Biomechanical analysis of narrow dental implants for maxillary anterior rehabilitation / Análise biomecânica de implantes de diâmetro reduzido para reabilitação da região anterior da maxila

Introdução: O conhecimento da biomecânica de implantes de diâmetro reduzido indica dimensões seguras para uso clínico. Objetivo: O objetivo do presente estudo foi comparar biomecanicamente implantes de diâmetro regular e reduzido para suporte de próteses implantossuportadas unitárias na região anterior da maxila por meio de análise de elementos finitos 3D (3D-FEA). Material e método: Quatro modelos 3D-FEA foram desenvolvidos a partir de recomposição de tomografia computadorizada e dados da literatura: um bloco ósseo na região incisiva lateral superior direita com implante e coroa. M1: 3,75 x 13 mm, M2: 3,75 x 8,5 mm, M3: 2,9 x 13 mm e M4: 2,9 x 8,5 mm. Foi aplicada carga de 178 N nos ângulos 0, 30 e 60 graus em relação ao longo eixo do implante. Foram avaliados mapas de tensão de Von Mises, tensão principal máxima e microdeformação. Resultado: M3 e M4 apresentaram maiores valores de tensão e microdeformação que M1 e M2, principalmente quando foram aplicadas forças inclinadas. Porém, M3 apresentou comportamento biomecânico melhor do que M4. Conclusão: Pode-se concluir que reduzir o diâmetro dos implantes pode prejudicar a biomecânica durante a aplicação de forças, mas a distribuição e intensidade das tensões, bem como os valores de microdeformação podem ser melhorados se o comprimento do implante for aumentado

Introduction: Narrow diameter implants biomechanics knowledge indicates safe dimensions for clinical use. Objective: Purpose of the present study was biomechanically to compare regular and narrow diameter implants to support single implant-supported prosthesis in the anterior region of the maxilla by 3D finite element analysis (3D-FEA). Material and method: Four 3D-FEA models were developed form CT scan recompositing and literature data: a bone block in the right upper lateral incisive region with implant and crown. M1: 3.75 x 13 mm, M2: 3.75 x 8.5 mm, M3: 2.9 x 13 mm and M4: 2.9 x 8.5 mm. It was applied load was of 178 N at 0, 30 and 60 degrees in relation to implant long axis. Von Mises stress, maximum principal stress and microdeformation maps were evaluated. Result: M3 and M4 did show higher tension and higher microdeformation values than M1 and M2, especially when inclined forces were applied. However, M3 presented enhanced biomechanical behavior than M4. Conclusion: It can be concluded that reduce the diameter of the implants can disadvantage to the biomechanics during the application of forces, but the distribution and intensity of the stresses, as well as the micro deformation values can be improved if the length of the implant is increased

Stress distribution in lower second molar mesialization using mini-implants: a pilot study using 3D finite element analysis / Distribuição de tensões na mesialização do segundo molar inferior usando mini-implantes: um estudo piloto usando análise de elementos finitos 3D

Objective: to analyze the stress distribution in a 3D model that simulates second molar mesialization using two different types of mini-implants. Material and Methods: a mandible bone model was obtained by recomposing a computed tomography performed by a software program. The cortical and trabecular bone, a lower second molar, periodontal ligament, orthodontic tube, resin cement and the mini-implants were designed and modeled using the Rhinoceros 4.0 software program. The characteristics of self-drilling orthodontic mini-implants were: one with 7 mm length, 1 mm transmucosal neck section and 1.6 mm diameter and another with 5 mm length and 1.5 mm diameter. A total of 235.161 and 224.505 elements were used for the mesh. These models were inserted into the bone block and then subjected to loads of 200 cN (centinewton). The results were calculated and analyzed by the Ansys 17.0 software program for qualitative verification through displacement and maximum principal stress maps. Results: it was possible to observe that the periodontal ligament presented low displacement and stress values. However, the physiological values presented are among those capable to provide orthodontic movement, with compression and tensile area visualization staggered between 0.1 and -0.1 MPa (megapascal). Conclusion: within the limitations of the study, the mini-implants tested showed similar results where the load on the tooth allowed dental displacement (molar mesialization), with a tendency to rotate it, theoretically allowing the second molar to take the location of the first molar. (AU)

