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At least 19 recordsLinked to original sources
PubMed1991

Friction ... Friction resistance between edgewise brackets and archwires.

This study quantified the dynamic frictional force encountered when TMA, Orthonol and multistranded stainless steel archwires were pulled a distance of 2mm through ceramic and stainless steel brackets. The current literature is inadequate and incomplete, for example, no data was found on rectangular multistranded archwires. The following factors were investigated: archwire material, archwire size, archwire-to-bracket angulation, bracket material, archwire and bracket slot surface roughness and lubrication in the form of artificial saliva. A total of 156 different combinations were investigated. A universal testing machine was used to pull the ligated archwires through the brackets, and record the friction. A four way analysis of variance with one nesting (archwire size) was carried out on 1,560 measurements to assess the results. All factors and interactions tested were significant in determining friction. Friction was found to increase with: archwire angulation and archwire size (exceptions were seen in some TMA archwires). Friction decreased with lubrication. There was a definite relationship between friction and archwire and bracket material. There was no definite relationship between archwire surface roughness and friction. Highest friction was observed with ceramic bracket and TMA archwire. The range of friction was 1.02 to 9.95 Newtons. The magnitude of the friction recorded is substantially larger than the forces applied in orthodontic movement clinically. It is proposed that the values recorded should be utilised as a means of comparing the effects of different factors, rather than for the quantification of friction in vivo.

Analysis of Variance↗
PubMed1988

Wear, creep, and frictional heating of femoral implant articulating surfaces and the effect on long-term performance--Part II, Friction, heating, and torque.

In Part I, (J.A. Davidson and G. Schwartz, "Wear, creep, and frictional heating of femoral implant articulating surfaces and the effect on long-term performance--Part I, A review," J. Biomed. Mater. Res., 21, 000-000 (1987) it was shown that lubrication of the artificial hip joint was complex and that long-term performance is governed by the combined wear, creep, and to a lesser extent, oxidation degradation of the articulating materials. Importantly, it was shown that a tendency for heating exists during articulation in the hip joint and that elevated temperatures can increase the wear, creep, and oxidation degradation rate of UHMWPE. The present study was performed to examine closely the propensity to generate heat during articulation in a hip joint simulator. The systems investigated were polished Co-Cr-Mo alloy articulating against UHMWPE, polished alumina ceramic against UHMWPE, and polished alumina against itself. Frictional torque was also evaluated for each system at various levels of applied loads. A walking load history was used in both the frictional heating and torque tests. The majority of tests were performed with 5 mL of water lubricant. However, the effect of various concentrations of hyaluronic acid was also evaluated. Results showed frictional heating to occur in all three systems, reaching an equilibrium after roughly 30 min articulation time. Ceramic systems showed reduced levels of heating compared to the cobalt alloy-UHMWPE system. The level of frictional torque for each system ranked similar to their respective tendencies to generate heat. Hyaluronic acid had little effect, while dry conditions and the presence of small quantities of bone cement powder in water lubricant significantly increased frictional torque.

Hip Prosthesis↗
PubMed1979

[Importance of the friction between plate and bone in the anchoring of plates for osteosynthesis. Determination of the coefficient of metal-bone friction in animal in vivo].

In mechanical devices in general the friction plays an important role in force transmission. To find out about the magnitude of frictional forces between internal fixation plate and bone in vivo, simultaneous strain recording in plated bone and instrumented plate were performed. After 3 weeks of implantation the torque applied to a single plate-screw was set to definite levels. Thus it could be determined at what level of screw compression and at what tangential load of the related surface bone-plate, gliding occurred. The coefficient of friction was found to be 0.2 +/- 0.09 (x +/- Sx). It can be concluded that in vivo friction produced at the plate-bone contact surface is able to guarantee stability of fixation.

Animals↗
PubMed1989

[Study on frictional characteristics of KB horizontal brackets. A comparative study of kinetic frictional forces to be caused between various kinds of brackets and wires].

