Types Of Archwires Research Articles

Effect of archwire size and material on the resistance to sliding of self-ligating brackets with second-order angulation in the dry state

When paired with a particular self-ligating bracket design, the material and the geometric characteristics of an archwire influence its resistance to sliding. Four designs of self-ligating brackets (1 with a slide, 3 with clips) were coupled with 5 types of archwires: 14-mil round austenitic nickel-titanium, 16 × 22-mil rectangular austenitic nickel-titanium, 19 × 25-mil rectangular austenitic nickel-titanium, 19 × 25-mil rectangular martensitic nickel-titanium, and 19 × 25-mil rectangular stainless steel. The resistance to sliding (RS) of each archwire-bracket couple was measured at second-order angles between −9° and 9°. Interbracket distances of 8 and 18 mm between the test bracket and the adjacent brackets mimicked closure of a premolar extraction. When clearance exists, the RS is negligible for self-ligating brackets with slides coupled to any size of wire as well as for those with clips when coupled to wires that do not contact the clip. Once the wire attains a certain size and contacts the clip, the RS depends on the archwire size, the bracket design, and the materials of the couple. When coupled with the 16 × 22-mil wire, the brackets with clips applied normal forces ranging from a low of 5.6 centi-Newtons (cN) (1 cN = 1 g) to a high of 230 cN. When clearance disappears, the RS increased proportionally with the second-order angle. The 19 × 25-mil stainless steel wires, which were the most stiff, increased at rates between 75 and 84 cN/degree; the 14-mil austenitic nickel-titanium wires, which were the least stiff, increased at rates from 2.6 to 5.4 cN/degree. The treatment objectives for a particular patient at a specific stage should determine the appropriate archwire-bracket combination. (Am J Orthod Dentofacial Orthop 2002;122:295-305)

The influence of bracket type on the force delivery of Ni-Ti archwires

This study investigated the force delivery of an 0.014 inch nickel-titanium (Ni-Ti) archwire used in combination with a range of commercially available bracket systems, and using a model based on an 'ideal' mandibular archform. The model aimed to replicate the clinical interbracket span. The force delivery was measured at four different sites on an archwire for one batch of 10 nickel titanium archwires from one manufacturer, using one bracket/archwire combination. The four sites represented the lateral incisor, canine, second premolar and first molar positions. Force delivery was also measured for a further four different bracket designs at four different sites on the archwire using five fresh wires of the same archwire type. The wires were loaded with an M5 Nene Universal testing machine. The results demonstrate that the peak and plateau force, both of which are clinically important, are dependent on several factors of the archwire/bracket combination. The results showed that 20 per cent of the batch of 10 wires behaved differently by delivering a higher peak force. There was a statistically significant difference (P < 0.05) between the four bracket/archwire combinations for the peak forces delivered, but there was very little difference between the four bracket/archwire unloading force delivery values. The wires delivered a predictable force on the unloading curves, but self-ligating brackets may not develop sufficient strain within the wire to take full advantage of the superelastic effect of Ni-Ti wires.

Predicting and preventing root resorption: Part II. Treatment factors.

The main objective of this study was to determine which treatment factors are most clearly identified with external apical root resorption that is detectable on periapical radiographs at the end of orthodontic treatment. The records of 868 patients who completed fixed, edgewise treatment from experienced clinicians in private practice were examined. The horizontal and vertical displacement of the root apex of the maxillary central incisor was measured on cephalometric radiographs. Patients who underwent first premolar extraction therapy had more resorption than those patients who had no extractions or had only maxillary first premolars removed. Duration of treatment and the horizontal (but not vertical) displacement of the incisor apices were significantly associated with root resorption. No differences were found for slot size, archwire type, use of elastics, and types of expansion. However, there was considerable variation among the 6 offices that were surveyed; 1 office averaged nearly a full millimeter more of resorption per anterior tooth than the office with the least amount of root resorption. We conclude that the clinician should exercise caution with those patients in whom extraction therapy is planned for overjet correction that requires above average treatment time. Finally, each clinician should be aware that the root resorption seen in one practice may be different from the root resorption found in another practice.

NITANIUM PALATAL EXPANDER – A NEW ADDITION TO CONTEMPORARY ORTHODONTICS

With the advent of 'Shape Memory' (NiTi) alloys and their subsequent introduction in the field of Orthodontics, there have been enhanced efforts to utilize this property in different types of archwires and springs. Greater familiarity and skill has led to designing of Nitanium Palatal Expander (NPE). This appliance has been introduced for slow maxillary expansion and leads to dramatic reduction of clinical time and enhancement of successful results.

Frictional resistances using Teflon-coated ligatures with various bracket-archwire combinations.

Static frictional resistances were compared between Teflon-coated stainless steel and clear elastomeric ligatures used with various combinations of brackets and archwires. Stainless steel metal, polycrystalline ceramic and single crystal ceramic 0.022-inch slot brackets were used in combination with stainless steel and nickel titanium archwires, 0.018 inch and 0.016 x 0.022 inch. Friction was measured in the dry state at bracket-archwire angulations of 0, 5, 10, and 15 degrees. Moments induced by engagement of the archwires into the brackets were measured for each archwire type and bracket-archwire angulation. Teflon-coated ligatures produced less friction than elastomers for all bracket-archwire combinations. The ceramic brackets generally elicited greater frictional resistances than stainless steel brackets. Regarding both friction and control of tooth movement, these data suggest that sliding mechanics are best executed with stainless steel brackets and stainless steel archwires. Moreover, these data reveal the usefulness of Teflon-coated ligatures in minimizing the high friction of ceramic brackets when an esthetic appliance is imperative.

The effect of clinical use and sterilization on selected orthodontic arch wires

The effect of clinical use and various sterilization/disinfection protocols on three types of nickel-titanium, and one type each of beta-titanium and stainless steel arch wire was evaluated. The sterilization/disinfection procedures included disinfection alone or in concert with steam autoclave, dry heat, or cold solution sterilization. No clinically significant differences were found between new and used arch wires. The direction of load application to the arch wire and the particular segment of arch wire tested was found to cause substantial differences in generated loads for certain arch wire types.