RESUMO
OBJECTIVE: To evaluate the effect of the labiolingual diameter and construction of an endodontically treated (ET) anterior tooth with crown restoration on stress distribution and biomechanical safety under occlusal loading. METHODOLOGY: Three-dimensional finite element models were generated for maxillary central incisors with all-ceramic crown restorations. The labiolingual diameters of the tooth, defined as the horizontal distance between the protrusion of the labial and lingual surfaces, were changed as follows: (D1) 6.85 mm, (D2) 6.35 mm, and (D3) 5.85 mm. The model was constructed as follows: (S0) vital pulp tooth; (S1) ET tooth; (S2) ET tooth with a 2 mm ferrule, restored with a fiber post and composite resin core; (S3) ET tooth without a ferrule, restored with a fiber post and composite resin core. A total of 12 models were developed. In total, two force loads (100 N) were applied to the crown's incisal edge and palatal surface at a 45° oblique angle to the longitudinal axis of the teeth. The Von Mises stress distribution and maximum stress of the models were analyzed. RESULTS: Regardless of the loading location, stress concentration and maximum stress (34.07~66.78MPa) in all models occurred in the labial cervical 1/3 of each root. Both labiolingual diameter and construction influenced the maximum stress of the residual tooth tissue, with the impact of the labiolingual diameter being greater. A reduction in labiolingual diameter led to increased maximum stress throughout the tooth. The ferrule reduced the maximum stress of the core of S2 models (7.15~10.69 MPa), which is lower compared with that of S3 models (19.45~43.67 MPa). CONCLUSION: The labiolingual diameter exerts a greater impact on the biomechanical characteristics of ET anterior teeth with crown restoration, surpassing the influence of the construction. The ferrule can reduce the maximum stress of the core and maintain the uniformity of stress distribution.
Assuntos
Resinas Compostas , Coroas , Análise do Estresse Dentário , Análise de Elementos Finitos , Incisivo , Dente não Vital , Dente não Vital/fisiopatologia , Humanos , Fenômenos Biomecânicos , Incisivo/anatomia & histologia , Incisivo/fisiologia , Resinas Compostas/química , Análise do Estresse Dentário/métodos , Técnica para Retentor Intrarradicular , Reprodutibilidade dos Testes , Estresse Mecânico , Valores de Referência , Força de Mordida , Imageamento Tridimensional/métodos , Planejamento de Prótese Dentária , Teste de Materiais , Coroa do Dente/anatomia & histologia , Coroa do Dente/fisiologiaRESUMO
Finite element analysis (FEA) has been used to analyze the behavior of dental materials, mainly in implantology. However, FEA is a mechanical analysis and few studies have tried to simulate the biological characteristics of the healing process of loaded implants. This study used the rule of mixtures to simulate the biological healing process of immediate implants in an alveolus socket and bone-implant junction interface through FEA. Three-dimensional geometric models of the structures were obtained, and material properties were derived from the literature. The rule of mixtures was used to simulate the healing periods-immediate and early loading, in which the concentration of each cell type, based on in vivo studies, influenced the final elastic moduli. A 100 N occlusal load was simulated in axial and oblique directions. The models were evaluated for maximum and minimum principal strains, and the bone overload was assessed through Frost's mechanostat. There was a higher strain concentration in the healing regions and cortical bone tissue near the cervical portion. The bone overload was higher in the immediate load condition. The method used in this study may help to simulate the biological healing process and could be useful to relate FEA results to clinical practice.
