Clinical Implications of Preformed Archwire Selection on the Treatment of Angle Class I/II division 1 Malocclusions in Thais

Agreement of the clinician's choice of archwire selection on conventional and virtual models

OBJECTIVES

To compare archwire selection on dental casts with archwire selection using a three-dimensional (3D) software program (OrthoAid) and assess agreement between clinicians.

MATERIALS AND METHODS

The best-fitting archwires were selected for dental casts of 100 patients with malocclusion using two approaches by three orthodontists. The first method was to visually determine the fitness of five preformed nickel titanium archwires to the arch form on a dental cast (subjective method). The second method was archwire selection on a virtual image of the same cast by means of 3D software (objective method). Agreement between selections performed by the orthodontists was calculated using Kappa statistics. The accuracy of fit of the archwires to the curves fitted to the arch form was also calculated or reversely assessed by means of the root mean square (RMS) for both methods using the Dahlberg formula.

RESULTS

The mean RMS of the distances between the patient arch forms and the archwires for the subjective method was 1.163-1.366 mm. The agreement of selections between orthodontists was 42%-58% (Kappa ranged from .074 to .382). Using the 3D software (objective method), the mean RMS decreased to 0.966-1.171 mm, and agreement increased to 47% to 84% (Kappa ranged from .444 to .747).

CONCLUSIONS

The use of 3D computer software for archwire selection in patients with malocclusion provided better adaptation and interexaminer reliability.

Forces in initial archwires during leveling and aligning: An in-vitro study

AIM

This in-vitro study measured the force deflection behavior of selected initial alignment archwires by conducting three-point bending tests under controlled tests. The study tested three wire designs, namely, co-axial multistranded stainless steel wires, nickel-titanium, and copper-nickel-titanium archwires.

MATERIALS AND METHODS

The archwires were ligated to a specially designed metal jig, simulating the arch. A testing machine (Instron) recorded activation and deactivation forces of different deflections at 37°C. Forces on activation and deactivation were compared by one-way analysis of variance (ANOVA).

RESULTS

Significant differences (P < 0.05) in activation and deactivation forces were observed among the tested wires. The co-axial multistranded wire had the lowest mean activation and deactivation forces, whereas conventional nickel-titanium wires had more mean activation and deactivation forces at different deflections.

CONCLUSION

The activation and deactivation forces were higher for nickel-titanium followed by copper-nickel titanium and co-axial wires. The amount of percentage force loss was more for co-axial wire, indicating that these wires are not ideal for initial leveling and aligning.