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BACKGROUND: The combination of a prosthetic index with Morse taper connection was developed, with the purpose of making prosthetic procedures more precise. However, the presence of the index may compromise the mechanical performance of the abutment. The aim of this study is to evaluate the effect of prosthetic index on stress distribution in implant-abutment-screw system and peri-implant bone by using the 3D finite element methodology. METHODS: Two commercial dental implant systems with different implant-abutment connections were used: the Morse taper connection with platform switching (MT-PS) implant system and the internal hex connection with platform matching (IH-PM) implant system. Meanwhile, there are two different designs of Morse taper connection abutment, namely, abutments with or without index. Consequently, three different models were developed and evaluated: (1) MT-PS indexed, (2) MT-PS non-indexed, and (3) IH-PM. These models were inserted into a bone block. Vertical and oblique forces of 100 N were applied to each abutment to simulate occlusal loadings. RESULTS: For the MT-PS implant system, the maximum stress was always concentrated in the abutment neck under both vertical and oblique loading. Moreover, the maximum von Mises stress in the neck of the MT-PS abutment with index even exceed the yield strength of titanium alloy under the oblique loading. For the IH-PM implant system, however, the maximum stress was always located at the implant. Additionally, the MT-PS implant system has a significantly higher stress level in the abutment neck and a lower stress level around the peri-implant bone compared to the IH-PM implant system. The combined average maximum stress from vertical and oblique loads is 2.04 times higher in the MT-PS indexed model, and 1.82 times for the MT-PS non-indexed model than that of the IH-PM model. CONCLUSIONS: MT-PS with index will cause higher stress concentration on the abutment neck than that of without index, which is more prone to mechanical complications. Nevertheless, MT-PS decreases stress within cancellous bone and may contribute to limiting crestal bone resorption.
Assuntos
Implantes Dentários , Ligas , Fenômenos Biomecânicos , Análise do Estresse Dentário/métodos , Análise de Elementos Finitos , Humanos , Estresse Mecânico , TitânioRESUMO
BACKGROUND: The objective of the study was to validate biomechanical characteristics of a 3D-printed, novel-designated fixation plate for treating mandibular angle fracture, and compare it with two commonly used fixation plates by finite element (FE) simulations and experimental testing. METHODS: A 3D virtual mandible was created from a patient's CT images as the master model. A custom-designed plate and two commonly used fixation plates were reconstructed onto the master model for FE simulations. Modeling of angle fracture, simulation of muscles of mastication, and defining of boundary conditions were integrated into the theoretical model. Strain levels during different loading conditions were analyzed using a finite element method (FEM). For mechanical test design, samples of the virtual mandible with angle fracture and the custom-designed fixation plates were printed using selective laser sintering (SLS) and selective laser melting (SLM) printing methods. Experimental data were collected from a testing platform with attached strain gauges to the mandible and the plates at different 10 locations during mechanical tests. Simulation of muscle forces and temporomandibular joint conditions were built into the physical models to improve the accuracy of clinical conditions. The experimental vs the theoretical data collected at the 10 locations were compared, and the correlation coefficient was calculated. RESULTS: The results show that use of the novel-designated fixation plate has significant mechanical advantages compared to the two commonly used fixation plates. The results of measured strains at each location show a very high correlation between the physical model and the virtual mandible of their biomechanical behaviors under simulated occlusal loading conditions when treating angle fracture of the mandible. CONCLUSIONS: Based on the results from our study, we validate the accuracy of our computational model which allows us to use it for future clinical applications under more sophisticated biomechanical simulations and testing.