KB horizontal brackets were designed to tip no more than 6 degrees at the maximum. This tipping amount is based on the idea of reducing friction between a wire and brackets to allow the effective tooth movement of the Begg technique even with horizontally long brackets, and does not originate in the concept of carrying out tipping movement. Thereon, experimental measurements by use of Rheometer were conducted to review for comparison of the kinetic frictional forces caused between various wires and the following four types of brackets; KB horizontal brackets, Tip edge brackets, Straight edge brackets and Begg brackets. 1. In case of utilizing ribbon arch wires and rectangular wires, no significant difference was acknowledged among Tip edge, KB horizontal and Straight edge brackets. 2. There proved to be a reduction in the kinetic frictional forces by incorporating tip into the edgewise slots, when using smaller dimensions of the wires which call for the effective tooth movement, however, Begg brackets (in conjunction with Ordinary T-pins and/or Safety T-pins) showed the small value which is far less than that of the three kinds of brackets.

Orthodontic Appliances↗
PubMed1986

Comparative friction of orthodontic wires under dry and wet conditions.

Kinetic coefficients of friction for stainless steel, beta-titanium, nickel-titanium, and cobalt-chromium arch wires were measured on a smooth stainless steel or Teflon surface. A universal materials testing instrument was used to pull 0.017 X 0.025-inch rectangular arch wires through a pneumatically controlled binding surface. Classical friction relationships were evaluated by varying applied normal force--similar to ligature tie force--via this pneumatic control. Coefficients of friction were determined under dry and wet (artificial saliva) conditions. Frictional force values, and thus coefficients of friction, were found to increase with increasing normal force for all materials. Beta-titanium and stainless steel wires sliding against stainless steel, and stainless steel wire on Teflon consistently exhibited the lowest dry friction values. Artificial saliva increased friction for stainless steel, beta-titanium, and nickel-titanium wires sliding against stainless steel. Artificial saliva did not increase friction for cobalt chromium, stainless steel sliding against stainless steel, or stainless steel wire on Teflon compared to the dry condition. Stainless steel and beta-titanium wires sliding against stainless steel and stainless steel wire on Teflon showed the lowest friction values for the wet condition.

Chromium Alloys↗
PubMed1992

Ice friction during speed skating.

During speed skating, the external power output delivered by the athlete is predominantly used to overcome the air and ice frictional forces. Special skates were developed and used to measure the ice frictional forces during actual speed skating. The mean coefficients of friction for the straights and curves were, respectively, 0.0046 and 0.0059. The minimum value of the coefficient of ice friction was measured at an ice surface temperature of about -7 degrees C. It was found that the coefficient of friction increases with increasing speed. In the literature, it is suggested that the relatively low friction in skating results from a thin film of liquid water on the ice surface. Theories about the presence of water between the rubbing surfaces are focused on the formation of water by pressure-melting, melting due to frictional heating and on the 'liquid-like' properties of the ice surface. From our measurements and calculations, it is concluded that the liquid-like surface properties of ice seem to be a reasonable explanation for the low friction during speed skating.

Biomechanical Phenomena↗
PubMed1990

Evaluation of friction between edgewise stainless steel brackets and orthodontic wires of four alloys.

This investigation was designed to determine the effects of wire size and alloy on frictional force generated between bracket and wire during in vitro translatory displacement of bracket relative to wire. Stainless steel (SS), cobalt-chromium (Co-Cr), nickel-titanium (NiTi), and beta-titanium (beta-Ti) wires of several sizes were tested in narrow single (0.050-inch), medium twin (0.130-inch) and wide twin (0.180-inch) stainless steel brackets in both 0.018- and 0.022-inch slots. The wires were ligated into the brackets with elastomeric ligatures. Bracket movement along the wire was implemented by means of a mechanical testing instrument, and frictional forces were measured by a compression cell and recorded on an X-Y recorder. beta-Ti and NiTi wires generated greater amounts of frictional forces than SS or Co-Cr wires did for most wire sizes. Increase in wire size generally resulted in increased bracket-wire friction. The wire size-alloy interaction on the magnitude of bracket-wire friction was statistically significant (p less than 0.005). With most wire sizes and alloys, narrow single brackets were associated with lower amounts of friction than wider brackets were. The levels of frictional forces in 0.018-inch brackets ranged from 49 gm with 0.016-inch SS wires in narrow single brackets to 336 gm with 0.017 x 0.025-inch beta-Ti wires in wide twin brackets. Similarly for 0.022-inch brackets, frictional forces ranged from 40 gm with 0.018-inch SS wires in narrow single brackets to 222 gm with 0.019 x 0.025-inch NiTi wires in wide twin brackets.