Assuntos
Implantes Dentários , Módulo de Elasticidade , Análise de Elementos Finitos , Carga Imediata em Implante Dentário , Alvéolo Dental , Cicatrização , Humanos , Alvéolo Dental/fisiologia , Cicatrização/fisiologia , Fenômenos Biomecânicos , Simulação por Computador , Interface Osso-Implante/fisiologia , Estresse Mecânico , Processo Alveolar/fisiologia , Modelos Biológicos , Osseointegração/fisiologia , Força de Mordida , Análise do Estresse Dentário/métodos , Osteoblastos/fisiologia , Osso Cortical/fisiologia , Imageamento Tridimensional/métodosRESUMO
INTRODUCTION: Different types of intraradicular restorations and their insertion have an impact on teeth biomechanics. This study aimed to analyze the biomechanical behavior of maxillary central incisors restored with glass fiber post (GFP) and cast metal post and core (CMP) subjected to buccolingual and mesiodistal orthodontic forces using the finite element method. METHODS: Two models of the maxillary central incisor with periodontal ligament, cortical bone, and trabecular bone were made. One of the models included intraradicular restoration with GFP, whereas, in the other, the incisor was restored with CMP. After creating the tridimensional mesh of finite elements, applying 2 orthodontic forces were simulated: 65 g of buccolingual force and 70 g of mesiodistal force. The forces were applied parallel to the palatal plane in the region of the bracket slot, located 4 mm to the incisal edge. RESULTS: The maximum stresses generated in the GFP-restored root were 3.642 × 10-1 MPa and 4.755 × 10-1 MPa from the buccolingual and mesiodistal forces, respectively. Likewise, the stresses in the CMP restored root were 2.777 × 10-1MPa and 3.826 × 10-1MPa. The radicular area with higher stress on both models was located in the cervical third: on the buccal surface when the buccolingual force was applied and on the mesial surface when the mesiodistal force was applied. The highest stress levels were found on the CMP structure. CONCLUSIONS: The incisor restored with cast metal post revealed lower stress values transferred to the root than the one restored with GFP. The stresses on the structure of the GFP were lower and more homogeneous than the ones found on the cast metal post. The difference among the stress values in the materials is within a safe margin for using both materials in relation to orthodontic forces.
Assuntos
Vidro , Incisivo , Humanos , Vidro/química , Fenômenos Mecânicos , Ligamento Periodontal , Análise de Elementos Finitos , Estresse Mecânico , Análise do Estresse Dentário/métodosRESUMO
AIM: Evaluate the influence of occlusal loading on the stress distribution of endodontically treated teeth after root canal preparation with different file's sizes and tapers by means of finite element analysis. METHODOLOGY: Seven three-dimensional models of a single-rooted, single-canal lower second premolar were established, one healthy control and six endodontically treated and restored models. The shape of root canal preparations followed file configurations 30/.05, 30/.09, 35/.04, 35/.06, 40/.04, and 40/.06. Von- Mises equivalent stresses were calculated by applying 30 N, 90 N and 270 N loads to the buccal cusp tip, each one at 90º, 45º and 20º angles from the occlusal plane simulating occlusion, dental interference and laterality, respectively. RESULTS: 45º loading was more prone to formation of higher stress values. The simulation of occlusion and laterality resulted in maximum stress areas located at the inner side of the root curvature, while under occlusal interference they were on the lingual surface over the tooth's long axis. CONCLUSIONS: The angulation of occlusal loading and magnitude were determinants for stress distribution on dental structure. Both variations of size and taper were not determinants for the increase in the maximum stress areas.
Assuntos
Dente não Vital , Humanos , Dente não Vital/terapia , Análise de Elementos Finitos , Oclusão Dentária , Simulação por Computador , Preparo de Canal Radicular , Análise do Estresse Dentário/métodos , Estresse MecânicoRESUMO
PURPOSE: To evaluate the tendency of movement, stress distribution, and microstrain of single-unit crowns in simulated cortical and trabecular bone, implants, and prosthetic components of narrow-diameter implants with different lengths placed at the crestal and subcrestal levels in the maxillary anterior region using 3D finite element analysis (FEA). MATERIALS AND METHODS: Six 3D models were simulated using Invesalius 3.0, Rhinoceros 4.0, and SolidWorks software. Each model simulated the right anterior maxillary region including a Morse taper implant of Ø2.9 mm with different lengths (7, 10, and 13 mm) placed at the crestal and subcrestal level and supporting a cement-retained monolithic single crown in the area of tooth 12. The FEA was performed using ANSYS 19.2. The simulated applied force was 178 N at 0°, 30°, and 60°. The results were analyzed using maps of displacement, von Mises (vM) stress, maximum principal stress, and microstrain. RESULTS: Models with implants at the subcrestal level showed greater displacement. vM stress increased in the implant and prosthetic components when implants were placed at the subcrestal level compared with the crestal level; the length of the implants had a low influence on the stress distribution. Higher stress and strain concentrations were observed in the cortical bone of the subcrestal placement, independent of implant length. Non-axial loading influenced the increased stress and strain in all the evaluated structures. CONCLUSIONS: Narrow-diameter implants positioned at the crestal level showed a more favorable biomechanical behavior for simulated cortical bone, implants, and prosthetic components. Implant length had a smaller influence on stress or strain distribution than the other variables.