Assuntos
Placas Ósseas , Análise de Elementos Finitos , Fixação Interna de Fraturas/instrumentação , Fraturas Mandibulares/cirurgia , Fenômenos Biomecânicos , Humanos , Estresse MecânicoRESUMO
The specific aim of this study was to examine whether slow drilling speeds (15 rpm) produce pilot holes that result in different implant insertion torques than pilot holes made with higher speed drilling (1500 rpm). To accomplish this, a new method is presented for transferring samples from a drilling machine onto an implant insertion torque measuring apparatus while maintaining the same center of rotation. Simulated bone blocks of polyurethane were used with 2 densities of foam to mimic trabecular and cortical bone. Pilot holes drilled using both drilling methods were morphologically characterized at macro and micro scales. Nobel Biocare Nobel Active implants were then placed. Profilometer and optical imaging were used to determine changes in the pilot hole morphology. Recorded insertion torque measurements were used to quantitatively contrast implants inserted into holes drilled using the 2 speeds. Although there were slight qualitative and quantitative differences between the low- and high-speed drilled pilot holes, the differences were insufficient to cause a statistically significant change in insertion torque.
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Implantes Dentários , Osso Cortical , Implantação Dentária Endóssea , Poliuretanos , TorqueRESUMO
STATEMENT OF PROBLEM: Most fractures of dentures occur during function, primarily because of the flexural fatigue of denture resins. PURPOSE: The purpose of this study was to evaluate a polymethyl methacrylate denture base material modified with multiwalled carbon nanotubes in terms of fatigue resistance, flexural strength, and resilience. MATERIAL AND METHODS: Denture resin specimens were fabricated: control, 0.5 wt%, 1 wt%, and 2 wt% of multiwalled carbon nanotubes. Multiwalled carbon nanotubes were dispersed by sonication. Thermogravimetric analysis was used to determine quantitative dispersions of multiwalled carbon nanotubes in polymethyl methacrylate. Raman spectroscopic analyses were used to evaluate interfacial reactions between the multiwalled carbon nanotubes and the polymethyl methacrylate matrix. Groups with and without multiwalled carbon nanotubes were subjected to a 3-point-bending test for flexural strength. Resilience was derived from a stress and/or strain curve. Fatigue resistance was conducted by a 4-point bending test. Fractured surfaces were analyzed by scanning electron microscopy. One-way ANOVA and the Duncan tests were used to identify any statistical differences (α=.05). RESULTS: Thermogravimetric analysis verified the accurate amounts of multiwalled carbon nanotubes dispersed in the polymethyl methacrylate resin. Raman spectroscopy showed an interfacial reaction between the multiwalled carbon nanotubes and the polymethyl methacrylate matrix. Statistical analyses revealed significant differences in static and dynamic loadings among the groups. The worst mechanical properties were in the 2 wt% multiwalled carbon nanotubes (P<.05), and 0.5 wt% and 1 wt% multiwalled carbon nanotubes significantly improved flexural strength and resilience. All multiwalled carbon nanotubes-polymethyl methacrylate groups showed poor fatigue resistance. The scanning electron microscopy results indicated more agglomerations in the 2% multiwalled carbon nanotubes. CONCLUSIONS: Multiwalled carbon nanotubes-polymethyl methacrylate groups (0.5% and 1%) performed better than the control group during the static flexural test. The results indicated that 2 wt% multiwalled carbon nanotubes were not beneficial because of the inadequate dispersion of multiwalled carbon nanotubes in the polymethyl methacrylate matrix. Scanning electron microscopy analysis showed agglomerations on the fracture surface of 2 wt% multiwalled carbon nanotubes. The interfacial bonding between multiwalled carbon nanotubes and polymethyl methacrylate was weak based on the Raman data and dynamic loading results.
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Resinas Compostas/química , Materiais Dentários/química , Bases de Dentadura , Nanotubos de Carbono/química , Polimetil Metacrilato/química , Resinas Acrílicas/química , Elasticidade , Humanos , Teste de Materiais , Microscopia Eletrônica de Varredura , Maleabilidade , Análise Espectral Raman , Estresse Mecânico , Propriedades de Superfície , Temperatura , TermogravimetriaRESUMO
Surgery of jawbones has a high potential risk of causing complications associated with temporomandibular joint disorder (TMD). The objective of this study was to investigate the effects of two drive modeling methods on the biomechanical behavior of the temporomandibular joint (TMJ) including articular disc during mandibular movements. A finite element (FE) model from a healthy human computed tomography was used to evaluate TMJ dynamic using two methods, namely, a conventional spatial-oriented method (displacement-driven) and a compliant muscle-initiated method (masticatory muscle-driven). The same virtual FE model was 3D printed and a custom designed experimental platform was established to validate the accuracy of experimental and theoretical results of the TMJ biomechanics during mandibular movements. The results show that stress distributed to TMJ and articular disc from mandibular movements provided better representation from the muscle-driving approach than those of the displacement-driven modeling. The simulation and experimental data exhibited significant strong correlations during opening, protrusion, and laterotrusion (with canonical correlation coefficients of 0.994, 0.993, and 0.932, respectively). The use of muscle-driven modeling holds promise for more accurate forecasting of stress analysis of TMJ and articular disc during mandibular movements. The compliant approach to analyze TMJ dynamics would potentially contribute to clinic diagnosis and prediction of TMD resulting from occlusal disease and jawbone surgery such as orthognathic surgery or tumor resection.
