T/L2 and M4S/L2, M6S/L2, M4S/L1, and M6S/L1. CONCLUSIONS: The presence of distal tilted (all-on-four) and distal short implants (all-on-six) resulted in higher stresses in both situations in the maxillary bone in comparison to the presence of vertical implants (all-on-four).

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. .

Effect of microthread presence and restoration design (screw versus cemented) in dental implant reliability and failure modes.

OBJECTIVES: This study evaluated the reliability and failure modes of implants with a microthreaded or smooth design at the crestal region, restored with screwed or cemented crowns. The postulated null hypothesis was that the presence of microthreads in the implant cervical region would not result in different reliability and strength to failure than smooth design, regardless of fixation method, when subjected to step-stress accelerated life-testing (SSALT) in water. MATERIALS AND METHODS: Eighty four dental implants (3.3 × 10 mm) were divided into four groups (n = 21) according to implant macrogeometric design at the crestal region and crown fixation method: Microthreads Screwed (MS); Smooth Screwed (SS); Microthreads Cemented (MC), and Smooth Cemented (SC). The abutments were torqued to the implants and standardized maxillary central incisor metallic crowns were cemented (MC, SC) or screwed (MS, SS) and subjected to SSALT in water. The probability of failure versus cycles (90% two-sided confidence intervals) was calculated and plotted using a power law relationship for damage accumulation. Reliability for a mission of 50,000 cycles at 150 N (90% 2-sided confidence intervals) was calculated. Differences between final failure loads during fatigue for each group were assessed by Kruskal-Wallis along with Benferroni's post hoc tests. Polarized-light and scanning electron microscopes were used for failure analyses. RESULTS: The Beta (ß) value (confidence interval range) derived from use level probability Weibull calculation of 1.30 (0.76-2.22), 1.17 (0.70-1.96), 1.12 (0.71-1.76), and 0.52 (0.30-0.89) for groups MC, SC, MS, and SS respectively, indicated that fatigue was an accelerating factor for all groups, except for SS. The calculated reliability was higher for SC (99%) compared to MC (87%). No difference was observed between screwed restorations (MS - 29%, SS - 43%). Failure involved abutment screw fracture for all groups. The cemented groups (MC, SC) presented more abutment and implant fractures. Significantly higher load to fracture values were observed for SC and MC relative to MS and SS (P < 0.001). CONCLUSION: Since reliability and strength to failure was higher for SC than for MC, our postulated null hypothesis was rejected.

Reliability and failure modes of internal conical dental implant connections.

OBJECTIVE: Biological and mechanical implant-abutment connection complications and failures are still present in clinical practice, frequently compromising oral function. The purpose of this study was to evaluate the reliability and failure modes of anterior single-unit restorations in internal conical interface (ICI) implants using step-stress accelerated life testing (SSALT). MATERIALS AND METHODS: Forty-two ICI implants were distributed in two groups (n = 21 each): group AT-OsseoSpeed(™) TX (Astra Tech, Waltham, MA, USA); group SV-Duocon System Line, Morse Taper (Signo Vinces Ltda., Campo Largo, PR, Brazil). The corresponding abutments were screwed to the implants and standardized maxillary central incisor metal crowns were cemented and subjected to SSALT in water. Use-level probability Weibull curves and reliability for a mission of 50,000 cycles at 200 N were calculated. Differences between groups were assessed by Kruskal-Wallis along with Bonferroni's post-hoc tests. Polarized-light and scanning electron microscopes were used for failure analyses. RESULTS: The Beta (ß) value derived from use level probability Weibull calculation was 1.62 (1.01-2.58) for group AT and 2.56 (1.76-3.74) for group SV, indicating that fatigue was an accelerating factor for failure of both groups. The reliability for group AT was 0.95 and for group SV was 0.88. Kruskal-Wallis along with Bonferroni's post-hoc tests showed no significant difference between the groups tested (P > 0.27). In all specimens of both groups, the chief failure mode was abutment fracture at the conical joint region and screw fracture at neck's region. CONCLUSIONS: Reliability was not different between investigated ICI connections supporting maxillary incisor crowns. Failure modes were similar.

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.

Biomechanical evaluation of internal and external hexagon platform switched implant-abutment connections: An in vitro laboratory and three-dimensional finite element analysis.

OBJECTIVES: The aim of this study was to assess the effect of abutment's diameter shifting on reliability and stress distribution within the implant-abutment connection for internal and external hexagon implants. The postulated hypothesis was that platform-switched implants would result in increased stress concentration within the implant-abutment connection, leading to the systems' lower reliability. METHODS: Eighty-four implants were divided in four groups (n=21): 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). The corresponding abutments were screwed to the implants and standardized maxillary central incisor metal crowns were cemented and subjected to step-stress accelerated life testing. Use-level probability Weibull curves and reliability were calculated. Four finite element models reproducing the characteristics of specimens used in laboratory testing were created. The models were full constrained on the bottom and lateral surface of the cylinder of acrylic resin and one 30° off-axis load (300N) was applied on the lingual side of the crown (close to the incisal edge) in order to evaluate the stress distribution (s(vM)) within the implant-abutment complex. 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 higher levels of σ(vM) within the implant-abutment connection observed for platform-switched implants (groups SWT-EH and SWT-IH) were in agreement with the lower reliability observed for the external hex implants, but not for the internal hex implants. The reliability 90% confidence intervals (50,000 cycles at 300N) 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), for the SWT-EH, REG-EH, SWT-IH, and REH-IH, respectively. SIGNIFICANCE: The postulated hypothesis was partially accepted. The higher levels of stress observed within implant-abutment connection when reducing abutment diameter (cross-sectional area) resulted in lower reliability for external hex implants, but not for internal hex implants.

