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PubMed2003

[Comparative study of friction and wear behavior of different human enamel in vitro].

OBJECTIVE: To investigate the friction and wear behavior of different human enamels. METHODS: 24 enamel samples selected from aged, young permanent and faded deciduous teeth were classified into 3 groups and slid against artificial porcelain teeth in the presence of artificial saliva on an oscillating friction and wear test rig. The wear volume loss, microhardness and toughness of each group of the enamel specimens were measured, the wear scars were observed with a scanning electron microscope, and the elemental compositions of Ca, P, and Si of the wear scar and wear debris were determined with an energy dispersion spectrometer. RESULTS: The wear volume losses of aged, young permanent and deciduous tooth enamels are (2.40 +/- 1.10) x 10(-12) m(3), (3.50 +/- 1.83) x 10(-12) m(3) and (4.86 +/- 2.49) x 10(-12) m(3). The data of aged tooth enamels are statistically greater than that of deciduous tooth enamels (P < 0.05). There is no significant difference between the wear volume loss of aged and young permanent tooth enamels or between the young permanent and deciduous tooth enamels (P > 0.05). However, the friction and wear behavior of each group of enamel specimens is different from each other. CONCLUSIONS: In the present testing condition, the wear scars of each kind of enamel specimens is characterized by ploughing and cracking. The different wear resistance of the three kinds of enamels is attributed to the different microstructure of the enamel, while the hardness and toughness of the enamels are not correlated with the wear resistance.

Adolescent↗
PubMed1991

Materials and appliances in orthodontics: brackets, arch wires, and friction.

The focal point for any orthodontic patient is the form and comfort of his or her appliance. To the practitioner, both can influence the function of the arch wire-bracket combination. The most critical interaction that occurs within the so-called couple is friction. When friction is high, sliding is hampered, as the efficiency and reproducibility of the appliance may be impaired. In this review, the recent advances to control friction and to modify the arch wire-bracket combination are reviewed.

Alloys↗
PubMed1987

Wear, creep, and frictional heat of femoral implant articulating surfaces and the effect on long-term performance--Part I, A review.

Creep and wear of articulating reconstructed joints is a complex process, resulting in adverse tissue response, decreased range of motion, and eventual revision. As improvements are made in the design and surgical techniques of reconstructed joints, the long-term performance of the articulating system and materials becomes more important, particularly for younger, heavier, and more active patients. One aspect previously ignored in the long-term performance of articulating systems is the tendency for these systems to generate heat during articulation, particularly for extended periods of relatively strenuous activity. The present study reviews the various aspects of joint lubrication, friction, wear, and overall system performance. Local heating can increase the creep, wear, and oxidation degradation of UHMWPE, thus, specific attention is given to the effect that heat generation can have on long-term performance of these systems. Because of the complexity of this issue, the treatment of these various performance aspects is divided into two parts. The present part, Part I, reviews the various aspects of articulation performance. Part II presents results of friction, heating, and torque testing of various metal and ceramic hip systems. Criteria for frictional heating is also presented, along with discussion related to the various heat transfer mechanisms involved with heat dissipation.

Biomechanical Phenomena↗
PubMedDate not supplied

[Study and calculation of friction losses in microturbines and burs for dentistry].

The method to compute friction loss in medical microturbines and tips at the stage of their development is proposed. It is verified when designing friction loss of the following devices: a turbine tip HTC-300-02, a pneumatic micromotor MMP-20, and micromotor tips (NVP-30M) and (NP-30M). The method may be useful in estimated designs of friction loss.

Dental High-Speed Equipment↗
PubMed1984

Morphometric studies of the epidermal-dermal junction in the rat ear: some effects of experimental friction on epidermis and anchoring fibrils.