RESUMO
Long-term excessive forces loading from muscles of mastication during mandibular motions may result in disorders of temporomandibular joint (TMJ), myofascial pain, and restriction of jaw opening and closing. Current analysis of mandibular movements is generally conducted with a single opening, protrusive and lateral movements rather than composite motions that the three can be combined arbitrarily. The objective of this study was to construct theoretical equations reflecting the correlation between composite motions and muscle forces, and consequently to analyze the mandibular composite motions and the tensions of muscles of mastication in multiple dimensions. The muscle performances such as strength, power, and endurance of mandibular motions were analyzed and the effective motion range of each muscle was derived. The mandibular composite motion model was simplified by calculating muscle forces. An orthogonal rotation matrix based on muscle forces was established. A 3D printed mandible was used for in vitro simulation of mandibular motions on a robot and measurements of force were conducted. The theoretical model and forces were verified through a trajectory tracing experiment of mandibular motions driven by a 6-axis robot with force/torque sensors. Through the analysis of the mandibular composite motion model, the motion form was obtained and transferred to guide the motions of the robot. The error between the experimental data obtained by the 6-axis force/torque sensors and the theoretical data was within 0.6 N. Our system provides excellent visualization for analyzing the changes of muscle forces and locations during various mandibular movements. It is useful for clinicians to diagnose and formulate treatment for patients who suffer from (temporomandibular joint disorders) TMDs and restrict jaw movements. The system can potentially offer the comparison before and after treatment of TMDs or jaw surgery.
Assuntos
Mandíbula , Transtornos da Articulação Temporomandibular , Humanos , Articulação Temporomandibular , Movimento , Mastigação/fisiologia , Amplitude de Movimento Articular/fisiologiaRESUMO
Polyetheretherketone (PEEK) and its derivative polyetherketoneketone (PEKK) have been used as implant materials for spinal fusing and enjoyed their success for many years because of their mechanical properties similar to bone and their chemical inertness. The osseointegration of PEEKs is datable. Our strategy was to use custom-designed and 3D printed bone analogs with an optimized structure design and a modified PEKK surface to augment bone regeneration for mandibular reconstruction. Those bone analogs had internal porosities and a bioactive titanium oxide surface coating to promote osseointegration between native bone and PEKK analogs. Our workflow was 3D modeling, bone analog designing, structural optimization, mechanical analysis via finite element modeling, 3D printing of bone analogs and subsequently, an in vivo rabbit model study on mandibular reconstruction and histology evaluation. Our results showed the finite element analysis validated that the porous PEKK analogs provided a mechanical-sound structure for functional loadings. The bone analogs offered a perfect replacement for segmented bones in the terms of shape, form and volume for surgical reconstruction. The in vivo results showed that bioactive titanium oxide coating enhanced new bone in-growth into the porous PEKK analogs. We have validated our new approach in surgical mandibular reconstruction and we believe our strategy has a significant potential to improve mechanical and biological outcomes for patients who require mandibular reconstruction procedures.