Objetivo: analisar a distribuição de tensões em um modelo 3D que simula a mesialização do segundo molar usando dois tipos diferentes de mini-implantes. Material e Métodos: um modelo de osso mandibular foi obtido por recomposição de uma tomografia computadorizada realizada por um software. O osso cortical e trabecular, um segundo molar inferior, ligamento periodontal, tubo ortodôntico, cimento resinoso e os mini-implantes foram projetados e modelados no software Rhinoceros 4.0. As características dos mini-implantes ortodônticos auto perfurantes foram: um com 7 mm de comprimento, 1 mm de secção transmucosa e 1,6 mm de diâmetro e outro com 5 mm de comprimento e 1,5 mm de diâmetro. Para a malha, foram utilizados 235.161 e 224.505 elementos. Esses modelos foram inseridos no bloco ósseo e então submetidos a cargas de 200 cN (centinewton). Os resultados foram calculados e analisados pelo software Ansys 17.0 para verificação qualitativa por meio de mapas de deslocamento e tensões máximas principais. Resultados: foi possível observar que o ligamento periodontal apresentou baixos valores de deslocamento e tensões. Porém, os valores fisiológicos apresentados são capazes de proporcionar movimentação ortodôntica, com visualização da área de compressão e tração escalonada entre 0,1 e -0,1 MPa (megapascal). Conclusão: dentro das limitações do estudo, os mini-implantes testados apresentaram resultados semelhantes onde a carga sobre o dente permitiu o deslocamento dentário (mesialização do molar), com tendência a girá-lo, permitindo teoricamente que o segundo molar ocupe do lugar do primeiro molar (AU)

Clinical comparison between crestal and subcrestal dental implants: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: How the performance of dental implants is related to their occlusogingival placement, crestal or subcrestal, is unclear. PURPOSE: The purpose of this systematic review and meta-analysis was to evaluate marginal bone loss, implant survival rate, and peri-implant soft tissue parameters between implants placed at the crestal and subcrestal bone level. MATERIAL AND METHODS: Two independent reviewers searched the PubMed/MEDLINE, Embase, and Cochrane Library databases for randomized clinical trials published up to September 2020. The meta-analysis was based on the Mantel-Haenszel and the inverse variance methods (α=.05). RESULTS: The search identified 928 references, and 10 studies met the eligibility criteria. A total of 393 participants received 709 implants, 351 at crestal bone levels and 358 at subcrestal bone levels. Meta-analysis indicated that crestal bone level implants showed similar marginal bone loss to that seen with subcrestal bone level implants (mm) (P=.79), independent of the subcrestal level (P=.05) and healing protocol (P=.24). The bone level implant placement did not affect the implant survival rate (P=.76), keratinized tissue (mm) (P=.91), probing depth (mm) (P=.70), or plaque index (%) (P=.92). CONCLUSIONS: The evidence suggests that both approaches of implant placement are clinically acceptable in terms of peri-implant tissue parameters and implant-supported restoration survival.

Biomechanical Evaluation of Different Implant-Abutment Connections, Retention Systems, and Restorative Materials in the Implant-Supported Single Crowns Using 3D Finite Element Analysis.

This is an in silico study aimed to evaluate the biomechanical influence of different implant-abutment interfaces (external hexagon and Morse taper implants), retention systems (cement and screw retained), and restorative crowns (metal-ceramic and monolithic) using 3-dimensional finite element analysis (3D-FEA). Eight 3D models were simulated for the maxillary first molar area using InVesalius, Rhinoceros, and SolidWorks and processed using Femap and NEi Nastran software. Axial and oblique forces of 200 and 100 N, respectively, were applied on the occlusal surface of the prostheses. Microstrain and von Mises stress maps were used to evaluate the deformation (cortical bone tissue) and stress (implants/fixation screws/crowns), respectively, for each model. For both loadings, Morse taper implants had lower microstrain values than the external hexagon implants. The retention system did not affect microstrain on the cortical bone tissue under both loadings. However, the cemented prosthesis displayed higher stress with the fixation screw than the external hexagon implants. No difference was observed between the metal-ceramic and zirconia monolithic crowns in terms of microstrain and stress distribution on the cortical bone, implants, or components. Morse taper implants can be considered as a good alternative for dental implant rehabilitation because they demonstrated better biomechanical behavior for the bone and fixation screw as compared to external hexagon implants. Cement-retained prosthesis increased the stress on the fixation screw of the external hexagon implants, thereby increasing the risk of screw loosening/fracture in the posterior maxillary area. The use of metal-ceramic or monolithic crowns did not affect the biomechanical behavior of the evaluated structures.

Effect of bone quality and bone loss level around internal and external connection implants: A finite element analysis study.

STATEMENT OF PROBLEM: A consensus regarding the biomechanical effects of vertical bone loss in normal and osteoporotic bone tissue according to different implant-abutment interfaces is lacking. PURPOSE: The purpose of this finite element analysis study was to evaluate the effect of vertical bone loss (without bone loss; with 1.5-mm bone loss; with 3-mm bone loss; and with 4.5-mm bone loss) in normal and osteoporotic bone that received a Ø4×10-mm implant with different implant-abutment connections (external connection [external hexagon] and internal connection [Morse taper]) by using 3D finite element analysis. MATERIAL AND METHODS: Sixteen 3D models were simulated. Axial and oblique forces of 200 N and 100 N, respectively, were applied on the occlusal surfaces of the prostheses. Maximum principal stress and microstrain were determined from the bone tissue of each model. von Mises stress analysis was used to evaluate the stress distribution in implants and prosthetic components (fixation screws, abutment, and crown). RESULTS: The results showed higher stress concentrations in models with bone loss as increased vertical bone loss contributed to higher stress and microstrain in the bone tissue, regardless of the quality of bone and implant-abutment connection. Osteoporotic bone contributed to increase in microstrain in the trabecular bone. The internal connection showed lower stress than the external connection implants only in models without marginal bone loss. Furthermore, higher stress concentrations were observed in the implants and fixation screws in models with increased bone loss and external connection implants, mainly under oblique loading. Osteoporotic bone did not affect stress distribution in the implants and prosthetic components. CONCLUSIONS: Progressive bone loss contributed to higher stress in the bone tissue, implants, and prosthetic components. The osteoporotic bone affects only the microstrain in the trabecular bone, but not the stress in the implants and prosthetic components. The internal connection implants showed lower stress in the cortical bone only in models without bone loss, while external connection implants exhibited higher stress in the implants and screws under oblique loading.