Assuntos
Implantes Dentários , Análise de Elementos Finitos , Análise do Estresse Dentário/métodos , Planejamento de Prótese Dentária , Software , Estresse Mecânico , Fenômenos BiomecânicosRESUMO
Based on its mechanical properties, PEEK (polyether-ether-ketone) might be useful in restorative procedures. In oral rehabilitation, its viability has been studied mainly for prostheses and dental implants. AIM: The aim of this study was to evaluate the fit accuracy of dental implant bars made of either PEEK or cobalt-chrome submitted to cycling mechanics. MATERIALS AND METHOD: This was an experimental in vitro study, where units were treated with two implants and mini-abutments, joined by cobalt-chrome or polyether-ether-ketone PEEK bars. A total 20 bars were prepared (n=10 per group) and subjected to mechanical cycling tests (1 million cycles on the distal cantilever of the bar in the vertical direction, 120N and sinusoidal loading, at a frequency of 2Hz). The fit at the abutment/implant interface was measured before and after cycling, and the counter-torque of the vertical screw of the mini abutments was measured after cycling, using a digital torquemeter. Data were analyzed by three-way ANOVA and Tukey's test at 5% significance level. RESULTS: No statistically significant interaction was found among the three factors considered (bar material, implant positioning and mechanical cycling) (p = 0.592). No significant difference was identified in the interaction between bar material and implant positioning (p = 0.321), or between implant positioning and mechanical cycling (p = 0.503). The association between bar material and mechanical cycling was statistically significant (p = 0.007), with the cobalt-chrome bar resulting in greater misfit with mechanical cycling. There was no difference in counter-torque values between groups. CONCLUSIONS: The PEEK bar provided better fit of the mini abutments to the implants, even after mechanical cycling. The counter-torque of the screws was similar in all scenarios considered.
O PEEK (Poli-éter-éter-cetona) é um material considerado para uso em procedimentos restauradores devido às suas propriedades mecânicas. Na reabilitação oral, sua viabilidade tem sido estudada principalmente para uso em próteses e implantes dentários. Objetivos: O objetivo deste estudo foi avaliar a precisão da adaptação de duas barras diferentes do tipo protocolo confeccionadas em PEEK ou Cobalto-Cromo, após serem submetidas à mecânica ciclística. Materiais e Método: As unidades experimentais foram constituídas por barras confeccionadas em Poli-ether-ether-Ketone (PEEK) e em Cobalto-Cromo (Co-Cr). Trata-se de um estudo experimental, in vitro, onde verificou-se unidades constituídas por dois implantes e mini pilares unidos com barras de Cobalto-Cromo ou PEEK. Foram confeccionados um total de 20 barras (n=10 em cada grupo) e as barras foram submetidas a ensaios de ciclagem mecânica (1 milhão de ciclos no cantilever distal da barra no sentido vertical, 120N e carregamento senoidal, a uma frequência de 2Hz). Antes e após a ciclagem realizou-se a mensuração da desadaptação na interface pilar/implante e após a ciclagem foi medido o contra-torque do parafuso vertical dos mini-pilares através de torquímetro digital TQ 8800 (LT Lutron, Taiwan). Os dados foram submetidos a ANOVA a três critérios e teste de Tukey ao nível de significância a 5%. Resultados: Constatou-se que não houve interação estatisticamente significativa entre os três fatores estudados, ou seja, entre o material da barra, o posicionamento do implante e a ciclagem mecânica (p = 0,592). Também não se identificou diferença estatística significativa da interação entre o material da barra e o posicionamento do implante (p = 0,321), nem entre o posicionamento do implante e a ciclagem mecânica (p = 0,503). Já a associação entre o material da barra e a ciclagem mecânica foi estatisticamente significativa (p = 0,007), onde a barra de Cobalto-Cromo resultou em maior desadaptação com a ciclagem mecânica. Não houve diferença nos valores dos contra-torques entre os grupos. Conclusões: Conclui-se que a barra de protocolo fabricada em PEEK proporcionou melhor adaptação dos mini pilares aos implantes mesmo após a ciclagem mecânica. Por fim, o contra-torque dos parafusos foi semelhante em todos os cenários avaliados.