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Reconstrução Mandibular , Animais , Coelhos , Porosidade , Polietilenoglicóis/farmacologia , Polietilenoglicóis/química , Cetonas/farmacologia , Cetonas/química , Impressão Tridimensional , Mandíbula/cirurgiaRESUMO
BACKGROUND: The purpose of this study is to develop a methodology to better control a human-robot collaboration for robotic dental implant placement. We have designed a human-robot collaborative implant system (HRCDIS) which is based on a zero-force hand-guiding concept and a operational task management workflow that can achieve highly accurate and stable osteotomy drilling based on a surgeon's decision and robotic arm movements during implant surgery. METHOD: The HRCDIS brings forth the robot arm positions, exact drilling location, direction and performs automatic drilling. The HRCDIS can also avoid complex programing in the robot. The purpose of the study is to evaluate the accuracy of drilling resulting from our developed operational task management method (OTMM). The OTMM can enable the robot to switch, pause, and resume drilling tasks. The force required for hand-guiding in a zero-force control mode of the robot was detected by a 6D force sensor. We compared our force data to those provided by the manufacturer's manual. The study was conducted on a phantom head with a 3D-printed jaw bone to verify the validity of our HRCDIS. We appraised the discrepancies between free-hand drillings and the HRCDIS controlled drillings at apical centre and head centre of the implant and implant angulation to the baseline data from a virtual surgical planning model. RESULTS: The average required force used by hand-guiding to operate the robot with HRCDIS was near 7 Newton which is much less than the manufacturer's specification (30 Newton). The results from our study showed that the average error at implant head was 1.04 ± 0.37 mm, 1.56 ± 0.52 mm at the implant apex, and deviation of implant angle was 3.74 ± 0.67°. CONCLUSIONS: The results from this study validate the merit of the human-robot collaboration control by the HRCDIS. Based on the improved navigation system using HRCDIS, a robotic implant placement can provide seamless drilling with ease, efficiency and accuracy.
Assuntos
Implantes Dentários , Procedimentos Cirúrgicos Robóticos , Robótica , Cirurgia Assistida por Computador , Humanos , Imagens de FantasmasRESUMO
This study aims to characterize biomechanical behavior of various designs of posterior mandibular marginal resection under functional loadings using finite element method. The ultimate goal of this work is to provide clinically relevant information to prevent postoperative fracture and to stipulate prophylactic internal fixation for planning of marginal mandibulectomy. A 3D mandibular master model was reconstructed from cone beam computed tomography images. Different marginal resection models were created based on three design parameters, namely, defect curvilinear radius, anterior-posterior defect width and residual height of the mandibular body. Functional loadings from incisors (60 N) and contralateral first molar area (200 N) were applied to designed models and stress patterns were compared of five groups with curvilinear radius from 0 (conventional rectangular shape), 2.5, 3.5, 5, and 6 mm. Models with 25, 35 and 45 mm defect width mimic defects varied from canine to 3rd molar were tested. Residual height range from 10 to 4 mm was assessed. The results show high stresses predominated in the occlusal area and the posterior inferior border near the resection corner. The average maximum stress decreased by 29.8% (r = 2.5 mm), 51.9% (r = 3.5 mm), 54.4% (r = 5 mm), and 59.3% (r = 6 mm) compared to the baseline of r = 0 mm. The results from the combined defect width/residual height models demonstrate the increase of defect width and the decrease in residual height resulted in the increase of maximum stress. Our data also confirm that the factor of residual height supersedes defect width in terms of prevention of postoperative fracture when considering resection design.
