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1.
J Sports Sci ; 38(2): 206-213, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31722621

RESUMO

A novel 3D motion capture analysis assessed the efficacy of insoles in maintaining the foot position on the midsole platform inside the shoe during rapid change of direction manoeuvres used in team sports. An insole (TI) with increased static (35%) and dynamic (49%) coefficient of friction compared to a regular insole (SI) was tested. Change of direction performance was faster (p < .001) and perceived to be faster (p < .001) in TI compared to SI. Participants utilised greater coefficient of friction in TI compared to SI during a complete turn, but not during a 20 degree side-cut. In-shoe foot sliding reduced across the forefoot and midfoot during the braking phase of the turn and in the rearfoot during the side-cut in TI. Greater in-shoe foot sliding occurred in the turn than the side-cut across all foot regions. Results provide guidance for athletic footwear design to help limit in-shoe foot sliding and improve change of direction performance.


Assuntos
Desempenho Atlético/fisiologia , Desenho de Equipamento , Destreza Motora/fisiologia , Sapatos , Adulto , Desempenho Atlético/psicologia , Fenômenos Biomecânicos , Feminino , Fricção , Humanos , Masculino , Percepção , Estudos de Tempo e Movimento , Adulto Jovem
2.
J Phys Chem Lett ; 11(1): 292-296, 2020 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-31841337

RESUMO

Urea is a strong denaturing osmolyte that disrupts noncovalent bonds in proteins. Here, we present a small-angle neutron scattering (SANS) and neutron spin-echo spectroscopy (NSE) study on the structure and dynamics of the intrinsically disordered myelin basic protein (MBP) denatured by urea. SANS results show that urea-denatured MBP is more compact than ideal polymers, while its secondary structure content is entirely lost. NSE experiments reveal concomitantly an increase of the relaxation time and of the amplitude of internal motions in urea-denatured MBP as compared to native MBP. If interpreted in terms of the Zimm model including internal friction (ZIF), the internal friction parameter decreased by a factor of 6.5. Urea seems to not only smooth local energy barriers, reducing internal friction on a local scale, but also significantly reduces the overall depth of the global energy landscape. This leads to a nearly complete loss of restoring forces beyond entropic forces and in turn allows for larger motional amplitudes. Obviously, the noncovalent H-bonds are largely eliminated, driving the unfolded protein to be more similar to a synthetic polymer.


Assuntos
Proteína Básica da Mielina/química , Ureia/química , Fricção , Modelos Moleculares , Difração de Nêutrons , Conformação Proteica , Desnaturação Proteica , Espalhamento a Baixo Ângulo , Software
3.
Accid Anal Prev ; 134: 105297, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31683233

RESUMO

The motorcyclist is exposed to the risk of falling and impacting ground head-first at a wide range of travelling speeds - from a speed limit of less than 50 km/h on the urban road to the race circuit where speed can reach well above 200 km/h. However, motorcycle helmets today are tested at a single and much lower impact speed, i.e. 30 km/h. There is a knowledge gap in understanding the dynamics and head impact responses at high travelling speeds due to the limitation of existing laboratory rigs. This study used a finite element head model coupled with a motorcycle helmet model to simulate head-first falls at travelling speed (or tangential velocity at impact) from 0 to 216 km/h. The effect of different falling heights (1.6 m and 0.25 m) and coefficient of frictions (0.20 and 0.45) between the helmet outer shell and ground were also examined. The simulation results were analysed together with the analytical model to better comprehend rolling and/or sliding phenomena that are often observed in helmet oblique impacts. Three types of helmet-to-ground interactions are found when the helmet impacts ground from low to high tangential velocities: (1) helmet rolling without slipping; (2) a combination of sliding and rolling; and (3) continuous sliding. The tangential impulse transmitted to the head-helmet system, peak angular head kinematics and brain strain increase almost linearly with the tangential velocity when the helmet rolls but plateaus when the helmet slides. The critical tangential velocity at which the motion transit from the rolling regime to the sliding regime depends on both the falling height and friction coefficient. Typically, for a fall height of 1.63 m and a friction coefficient of 0.45, the rolling/sliding transition occurs at a tangential velocity of 10.8 m/s (38.9 km/h). Low sliding resistance in helmet design, i.e. by the means of a lower friction coefficient between the helmet outer shell and ground, has shown a higher reduction of brain tissue strain in the sliding regime than in the rolling regime. This study uncovers the underlying dynamics of rolling and sliding phenomena in high-speed oblique impacts, which largely affect head impact biomechanics. Besides, the study highlights the importance of testing helmets at speeds covering both the rolling and sliding regime since potential designs for improved head protection at high-speed impacts can be more distinguishable in the sliding regime than in the rolling regime.