Análise biomecânica envolvendo implantes estreitos para reabilitações unitárias na região maxilar anterior / Biomechanical analysis involving narrow implants for unitary rehabilitation in the anterior maxillary region

Proposição: Avaliar biomecanicamente a possibilidade de uso de implantes de diâmetro reduzido em reabilitações unitárias em região maxilar anterior. Foram avaliados biomecanicamente o uso de implantes de diâmetro 2,9 mm com implantes de 3,5 mm instalados a nível ósseo e 1,5 mm infraósseo, variando-se o comprimento dos implantes (7 mm, 8,5 mm, 10 mm, 11,5 mm, 13 mm e 15 mm), por meio da análise dos elementos finitos 3D. Material e métodos: 12 modelos tridimensionais foram simulados com ajuda dos programas Invesalius, Rhinoceros 3D e SolidWorks. Cada modelo possuía um bloco ósseo da região anterior maxilar (osso tipo III) com a presença dos dentes incisivo central e canino, simulando uma reabilitação com coroa unitária metal free cimentada (dente incisivo lateral direito), suportada por um implante de 7 mm, 8,5 mm, 10 mm, 11,5 mm, 13 mm ou 15 mm, variando-se o diâmetro do implante (2,9 mm e 3,5 mm) e a instalação dos implantes no tecido ósseo (ao nível e 1,5 mm infraósseo). Os modelos foram processados pelos programas ANSYS 19.2, utilizando uma força de 178 N em diferentes inclinações (0º, 30º e 60º). Os resultados foram plotados em mapas de Tensão de Von Mises (VM), Tensão Máxima Principal (TMP), Microdeformação (µÎµ) e Deslocamento. Resultados: Na análise de VM houve um aumento da concentração de tensão com o aumento da inclinação da força nos implantes/componentes e tecido ósseo. Foi possível observar maiores concentrações de tensões para os implantes instalados 1,5 mm infraósseo, além disso, os implantes de 2,9 mm de diâmetro apresentaram maiores concentrações de tensões. Sob análise de TMP e µÎµ, o tecido ósseo apresentou maiores concentrações de tensões de tração e microdeformação sob cargas oblíquas (30° e 60°) ao redor do pescoço do implante (tecido ósseo cortical) na técnica de instalação ao infraósseo, além isso, foi possível observar que os implante menor diâmetro apresentaram maiores concentrações de tensões nos implantes/componentes e tecido ósseo e menor tendência de deslocamento na técnica de instalação ao nível ósseo. Conclusão: Os implantes de 3,5 mm de diâmetro foram mais favoráveis biomecanicamente que os implante de 2,5 mm, independentemente do tipo de técnica de instalação utilizadas. A instalação de implantes por técnica ao nível ósseo nas condições do estudo, favoreceu uma diminuição de concentração de tensões no tecido ósseo adjacente ao implante(AU)

Proposition: Biomechanically evaluate the possibility of using small diameter implants in unitary rehabilitation in the anterior maxillary region. Biomechanically evaluated the use of 2.9 mm diameter implants with 3.5 mm implants placement at bone level and 1.5 mm subcrestal, through 3D finite element analysis. Material and methods: 12 three-dimensional models were simulated with the help of the Invesalius, Rhinoceros 3D and SolidWorks programs. Each model had a bone block from the anterior maxillary region (type III bone) with the presence of the central and canine incisor teeth, simulating a rehabilitation with a cemented metal free unitary crown (right lateral incisor tooth), supported by implant the 7 mm, 8,5 mm, 10 mm, 11.5 mm, 13 mm or 15 mm, varying the implant diameter (2.9 mm and 3.5 mm), the placement of the implants in the bone tissue at level 1, 5 mm subcrestal. The models were processed by the ANSYS 19.2 programs, using a force of 178 N at different slopes (0º, 30º and 60º). The results were plotted on Von Mises Stress (VM), Maximum Main Stress (TMP), Microdeformation (µÎµ) and Displacement. Results: In the analysis of VM there was an increase in the concentration of tension with the increase of the inclination of the force in the implants/components and bone tissue. It was possible to observe higher concentrations of stresses for the implants installed in the subcrestal, in addition, the implants of 2.9 mm in diameter presented higher concentrations of stresses. Under analysis of TMP and µÎµ, the bone tissue showed higher concentrations of tensile stresses and microdeformation under oblique loads (30° and 60°) around the implant neck (cortical bone tissue) in the placement the technique at the subcrestal, in addition , it was possible to observe that the smaller diameter implants showed higher concentrations of stress in the implants/components and bone tissue and and less tendency of displacement in the installation technique at the bone level. Conclusion: The 3.5 mm diameter implants were more favorable biomechanically than the 2.5 mm implants, regardless of the type of placement the technique used. The placement of implants by crestal technique under the conditions of the study, favored a decrease of stress concentration in the bone tissue adjacent to the implant(AU)