Assuntos
Tomografia Computadorizada de Feixe Cônico , Mandíbula , Fenômenos Biomecânicos , Análise de Elementos Finitos , Fixação Interna de Fraturas/métodos , Incisivo , Mandíbula/diagnóstico por imagem , Mandíbula/cirurgia , Estresse MecânicoRESUMO
BACKGROUND: Customized prosthetic joint replacements have crucial applications in severe temporomandibular joint problems, and the combined use of porous titanium scaffold is a potential method to rehabilitate the patients. OBJECTIVE: The objective of the study was to develop a design method to obtain a titanium alloy porous condylar prosthesis with good function and esthetic outcomes for mandibular reconstruction. METHODS: A 3D virtual mandibular model was created from CBCT data. A condylar defect model was subsequently created by virtual condylectomy on the initial mandibular model. The segmented condylar defect model was reconstructed by either solid or porous condyle with a fixation plate. The porous condyle was created by a density-driven modeling scheme with an inhomogeneous tetrahedral lattice structure. The porous condyle, supporting fixation plate, and screw locations were topologically optimized. Biomechanical behaviors of porous and solid condylar prostheses made of Ti-6Al-4V alloy were compared. Finite element analysis (FEA) was used to evaluate maximum stress distribution on both prostheses and the remaining mandibular ramus. RESULTS: The FEA results showed levels of maximum stresses were 6.6%, 36.4% and 47.8% less for the porous model compared to the solid model for LCI, LRM, and LBM loading conditions. Compared to the solid prosthesis, the porous prosthesis had a weight reduction of 57.7% and the volume of porosity of the porous condyle was 65% after the topological optimization process. CONCLUSIONS: A custom-made porous condylar prosthesis with fixation plate was designed in this study. The 3D printed Ti-6Al-4V porous condylar prosthesis had reduced weight and effective modulus of elasticity close to that of cortical bone. The.
Assuntos
Prótese Articular , Titânio , Análise de Elementos Finitos , Humanos , Mandíbula , Porosidade , Impressão Tridimensional , Desenho de Prótese , Articulação Temporomandibular/cirurgia , Titânio/químicaRESUMO
PURPOSE: The purpose of this study was to analyze mechanical behaviors of a topologically optimized and 3D-printed mandibular bone block with polyetherketoneketone (PEKK) for surgical mandibular reconstruction. MATERIALS AND METHODS: 3D virtual mandibular models were reconstructed from cone beam computed tomography images. A proposed mandibular resection of the mandibular body (40 mm anterior-posteriorly) was segmented. Internal structure of the resected bone was designed with topological optimization. Dental implants and implant-supported crowns were integrated into the design. A second 3D virtual model was created with the same size and location of the defect but was reconstructed with a fibular graft and implant-supported crowns. The biomechanical behaviors of the two models were compared by finite element method (FEM) under the same boundary constraints and three loading locations, namely, central incisors, lower left and right side first molar areas. RESULTS: The FEM results showed the maximum stresses and displacements of the topology optimized model were much lower than those of the model with fibular bone graft. The highest stress of the optimized mandibular model was located on the lower edge of the posterior border of bone analog, and fixation screws. The maximum displacement occurred at the lower edge of the proximal mandibular stump or the lower edge of the distal mandibular body on the contralateral site. Under the same three loading locations, the maximum stress of the optimized model significantly decreased by 67.9%, 71.9% and 68.6% compared to the fibular graft model. CONCLUSIONS: The 3D printed bone analog with topological optimization is patient-specific and has advantages over the conventional fibular bone graft for surgical mandibular reconstruction. The optimized PEKK bone analog model creates more normal stress-strain trajectories than the fibular graft model and likely provides better functional and cosmetic outcomes.