Assuntos
Fricção , Dispositivos de Proteção da Cabeça , Motocicletas/estatística & dados numéricos , Aceleração , Acidentes de Trânsito/classificação , Fenômenos Biomecânicos/fisiologia , Traumatismos Craniocerebrais/etiologia , Traumatismos Craniocerebrais/prevenção & controle , Humanos , Fatores de Risco
4.
Int J Oral Maxillofac Implants ; 34(5): 1047-1052, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31528860

RESUMO

PURPOSE: The purpose of this in vitro study was to evaluate the behavior of abutments attached to Morse taper connection implants, with and without internal index, against oblique cyclic loads. MATERIALS AND METHODS: Twenty test pieces composed of abutments connected to Morse taper implants solely by friction action were subdivided into two groups (n = 10): group NI (no index) and group I (index). The test units were submitted to tensile tests, before and after cycling loads. Paired t tests were used for intragroup data at different times, and independent t tests were used for the comparisons between the groups. RESULTS: There was a statistically significant difference in both the groups when the precycling and postcycling tensile values were compared. In the comparison between the no index and index groups, there was no statistically significant difference in precycling and postcycling tests. CONCLUSION: Within the limitations of this in vitro study, it can be concluded that the cyclic loads increased the tensile strength of abutments on Morse taper implants regardless of the index presence. On the other hand, the presence of an index did not significantly alter the values of tensile tests, before and after cyclic loads.


Assuntos
Projeto do Implante Dentário-Pivô , Implantes Dentários , Dente Suporte , Análise do Estresse Dentário , Fricção , Resistência à Tração
6.
Sensors (Basel) ; 19(17)2019 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-31484311

RESUMO

MEMS-based skin friction sensors are used to measure and validate skin friction and its distribution, and their advantages of small volume, high reliability, and low cost make them very important for vehicle design. Aiming at addressing the accuracy problem of skin friction measurements induced by existing errors of sensor fabrication and assembly, a novel fabrication technology based on visual alignment is presented. Sensor optimization, precise fabrication of key parts, micro-assembly based on visual alignment, prototype fabrication, static calibration and validation in a hypersonic wind tunnel are implemented. The fabrication and assembly precision of the sensor prototypes achieve the desired effect. The results indicate that the sensor prototypes have the characteristics of fast response, good stability and zero-return; the measurement ranges are 0-100 Pa, the resolution is 0.1 Pa, the repeatability accuracy and linearity are better than 1%, the repeatability accuracy in laminar flow conditions is better than 2% and it is almost 3% in turbulent flow conditions. The deviations between the measured skin friction coefficients and numerical solutions are almost 10% under turbulent flow conditions; whereas the deviations between the measured skin friction coefficients and the analytical values are large (even more than 100%) under laminar flow conditions. The error resources of direct skin friction measurement and their influence rules are systematically analyzed.


Assuntos
Pele , Animais , Técnicas Biossensoriais , Fricção , Humanos , Sistemas Microeletromecânicos
7.
J Oleo Sci ; 68(9): 873-879, 2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31413244

RESUMO

Gels exhibit complex friction behavior. This study aims to evaluate the friction forces between two fractal agar gel substrates under sinusoidal motion to show the effect of rough surfaces on friction dynamics. In a previous study, we observed an asymmetric friction profile during reciprocating motion and an ultra-low friction state on flat agar gel surfaces. On the other hand, these distinct friction profiles were not observed on rough agar gel surfaces. We determined that this distinction was caused by the contact state between fractal agar gel surfaces; no thick water film was formed on the fractal surfaces because the rough structure provided channels to drain water from the interface. These physical insights are useful not only for developing biofunctional materials but also for understanding surface phenomena on biosurfaces including tongues and small intestinal walls.