Systematic review and meta-analysis of welding procedures in one-piece cast implant-supported frameworks.

The objective of this systematic review and meta-analysis was to evaluate the effect of welding techniques on implant-supported prostheses and determine whether they contribute to a better adaptation compared with a one-piece cast. A search was conducted using the PubMed/MEDLINE, Embase, and Cochrane Library databases, and articles published until November 2017 were obtained from these databases. This review followed the PRISMA criteria and is registered on the PROSPERO platform (CRD42017081865). The PICO question was "Do welding procedures in one-piece cast implant-supported frameworks influence implant/abutment-framework marginal misfits?" Eleven studies were selected for a qualitative analysis, and seven studies were selected for a quantitative analysis. A total of 189 specimens were fabricated using different materials (cp-Ti, Ni-Cr, Cr-Co, and noble alloys), and welding techniques such as laser welding, conventional welding, tungsten inert gas, and brazing were applied. A vertical marginal misfit was measured using an optical microscope, a stereomicroscope, and/or a scanning electron microscopy. The qualitative analysis in the studies demonstrated a positive effect of the welding techniques on the adaptation of the infrastructures. The meta-analysis confirmed the results (p < 0.00001; MD: -36.14; 95%CI: -48.69 to -23.59). Within the limitations of this study and regarding the heterogeneity of the samples, we conclude that the soldering point technique is effective for obtaining relatively low values of marginal misfit, with laser welding as the most effective technique. However, additional studies were recommended due to the heterogeneity of different variables (alloys, connection, and misfit evaluation) in the included studies.

Ceramic versus metal-ceramic implant-supported prostheses: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: There is insufficient evidence to recommend the restorative material for implant-supported prostheses. PURPOSE: The purpose of this systematic review and meta-analysis was to evaluate studies that compared ceramic and metal-ceramic restorations for implant-supported prostheses (within the same study to avoid indirect comparison) in terms of the mechanical and biological complication rates, prosthesis survival rate, and marginal bone loss. MATERIAL AND METHODS: Two independent reviewers performed a comprehensive search in databases (PubMed/MEDLINE, Web of Science, and Cochrane Library) for articles indexed until March 31, 2018. The search was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and methods were registered in the International Prospective Register of Systematic Reviews (PROSPERO). The focused question was "Do ceramic restorations have mechanical/biological complication rates, prosthesis survival rates, and marginal bone loss similar to those of metal-ceramic restorations?" RESULTS: The search identified 949 references. The interinvestigator agreement using kappa values was 0.87 for PubMed/MEDLINE, 0.93 for Scopus, and 1.0 for the Cochrane Library. After analysis, 12 studies were selected for qualitative and quantitative analysis. The mechanical complication rate did not differ between ceramic and metal-ceramic restorations (P=.89), independent of the type of prostheses (single crown: P=.63; fixed partial denture: P=.65). The biological complication rate was also not significantly different between ceramic and metal-ceramic restorations (P=.21). The prosthesis survival rate showed no significant differences between the 2 types of restorations (P=.56). Marginal bone loss was also similar for both types of restorations (P=.12). CONCLUSIONS: This systematic review indicated that ceramic and metal-ceramic implant-supported prostheses have similar mechanical and biological complication rates, prosthesis survival rates, and marginal bone loss. Thus, both treatments are appropriate options for long-term rehabilitation treatment.

Short implants versus longer implants with maxillary sinus lift. A systematic review and meta-analysis.

This study compared the survival rate of dental implants, amount of marginal bone loss, and rates of complications (biological and prosthetic) between short implants and long implants placed after maxillary sinus augmentation. This systematic review has been registered at PROSPERO under the number (CRD42017073929). Two reviewers searched the PubMed/MEDLINE, Embase, LILACS, and Cochrane Library databases. Eligibility criteria included randomized controlled trials, comparisons between short implants and long implants placed after maxillary sinus augmentation in the same study, and follow-up for >6 months. The Cochrane Collaboration's tool for assessing the risk of bias in randomized trials was used to assess the quality and risk of bias of the included studies. The search identified 1366 references. After applying the inclusion criteria, 11 trials including 420 patients who received 911 dental implants were considered eligible. No significant difference was observed in the survival rate [p = 0.86; risk ratio (RR): 1.08; 95% confidence interval (CI): 0.46-2.52] or in the amount of marginal bone loss (p = 0.08; RR: -0.05; 95%CI: -0.10 to 0.01). However, higher rates of biological complications for long implants associated with maxillary sinus augmentation were observed (p < 0.00001; RR: 0.21; 95%CI: 0.10-0.41), whereas a higher prosthetic complication rate for short implants was noted (p = 0.010; RR: 3.15; 95%CI: 1.32-7.51). Short implant placement is an effective alternative because of fewer biological complications and similar survival and marginal bone loss than long implant placement with maxillary sinus augmentation. However, the risk of mechanical complications associated with the prostheses fitted on short implants should be considered.

