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1.
Biomech Model Mechanobiol ; 19(1): 133-145, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31396806

RESUMO

The biomechanics associated with buccal bone thickness (BBT) augmentation remains poorly understood, as there is no consistent agreement in the adequate BBT to avoid over-loading resorption or over-augmenting surgical difficulty. This study utilizes longitudinal clinical image data to establish a self-validating time-dependent finite element (FE)-based remodeling procedure to explore the effects of different buccal bone thicknesses on long-term bone remodeling outcomes in silico. Based upon the clinical computed tomography (CT) scans, a patient-specific heterogeneous FE model was constructed to enable virtual BBT augmentation at four different levels (0.5, 1.0, 1.5, and 2.0 mm), followed by investigation into the bone remodeling behavior of the different case scenarios. The findings indicated that although peri-implant bone resorption decreased with increasing initial BBT from 0.5 to 2 mm, different levels of the reduction in bone loss were associated with the amount of bone augmentation. In the case of 0.5 mm BBT, overloading resorption was triggered during the first 18 months, but such bone resorption was delayed when the BBT increased to 1.5 mm. It was found that when the BBT reached a threshold thickness of 1.5 mm, the bone volume can be better preserved. This finding agrees with the consensus in dental clinic, in which 1.5 mm BBT is considered clinically justifiable for surgical requirement of bone graft. In conclusion, this study introduced a self-validating bone remodeling algorithm in silico, and it divulged that the initial BBT affects the bone remodeling outcome significantly, and a sufficient initial BBT is considered essential to assure long-term stability and success of implant treatment.

2.
J Mech Behav Biomed Mater ; 102: 103490, 2019 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-31877512

RESUMO

Mechanical failure of zirconia-based full-arch implant-supported fixed dental prostheses (FAFDPs) remains a critical issue in prosthetic dentistry. The option of full-arch implant treatment and the biomechanical behaviour within a sophisticated screw-retained prosthetic structure have stimulated considerable interest in fundamental and clinical research. This study aimed to analyse the biomechanical responses of zirconia-based FAFDPs with different implant configurations (numbers and distributions), thereby predicting the possible failure sites and the optimum configuration from biomechanical aspect by using finite element method (FEM). Five 3D finite element (FE) models were constructed with patient-specific heterogeneous material properties of mandibular bone. The results were reported using volume-averaged von-Mises stresses (σVMVA) to eliminate numerical singularities. It was found that wider placement of multi-unit copings was preferred as it reduces the cantilever effect on denture. Within the limited areas of implant insertion, the adoption of angled multi-unit abutments allowed the insertion of oblique implants in the bone and wider distribution of the multi-unit copings in the prosthesis, leading to lower stress concentration on both mandibular bone and prosthetic components. Increasing the number of supporting implants in a FAFDPs reduced loading on each implant, although it may not necessarily reduce the stress concentration in the most posterior locations significantly. Overall, the 6-implant configuration was a preferable configuration as it provided the most balanced mechanical performance in this patient-specific case.

3.
Nanoscale ; 11(45): 22134, 2019 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-31701986

RESUMO

Correction for 'MoS2 nanoflowers encapsulated into carbon nanofibers containing amorphous SnO2 as an anode for lithium-ion batteries' by Huanhui Chen et al., Nanoscale, 2019, 11, 16253-16261.