Assuntos
Implantes Dentários , Dente Suporte , Polietilenoglicóis , Cetonas , Cobalto , Éteres , Análise do Estresse Dentário/métodos , Teste de MateriaisRESUMO
BACKGROUND: Abutment screw loosening is a common complication of implant supported prostheses, especially for single crowns. In engineering, anaerobic adhesives (AA) are used to provide chemical locking between screw surfaces, but their application in implantology remains unclear. PURPOSE: The purpose of this article is to evaluate, in vitro, the effect of AA on counter-torque of abutment screws for cemented prosthesis on dental implants with external hexagon connection (EHC) and conical connection (CC). MATERIALS AND METHODS: Sample was composed by 60 specimens, 30 dental implants with EHC and 30 with CC. Abutments (transmucosal 3 mm straight universal abutment) were installed without AA (control group) or with application of AA with two different adhesive strength: medium strength (LOCTITE® 242) and high strength (LOCTITE® 277). The specimens were subjected to mechanical cycling at 37°C, with a load setting of 133 N, a 1.3 Hz frequency, and 1 200 000 cycles. The abutments were removed, and the counter-torque values were registered. Screws and implants were inspected using a stereomicroscope to verify the presence of residual adhesive and damage the internal structures. The data were analyzed using descriptive statistics and comparison tests (p < 0.05). RESULTS: Comparing to the torque of installation, the medium strength AA kept the counter-torque values for CC implants and the high strength AA kept the counter-torque for EHC implants and increased for CC implants. In the intergroup comparisons, control group presented significantly lower counter-torque values than other groups, both for EHC and CC implants. High strength AA presented similar results to medium strength AA in the EHC implants, but in the CC implants presented higher counter-torque values. Damage in threads was more frequent in the groups that received high strength AA. CONCLUSION: The use of AA increased the counter-torque of abutment screws, both in implants with EHC and CC.
Assuntos
Implantes Dentários , Projeto do Implante Dentário-Pivô , Torque , Anaerobiose , Cimentos Dentários , Análise do Estresse Dentário/métodos , Parafusos Ósseos , Dente SuporteRESUMO
Aim: To evaluate the bond strength of a universal adhesive system to dentin submitted to radiotherapy. Materials and Methods: Sixty extracted human teeth were divided into two groups (n = 30): without radiotherapy (control); with radiotherapy, according to the adhesive protocol (n=15): ER-etch-and-rinse (acid + Single Bond Uni-versal); SE-self-etch (Single Bond Universal). The analyzes were shear bond strength (SBS) (n=10), failure pattern (n=10) and scanning electron microscopy (n=5). Data was analyzed by a two-way ANOVA (α =0.05). Results: The radiotherapy decreased SBS of the restorative material to dentin (p<0.0001). The ER protocol provided lower bond strength values (p<0.001). The predominant type of fracture without radiotherapy was mixed (SE), cohesive to the material (ER). Both protocols presented adhesive failures with radiotherapy. Teeth had a hybrid layer and long resin tags (without radiotherapy) and few tags (with radiotherapy). Conclusions: The SE adhesive mode favors the shear bond strength of resin to dentin in teeth submitted to radiotherapy.