Comparison of the Use of Titanium-Zirconium Alloy and Titanium Alloy in Dental Implants: A Systematic Review and Meta-Analysis.

The aim of this study was to compare the values of bone-implant contact (BIC) and removal torque (RTQ) reported in different animal studies for titanium-zirconium (TiZr) and titanium (Ti) dental implants. This review has been registered at PROSPERO under number CRD42016047745. We undertook an electronic search for data published up until November 2017 using the PubMed/Medline, Embase, and The Cochrane Library databases. Eligibility criteria included in vivo studies, comparisons between Ti and TiZr implants in the same study, and studies published in English that evaluated BIC and RTQ. After inclusion criteria, 8 studies were assessed for eligibility. Of the 8 studies, 7 analyzed BIC outcome and 3 analyzed RTQ outcome. Among such studies, 6 studies were considered for meta-analysis of quantitative for BIC and 2 studies for RTQ. There was no significant difference for BIC analysis ( P = .89; random ration [RR]: -0.21; 95% confidence interval [CI]: -3.14 to 2.72). The heterogeneity of the primary outcome studies was considered low (7.19; P = .21; I 2 : 30%). However, the RTQ analysis showed different results favoring the TiZr dental implants ( P = .001; RR: 23.62; 95%CI: 9.15 to 38.10). Low heterogeneity was observed for RTQ (χ2: 1.25; P = .26; I 2 : 20%). Within the limitations of this study, there was no difference between TiZr and Ti alloys implants in terms of BIC. However, TiZr implants had higher RTQ than Ti alloys.

Short implants versus longer implants with maxillary sinus lift. A systematic review and meta-analysis

Abstract This study compared the survival rate of dental implants, amount of marginal bone loss, and rates of complications (biological and prosthetic) between short implants and long implants placed after maxillary sinus augmentation. This systematic review has been registered at PROSPERO under the number (CRD42017073929). Two reviewers searched the PubMed/MEDLINE, Embase, LILACS, and Cochrane Library databases. Eligibility criteria included randomized controlled trials, comparisons between short implants and long implants placed after maxillary sinus augmentation in the same study, and follow-up for >6 months. The Cochrane Collaboration's tool for assessing the risk of bias in randomized trials was used to assess the quality and risk of bias of the included studies. The search identified 1366 references. After applying the inclusion criteria, 11 trials including 420 patients who received 911 dental implants were considered eligible. No significant difference was observed in the survival rate [p = 0.86; risk ratio (RR): 1.08; 95% confidence interval (CI): 0.46-2.52] or in the amount of marginal bone loss (p = 0.08; RR: −0.05; 95%CI: −0.10 to 0.01). However, higher rates of biological complications for long implants associated with maxillary sinus augmentation were observed (p < 0.00001; RR: 0.21; 95%CI: 0.10-0.41), whereas a higher prosthetic complication rate for short implants was noted (p = 0.010; RR: 3.15; 95%CI: 1.32-7.51). Short implant placement is an effective alternative because of fewer biological complications and similar survival and marginal bone loss than long implant placement with maxillary sinus augmentation. However, the risk of mechanical complications associated with the prostheses fitted on short implants should be considered.

Three-dimensional finite element analysis of glass fiber and cast metal posts with different alloys for reconstruction of teeth without ferrule.

The aim of this study was to evaluate different materials for restoration of teeth without ferrule by three-dimensional (3D) finite element analysis (FEA). Five models simulating the maxillary central incisor and surrounding bone were simulated according to the type of post: glass fibre post (GFP) or cast metal post (CMP) with different alloys such as gold (Au), silver-palladium (AgPd), copper-aluminum (CuAl) and nickel-chromium (NiCr). Models were designed using Invesalius and Rhinoceros. FEAs were made using FEMAP and NeiNastran, with an applied axial force of 100 N and oblique occlusal load at 45°. Stress distribution among groups was analysed by two-way analysis of variance (ANOVA), followed by post-hoc Tukey's test. The GFP showed the best stress distribution in the post, followed by CMP with Au, AgPd, CuAl and NiCr alloys, respectively (p < .001). No statistically significant difference in the stress distribution in teeth was found under application of axial load (p > .05). Under oblique load, the GFP generated the highest values of tension among the models, followed by the CMP with NiCr alloy than other models (p < .001). The use of GFP resulted in a lower stress concentration in the post, but increased stress in the tooth without ferrule. The CMP with NiCr alloy exhibited the highest stress distribution among other CMP. To avoid higher stress in teeth, alloys of Au, AgPd and CuAl, respectively, are recommended.