Assuntos
Implantes Dentários , Reconstrução Mandibular , Impressão Tridimensional , Benzofenonas , Fenômenos Biomecânicos , Análise do Estresse Dentário , Análise de Elementos Finitos , Humanos , Mandíbula/diagnóstico por imagem , Mandíbula/cirurgia , Polímeros , Estresse MecânicoRESUMO
BACKGROUND: For large mandibular defects, surgical reconstruction using microvascular fibular grafts has advantages over other alternatives in terms of blood supply and good quality of grafted bone. However, the fibular segment is usually lower in height than that of the original mandible, meaning that the vertical positioning of the fibular graft is variable, with different biomechanical consequences on the reconstructed mandible. OBJECTIVES: To use finite element method (FEM) to evaluate stress distribution and displacement of a reconstructed mandible versus an intact mandible under occlusal loads. METHODS: A three-dimensional intact edentulous mandibular bone (Model I) and a reconstructed mandible bone with fibular graft were created from CBCT images. Calculation models were generated with fibular bone graft extracted from the reconstructed mandible of identical length placed into a mimicked defect area on the right-hand side of the mandible at three different vertical positions: superior (Model II), intermediate (Model III), and inferior (Model IV). Forces were applied at lower left first molar region and lower left central incisor area. Von Mises stresses and mandibular displacement were calculated as outcome measurements during loadings. RESULTS: Maximum stress and strain within the reconstructed mandible were identified at the posterior border of the graft and the contralateral condyle. Maximum displacement occurred near the interface of fibular graft and anterior segment of the mandible. Stress distribution in the graft under functional loads is much higher than that in the residual mandibular segments from Models II to IV. The combined average maximum stress from anterior and posterior loads is 10.66 times higher in the mandible with inferiorly positioned graft (Model IV), 8.72 times for superior graft (Model II), and 3.68 times for intermediate graft (Model III) than that in the control group (Model I). The worst displacement result during functional loadings was in the group with fibular graft located at the inferior border of the mandible. CONCLUSIONS: The position of fibular graft placed in the surgical resection site has significant effects on the mechanical behavior of the reconstructed mandible. The fibular graft aligned with the inferior border of the mandible, the most common site designated location by clinicians, has the worst effects on the stress distribution and displacement to the mandibular under functional loads. The fibular graft placed at the intermediate location has the best biomechanics and provides favorable condition for subsequent prosthetic reconstruction.
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Fíbula/transplante , Mandíbula/fisiologia , Mandíbula/cirurgia , Reconstrução Mandibular/métodos , Fenômenos Biomecânicos , Fíbula/irrigação sanguínea , Análise de Elementos Finitos , Humanos , Imageamento Tridimensional , Mandíbula/irrigação sanguínea , Mandíbula/diagnóstico por imagemRESUMO
OBJECTIVE: To investigate the stress distribution to the mandible, with and without impacted third molars (IM3s) at various orientations, resulting from a 2000-Newton impact force either from the anterior midline or from the body of the mandible. MATERIALS AND METHODS: A 3D mandibular virtual model from a healthy dentate patient was created and the mechanical properties of the mandible were categorized to 9 levels based on the Hounsfield unit measured from computed tomography (CT) images. Von Mises stress distributions to the mandibular angle and condylar areas from static impact forces (Load I-front blow and Load II left blow) were evaluated using finite element analysis (FEA). Six groups with IM3 were included: full horizontal bony, full vertical bony, full 450 mesioangular bony, partial horizontal bony, partial vertical, and partial 450 mesioangular bony impaction, and a baseline group with no third molars. RESULTS: Von Mises stresses in the condyle and angle areas were higher for partially than for fully impacted third molars under both loading conditions, with partial horizontal IM3 showing the highest fracture risk. Stresses were higher on the contralateral than on the ipsilateral side. Under Load II, the angle area had the highest stress for various orientations of IM3s. The condylar region had the highest stress when IM3s were absent. CONCLUSIONS: High-impact forces are more likely to cause condylar rather than angular fracture when IM3s are missing. The risk of mandibular fracture is higher for partially than fully impacted third molars, with the angulation of impaction having little effect on facture risk.