Assuntos
Ágar/química , Fricção , Géis/química , Propriedades de Superfície
8.
Medicina (Kaunas) ; 55(8)2019 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-31409027

RESUMO

Background: Deep friction massage (DFM) is a widely used technique by physical therapists worldwide for chronic pain management. According to Dr. James Cyriax, compliance with the proposed guidelines is vital to obtain the desired therapeutic results. Objectives: This study explored the beliefs and attitudes of Cypriot physical therapists to DFM and their compliance with the suggested guidelines to identify any empirical-based application patterns and compare them to the suggestions of Cyriax. In addition, the prevalence of DFM use in clinical practice in Cyprus was investigated. Methods: Questionnaires, consisting of 18 multiple choice questions and a table of six sub-questions, were distributed to 90 local physical therapists. Results: A total of 70% of respondents declared that they perform DFM in their daily practice. The respondents answered 11 out of the 19 technical questions in compliance with the guidelines. Conclusion: The study revealed the DFM application pattern of Cypriot physical therapists. The compliance percentage of this pattern to Cyriax guidelines was 58% in general and 62.5% for patients with chronic conditions.


Assuntos
Dor Crônica/terapia , Fricção , Conhecimentos, Atitudes e Prática em Saúde , Massagem , Dor Musculoesquelética/terapia , Fisioterapeutas , Chipre , Humanos , Inquéritos e Questionários
9.
J Orofac Orthop ; 80(5): 223-235, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31410493

RESUMO

OBJECTIVE: In vitro testing of archwires in a multibracket model may provide estimates of force-moment (F/M) systems applied to individual teeth in a realistic geometry. Such investigations have mostly been performed by continuous wire deflection, leading to frictional forces biasing the pure deflection forces. Aim of this study was to quantify this bias and the pure deflection forces for leveling archwires. MATERIALS AND METHODS: Three nickel-titanium (NiTi) and two multistranded wires were tested in a three-bracket model simulating vertical movement of an upper incisor with a typical interbracket distance of 8 mm (intercenter). To determine pure deflection forces, the middle bracket was first leveled incrementally from its vertical malposition to neutral position with repeated wire insertion at each step (so-called "static leveling mode"). For comparison, forces at the middle bracket were also determined during dynamic leveling with or without ligation of the wire at the lateral brackets by either elastic, tight or loose steel ligatures. RESULTS: The dynamic mode resulted in significantly lower mean leveling forces for all the tested wires (ANOVA [analysis of variance], p < 0.01) compared to the static mode. Expressed in numbers, dynamic wire unloading resulted in mean force underestimation of 53 ± 9% (loose steel ligatures), 56 ± 11% (elastic ligatures) or 91 ± 29% (tight steel ligatures). CONCLUSIONS: Orthodontic tooth movement is quasi-static. This concerns the initial hyalinization phase in particular. Thus, especially static testing of archwires provides valid reference data for the peak forces exerted directly after clinical insertion of a leveling wire. In dynamic wire testing, significant underestimation of actual forces exerted on individual teeth may occur due to experimental friction, which might considerably differ from that occurring during clinical therapy. This aspect has to be taken into account in the interpretation of published stiffness values for orthodontic wires, and in the selection of the appropriate archwire for leveling of the present tooth malposition, respectively.


Assuntos
Braquetes Ortodônticos , Análise do Estresse Dentário , Fricção , Teste de Materiais , Desenho de Aparelho Ortodôntico , Fios Ortodônticos , Titânio , Técnicas de Movimentação Dentária
10.
Int J Mol Sci ; 20(16)2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31394762

RESUMO

It was discovered that a sudden jump of the output torque moment from a rotation transmission nanosystem made from carbon nanotubes (CNTs) occurred when decreasing the system temperature. In the nanosystem from coaxial-layout CNTs, the motor with specified rotational frequency (ωM) can drive the inner tube (rotor) to rotate in the outer tubes. When the axial gap between the motor and the rotor was fixed, the friction between their neighbor edges was stronger at a lower temperature. Especially at temperatures below 100 K, the friction-induced driving torque increases with ωM. When the rotor was subjected to an external resistant torque moment (Mr), it could not rotate opposite to the motor even if it deformed heavily. Combining molecular dynamics simulations with the bi-sectioning algorithm, the critical value of Mr was obtained. Under the critical torque moment, the rotor stopped rotating. Accordingly, a transmission nanosystem can be designed to provide a strong torque moment via interface friction at low temperature.