The aim of this investigation was to determine whether, following the application of experimental friction to the skin, qualitative an quantitative differences could be induced in the epidermis and in anchoring fibrils. The skin of rat ears was subjected to repeated mild fractional stimulation with a rotating bristle brush moistened with saline thrice weekly for three weeks, untreated ears being used as controls. A stratified random sampling design was followed for the morphometric analysis of interfollicular epidermis. With the light microscope, the lengths of the granular cell/keratin (BGK) and epithelial-connective tissue (BEC) junctions were measured using an image analyser, as was the epithelial thickness (T). The ratio BEC/BGK provides an index of the degree of irregularity of the epithelial-connective tissue junction. Using electron microscopy, the numbers of anchoring fibrils per unit length of lamina densa (NB) were determined using stereological intersection counting. There are no significant differences in BEC/BGK or T between control and experimental groups, but anchoring fibril frequency NB increased from 10.29 micrometers in control epidermis to 18.9 micrometers in friction-treated epidermis. It is concluded that a mild frictional stimulus which fails to produce significant alterations in epidermal thickness can produce a marked increase in anchoring fibril frequency. This response may reflect a functional alteration associated with increased mechanical loading, in which epidermal-dermal adherence is augmented by either synthesis of anchoring fibrils or their insertion into the lamina densa.

Animals↗
PubMed1983

Frictional torque in surface and conventional hip replacement.

UNLABELLED: The frictional torque of the Trapezoidal-28 total hip replacement and the Tharies SR-3 and SR-5 surface replacements were measured in the University of California at Los Angeles hip-joint simulator in calf serum. Loads of as much as 890 newtons were applied while the femoral component oscillated through a 60-degree arc at forty cycles per minute. Frictional torque, as measured by a ring transducer at a fixed distance from the center of rotation, was seen to diminish as the thickness of the polyethylene increased and was found to be relatively proportional to the diameter of the femoral component. The torques measured in this study were found to be twenty to 100 times smaller than the static torques to failure for acetabular fixation that have been reported in the literature. Finally, no permanent deformation of the thin acetabular shells attributable to the cementing process was apparent when the recommended technique of surgical insertion was utilized. CLINICAL RELEVANCE: Surface replacement components have been shown to generate greater frictional torques at the acetabular bone-cement interface than do smaller-diameter conventional hip replacements. This indicates that the local mechanical-loading conditions of the hip joint are not the same for both types of replacements, and this should be considered when selecting the type of arthroplasty for an individual patient.

Biomechanical Phenomena↗
PubMed1977

High friction compression in the treatment of complicated fractures of the lower extremity.

Charnley's compression clamps have hastened the union of cancellous bones but not much success has been obtained in the slender shafts of cortical bones. The principles of biophysics show that a fracture site under compression acts as a hinge joint. If friction is increased in such "joints" along indicated axes, immobility of the fracture fragments can be obtained and lead to bone union. We have developed a modified device based on Charnley's compression clamps to create high friction compression. We successfully applied it in the treatment of eight fractures of the shafts of the femur or tibia which would not unite because of infection, soft tissue interposition or gross incongruity of fragments. The mechanical aspects of creating friction with the device are discussed.

Adult↗
PubMed1993

Measurement of friction between pulley and flexor tendon.

When tendon excursion takes place through the pulley, friction and drag are encountered at the interface. Repetitive exposure to such friction and attrition of the tendon has been considered one of the important factors causing cumulative trauma and leading to disorders such as tendinitis and tenosynovitis. In this study, development of an experimental method to evaluate friction and drag between the pulley and tendon under different loading conditions and joint configurations is considered. Verification of the model under an ideal situation of sutures across a mechanical pulley was performed.

Biomechanical Phenomena↗
PubMed1993

The use of transverse friction massage in the management of chronic bursitis of the hip or shoulder.

This article discusses two cases of chronic bursitis of the hip and shoulder treated by transverse friction massage. While clinical evidence has substantiated the benefits of friction massage on chronic tendinitis, previous literature has discouraged the use of friction massage in chronic bursitis. A functional examination and attention to associated biomechanical faults are also necessary for a complete noninvasive manual resolution of the problem.