4.
Nanoscale ; 11(35): 16253-16261, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31454008

RESUMO

SnO2 with high abundance, large theoretical capacity, and nontoxicity is considered to be a promising candidate for use as advanced electrodes. However, the poor electronic conductivity and large volume variations hinder the practical applications of SnO2-based electrodes for use in lithium-ion batteries (LIBs). Herein, the MoS2-SnO2 heterostructures were encapsulated into carbon nanofibers (CNFs) via facile solvothermal and electrospinning methods. Remarkably, when the binder-free and robust MoS2-SnO2@CNF is employed as the anode for LIBs, such a clever structure yields a discharge capacity of 983 mA h g-1 at a current density of 200 mA g-1 after 100 cycles and a capacity of 710 mA h g-1 after 800 cycles at a current density of 2000 mA g-1. Moreover, full cells and flexible full cells were constructed, which exhibited high flexibility and delivered a high reversible capacity of 463 mA h g-1 after 100 cycles at 500 mA g-1. The exceptional performance of MoS2-SnO2@CNF could be attributed to the rational design of the electrode structure. On one hand, the robust structure of the amorphous SnO2 and MoS2 nanoflowers in the conductive carbon network not only provides direct current pathways, but also enhances electron transfer. On the other hand, the abundance of p-n heterogeneous interfaces considerably reduces the charge transfer resistance and enhances the surface reaction kinetics. This work proposes a feasible strategy to enhance the capacity and stability of SnO2-based electrodes and opens up a new avenue for the potential applications of SnO2 anode materials.

5.
J R Soc Interface ; 16(154): 20190108, 2019 05 31.
Artigo em Inglês | MEDLINE | ID: mdl-31039696

RESUMO

Orthodontic root resorption is a common side effect of orthodontic therapy. It has been shown that high hydrostatic pressure in the periodontal ligament (PDL) generated by orthodontic forces will trigger recruitment of odontoclasts, leaving resorption craters on root surfaces. The patterns of resorption craters are the traces of odontoclast activity. This study aimed to investigate resorptive patterns by: (i) quantifying spatial root resorption under two different levels of in vivo orthodontic loadings using microCT imaging techniques and (ii) correlating the spatial distribution pattern of resorption craters with the induced mechanobiological stimulus field in PDL through nonlinear finite-element analysis (FEA) in silico. Results indicated that the heavy force led to a larger total resorption volume than the light force, mainly by presenting greater individual crater volumes ( p < 0.001) than increasing crater numbers, suggesting that increased mechano-stimulus predominantly boosted cellular resorption activity rather than recruiting more odontoclasts. Furthermore, buccal-cervical and lingual-apical regions in both groups were found to have significantly larger resorption volumes than other regions ( p < 0.005). These clinical observations are complemented by the FEA results, suggesting that root resorption was more likely to occur when the volume average compressive hydrostatic pressure exceeded the capillary blood pressure (4.7 kPa).

6.
J Biomech ; 90: 1-8, 2019 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-31079877

RESUMO

The human masticatory system has received significant attention in the areas of biomechanics due to its sophisticated co-activation of a group of masticatory muscles which contribute to the fundamental oral functions. However, determination of each muscular force remains fairly challenging in vivo; the conventional data available may be inapplicable to patients who experience major oral interventions such as maxillofacial reconstruction, in which the resultant unsymmetrical anatomical structure invokes a more complex stomatognathic functioning system. Therefore, this study aimed to (1) establish an inverse identification procedure by incorporating the sequential Kriging optimization (SKO) algorithm, coupled with the patient-specific finite element analysis (FEA) in silico and occlusal force measurements at different time points over a course of rehabilitation in vivo; and (2) evaluate muscular functionality for a patient with mandibular reconstruction using a fibula free flap (FFF) procedure. The results from this study proved the hypothesis that the proposed method is of certain statistical advantage of utilizing occlusal force measurements, compared to the traditionally adopted optimality criteria approaches that are basically driven by minimizing the energy consumption of muscle systems engaged. Therefore, it is speculated that mastication may not be optimally controlled, in particular for maxillofacially reconstructed patients. For the abnormal muscular system in the patient with orofacial reconstruction, the study shows that in general, the magnitude of muscle forces fluctuates over the 28-month rehabilitation period regardless of the decreasing trend of the maximum muscular capacity. Such finding implies that the reduction of the masticatory muscle activities on the resection side might lead to non-physiological oral biomechanical responses, which can change the muscular activities for stabilizing the reconstructed mandible.