Assuntos
Temperatura Baixa , Fricção , Nanotubos de Carbono/química , Rotação , Algoritmos , Modelos Teóricos , Conformação Molecular , Simulação de Dinâmica Molecular
12.
Artigo em Inglês | MEDLINE | ID: mdl-31295887

RESUMO

It is important to find criteria for preventive measures and appropriate assistive devices to reduce pedestrian injuries and increase walking in winter. Reducing the rate of falls on icy surfaces and improving people's ability to safely cross a street in winter conditions by achieving an adequate walking speed, for example, need to be considered. This study explores pedestrian perceptions of fall risk, balance, and footfall transitions while using different designs for anti-slip devices on ice and snow-covered ice and relates these to measures of gait speed and friction. Trials were performed with nine pedestrians testing 19 anti-slip devices on ice and ice covered with snow. Laboratory tests of the dynamic coefficient of friction (DCOF) on plain ice were also performed. The findings suggest that there was conformity in the participants' perceptions of good balance and low fall risk for one-fifth of the devices (three whole-foot designs and one design with built-in spikes). We also found that gait speed on icy pedestrian crossings is related to perceived fall-risk and balance control, but not to DCOF of the anti-slip devices.


Assuntos
Acidentes por Quedas/prevenção & controle , Gelo , Equilíbrio Postural/fisiologia , Roupa de Proteção , Estações do Ano , Sapatos , Velocidade de Caminhada/fisiologia , Adulto , Idoso , Feminino , Fricção , Humanos , Masculino , Pessoa de Meia-Idade , Pedestres , Percepção , Risco , Neve , Caminhada/lesões
13.
Dent Med Probl ; 56(2): 173-177, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31274255

RESUMO

BACKGROUND: Frictional resistance is an important parameter in orthodontics that influences the effectiveness of archwire-guided tooth movement. Since the consumption of dietary acids has increased considerably over the last 2 decades, there is a rationale for investigating the process of degradation of orthodontic materials in an acidic environment and its effect on clinical efficiency. OBJECTIVES: The aim of this study was to evaluate the effect of simulated erosive conditions on the frictional behavior between the brackets of 3 different materials and 3 different wire alloys. MATERIAL AND METHODS: Three types of twin orthodontic brackets (stainless steel (SS), monocrystalline ceramic and titanium) and 3 types of archwires of the same dimension (SS, nickel-titanium (Ni-Ti) and beta-titanium (titanium-molybdenum alloy - TMA) were tested in 9 different combinations under simulated erosive and non-erosive conditions (18 groups, n = 10). Bracket-wire specimens in the erosivecondition groups were subjected to a pH cycling regimen with 1% citric acid and artificial saliva for 5 consecutive days. Bracket-wire specimens from the non-erosive-condition groups were incubated only in artificial saliva for 5 days. Static and kinetic friction were determined by measuring the force needed to move the wire through the bracket. A three-way analysis of variance and pairwise comparisons with the Student-Newman-Keuls test were performed. RESULTS: Irrespective of the conditions, SS brackets with SS wire demonstrated significantly lower mean static and kinetic frictional resistance than other bracket-wire combinations (p < 0.01). Ceramic and titanium brackets generated high frictional forces with all 3 types of wire tested. Erosive conditions did not significantly influence static and kinetic frictional resistance in all bracket-wire groups. CONCLUSIONS: Erosive conditions do not affect the frictional behavior of SS, Ni-Ti and TMA orthodontic archwires at a clinically significant level.