Influence of bicortical techniques in internal connection placed in premaxillary area by 3D finite element analysis.

The aim of study was to evaluate the stress distribution in implant-supported prostheses and peri-implant bone using internal hexagon (IH) implants in the premaxillary area, varying surgical techniques (conventional, bicortical and bicortical in association with nasal floor elevation), and loading directions (0°, 30° and 60°) by three-dimensional (3D) finite element analysis. Three models were designed with Invesalius, Rhinoceros 3D and Solidworks software. Each model contained a bone block of the premaxillary area including an implant (IH, Ø4 × 10 mm) supporting a metal-ceramic crown. 178 N was applied in different inclinations (0°, 30°, 60°). The results were analyzed by von Mises, maximum principal stress, microstrain and displacement maps including ANOVA statistical test for some situations. Von Mises maps of implant, screws and abutment showed increase of stress concentration as increased loading inclination. Bicortical techniques showed reduction in implant apical area and in the head of fixation screws. Bicortical techniques showed slight increase stress in cortical bone in the maximum principal stress and microstrain maps under 60° loading. No differences in bone tissue regarding surgical techniques were observed. As conclusion, non-axial loads increased stress concentration in all maps. Bicortical techniques showed lower stress for implant and screw; however, there was slightly higher stress on cortical bone only under loads of higher inclinations (60°).

Avaliação biomecânica de próteses unitárias sobre implantes de hexágono interno em maxila anterior com diferentes tipos de ancoragem óssea e comprimentos de implantes: estudo pelo método dos elementos finitos 3-D / Biomechanical evaluation of unitary prostheses on implants of internal hexagon in anterior maxilla with different types of bone anchorage and implant lengths: study by the finite element method 3-D

Proposição: A proposta dessa pesquisa foi avaliar a distribuição de tensões em próteses unitárias implantossuportadas de hexágono interno (HI) na região maxilar anterior, variando a técnica de ancoragem óssea (Convencional (C), Bicorticalização (B) e Bicorticalização com elevação do assoalho nasal (BEAN) e as direções de carregamento (0°, 30° e 60°) por análise tridimensional (3D) de elementos finitos. Material e métodos: Três modelos tridimensionais foram simulados com ajuda dos programas Invesalius, Rhinoceros 3D 4.0 e SolidWorks 2011. Cada modelo possuía um bloco ósseo da região anterior do maxilar (osso tipo III) com 10m de altura padrão com um implante (4×8,5 mm (C), 4x10mm (B) e 4x11,5mm (BEAN), suportando uma coroa cimentada metal free. Os modelos foram processados pelos programas FEMAP v.11.0 e NEiNastran 11, utilizando uma força de 178 N em diferentes inclinações (0°, 30°, 60°). Os resultados foram plotados em mapas de tensão de von Mises (TvM), tensão máxima principal (TMxP), Microstrain (µÎµ) e Tendência de deslocamento (TD). Resultados: Análise de TvM mostrou aumento da concentração de tensão com o aumento da inclinação da força para os implantes, parafusos de fixação e abutments, com padrão similar de distribuição para os modelos testados. Sob análise de TMxP e µÎµ, o tecido ósseo apresentou maiores concentrações de tensões de tração sob cargas oblíquas (30° e 60°) ao redor do pescoço do implante na técnica convencional. Análise de deslocamento mostrou aumento da tendência de inclinação de forma similar para todos os modelos com o aumento da inclinação da força. Conclusão: As técnicas bicorticais utilizando implantes mais longos mostraram menor concentração de tensões no tecido ósseo e aumento na inclinação de força mostrou padrão mais intenso de distribuição de tensões para todas as situações testadas(AU)

Proposition: The purpose of this research was to evaluate the stress distribution of single crowns supported by internal hexagon (HI) implants in the anterior region of the maxilla, varying the bone anchoring technique (conventional (C), bicorticalization (B) and bicorticalization with nasal floor elevation (BNFE) at loading directions (0° , 30° and 60°) by three-dimensional (3D) finite elemento analysis. Material and methods: Three 3D models were designed with aid of Invesalius, Rhinoceros 3D 4.0 and SolidWorks 2011 software. Each model contained a bone block of the premaxillary área (type III bone) with 10m of standard height with one implant (4×8, 5mm (C), 4x10mm (B) and 4x11.5mm (BNFE)), supporting a cemented metal free crown. The models were processed by the FEMAP v.11.0 and NEiNastran 11 using load of 178 N at different inclinations (0°, 30°, 60°). Von Mises (TvM), maximum principal stress (TMxP), microstrain (µÎµ) and displacement maps (D) were plotted to results analysis. Results: Analysis of TvM showed increased of stress concentration with increasing load inclination for implants, fixation screws and abtments, with similar pattern of distribution for the tested models. Under TMxP and µÎµ analysis, bone tissue showed higher traction stress concentrations under oblique loads (30 ° and 60 °) around the implant neck for the conventional technique. Displacement analysis showed increase of inclination tendency similar for all models as the load increased inclination. Conclusion: Bicortical techniques using longer implants showed lower stress distribution to the bone tissue and increase of force inclination showed more concentrated pattern of stress distribution for all tested situations(AU)