7.
Front Psychiatry ; 9: 556, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30459653

RESUMO

Introduction: Relapse is very common in drug abusers and contributes to a series of negative consequences. Effective addiction treatment exists but there are some problems in the implementation process. Mobile health (mHealth) offers a potential solution to improving recovery outcome for drug abusers in the community. The research team developed a community-based addiction rehabilitation electronic system (CAREs). The primary aim of this study is to explore whether the integrated rehabilitation based on program CAREs promotes drug abusers to keep abstinence. The secondary aim is to evaluate the impact of CAREs on interaction between drug users and service providers, and on addiction-related physical and social functions. Method and analysis: A randomized controlled trial (RCT) will be conducted. The study is a superiority trial with parallel group design. Seventy drug abusers who are newly ordered to undergo community rehabilitation will be recruited from the community in Shanghai. Participants will be 1:1 randomly assigned to receive integrated community rehabilitation by using CAREs or only receiving routine community rehabilitation for 6 months. Corresponding social workers will provide service and monitor their drug use behavior in accordance with the routine work-flow. Outcomes will be assessed at baseline and in the 6th month. The primary outcome is the performance on illicit drug urine test which will be carried out regularly twice per week during the study period. Secondary study outcomes include longest duration of sustained abstinence, days that participants interact with social workers, and the decrease rate of addiction-related issues severity index. Chi-square tests and ANOVAs will be used to compare characteristics of the members of the two groups. GEE will be used to compare the seven dimensions scores of the ASI between groups. Discussion: The study provides evidence for the feasibility and effectiveness of the "CAREs" system through comparing the results of the intervention group with the control group. This paper describes the design and methodology of the study. Ethics and dissemination: The Ethical Board of SMHC approved the study protocol. All participants will present for the informed consent process. After study completion, the results will be published. Trial Registration: ClinicalTrials.gov NCT03451344, https://clinicaltrials.gov/ct2/show/NCT03451344.

8.
Comput Biol Chem ; 77: 261-271, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30393100

RESUMO

The NS2B-NS3 protease is essential for the replication process of Dengue Virus, which make it an attractive target for anti-virus drugs. Since a considerable number of NS2B-NS3 protease inhibitors have been reported so far, it is significant for the discovery of more effective antivirus compounds with the essential structure-activity relationship extracted from known inhibitors. In this perspective, the relationship between the chemical features of inhibitors and their biological activities was investigated with a combined ligand- and structure-based approach. Furthermore, 3D pharmacophore models were generated with the best selected, which consisted of five chemical features: one ring aromatic group, one hydrophobic group, one hydrogen bond donor and two hydrogen bond acceptors (RHDAA). Subsequently, molecular docking was employed to explore the specific allosteric site for non-peptidic inhibitors to bind, which was proved to be located behind the catalytic triad. Taken the results of both molecular docking and pharmacophore modeling into consideration, a model of receptor-ligand interaction was obtained with four essential chemical features including aromatic rings and hydrogen bonds. This research provided an accurate binding model for the discovery and optimization of NS2B-NS3 protease inhibitors.


Assuntos
Vírus da Dengue/enzimologia , Dengue/virologia , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacologia , Serina Endopeptidases/metabolismo , Sequência de Aminoácidos , Antivirais/química , Antivirais/farmacologia , Dengue/tratamento farmacológico , Vírus da Dengue/efeitos dos fármacos , Desenho de Fármacos , Humanos , Ligantes , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular
9.
Oncol Rep ; 40(3): 1650-1656, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30015973

RESUMO

Vascular endothelial growth factor receptor 2 (VEGFR2) and c­Met are tyrosine kinases, which are involved in the tumorigenesis of various types of cancer. Previous studies have demonstrated that the elevated activation of c­Met is associated with the drug resistance of VEGFR2 inhibitors. Therefore, dual c­Met and VEGFR2 kinase inhibitors are expected to overcome VEGFR2 inhibitor resistance and subsequently lead to a superior therapeutic outcome to regular VEGFR2 inhibitors. In the present study, it was found that chrysoeriol, which can be extracted from several natural plants, was a potential dual c­Met and VEGFR2 kinase inhibitor. The results of docking experiments revealed that chrysoeriol was able to efficiently bind in the active site cavity of c­Met and VEGFR2. The results of enzymatic assays showed relatively high binding affinities of chrysoeriol to c­Met (Kd=12 µM) and VEGFR2 (Kd=11 µM). The structure activity relationships (SARs) of chrysoeriol and its analogs were investigated using pharmacological and molecular docking experiments. To the best of our best knowledge, the present study is the first to report a natural product with both c­Met and VEGFR2 inhibitory profiles, and provides insights into future dual c­Met and VEGFR2 kinase inhibitor development.