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.

Effect of implant-abutment connection design on reliability of crowns: regular vs. horizontal mismatched platform.

OBJECTIVES: To evaluate the reliability and failure modes of regular and horizontal mismatched platforms for implant-abutment connection varying the implant diameter. MATERIAL AND METHODS: Regular (REG, n = 21, 4.0-mm-diameter implant) and horizontal mismatched (HM, n = 21, 4.6-mm-diameter implant) platform Ti-6Al-4V implants were restored with proprietary identical Ti-6Al-4V abutments and metal crowns (cobalt-chrome, Wirobond 280, BEGO, Bremen, Germany) cemented. Mechanical testing comprised step-stress accelerated-life testing, where crowns were distributed in three loading profiles for fatigue in water, producing timely and clinically relevant fractures. The probability of failure vs. cycles (95% two-sided confidence intervals) was calculated and plotted using a powerlaw relationship for damage accumulation, Weibull modulus (95% two-sided confidence intervals) and then the reliability for a mission of 50,000 cycles at 125 N load (95% two-sided confidence interval) were calculated. Fractography was performed in the scanning electron microscope. RESULTS: The ß-value for group REG (ß = 1.37) indicated that fatigue was a factor accelerating the failure, whereas load alone dictated the failure for group HM (ß = 0.71). The Weibull parameter contour plot showed no significantly different Weibull modulus for REG (10.24) compared to HM (10.20) and characteristic strength of 162.6 and 166.8 N, respectively (P > 0.91). The calculated reliability for a mission of 50,000 cycles at 125 N load was not significantly different (0.71 for REG and 0.73 for HM). Abutment screw failure was the chief failure mode. CONCLUSIONS: Reliability was not significantly different between groups and failure modes were similar.

Pre-prosthetic orthodontic treatment using personalized elastic separators for optimization of emergence profile in esthetic crowns: a clinical report.

Restoring a misaligned tooth with an inadequate contact point is a challenge to the practitioner. In some instances, teeth that could be repositioned and adequately restored are extracted. Thus, the aim of this article was to describe a treatment using orthodontic and prosthetic techniques to restore esthetics and function in a patient with a distally drifted maxillary lateral incisor. The patient's functional and esthetic expectations were successfully met with the outlined treatment.

Recovering the function and esthetics of fractured teeth using several restorative cosmetic approaches. Three clinical cases.

The teeth most commonly affected by trauma are the maxillary central incisors. The most frequent types of traumatic dental injuries to permanent teeth are enamel fractures, enamel and dentine fractures, and enamel and dentine fractures with pulp involvement. This article describes three clinical cases with different levels of traumatized maxillary incisors and several cosmetic approaches for recovery of the esthetics and the masticatory function, as well as the social/psychological aspects of treatment. All cases involved young adult men. The three clinical cases involve dentin and enamel fractures, dentin and enamel fractures with pulp exposure, and dentin and enamel fractures with pulp exposure associated with root fracture. The cosmetic treatments used to resolve fractures were direct composite resin by layering technique, indirect all-ceramic restorations (laminate veneer and ceramic crowns over the teeth), and immediate implant after extraction followed by immediate loading (ceramic abutments with ceramic crown over implant). In all three cases, excellent functional and esthetic results were achieved by use of these treatment modalities. The patients were very satisfied with the results.

Effect of implant diameter on reliability and failure modes of molar crowns.

The reliability and failure modes of molar crowns supported by three different implant-supported designs were tested according to the following groups: group 1, one standard-diameter implant (3.75 mm); group 2, one narrow-diameter implant (3 mm); and group 3, two narrow-diameter implants (3 mm). Loads were applied as mouth-motion cycles using a step-stress accelerated life-testing method. ? values for groups 1 and 3 (1.57 and 2.48, respectively) indicated that fatigue accelerated the failure of both groups, but not for group 2 (0.39). Abutment screw failure was the chief failure mode. Strength and reliability were significantly higher for groups 1 and 3 compared to group 2.

The influence of the alveolar ridge shape on the stress distribution in a free-end saddle removable partial denture supported by implant.

The alveolar ridge shape plays an important role in predicting the demand on the support tooth and alveolar bone in the removable partial denture (RPD) treatment. However, these data are unclear when the RPD is associated with implants. This study evaluated the influence of the alveolar ridge shape on the stress distribution of a free-end saddle RPD partially supported by implant using 2-dimensioanl finite element analysis (FEA). Four mathematical models (M) of a mandibular hemiarch simulating various alveolar ridge shapes (1-distal desceding, 2-concave, 3-horizontal and 4-distal ascending) were built. Tooth 33 was placed as the abutment. Two RPDs, one supported by tooth and fibromucosa (MB) and other one supported by tooth and implant (MC) were simulated. MA was the control (no RPD). The load (50N) were applied simultaneously on each cusp. Appropriate boundary conditions were assigned on the border of alveolar bone. Ansys 10.0 software was used to calculate the stress fields and the von Mises equivalent stress criteria (sigmavM) was applied to analyze the results. The distal ascending shape showed the highest sigmavM for cortical and medullar bone. The alveolar ridge shape had little effect on changing the sigmavM based on the same prosthesis, mainly around the abutment 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…