Uso de reforço metálico para resolução de fraturas recorrente em reabilitação com prótese total superior ­ relato de caso / Use of metallic reinforcement for resolution of recurrent fractures in rehabilitation with maxillary complete denture ­ case report

Tratamentos envolvendo Prótese Total (PT) baseiam-se na devolução da qualidade de vida pela recuperação da função mastigatória e estética; porém, um problema cotidiano são as fraturas das bases e/ou dentes de resina acrílica, que podem gerar problemas inclusive psicológicos. Assim, a presente descrição tem por objetivo relatar um caso clínico no qual foi utilizado reforço metálico na PT superior, associado à confecção de uma PPR convencional inferior, para reabilitação estética e funcional. Paciente de 58 anos, feminino, branca, compareceu a clínica de Reabilitação Oral da faculdade de Odontologia de Araçatuba, com queixa estética da prótese superior, além de fraturas recorrentes. Após anamnese observou-se que a prótese apresentava regiões de fratura, com excessivo desgaste nos dentes e vários consertos. Assim, foi planejado confecção de uma PT com reforço metálico além de uma PPR na arcada inferior. foram realizados procedimentos convencionais de confecção da PT superior e PPR inferior incluindo registro para pequeno aumento da dimensão vertical. Após a aprovação durante a prova funcional, foi realizada a inclusão da prótese, sendo realizada então a fase laboratorial da confecção da barra metálica que, após construída, recebeu uma camada de opacificador cerâmico para favorecer a estética. Após o tratamento foi possível observar que o procedimento atingiu seu objetivo, eliminando o problema de fraturas recorrentes sem interferência estética, e devolveu qualidade de vida para a paciente. Após 2,5 anos de controle foi possível constatar que a utilização de reforço metálico foi uma alternativa viável para redução das fraturas sem comprometimento estético quando bem indicada.

Treatments involving complete dentures (CD) consist on the recovery of patients' quality of live restoring booth function and aesthetics. however fractures on the saddle or of the resin elements are common and may result on psycological problems. Therefore this study aims to report a clinical case that used metallic reinforcement of upper CD associated to fabrication of a conventional lower removable partial denture (RPD) for aesthetic and functional rehabilitation. A 58 years-old female Caucasian patient sought treatment at Clinics of Oral Rehabilitation of Dental School of Araçatuba complaining of poor aesthetics and recurrent fractures of upper CD. Anamnesis showed many fractures and repairs on the prostheses with excessive wear of teeth. Thus were planned the fabrication of a CD with metallic reinforcement and a RPD for lower jaw. Standard procedures for fabrication of the prostheses were performed, including record for a little increase of vertical dimension. After approval of the patient, in the clinical test the prostheses was included and followed by the laboratorial phase of the manufacture of a metallic bar that covered in opaque ceramic to preserve aesthetics. After treatment it was possible to observe that the procedure has achieved its objective eliminating the problem of recurrent fractures without compromising dental aesthetic restoring patient's quality of life. After a 2.5 years follow-up it was possible to find that when properly indicated the use of metallic reinforcement was a viable alternative for reducing recurrent fractures without compromising aesthetic.

Utilização de implante curto associado a micro pilar protético, uma alternativa para não realização de cirurgia de levantamento de seio maxilar ­ relato de caso / The use of short implant associated with micro prosthetic abutment, an alternative for not performing maxillary sinus lifting surgery ­ case report

A reabilitação com implantes tem como desafio as limitações de quantidade e qualidade óssea, sendo necessárias técnicas cirúrgicas de enxerto ósseo, permitindo a instalação dos implantes convencionais. Para pacientes que preferem opções menos complexas e traumáticas, os implantes curtos são uma opção de tratamento menos invasiva e com boa previsibilidade. Porém, para o seu melhor desempenho, princípios biomecânicos devem ser empregados, como utilização de mesa oclusal reduzida, ferulização de implantes, conexão interna do tipo Cone Morse e plataforma Switching. O objetivo desse trabalho foi relatar um caso clínico de uma paciente que descartou a cirurgia de levantamento de seio maxilar, sendo então proposto o tratamento com a utilização de implante curto do tipo Cone Morse, em que foi realizado o planejamento reverso e o uso de princípios biomecânicos.