Adult↗
PubMed1981

Friction and wear properties of polymer, metal, and ceramic prosthetic joint materials evaluated on a multichannel screening device.

A 12-channel wear screening device was used to compare the wear properties of a variety of prosthetic joint materials. Two types of tests were run: (1) Ultrahigh molecular weight (UHMW) polyethylene bearing against metal or ceramic counterfaces and (2) various polymers bearing against 316 stainless steel as a standard counterface. Wear was quantified by weighing the polymer specimens, with presoaking and control-soak specimens used to minimize the error due to fluid absorption. The specimens were lubricated with bovine blood serum. Friction and polyethylene wear was very low with each of the metals (316 stainless steel, cobalt-chrome alloy, multiphase alloy, and titanium 6-4 alloy) such that the differences in wear rate would not be significant in terms of choosing a material for clinical application. However, titanium 6-4 alloy was found to be especially susceptible to abrasive wear by particles of acrylic cement. Nitrided titanium 6-4 counterfaces were impervious to acrylic abrasion. Polyethylene wear against highly polished, fully dense ceramics (Sialon, Alumina, Macor, and pyrolytic graphite) was as low as that with the metal counterfaces. Wear increased slightly with increasing ceramic surface roughness. The coefficient of friction of polyethylene against pyrolytic graphite was two to three times higher than with the metals or other ceramics. All of the alternate polymers underwent more wear than UHMW polyethylene. Teflon and polyester, two polymers that have proven unsuccessful in prior clinical use, had wear rates 1,600 and 830 times greater than polyethylene, respectively, an indication that the laboratory wear test provided a quantitative prediction of the behavior of the materials in vivo. However, it was difficult to assess the clinical significance of the less extreme wear rates since the ability of the tissues encapsulating a prosthesis to accomodate wear debris is not known on a quantitative basis.

Animals↗
PubMed1999

The influence of bracket design on frictional losses in the bracket/arch wire system.

In arch guided tooth movement, the essential role played by bracket configuration with respect to sliding friction has been recognized by the manufacturers, a fact which has had an increasing impact on the design and marketing of new bracket models in recent years. The aim of the present in-vitro study was to investigate the influence of different bracket designs on sliding mechanics. Five differently shaped stainless steel brackets (Discovery: Dentaurum, Damon SL: A-Company, Synergy: Rocky Mountain Orthodontics, Viazis bracket and Omni Arch appliance: GAC) were compared in the 0.022"-slot system. The Orthodontic Measurement and Simulation System (OMSS) was used to quantify the difference between applied force (NiTi coil spring, 1.0 N) and orthodontically effective force and to determine leveling losses occurring during the sliding process in arch guided tooth movement. Simulated canine retraction was performed using continuous arch wires with the dimensions 0.019" x 0.025" (Standard Steel, Unitek) and 0.020" x 0.020" (Ideal Gold, GAC). Comparison of the brackets revealed friction-induced losses ranging from 20 to 70%, with clear-cut advantages resulting from the newly developed bracket types. However, an increased tendency towards leveling losses in terms of distal rotation (maximum 15 degrees) or buccal root torque (maximum 20 degrees) was recorded, especially with those brackets giving the arch wire increased mobility due to their shaping or lack of ligature wire.

Cuspid↗
PubMed2006

Surgical treatment of iliotibial band friction syndrome with the mesh technique.

Iliotibial band friction syndrome is an overuse injury caused by repetitive friction of the iliotibial band across the lateral femoral epicondyle. It has been reported to afflict long-distance runners, cyclists and military personnel. Initial treatments include rest, anti-inflammatory medication, modalities (ice or heat), stretching, physical therapy, and possibly a corticosteroid injection. If the conservative treatment is unsuccessful, surgery has been advocated. This report describes a new surgical technique to release the pressure on the lateral femoral epicondyle in a patient who failed the nonoperative efforts. The surgery was performed with the knee held in 30 degrees of flexion and consisted of multiple 2 mm long incisions across the fiber of the iliotibial band covering the lateral femoral epicondyle. There were six incisions, each of which was 4 mm apart. The incisions were spontaneously enlarged and changed to several punctured wounds (mesh appearance) by the tension of iliotibial band, resulted in relaxing the tight iliotibial band over the lateral femoral epicondyle. At the final follow-up 2 years after surgery the patient was pain free and could resume his previous occupational activities. The surgical result of the present technique is encouraging.