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Análise do Estresse Dentário , Mandíbula/fisiopatologia , Fraturas Mandibulares/diagnóstico por imagem , Fraturas Mandibulares/fisiopatologia , Dente Serotino/fisiopatologia , Adulto , Algoritmos , Fenômenos Biomecânicos , Simulação por Computador , Módulo de Elasticidade , Feminino , Análise de Elementos Finitos , Humanos , Imageamento Tridimensional , Modelos Biológicos , Estresse Mecânico , Tomografia Computadorizada por Raios XRESUMO
BACKGROUND: The aim of this study was to simulate stress and strain distribution numerically on a normal mandible under physiological occlusal loadings. The results were compared with those of mandibles that had an angle fracture stabilized with different fixation designs under the same loadings. The amount of displacement at two interfragmentary gaps was also studied. MATERIALS AND METHODS: A three-dimensional (3D) virtual mandible was reconstructed with an angle fracture that had a fracture gap of either 0.1 or 1 mm. Three types of plate fixation designs were used: Type I, a miniplate was placed across the fracture line following the Champy technique; Type II, two miniplates were used; and Type III, a reconstruction plate was used on the inferior border of the mandible. Loads of 100 and 500 N were applied to the models. The maximum von Mises stress, strain, and displacement were computed using finite element analysis. The results from the control and experimental groups were analyzed and compared. RESULTS: The results demonstrated that high stresses and strains were distributed to the condylar and angular areas regardless of the loading position. The ratio of the plate/bone average stress ranged from 215% (Type II design) to 848% (Type I design) irrespective of the interfragmentary gap size. With a 1-mm fracture gap, the ratio of the plate/bone stress ranged from 204% (Type II design) to 1130% (Type I design). All strains were well below critical bone strain thresholds. Displacement on the cross-sectional mapping at fracture interface indicated that uneven movement occurred in x, y, and z directions. CONCLUSIONS: Interfragmentary gaps between 0.1 and 1 mm did not have a substantial effect on the average stress distribution to the fractured bony segments; however, they had a greater effect on the stress distribution to the plates and screws. Type II fixation was the best mechanical design under bite loads. Type I design was the least stable system and had the highest stress distribution and the largest displacement at the fracture site.
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Mandíbula/fisiologia , Traumatismos Mandibulares/fisiopatologia , Simulação por Computador , Fixação Interna de Fraturas/métodos , Humanos , Imageamento Tridimensional , Masculino , Mandíbula/cirurgia , Traumatismos Mandibulares/cirurgia , Pessoa de Meia-Idade , Estresse Mecânico , Tomografia Computadorizada por Raios XRESUMO
The specific aim of this study was to examine the relative contributions to the implant insertion torque value (ITV) by cortical and trabecular components of an in vitro bone model. Simulated bone blocks of polyurethane were used with 2 densities of foam (0.08 g/cm(3) to mimic trabecular bone and 0.64 g/cm(3) to mimic cortical bone). We have developed a new platform technology to collect data that enables quantitative evaluation of ITV at different implant locations. Seven groups were used to model varying thicknesses of cortical bone over a lower-quality trabecular bone that have clinical significance: a solid 0.08 g/cm(3) block; 1 mm, 2 mm, and 3 mm thick 0.64 g/cm(3) sheets with no underlayer; and 1 mm, 2 mm, and 3 mm thick 0.64 g/cm(3) sheets laminated on top of a 4 cm thick 0.08 g/cm(3) block. The ITVs were recorded as a function of insertion displacement distance. Relative contributions of ITV ranged from 3% to 18% from trabecular bone, and 62% to 74% from cortical bone depending on the thickness of the cortical layer. Inserting an implant into 2-mm and 3-mm cortical layers laminated atop trabecular blocks had a synergistic effect on ITVs. Finally, an implant with a reverse bevel design near the abutment showed final average torque values that were 14% to 34% less than their maximum torque values. This work provides basic quantitative information for clinicians to understand the influence of composite layers of bone in relation to mechanical torque resistances during implant insertion in order to obtain desired primary implant stability.
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Osso Cortical , Implantes Dentários , Densidade Óssea , Osso e Ossos , TorqueRESUMO
The purpose of this study was to compare the effectiveness of three methods using calcium sulfate as a graft/barrier for the treatment of Class II mandibular furcation defects. Thirty-six defects in 17 patients were treated with a graft/barrier of pure calcium sulfate, calcium sulfate plus doxycycline, or demineralized freeze-dried bone allograft (DFDBA) in a 2:1 ratio by volume. Defects were randomly selected for treatment, and all measurement parameters were standardized to a light-cured acrylic resin stent at baseline and 6, 9, and 12 months. Linear regression, ANOVA, and chi-squared analysis revealed that all three groups showed significant bone fill (P < .05), vertical and horizontal probing depth reduction, defect volume reduction, and a gain in vertical clinical attachment. Furthermore, the addition of either doxycycline or DFDBA to calcium sulfate significantly enhanced the clinical outcome more than did the calcium sulfate alone, and the addition of DFDBA was more effective in the treatment of Class II mandibular furcation defects than doxycycline.