Assuntos
Braquetes Ortodônticos , Fios Ortodônticos , Ligas Dentárias , Análise do Estresse Dentário , Fricção , Humanos , Teste de Materiais
14.
Appl Ergon ; 80: 35-42, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31280808

RESUMO

Shoe wear is known to increase slipping risk, but few studies have systematically studied this relationship. This study investigated the impact of progressive shoe wear on the available coefficient of friction (ACOF) and under-shoe fluid dynamics. Five different slip-resistant shoes were progressively worn using an accelerated, abrasive, wear protocol. The ACOF and fluid forces (the load supported by the fluid) were measured as shoes were slipped across a surface contaminated with a diluted glycerol solution. As the shoes became worn, an initial increase in ACOF was followed by a steady decrease. Low fluid forces were observed prior to wear followed by increased fluid forces as the worn region became larger. Results suggest that traction performance decreases particularly when the heel region without tread exceeds a size of 800 mm2. This study supports the concept of developing shoe replacement guidelines based upon the size of the worn region to reduce occupational slips.


Assuntos
Acidentes por Quedas/prevenção & controle , Acidentes de Trabalho/prevenção & controle , Sapatos/efeitos adversos , Tração/efeitos adversos , Pisos e Cobertura de Pisos , Fricção , Humanos , Propriedades de Superfície
15.
Sensors (Basel) ; 19(13)2019 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-31288468

RESUMO

The objective of this paper is to study the ability of polymer optical fiber (POF) to be inserted in a knitted fabric and to measure both pressure and friction when walking. Firstly, POF, marketed and in development, have been compared in terms of the required mechanical properties for the insertion of the fiber directly into a knitted fabric on an industrial scale, i.e. elongation, bending rigidity, and minimum bending radius before plastic deformation. Secondly, the chosen optical fiber was inserted inside several types of knitted fabric and was shown to be sensitive to friction and compression. The knitted structure with the highest sensitivity has been chosen for sock prototype manufacturing. Finally, a feasibility study with an instrumented sock showed that it is possible to detect the different phases of walking in terms of compression and friction.


Assuntos
Vestuário , Monitorização Fisiológica/instrumentação , Fibras Ópticas , Têxteis , Acelerometria , Desenho de Equipamento , Fricção , Humanos , Monitorização Fisiológica/métodos , Polímeros , Pressão , Reprodutibilidade dos Testes , Caminhada
16.
Implant Dent ; 28(4): 317, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31205269
17.
Molecules ; 24(12)2019 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-31208115

RESUMO

In this paper, we explain the amphoteric character of the cartilage surface by studying a lipid bilayer model built from phospholipids. We examined the interfacial tension values and molecular dynamics simulation in solutions of varying pH. The effects of negative and positive charge density (or fixed charges) on the (cartilage/cartilage) friction coefficient were investigated. In physiological (or synovial) fluid, after the isoelectric point (pI), the curve of interfacial tension decreases rapidly as it reaches pH 7.4 and then approaches a constant value at higher pH. It was shown that the curve of the interfacial tension curve exhibits a maximum value at the isoelectric point with a Gaussian shape feature. The phospholipid bilayers facilitate an almost frictionless contact in the joint. Moreover, the slippage of the bilayer and the short-range repulsion between the surfaces of the negatively charged cartilage surfaces are the main determinants of the low frictional properties of the joint.


Assuntos
Cartilagem Articular/química , Articulações/química , Articulação do Joelho/química , Bicamadas Lipídicas/química , Animais , Cartilagem Articular/metabolismo , Cartilagem Articular/fisiologia , Fricção/fisiologia , Interações Hidrofóbicas e Hidrofílicas , Articulações/fisiologia , Mamíferos/fisiologia , Simulação de Dinâmica Molecular , Fosfolipídeos/química , Tensão Superficial , Líquido Sinovial/química , Molhabilidade
18.
Nature ; 571(7764): 261-264, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31243365