Assuntos
Flavonas/química , Flavonas/farmacologia , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacologia , Proteínas Proto-Oncogênicas c-met/antagonistas & inibidores , Bibliotecas de Moléculas Pequenas/farmacologia , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/antagonistas & inibidores , Ensaios de Triagem em Larga Escala , Humanos , Conformação Proteica , Relação Estrutura-Atividade
10.
Med Eng Phys ; 56: 1-8, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29609866

RESUMO

Whilst the newly established biomechanical conditions following mandibular reconstruction using fibula free flap can be a critical determinant for achieving favorable bone union, little has been known about their association in a time-dependent fashion. This study evaluated the bone healing/remodeling activity in reconstructed mandible and its influence on jaw biomechanics using CT data, and further quantified their correlation with mechanobiological responses through an in-silico approach. A 66-year-old male patient received mandibular reconstruction was studied. Post-operative CT scans were taken at 0, 4, 16 and 28 months. Longitudinal change of bone morphologies and mineral densities were measured at three bone union interfaces (two between the fibula and mandibular bones and one between the osteotomized fibulas) to investigate bone healing/remodeling events. Three-dimensional finite element models were created to quantify mechanobiological responses in the bone at these different time points. Bone mineral density increased rapidly along the bone interfaces over the first four months. Cortical bridging formed at the osteotomized interface earlier than the other two interfaces with larger shape discrepancy between fibula and mandibular bones. Bone morphology significantly affected mechanobiological responses in the osteotomized region (R2 > 0.77). The anatomic position and shape discrepancy at bone union affected the bone healing/remodeling process.


Assuntos
Remodelação Óssea , Fíbula/citologia , Retalhos de Tecido Biológico , Mandíbula/fisiologia , Mandíbula/cirurgia , Reconstrução Mandibular , Fenômenos Mecânicos , Idoso , Fenômenos Biomecânicos , Densidade Óssea , Humanos , Masculino , Mandíbula/diagnóstico por imagem , Tomografia Computadorizada por Raios X
11.
J Biomech ; 60: 57-64, 2017 07 26.
Artigo em Inglês | MEDLINE | ID: mdl-28743370

RESUMO

The aim of this study is to investigate the biomechanics for orthodontic tooth movement (OTM) subjected to concurrent single-tooth vibration (50Hz) with conventional orthodontic force application, via a clinical study and computational simulation. Thirteen patients were recruited in the clinical study, which involved distal retraction of maxillary canines with 1.5N (150g) force for 12weeks. In a split mouth study, vibration and non-vibration sides were randomly assigned to each subject. Vibration of 50Hz, of approximately 0.2N (20g) of magnitude, was applied on the buccal surface of maxillary canine for the vibration group. A mode-based steady-state dynamic finite element analysis (FEA) was conducted based on an anatomically detailed model, complying with the clinical protocol. Both the amounts of space closure and canine distalization of the vibration group were significantly higher than those of the control group, as measured intra-orally or on models (p<0.05). Therefore it is indicated that a 50Hz and 20g single-tooth vibration can accelerate maxillary canine retraction. The volume-average hydrostatic stress (VHS) in the periodontal ligament (PDL) was computationally calculated to be higher with vibration compared with the control group for maxillary teeth and for both linguo-buccal and mesial-distal directions. An increase in vibratory frequency further amplified the PDL response before reaching a local natural frequency. An amplification of PDL response was also shown to be induced by vibration based on computational simulation. The vibration-enhanced OTM can be described by mild, vigorous and diminishing zones among which the mild zone is considered to be clinically beneficial.