Objetivo: Evaluar la fuerza de adhesión de un sistema adhesivo universal a la dentina sometida a radioterapia. Materiales y Métodos: Sesenta dientes humanos extraídos se dividieron en dos grupos (n = 30): sin radioterapia (control); con radioterapia, según protocolo adhesivo (n=15): ER-grabado y enjuague (ácido + Single Bond Universal); autograbado SE (Single Bond Universal). Los análisis ejecutados fueron resistencia al cizallamiento (SBS) (n=10), patrón de falla (n=10) y microscopía electrónica de barrido (n=5). Los datos se sometieron al test de ANOVA de dos vías (α =0,05). Resultados: La radioterapia disminuyó la SBS del material restaurador a la dentina (p<0,0001). El protocolo ER proporcionó valores de fuerza de unión más bajos (p<0,001). El tipo de fractura predominante sin radioterapia fue mixta (SE), cohesiva al material (ER). Ambos protocolos presentaron fallas adhesivas con radioterapia. Los dientes tenían una capa híbrida y colas de resina largas (sin radioterapia) o pocas colas de resina (con radioterapia). Conclusión: El modo adhesivo SE favorece la resistencia al corte de la resina a la dentina en dientes sometidos a radioterapia.
Assuntos
Humanos , Colagem Dentária/métodos , Adesivos Dentinários/química , Cimentos Dentários/química , Análise do Estresse Dentário/métodos , Resinas Compostas , DentinaRESUMO
This study aimed to test and compare 2 novel dental mini-implant designs to support overdentures with a commercial model, regarding the stress distribution, by photoelastic analysis. Three different mini-implant designs (Ø 2.0 mm × 10 mm) were tested: G1-experimental threaded (design with threads and 3 longitudinal and equidistant self-cutting chamfers), G2-experimental helical (design with 2 long self-cutting chamfers in the helical arrangement), and G3-Intra-Lock System. After including the mini-implants in a photoelastic resin, they were subjected to a static load of 100 N under two situations: axial and inclined model (30°). The fringe orders (n), that represents the intensity of stresses were analyzed around the mini-implants body and quantified using Tardy's method that calculates the maximum shear stress (τ) value in each point selected. In axial models, less stress was observed in the cervical third mini-implants, mainly in G1 and G2. In inclined models (30°), higher stresses were generated on the opposite side of the load application, mainly in the cervical third of G2 and G3. All mini-implant models presented lower tensions in the cervical third compared with the middle and apical third. The new mini-implants tested (G1 and G2) showed lower stresses than the G3 in the cervical third under axial load, while loading in the inclined model generated greater stresses in the cervical of G2.
Assuntos
Implantes Dentários , Revestimento de Dentadura , Planejamento de Prótese Dentária , Prótese Dentária Fixada por Implante , Análise do Estresse Dentário/métodos , Estresse MecânicoRESUMO
STATEMENT OF PROBLEM: The mechanical behavior of the conical connection implant with different torque levels requires evaluation. PURPOSE: The purpose of this finite element analysis study was to investigate the impact of abutment screw torque on the formation of microgaps at the implant-to-abutment interface of a conical connection under oblique loading. This is important because it is thought that bacteria can invade the internal implant space through the abutment-implant microgaps, causing peri-implantitis. MATERIAL AND METHODS: Three-dimensional finite element analyses of the conical implant-abutment connection were performed by using screw torques of 20 Ncm and 30 Ncm. Oblique loads from 10 N to 280 N were applied to the prosthesis placed on the implant. The maximum von Mises stress in the abutment screw, the microgap formation process, and the critical load for bridging the internal implant space were evaluated. RESULTS: The stresses in the abutment screw under oblique loading had limited sensitivity to the screw torque. However, the residual stress in the screw with a 30-Ncm torque was 35% higher than that with a 20-Ncm torque in the absence of an external load. The area in contact at the implant-to-abutment interface decreased with increasing load for both torque values. The critical load for bridging the internal implant space was 160 N for a screw torque of 20 Ncm and 220 N for a screw torque of 30 Ncm. The maximum gap size was approximately 470 µm with all the loads. CONCLUSIONS: Increasing the screw torque can reduce the formation of microgaps at the implant-to-abutment interface. However, this will result in higher mean stress in the abutment screw, which may reduce its fatigue life and consequently that of the prosthesis. Further research is needed to evaluate the relationship between the abutment screw torque and microleakage in implant-supported restorations.