RESUMO

Until relatively recently, humans, similar to other animals, were habitually barefoot. Therefore, the soles of our feet were the only direct contact between the body and the ground when walking. There is indirect evidence that footwear such as sandals and moccasins were first invented within the past 40 thousand years1, the oldest recovered footwear dates to eight thousand years ago2 and inexpensive shoes with cushioned heels were not developed until the Industrial Revolution3. Because calluses-thickened and hardened areas of the epidermal layer of the skin-are the evolutionary solution to protecting the foot, we wondered whether they differ from shoes in maintaining tactile sensitivity during walking, especially at initial foot contact, to improve safety on surfaces that can be slippery, abrasive or otherwise injurious or uncomfortable. Here we show that, as expected, people from Kenya and the United States who frequently walk barefoot have thicker and harder calluses than those who typically use footwear. However, in contrast to shoes, callus thickness does not trade-off protection, measured as hardness and stiffness, for the ability to perceive tactile stimuli at frequencies experienced during walking. Additionally, unlike cushioned footwear, callus thickness does not affect how hard the feet strike the ground during walking, as indicated by impact forces. Along with providing protection and comfort at the cost of tactile sensitivity, cushioned footwear also lowers rates of loading at impact but increases force impulses, with unknown effects on the skeleton that merit future study.


Assuntos
Calosidades/fisiopatologia , Pé/patologia , Pé/fisiologia , Dor/fisiopatologia , Tato/fisiologia , Caminhada/fisiologia , Adulto , Boston , Calosidades/patologia , Feminino , Fricção/fisiologia , Dureza/fisiologia , Humanos , Quênia , Masculino , Pessoa de Meia-Idade , Estimulação Física , Pressão , Sapatos , Fenômenos Fisiológicos da Pele , Suporte de Carga/fisiologia , Adulto Jovem
19.
Carbohydr Polym ; 220: 228-235, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31196545

RESUMO

With the increasing requirement of environmental protection, the development of lubricating materials with non-toxicity and good biodegradability becomes more and more significant. As the novel green nanomaterial derived from natural cellulose, cellulose nanocrystals (CNCs) in the present work were prepared from native cotton and added into polyalphaolefin (PAO) base oil as the lubricant additive. To improve the compatibility of CNCs with PAO, the surface of CNCs were grafted by stearoyl chains, which entangled with polyolefin chains and led to a good dispersibility and stability of the colloidal solution. This hybrid oil with the elevated viscosity improved the formation of lubricant film in the boundary lubrication regime. Combining with the mending effect of CNC particles on the surface roughness and scars, both the friction and the wear were dramatically reduced. Specifically, the introduction of 2 wt% modified nanocrystals (mCNC) in PAO base oil reduced the coefficient of friction (COF) by 30%. The results of this study suggest that cellulose nanocrystal is a promising ecofriendly and effective lubricant additive.


Assuntos
Alcenos/química , Celulose/química , Gossypium/metabolismo , Lubrificantes/química , Nanopartículas/química , Fricção , Lubrificação , Propriedades de Superfície , Viscosidade
20.
Acta Bioeng Biomech ; 21(1): 129-139, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31197283

RESUMO

PURPOSE: The purpose of this work was to determine the influence of dental materials used as permanent fillings on the mechanical properties of the tooth enamel surface layer subjected to friction with these materials. METHODS: Dental composite materials (five types) were differentiated in terms of size and shape of the filler particles and matrix type over the course of tests on the chewing simulator under two different loads set during friction. Next, it was measured values of wear and nanoindentation for the resulting friction rates on the enamel (3 different load ranges). RESULTS: It was found that the enamel's resistance to tribological wear is significantly higher than that of the tested dental materials. It is also important to note that, depending on the penetration depth of the indenter (depends on the indenter pressure), different hardness values and Young's modulus of enamel were obtained after friction with different dental materials. This demonstrates the formation of a surface layer with different properties than the native material. CONCLUSIONS: Analysis of the obtained results suggests the existence of different tribological wear mechanisms, as evidenced by significant differences in the wear values of dental materials and enamel. The data show that the enamel surface layer modified by the contacting dental material is shaped to a certain depth, and different thickness ranges of the changed layer have different properties.


Assuntos
Esmalte Dentário/efeitos dos fármacos , Materiais Dentários/farmacologia , Módulo de Elasticidade , Luzes de Cura Dentária , Fricção , Dureza , Propriedades de Superfície
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