Analysis of Variance↗
PubMed1990

[The effect of the ligature on the friction between bracket and arch].

The combinations of five different wire materials and six ligatures were analysed with the help of a testing apparatus in order to determine the loss in orthodontic force caused by friction between arch wire and ligature. The bracket was fixed at an angulation of zero degrees with respect to the arch wire. The results of our measurements can be summarized as follows: 1. Friction is determined mostly by the sort of ligature and by the way of ligation and not by the dimensions of the different arch wires. 2. Friction caused by alastics is significantly less than friction caused by steel-ligatures. This can be observed especially if standard-steel wires are used. 3. Frictional forces are astonishingly low if multistrand wires are used. Even the 0.016 x 0.022 Force 9 wire shows little friction. 4. Orthodontic force may even be neutralized if a steel ligature is combined with standard steel wires (0.016 and 0.016 x 0.022). 5. This leads to the proposal that a steel ligature should be retwisted for about 90 to 180 degrees next to the bracket, if orthodontic tooth translation is to be achieved. 6. Using the Unitek Quicksticks causes least friction beneath the alastics.

Biomechanical Phenomena↗
PubMed1975

"Stiction-friction" of total hip prostheses and its relationship to loosening.

The static friction, or "stiction-friction", in McKee-Farrar and Charnley-Müller prostheses in a hip joint simulator was compared with dynamic friction determined while the prostheses were oscillated. Under physiological conditions stiction-friction differed little from dynamic friction in both metal-on-metal and metal-on-plastic prostheses, and was affected very little by the lubricant as long as some fluid was present. Stiction-friction increased significantly only after relatively long stationary periods and high loads. However, the frictional forces generated in total hip-replacement prostheses were at least forty times higher than those generated in normal joints and may well be enough to cause late loosening of acetabular components by fatigue failure.

Acetabulum↗
PubMed1985

Effect of suture material and construction on frictional properties of sutures.

The results overwhelmingly support the view that the coefficient of friction is not a material constant of the sutures but a function of several variables, including applied tension, suture construction and suture material. The coefficient of friction decreased with an increase in applied tension with the rate of change depending upon the suture material. Prolene and Ethilon had the highest frictional values among all sutures at low tension, but dropped to a position of lowest values at high tension. On an average, braided sutures gave higher frictional values than did the monofilament sutures. Sutures with special surface coatings (silicone or Teflon) generally gave lower values than did the sutures without any such coatings. Similar results were reported in other studies on coated materials. The differences in frictional profiles are governed by the differences in the viscoelastic nature of the suture materials. The unusual traces produced by Prolene were considered as being due to its high degree of stretch and elasticity. Others similarly found that Prolene behaved peculiarly due to a high degree of stretch. Finally, coefficient of friction is an important property of suture materials as it is expected to have a direct bearing on the security of knots. A careful study of this parameter under a variety of clinical conditions is essential to gain an understanding of the behavior of surgical knots in clinical practice. The present study gives detailed information on the frictional behavior of various types of surgical suture materials.

Sutures↗
PubMed1988

Heat transfer analysis of frictional heat dissipation during articulation of femoral implants.

Previous studies have shown the tendency for frictional heating to occur during articulation of total hip systems in vitro under simulated hip loading conditions. The magnitude of this heating is sufficient to accelerate wear, creep, and oxidation degradation of the UHMWPE bearing surface. It was shown that ceramic articulating systems generate less frictional heating than polished cobalt alloy against UHMWPE. This frictional heating is expected to occur primarily for younger, heavier, and more active patients. Thus, long-term performance of the articulating hip system in these patients may not be that predicted from current, body-temperature wear, creep, and degradation studies. Although the tendency to generate frictional heat has been observed only during in vitro simulated hip loading, a heat transfer analysis of this phenomenon is presented to evaluate the ability of the hip joint to dissipate such heating in vivo. Additional experiments were performed using controlled resistance heaters inside a cobalt femoral head to verify the calculated levels of frictional heat and to assess the heat dissipation under simulated in vivo conditions. The effect of blood perfusion on the effective thermal conductivity of the joint capsule is also discussed. The present study describes and analyzes the various heat dissipation mechanisms present both in vitro and in vivo during articulation of metal and ceramic hip systems. From these tests and analyses, it is concluded that frictional heating in the reconstructed hip cannot be effectively removed, and that degredative elevated temperature processes can be expected to occur in vivo to both the UHMWPE and adjacent tissue under extended periods of excessive patient activity. This is particularly true for metal cobalt alloy femoral heads articulating on UHMWPE versus ceramic heads which generate significantly lower levels of heat.