Assuntos
Anormalidades do Sistema Estomatognático/terapia , Técnicas de Movimentação Dentária/métodos , Dente/fisiopatologia , Adolescente , Criança , Simulação por Computador , Análise de Elementos Finitos , Humanos , Modelos Anatômicos , Modelos Biológicos , Ligamento Periodontal/fisiologia , Vibração
12.
Med Eng Phys ; 42: 26-34, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28209345

RESUMO

Medial opening wedge high tibial osteotomy (MOWHTO) is a surgical procedure to treat knee osteoarthritis associated with varus deformity. However, the ideal final alignment of the Hip-Knee-Ankle (HKA) angle in the frontal plane, that maximizes procedural success and post-operative knee function, remains controversial. Therefore, the purpose of this study was to introduce a subject-specific modeling procedure in determining the biomechanical effects of MOWHTO alignment on tibiofemoral cartilage stress distribution. A 3D finite element knee model derived from magnetic resonance imaging of a healthy participant was manipulated in-silico to simulate a range of final HKA angles (i.e. 0.2°, 2.7°, 3.9° and 6.6° valgus). Loading and boundary conditions were assigned based on subject-specific kinematic and kinetic data from gait analysis. Multiobjective optimization was used to identify the final alignment that balanced compressive and shear forces between medial and lateral knee compartments. Peak stresses decreased in the medial and increased in the lateral compartment as the HKA was shifted into valgus, with balanced loading occurring at angles of 4.3° and 2.9° valgus for the femoral and tibial cartilage respectively. The concept introduced here provides a platform for non-invasive, patient-specific preoperative planning of the osteotomy for medial compartment knee osteoarthritis.


Assuntos
Cartilagem Articular , Osteotomia , Medicina de Precisão , Estresse Mecânico , Tíbia/cirurgia , Adulto , Força Compressiva , Humanos , Masculino
13.
J Prosthodont Res ; 61(4): 393-402, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-28109795

RESUMO

PURPOSE: This study combines clinical investigation with finite element (FE) analysis to explore the effects of buccal bone thickness (BBT) on the morphological changes of buccal bone induced by the loaded implant. METHODS: One specific patient who had undergone an implant treatment in the anterior maxilla and experienced the buccal bone resorption on the implant was studied. Morphological changes of the bone were measured through a series of cone-beam computed tomography (CT) scans. A three-dimensional heterogeneous nonlinear FE model was constructed based on the CT images of this patient, and the in-vivo BBT changes are correlated to the FE in-silico mechanobiological stimuli; namely, von Mises equivalent stress, equivalent strain, and strain energy density. The anterior incisory bone region of this model was then varied systematically to simulate five different BBTs (0.5, 1.0, 1.5, 2.0, and 2.5mm), and the optimal BBT was inversely determined to minimize the risk of resorption. RESULTS: Significant changes in BBTs were observed clinically after 6 month loading on the implant. The pattern of bone resorption fell into a strong correlation with the distribution of mechanobiological stimuli onsite. The initial BBT appeared to play a critical role in distributing mechanobiological stimuli, thereby determining subsequent variation in BBT. A minimum initial thickness of 1.5mm might be suggested to reduce bone resorption. CONCLUSIONS: This study revealed that the initial BBT can significantly affect mechanobiological responses, which consequentially determines the bone remodeling process. A sufficient initial BBT is considered essential to assure a long-term stability of implant treatment.