Rehabilitation with implants is challenged by bone quantity and quality limitations, being necessary surgical techniques for bone grafting that allow conventional implants installation. for patients who prefer less complex and traumatic options, short implants are a less invasive treatment option and has good predictability. however, for best performance, biomechanical principles should be used, such as use of reduced occlusal table, splinting implants, internal connection of the Cone Morse type and Switching platform. The aim of this study was to report a case of a patient who dismissed the maxillary sinus lifting surgery, so the treatment proposed was the use of short implant Cone Morse type, in which reverse planning was done with the use of biomechanics principles.

Can the modeling for simplification of a dental implant surface affect the accuracy of 3D finite element analysis?

The aim of this study was to assess stress/strain of different implant modeling simplifications by 3D-FEA. Three variation of external hexagon implant (Ø3.75 × 10 mm) supporting one molar crown were simulated: A (no threads); B (slightly threads simplification); C (original design). 200 N (axial) and 100 N (oblique) were applied. Cortical bone was evaluated by maximum principal stress and microstrain qualitatively and quantitatively (ANOVA and Tukey post hoc (p < 0.05)). Higher stress levels (p < 0.05) were observed in model A. Models B and C presented similar stress transmission. It was possible to conclude that slightly simplification should be used for studies evaluating stress transferring for bone tissue.

Resolução protética para reabilitação de pacientes com implantes unitários inclinados na região maxilar anterior: relato de caso / Prosthetic resolution for rehabilitation of single implant inclined on anterior maxillary region: case report

A utilização de implantes dentários é considerada para reabilitar a falta de elementos dentários com o intuito de restabelecer função e estética em pacientes parcialmente ou totalmente desdentados. Quando a região a ser reabilitada não possui quantidade de tecido ósseo suficiente para a instalação ideal do implante o cirurgião dentista pode optar por uma instalação que pode não ter inclinação favorável do ponto de vista protético. Assim, o presente estudo tem por objetivo relatar um caso clínico no qual foi instalado um implante de conexão externa na região maxilar anterior com inclinação para lingual (“approach palatino”), sendo utilizado um pilar UCLA para confecção de uma prótese cimentada corrigindo a inclinação do implante e permitindo a cimentação da coroa protética. Após o término do tratamento foi possível observar que o procedimento adotado atingiu estética e harmonia satisfatórias do sorriso do paciente na região, além de não comprometer a função, deixando o mesmo bastante satisfeito em relação ao tratamento proposto

The use of dental implants has been made to rehabilitate the loosened teeth in order to recuperate function and aesthetics to partially or entirely edentulous patients. When the area of rehabilitation doesn’t have enough bone tissue for ideally implant placement, the surgeon may opt for an insertion that not favorable in relation to the inclination of the prosthetic axis. Therefore, the aim of this study is report a clinical case in which it was installed an external connection implant in the anterior maxillary region with buccal inclination (palatine approach) and using an UCLA for fabrication of a cemented prosthesis correcting the inclination of the implant and favoring cementation of the prosthetic crown. After the treatment it was possible to observed that the procedure adopted favored the aesthetics and the patient’s smile harmony in the region, not compromising the function and leave the patient too much satisfied with the treatment

A importância da geometria dos implantes para o planejamento em reabilitação oral: revisão de literatura / The importance of implants geometry for planning in oral rehabilitation: literature review

O desenho da estrutura do implante ainda é um questionamento por parte dos profissionais, visto que suas variações pode influenciar para a distribuição de tensões de maneira mais favorável ao longo do tecido ósseo. Assim, o objetivo deste estudo foi realizar uma revisão de literatura abordando o tema geometria dos implantes osseointegráveis estabelecendo respostas que procure fundamentar as reabilitações orais de acordo com as variações dos implantes que existem no mercado. Foi realizada uma busca detalhada no periódico PubMed/Medline e Bireme, com os descritores: “dental implants cylinder”; “dental implants thread”; “dental implants geometry”, até maio de 2014. A busca resultou em um total de 798 artigos, sendo realizado uma análise dos títulos e resumos, selecionando 18 artigos e realizado a complementação com um 1 livro da área, que avaliaram a influência das diferentes geometrias dos implantes, procurando comparar as diferentes formas de geometria e roscas para posterior discussão e conclusões. Dessa forma, conclui-se que os implantes rosqueáveis são mais utilizados, devido as suas vantagens em relação a dissipação de tensões e estabilidade primária. As variações dos diferentes tipos de roscas existentes apresentam influência para a dissipação das tensões

The design of implant structure is still a questioning to the professionals, while their variations can to influence of stress distribution favorably to bone. Therefore, the aim of study was to review addressing the topic of osseointegrated implants design establishing answers for the patient oral rehabilitation, according variations existing on the market. It was conducted a detailed search strategy by the PubMed/ Medline and Bireme, it was used as descriptors: “dental implants cylinder”; “dental implants thread”; “dental implants geometry”, until May 2014. From 798 articles, after review were selected 18 articles and 1 specific area book. The results were divided to compare design of implant and threads for further discussion and conclusions. Thus, conclude that the threads implants are best used because of its advantages with respect to the stress distribution and stability primary. The variations of the differents types of threads, have influence for stress distribution