Adult↗
PubMed2006

Friction and forces between cellulose model surfaces: a comparison.

Four different cellulose model surfaces, and one silica surface, have been studied by means of atomic force microscopy (AFM). The normal interactions have been found to consist of a longer range double layer force with a short range steric interaction, the nature of which is extensively discussed. Both the surface charge and range of the steric force depend on the type of cellulose substrate used, as does the magnitude of the adhesion. Studies of friction reveal that surface roughness is the determining factor for the friction coefficient, with which it increases monotonically. The absolute value, however, is determined by the surface chemistry. All studied cellulose surfaces show similar behavior in response to xyloglucan addition.

Cellulose↗
PubMed2006

Effect of incisional friction and ophthalmic viscosurgical devices on the heat generation of ultrasound during cataract surgery.

PURPOSE: To determine the thermal features of the Legacy (Alcon) and Sovereign (Advanced Medical Optics) phacoemulsification machines in a cadaver eye and with 7 ophthalmic viscosurgical devices (OVDs). SETTING: In situ and in vitro study. METHODS: Temperature without occlusion was recorded at the sleeve placed in the wound of a cadaver eye, and temperature over baseline was determined after 60 seconds. The result was then compared with the results in a previous study that used balanced salt solution (BSS) in artificial chambers. In the second portion of the experiment, with irrigation and aspiration lines occluded, temperature was recorded at the sleeve placed in an artificial chamber filled with sodium hyaluronate 2.3% (Healon5), sodium hyaluronate 1.4% (Healon GV), sodium hyaluronate 1.0% (Healon), sodium hyaluronate 1.6% (Amvisc Plus), sodium hyaluronate 1.0% (Provisc), sodium hyaluronate 3.0%-chondroitin sulfate 4.0% (Viscoat), or hyaluronate 3.0% (Vitrax). Temperature over baseline was also determined after 60 seconds. These results were compared with each set of OVD data and with the results in the prior BSS study. RESULTS: In the eye-bank model, the Legacy machine had a 62% temperature increase from incisional friction and the Sovereign machine had a decrease of 8.6% over results in an artificial anterior chamber. The OVD temperature increases were greater for the Sovereign (P<.001) and followed the same general trend for the Legacy. The least temperature increase was with Amvisc Plus, Healon, and Healon GV; the intermediate increases were with Provisc and Vitrax; and the greatest increases were with Viscoat and Healon5. The OVD findings did not correlate with viscosity or pseudoplasticity. CONCLUSIONS: Incisional friction alone increased heat generation in the Legacy, a stroke-length driven instrument, more than in the Sovereign, a power-driven instrument. Ophthalmic viscosurgical devices are not only a concern due to outflow occlusion but can also add up to 6 times the heat in comparison with BSS. The need to aspirate the OVD before using ultrasound is thus verified.

Aged↗
PubMed2004

Does support surface coefficient of friction influence postural dynamics and isometric force productions of the upper extremities performed by seated subjects?