Assuntos
Fenômenos Biomecânicos/fisiologia , Remodelação Óssea/fisiologia , Reabsorção Óssea/etiologia , Implantação Dentária/efeitos adversos , Implantes Dentários/efeitos adversos , Maxila/patologia , Maxila/fisiologia , Bochecha , Tomografia Computadorizada de Feixe Cônico , Feminino , Análise de Elementos Finitos , Humanos , Maxila/diagnóstico por imagem , Pessoa de Meia-Idade
14.
Biomech Model Mechanobiol ; 16(2): 411-423, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-27628910

RESUMO

This paper aimed to develop a clinically validated bone remodeling algorithm by integrating bone's dynamic properties in a multi-stage fashion based on a four-year clinical follow-up of implant treatment. The configurational effects of fixed partial dentures (FPDs) were explored using a multi-stage remodeling rule. Three-dimensional real-time occlusal loads during maximum voluntary clenching were measured with a piezoelectric force transducer and were incorporated into a computerized tomography-based finite element mandibular model. Virtual X-ray images were generated based on simulation and statistically correlated with clinical data using linear regressions. The strain energy density-driven remodeling parameters were regulated over the time frame considered. A linear single-stage bone remodeling algorithm, with a single set of constant remodeling parameters, was found to poorly fit with clinical data through linear regression (low [Formula: see text] and R), whereas a time-dependent multi-stage algorithm better simulated the remodeling process (high [Formula: see text] and R) against the clinical results. The three-implant-supported and distally cantilevered FPDs presented noticeable and continuous bone apposition, mainly adjacent to the cervical and apical regions. The bridged and mesially cantilevered FPDs showed bone resorption or no visible bone formation in some areas. Time-dependent variation of bone remodeling parameters is recommended to better correlate remodeling simulation with clinical follow-up. The position of FPD pontics plays a critical role in mechanobiological functionality and bone remodeling. Caution should be exercised when selecting the cantilever FPD due to the risk of overloading bone resorption.


Assuntos
Remodelação Óssea , Simulação por Computador , Prótese Parcial Fixa/estatística & dados numéricos , Modelos Biológicos , Algoritmos , Humanos
15.
Artigo em Inglês | MEDLINE | ID: mdl-26916052

RESUMO

Design of prosthetic implants to ensure rapid and stable osseointegration remains a significant challenge, and continuous efforts have been directed to new implant materials, structures and morphology. This paper aims to develop and characterise a porous titanium dental implant fabricated by metallic powder injection-moulding. The surface morphology of the specimens was first examined with a scanning electron microscope (SEM), followed by microscopic computerised tomography (µ-CT) scanning to capture its 3D microscopic features non-destructively. The nature of porosity and pore sizes were determined statistically. A homogenisation technique based on the Hills-energy theorem was adopted to evaluate its directional elastic moduli, and the conservation of mass theorem was employed to quantify the oxygen diffusivity for bio-transportation feature. This porous medium was found to have pore sizes varying from 50 to 400 µm and the average porosity of 46.90 ± 1.83%. The anisotropic principal elastic moduli were found fairly close to the upper range of cortical bone, and the directional diffusivities could potentially enable radial osseous tissue ingrowth and vascularisation. This porous titanium successfully reduces the elastic modulus mismatch between implant and bone for dental and orthopaedic applications, and provides improved capacity for transporting oxygen, nutrient and waste for pre-vascular network formation. Copyright © 2016 John Wiley & Sons, Ltd.


Assuntos
Implantes Dentários , Titânio , Microtomografia por Raio-X/métodos , Difusão , Módulo de Elasticidade , Humanos , Teste de Materiais , Microscopia Eletrônica de Varredura , Osseointegração , Oxigênio/metabolismo , Porosidade , Propriedades de Superfície
16.
Int J Prosthodont ; 29(6): 573-580, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27824977

