Measurement of the elastic modulus of fibre-reinforced composites used as orthodontic wires

Abstract

The mechanical properties of an orthodontic wire pultruded from S2-glass-reinforced polyethyleneterephthalate glycol (PETG) were measured using two experimental devices simulating clinical conditions. A comparison of moduli measured in the clinically relevant devices with those measured in a standard flexural test reveals that data obtained using small cross-section, short span length clinical specimens require corrections associated with clamping and shearing effects. The clamping effect dominates and is caused by the softening of the material near the clamps. The shear effect becomes important at high fibre volume fractions and small span/thickness ratios. With adoption of these corrections, good agreement between moduli calculated using rule of mixtures and those measured in clinical tests is achieved. The analytical base developed for prediction of the stiffness of the orthodontic wire for different span/thickness ratios improves .the procedure for design of dental appliances.

Thermoplastic fibre-reinforced composites for dentistry

“…A further difficulty is that when used in span-depth ratios below 15 damage at the clamping points, caused by high strain, results in a significant loss of longitudinal stiffness [22]. In this and previous studies we have shown that the limiting factors in the practical utilization of these materials are the weakness and relative instability in a moist environment of the transverse strength and ultimate strain-to-break.…”

“…Their stiffness was measured after different times of water immersion, using a device simulating clinical conditions [22] an d the percentage reduction in stiffness was plotted against the time of immersion. Their stiffness was measured after different times of water immersion, using a device simulating clinical conditions [22] an d the percentage reduction in stiffness was plotted against the time of immersion.…”

“…Earlier it was also found that under simulated clinical conditions the span/thickness ratio and clamping of the specimen ends are of critical importance in determining the elastic properties and failure of FRC wires [22]. Since these effects will also exacerbate problems associated with the stability of an appliance, it will be necessary to separate the end-effects from the inherent behaviour of the material.…”

Polymer nanocomposites: Current understanding and issues

“…As regards, changes in the conformation of long chain molecules in the immediate vicinity of the surface of fillers, there are a few reports in the literature. It was suggested by Dasari and Misra 85 6 Wide angle X-ray diffraction (WAXD) patterns for PP/glass bead composites crystallised at a 100 MPa and b ambient pressure and Jancar et al 86 that chains are less densely packed at interface, i.e. they exist as expanded coils.…”

Fibrous composite materials in dentistry and orthopaedics: review and applications

“…The major materials were epoxy resin [62], polyethylene-terephtalate-glycol (PETG) and poly(1,4 cyclohexylene dimethylene terephthalate glycol (PCTG) [6,63], and poly-methyl-methacrylate (PMMA) [62] reinforced by S-glass fiber which has higher strength than E-glass fiber. Photopolymerized dental resins, such as urethanedimethacrylate (UDMA) [63,64], bisphenol-A glycidyl methacrylate (bis-GMA) [8,[65][66][67], however have become popular matrix since they have been accepted for teeth restoration. The group of Watari et al, gave the biocompatible function to glass fibers and fabricated composite archwires with photopolymerized resins [62,64,[68][69][70].…”