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Materiais Biocompatíveis/uso terapêutico , Substitutos Ósseos/uso terapêutico , Sulfato de Cálcio/uso terapêutico , Defeitos da Furca/cirurgia , Dente Molar/cirurgia , Adulto , Idoso , Análise de Variância , Antibacterianos/uso terapêutico , Transplante Ósseo/métodos , Distribuição de Qui-Quadrado , Doxiciclina/uso terapêutico , Feminino , Seguimentos , Defeitos da Furca/classificação , Humanos , Modelos Lineares , Masculino , Mandíbula/cirurgia , Pessoa de Meia-Idade , Perda da Inserção Periodontal/classificação , Perda da Inserção Periodontal/cirurgia , Bolsa Periodontal/classificação , Bolsa Periodontal/cirurgia , Transplante Homólogo , Resultado do TratamentoRESUMO
Precision and surface quality of pure titanium (Ti) castings for dental and biomedical uses are limited because of the high melting temperature and the violent reactivity of Ti with mold materials during casting procedures. This feasibility study evaluates an experimental low-melting Ti-Co alloy in term of its microstructure and physical and mechanical properties. Tensile samples of Ti-12 wt % Co alloy were cast under a protective argon atmosphere. The melting range of the cast samplers was determined. Cast samples were annealed at 1010°C for various time intervals in order to homogenize microstructures. Microstructures were examined by optical and scanning electron microscopy. Tensile strength and microhardness tests were performed and correlated with microstructures resulting from annealing processes. Ti2Co intermetallic compound coexisted with Ti-Co solid solution in all samples. The melting range of the alloy was 1062-1088°C, which is 568°C lower than that of Ti. The thickness of the surface oxide scale on cast samples was dramatically reduced to 1-3 µm because of the low-melting nature of the alloy. Solution treatment at 1010°C for 100 h yields the highest tensile strength. Ultimate tensile strength is measured from 852 to 1240 MPa which is stronger than currently used dental alloys. Microhardness values were ranged from 341 to 488 KHN and elongation was from 1.2 to 1.8%. Both microhardness and percentage elongation are similar to those of dental Co-Cr alloys. One hundred hours of annealing dissolved dendritic boundaries and transformed the alloy to a more microductitle matrix, however, the intermetallic compound of Ti2Co remained.
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Cobalto/química , Ligas Dentárias/química , Titânio/química , Ligas , Argônio , Elasticidade , Dureza , Teste de Materiais , Microscopia Eletrônica de Varredura , Estresse Mecânico , Propriedades de Superfície , Temperatura , Resistência à TraçãoRESUMO
BACKGROUND: To examine the effect of the natural antimicrobial peptide human ß-defensin-3 (hBD-3), on the migration of a head and neck cancer cell line in vitro using microfabrication and soft-lithographic techniques. METHODS: TR146 cancer cells were seeded in Petri dishes with microfabricated wells for cell migration assays. Total 54 cell islands were used of various shape and size and experimental media type. Cell migration assays were analyzed in six group media: Dulbecco's modified medium (DMEM); DMEM with vascular endothelial growth factor (VEGF); Conditioned media of human embryonic kidney cells (HEK 239) expressing hBD-3 via transfected cloned pcDNA3 as CM/hBD-3; CM/hBD-3+ VEGF; conditioned medium from non-transfected HEK 239 (not expressing hBD-3) as control (CM); and the last group was CM + VEGF. Cell islands were circular or square and varied in size (0.25 mm(2), 0.125 mm(2), and 0.0625 mm(2)). Cell islands were imaged at t=0 h, 3 h, 6 h, and 24 h. RESULTS: The results show cancer cell islands that originally were smaller had higher migration indices. There was no difference of MIs between circular and square cell islands. MIs at the end point were significantly different among the groups except between CM and CM-hBD-3+ VEGF. CONCLUSIONS: VEGF enhanced cancer cell migration. The combination of DMEM and VEGF showed a synergistic effect on this phenomenon of cancer cell migration. Conditioned medium with hBD-3 suppressed cancer cell migration. hBD-3 suppressed VEGF enhancement of TR146 cancer cell migration.