RESUMO

PURPOSE: The objective of this clinical study was to determine the relationship of mandibular morphology with residual ridge resorption (RRR) of implant-retained overdenture (IRO) patients. MATERIALS AND METHODS: RRR was quantified as change in bone volume over 1- and 2-year periods using cone beam computed tomography and a medical imaging program. Features of the mandibular morphology, namely the gonial angle, ramus length, ramus width, corpus length, and corpus height, were measured on three-dimensional models and correlated to the RRR. A total of 25 participants were treated with mandibular IROs opposing maxillary complete dentures. By the 2-year follow-up, radiographic data for 18 patients were complete for analysis. Of these 18 participants, half fall into the low gonial angle category and the other half into the high angle. RESULTS: The extent of RRR was highly variable among participants and ranged from -2 to +2 mm in depth over the 2-year period. The mean decrease in bone volume after the first year was 3.8 ± 4.5%. This rate decreased to 3.2 ± 4.1% after the second year. RRR occurs either by translation of the entire thickness of cortical layer apically or by thinning of the outer cortical layer. RRR was significantly correlated to gonial angle (r = .471; P = .048) and predominantly occurred in the molar region in low-angle participants and more anteriorly in high-angle participants. There was no association between RRR and ramus length (r = -.341; P = .166), ramus width (r = -.183; P =.468), corpus length (r = .057; P = .821), and corpus height (r = .097; P = .702). CONCLUSION: Within the limitations of this study, it may be concluded that gonial angle is significantly related to RRR associated with IROs.


Assuntos
Prótese Dentária Fixada por Implante , Revestimento de Dentadura , Mandíbula , Perda do Osso Alveolar , Humanos , Mandíbula/anatomia & histologia , Maxila
17.
Int J Oral Maxillofac Implants ; 31(5): 1049-57, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27632259

RESUMO

PURPOSE: The aims of this study were to develop a device for in vivo measurement of three-dimensional (3D) loads on implants and to investigate the effects of implant configuration on the load distribution under a three-unit fixed partial denture (FPD). MATERIALS AND METHODS: A 67-year-old female patient with three implants (in the mandibular left second premolar, first molar, and second molar regions) was recruited. Four implant configurations for a three-unit FPD depending on the number and position of the implants were considered in this study. They included a three-implant prosthesis and three types of two-implant prosthesis: a central pontic, posterior cantilever, and anterior cantilever, with the same superstructure (splinted three crowns) for the same occlusal contact. Customized abutments and 3D piezoelectric force transducers were fixed to the implants of the four configurations with the superstructure. The loads on the implants were recorded during maximum voluntary clenching (MVC-test) and when chewing a piece of chewing gum (GUMtest). RESULTS: The occlusal forces on the dental arch during MVC-test with the four implant configurations did not exhibit significant differences. In the three-implant prosthesis, there were no significant differences in the mean maximum resultant load on each implant in both tests. In the central pontic, the load on the second premolar was significantly greater than that on the second molar in the MVC-test but there were no significant differences in the GUM-test. High loads were detected on the first molar in both the posterior cantilever and anterior cantilever. The highest load was detected on the first molar in the posterior cantilever during the GUMtest. CONCLUSION: The in vivo 3D load-measuring device using the piezoelectric force transducers enabled the measurement of the functional load on implants supporting a FPD. The results suggested, within the limitations of this study, that a three-implant prosthesis and central pontic provide biomechanically beneficial designs compared with the posterior cantilever and anterior cantilever in terms of the equal distribution of loads on supporting implants.


Assuntos
Implantes Dentários , Planejamento de Prótese Dentária , Prótese Dentária Fixada por Implante/métodos , Análise do Estresse Dentário/métodos , Prótese Parcial Fixa , Idoso , Força de Mordida , Condutividade Elétrica , Feminino , Humanos , Estresse Mecânico , Transdutores
18.
Arch Oral Biol ; 66: 98-107, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-26943815

RESUMO

OBJECTIVES: This paper aimed to precisely locate centres of resistance (CRe) of maxillary teeth and investigate optimal orthodontic force by identifying the effective zones of orthodontic tooth movement (OTM) from hydrostatic stress thresholds in the periodontal ligament (PDL). METHODS: We applied distally-directed tipping and bodily forces ranging from 0.075 N to 3 N (7.5 g to 300 g) onto human maxillary teeth. The hydrostatic stress was quantified from nonlinear finite element analysis (FEA) and compared with normal capillary and systolic blood pressure for driving the tissue remodelling. Two biomechanical stimuli featuring localised and volume-averaged hydrostatic stresses were introduced to describe OTM. Locations of CRe were determined through iterative FEA simulation. RESULTS: Accurate locations of CRes of teeth and ranges of optimal orthodontic forces were obtained. By comparing with clinical results in literature, the volume average of hydrostatic stress in PDL was proved to describe the process of OTM more indicatively. The optimal orthodontic forces obtained from the in-silico modelling study echoed with the clinical results in vivo. CONCLUSIONS: A universal moment to force (M/F) ratio is not recommended due to the variation in patients and loading points. Accurate computational determination of CRe location can be applied in practice to facilitate orthodontic treatment. Global measurement of hydrostatic pressure in the PDL better characterised OTM, implying that OTM occurs only when the majority of PDL volume is critically stressed. The FEA results provide new insights into relevant orthodontic biomechanics and help establish optimal orthodontic force for a specific patient.


