Preformed Archwires Research Articles

Analyse de l'évolution de la forme d'arcade après traitement par le logiciel «ARCAD'Image»

The dental arch post-therapeutic modification plays a significant role in relapse phenomenon. This article describes the design work of the dental arches used as a base for the study of modifications that have arisen during orthodontic treatment then during the retention stage using pre-formed arch wires. ARCAD'Image software tries to design the patients dental arches by submitting a linear regression mathematical design on some characteristic landmarks of a photograph of the buccal impression. The designed dental arch can then be considered as being the closest/nearest to the patients morphology. This model enables the practitioner to bend the arch wire and is used as a base for the study of arch shape modifications. Our study shows that the term "relapse" appears to be used excessively; it would be more matter of evolution due to changes in neuro-muscular balance along with facial aging.

An evaluation of the shape of some popular nickel titanium alloy preformed arch wires

The mathematical Beta function is shown to be an accurate planar representation of the natural human arch form defined by the spacial coordinates of the labial and buccal dental/bracket interfacing surfaces in the maxillary and mandibular arches. Graphic planar representations of the corresponding bracket base spacial coordinates of 33 popular preformed nickel titanium arch wires and bracket assemblies were superimposed on each of the relevant maxillary and mandibular natural forms. The arch forms of the preformed nickel titanium arch wires and bracket assemblies did not emulate the natural human arch form. The average mandibular natural human arch form first molar/canine width ratio is 2.38/1; the same preformed arch wire/bracket ratio is 1.87/1. These ratios for the maxillary arch are 1.92/1 and 1.54/1, respectively. The average canine width exceeded the natural canine width by 5.95 mm in the mandibular arch and 8.23 mm in the maxillary arch. The corresponding mandibular first molar and maxillary first molar widths exceeded the natural human first molar arch width by 0.84 mm and 2.68 mm, respectively. These findings have implications with respect to posttreatment stability and facial esthetics. “Round tripping” teeth resulting from subsequent change to stainless steel arch wires to restore a more natural human arch form and size may result in deleterious tissue effects. (Am J Orthod Dentofacial Orthop 1999;116:1-12)

Management of dental trauma: development of a 2D data acquisition system to evaluate passivity of dental splints.

Management of dental trauma in children sometimes requires the use of dental splints, which can be constructed from orthodontic materials. Past studies of the mechanical properties of dental splints have only been interested in their flexibility and not passivity. The purpose of this study is to determine the passivity of splints constructed from orthodontic materials. A specific data acquisition system, with a 2D transducer, is developed for evaluation of its neutrality. The transducer detects the displacements of the splinted tooth generated by the splint. The splints are constructed with 0.406 mm round, straight or Arch Blank preformed stainless-steel wires, with 0.559 mm standard edgewise brackets and with 0.254 mm stainless-steel or 3.05 mm elastomeric ligatures. Results show that mean output voltages generated by the splints range from 1.13 V to 2.48 V. The best control of passivity is obtained with the splints constructed with a preformed archwire and with elastomeric ligatures (p < 0.05), and the worst control is obtained with those constructed with a straight wire and with stainless-steel ligatures (p < 0.05).

An ideal preformed archwire?

(1993). An Ideal Preformed Archwire? British Journal of Orthodontics: Vol. 20, No. 1, pp. 65-70.

Localized, transverse, flexural stiffnesses of continuous arch wires

Elastic bending (flexure) theory, although apparently extendable to the arch wire, incorporates assumptions that are violated in orthodontic application, and neglects several influences confined to the clinical arena. The standard elastic-bending test for orthodontic wires uses a passively straight segment of wire, and a rotational bending stiffness rather than the force-deflection ratio akin to the transverse deformation of a leveling wire is determined. In this study the transverse flexural stiffnesses of five preformed arch wires were quantified in each of three activation directions at five separate sites on simulated dental arches to which appliances were affixed. The influences of elastic moduli, numbers of strands, and interbracket distances were found to be less substantial than theory suggests. Other parameters, including wire curvature at the activation site, malalignment direction relative to that curvature, bracket-wire friction, and preactivation fit of the preformed arch to the dentition, also affected the localized, transverse, flexural stiffnesses.

An investigation of linear dimensional changes as a function of temperature in an 0.010 inch 55cobalt-substituted annealed nitinol alloy wire

There are two frequently used methods of aligning malposed teeth by means of an arch wire. The first method is to deflect and tie the arch wire, which has a low modulus of elasticity, into the deepest part of the bracket slot. This low-modulus arch wire is not permanently deformed, and the elastic forces in it return the arch wire (which is tied to the bracket on the tooth) to its preformed shape. The second method is to stretch an elastic material (for example, Unitek ligature threads, Unitek Alastik modules, Ormco power threads, or Ormolast ligature modules) from the bracket tie wings to a preformed stiff arch wire which has a high modulus of elasticity and the teeth move from their malposed position to the stiff arch wire form. The objective of this investigation was to stretch a thermodynamic nitinol wire from 8 percent to 12 percent of its original length and measure the shrinkage of the wire in length. If the quantity of shrinkage of a 0.010-inch nitinol ligature type of wire were great enough, the second method of moving teeth to a stiff preformed arch wire by employing the thermodynamic nitinol stretched wire as a “wire rubber band” could be used to move teeth. This could serve as a possible alternative to Alastik and elastic modules in which there is a great deal of inherent force decay and permanent deformation. When the thermodynamic nitinol wire was heated through its transition temperature range, three different magnitudes of shrinkage occurred. The first was less than 1.0 percent of the original stretched length of the wire, the second was between 6 percent and 7 percent of the original stretched length of the wire, and the third was approximately 1.0 percent.

Preformed arch wires: Reliability of fit

The preformed arch wires currently available are unsuitable for many orthodontic cases, since these arch wires do not take into account all the variations in the size and dimensions of the human arch. In this study, nine theoretical arch wires are derived, based upon two-parameter curves. Tests were conducted which demonstrated that arch wires performed to these nine sets of dimensions would correspond with a reasonable degree of accuracy to a large section of the orthodontic population.

An evaluation of cobalt-substituted nitinol wire in orthodontics

Eight distinct types of wires were compared for the property of each wire's working range. Specifically, the two types of cobalt nitinol wires were compared with three typical 18-8 stainless steel leveling wires (0.014, 0.016, and 0.018 inch) and three typical Twist-Flex leveling wires (0.0175, 0.0195, and 0.0215 inch). The parameter measured was per cent elastic return of the deflected wire back to an original undeflected undeformed parabolic preformed arch shape. Double determinations of 480 measurements by two independent observers, abstracted and statistically quantified, are reported in two tables in addition to being graphically illustrated. Ten replications of each of the eight wire types were made in order to determine and quantify the following four variables: 1. 1. Millimeter return of the wire after being deflected and tied into the bracket slot. 2. 2. Millimeter distance of the undeflected undeformed “standard” preformed arch wire form from the bracket slot. 3. 3. Standard deviation of the millimeter return after the wire was cut loose from the bracket slot and had some degree of permanent deformation remaining in the wire. 4. 4. Per cent return of the permanently deformed test wire expressed as a ratio of the “standard” undeformed preformed wire's distance to the deepest part of the bracket slot. Measurements were achieved by the investigators' use of vernier calipers (Helios) with a dial read out to 1 20 mm., on standardized photographs of each wire's deformation compared to its standard.