Alloys↗
PubMed1990

Friction properties of the interface between porous-surfaced metals and tibial cancellous bone.

Friction tests between cancellous bone cubes and porous-surfaced metal plates were conducted in order to determine the mechanical properties of the interface in a knee porous-surfaced metal implant. Bone specimens were obtained from fresh frozen amputated tibiae and three metal plates were chosen: titanium bead porous-surfaced, titanium fiber mesh porous-surfaced, and smooth stainless steel. Results show that the friction curve is highly nonlinear. Friction coefficients measured vary between 0.3 and 1.3. The friction coefficient of the interface is independent of the excision site of the bone cubes and of the magnitude of the rate of relative displacement at the interface. The friction coefficient appears to vary slightly with the normal contact pressure for all the metal surfaces. Both porous surfaces have statistically a higher friction coefficient than the smooth surface. This is likely due to the presence of surface asperities whereby the metal ploughs the bone surface. However, no significant differences is observed between bead and fiber mesh types.

Biocompatible Materials↗
PubMed1991

[The effect of physiological tooth mobility on the friction between the bracket and the arch].

This study compared frictional forces which occurred in vivo and in vitro. A testing device was used which allowed reproduction of friction measurements carried out on upper central incisors of volunteers under laboratory conditions with the bracket fixed immovable. By this means changes of friction due to physiological tooth mobility and occlusal load of the bonded teeth could be investigated. While the friction measured in vitro with immovable brackets and in vivo without occlusal load did not differ significantly, additional tooth movement by occlusal load resulted in significant reduction of friction magnitude. It should be kept in mind that the mobility of those teeth investigated was absolutely normal, while it is usually increased during orthodontic treatment. Due to this effect and influences resulting from chewing various kinds of food, it can be estimated that the frictional forces occurring with orthodontic treatment are even smaller in comparison to in vitro experiments with immovable brackets.

Biophysical Phenomena↗
PubMed1990

Effects of surface roughness on the coefficients of friction in model orthodontic systems.

Orthodontists, like others (Engel, P.A. (1976) Impact Wear of Materials. Elsevier Scientific, New York.), often equate the smoothness of surfaces with the absence of friction. To investigate whether the surface roughness of opposing materials influence the coefficients of friction and ultimately the movement of teeth, arch wires were slid between contact flats to simulate orthodontic arch wire-bracket appliances. From laser specular reflectance measurements, the RMS surface roughness of these arch wires varied from 0.04 microns for stainless steel to 0.23 microns for nickel titanium. Using the same technique, the roughnesses of the contact flats varied from 0.03 microns for the 1 micron lapped stainless steel, to 0.26 microns for the as-received alumina. After each of the arch wire-contact flat couples was placed in a friction tester, fifteen normal forces were systemically applied at 34 degrees C. From plots of the static and kinetic frictional forces vs the normal forces, dry coefficients of friction was obtained that were greater than those reported in the dental literature. The all-stainless steel couples had lower kinetic coefficients (0.120-0.148) than the stainless steel-polycrystalline alumina couple (0.187). When pressed against the various flats, the beta-titanium arch wire (RMS = 0.14 microns) had the highest coefficients of friction (0.445-0.658), although the nickel titanium arch wire was the roughest (RMS = 0.23 microns). Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) verified that mass transfer of the beta-titanium arch wire occurred by adhesion onto the stainless steel flats or by abrasion from the sharply faceted polycrystalline alumina flats.

Aluminum Oxide↗