The purpose of this study is to determine if increasing the potential risk of slipping on support surface materials decreases postural dynamics and task performance. Seated subjects were asked to exert maximum horizontal two-handed isometric pushes as quickly as possible on a dynamometric bar. Reaction forces exerted at seat (Rxs and Rzs) and footrest (Rxf and Rzf) were measured using force sensors. A dynamometric bar measured horizontal push force (Fx). Global adherence ratio (micro) was calculated. Three support surface materials, characterised by different coefficients of friction, were tested. The same surfaces were placed on the seat and the footrest during a series of pushes. It was shown that the different support surfaces significantly influence Fx, Rxs, Rzs, Rzf and micro maximum values obtained at the end of the push. Even when the instructions given to the subject are to produce a maximum push, the maximum horizontal force applied to the bar differs according to the support surface material. Dynamic postural adjustments are influenced by characteristics of slipperiness of support surfaces. The coefficient of friction contributes an essential element to the program of postural dynamics, which in turn modulates the task performance. During brief isometric pushes, seated subjects have the capacity to control the potential risk of slipping.

Adult↗
PubMed2004

Reducing friction by chemically modifying the surface of extrasynovial tendon grafts.

In this study we evaluated methods to reduce the friction of an extrasynovial tendon under a pulley in vitro. The surface of canine peroneus longus (PL) tendons was modified with gelatin and/or hyaluronic acid (HA) under different conditions. The gliding resistance between treated or control tendons and the canine digital flexor pulley was measured during 500 cycles of simulated flexion/extension. After 500 cycles, the gliding resistance of normal PL tendon increased 10-fold (p<0.05), while the gliding resistance of tendons coated with carbodiimide derivatized gelatin (cd-gelatin) or carbodiimide derivatized gelatin/HA (cd-gelatin-HA) did not increase significantly. The PL tendon treated with cd-gelatin-HA had a similar friction response during the repetitive motion as the intrasynovial flexor digitorum profundus (FDP) tendon. Scanning electron microscopy after 500 cycles of motion showed that the tendon surface in the group treated with cd-gelatin-HA appeared smoother than tendons in the other groups.

Animals↗
PubMed2000

Force transfer between the plate and the bone: relative importance of the bending stiffness of the screws friction between plate and bone.

Stability in plate fixation of fractures relates to the motionless fastening between plate and bone. When the plate is affixed to the bone, high shear force may appear between plate and bone, particularly near the end screws, which can lead to motion under weight-bearing. Two mechanisms might be involved in the prevention of motion: the bending stiffness of the screws or the friction between the screw and the plate. Experiments performed in vivo and in vitro show that with conventional plates, motion is prevented by friction and depends upon the axial force of the screw, pressing the plate onto the bone. The torque applied to the screws is crucial. Motion appears under smooth plates under relatively low physiological loads. With newly developed internal fixators, the motion is prevented by the structural stiffness of the plate-screw system.

Animals↗
PubMed2003

Frictional properties of poly(MPC-co-BMA) phospholipid polymer for catheter applications.

A fundamental understanding of surface properties of the biomaterials at a nanometer scale should be generated in order to understand cellular responses of the tissue to biomaterials thereby minimizing or eliminating tissue trauma at a macrometer scale. In this study poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) ([poly(MPC-co-BMA]) was evaluated as a potential coating material for vascular applications to provide smooth catheterization using atomic force microscopy (AFM) techniques.A uniform coating of [poly(MPC-co-BMA] equivalent to a thickness of 2.5 microm on a polyurethane (PU) catheter material was provided using dip casting technique. Using a contact mode AFM, no significant difference in surface roughness (R(a)) and frictional force (f) between uncoated (R(a)=10.2+/-1.9 nm, f=0.907+/-0.02) and coated (R(a)=11.7+/-1.8 nm, f=0.930+/-0.06) surfaces was observed under dry conditions. However, under wet conditions the R(a) of the coated surface (3.4+/-1.0 nm) was significantly lower than uncoated PU surface (9.0+/-1.8 nm). The coating on PU substrate offered the least frictional resistance (f=0.004+/-0.001) illustrating enhanced boundary lubrication capability due to hydration of phosphorylcholine polymer as compared to a significantly higher f for uncoated PU (0.017+/-0.007) surfaces. These tribological and chemical characteristics of the [poly(MPC-co-BMA)] coating could increase the overall efficacy of PU for clinical applications.

Catheterization↗