Assuntos
Modelos Biológicos , Ligamento Periodontal/fisiologia , Técnicas de Movimentação Dentária/métodos , Fenômenos Biomecânicos , Remodelação Óssea/fisiologia , Simulação por Computador , Análise do Estresse Dentário/métodos , Análise de Elementos Finitos , Humanos , Imageamento Tridimensional , Maxila/anatomia & histologia , Maxila/fisiologia , Braquetes Ortodônticos , Ligamento Periodontal/anatomia & histologia , Tomógrafos Computadorizados
19.
Artigo em Inglês | MEDLINE | ID: mdl-26024011

RESUMO

Despite their considerable importance to biomechanics, there are no existing methods available to directly measure apparent Poisson's ratio and friction coefficient of oral mucosa. This study aimed to develop an inverse procedure to determine these two biomechanical parameters by utilizing in vivo experiment of contact pressure between partial denture and beneath mucosa through nonlinear finite element (FE) analysis and surrogate response surface (RS) modelling technique. First, the in vivo denture-mucosa contact pressure was measured by a tactile electronic sensing sheet. Second, a 3D FE model was constructed based on the patient CT images. Third, a range of apparent Poisson's ratios and the coefficients of friction from literature was considered as the design variables in a series of FE runs for constructing a RS surrogate model. Finally, the discrepancy between computed in silico and measured in vivo results was minimized to identify the best matching Poisson's ratio and coefficient of friction. The established non-invasive methodology was demonstrated effective to identify such biomechanical parameters of oral mucosa and can be potentially used for determining the biomaterial properties of other soft biological tissues.


Assuntos
Fricção , Mucosa Bucal/diagnóstico por imagem , Pressão , Idoso , Fenômenos Biomecânicos , Prótese Parcial , Feminino , Análise de Elementos Finitos , Humanos , Tomografia Computadorizada por Raios X
20.
Artigo em Inglês | MEDLINE | ID: mdl-26444905

RESUMO

Layered all-ceramic systems have been increasingly adopted in major dental prostheses. However, ceramics are inherently brittle, and they often subject to premature failure under high occlusion forces especially in the posterior region. This study aimed to develop mechanically sound novel topological designs for all-ceramic dental bridges by minimizing the fracture incidence under given loading conditions. A bi-directional evolutionary structural optimization (BESO) technique is implemented within the extended finite element method (XFEM) framework. Extended finite element method allows modeling crack initiation and propagation inside all-ceramic restoration systems. Following this, BESO searches the optimum distribution of two different ceramic materials, namely porcelain and zirconia, for minimizing fracture incidence. A performance index, as per a ratio of peak tensile stress to material strength, is used as a design objective. In this study, the novel XFEM based BESO topology optimization significantly improved structural strength by minimizing performance index for suppressing fracture incidence in the structures. As expected, the fracture resistance and factor of safety of fixed partial dentures structure increased upon redistributing zirconia and porcelain in the optimal topological configuration. Dental CAD/CAM systems and the emerging 3D printing technology were commercially available to facilitate implementation of such a computational design, exhibiting considerable potential for clinical application in the future. Copyright © 2015 John Wiley & Sons, Ltd.


Assuntos
Porcelana Dentária , Prótese Parcial Fixa , Cerâmica , Desenho Assistido por Computador , Humanos , Teste de Materiais , Estresse Mecânico
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