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

Biomechanical simulation of forces and moments of initial orthodontic tooth movement in dependence on the used archwire system by ROSS (Robot Orthodontic Measurement & Simulation System)

OBJECTIVES

Aim of this study was to determine the forces and moments during simulated initial orthodontic tooth movements using a novel biomechanical test setup.

METHODS

The test setup consisted of an industrial precision robot with a force-torque sensor, a maxillary model and a control computer and software. Forces and moments acting on the corresponding experimental tooth during the motion simulations were dynamically measured for two 0.016" NiTi round archwires (Sentalloy Light/Sentalloy Medium). Intrusive (#1), rotational (#2) and angular (#3) tooth movements were simulated by a control program based on the principle of force control and executed by the robot. The results were statistically analysed using K-S-test and Mann-Whitney U test with a significance level of α = 5%.

RESULTS

Sentalloy Medium archwires generated higher forces and moments than the Sentalloy Light archwires in all simulations. In simulation #1 the mean initial forces/moments reached 1.442 N/6.781 Nmm for the Light archwires and 1.637 N/9.609 Nmm for the Medium archwires. In movement #2 Light archwires generated mean initial forces/moments of 0.302 N/-8.271 Nmm whereas Medium archwires generated 0.432 N/-9.653 Nmm. Simulation #3 showed mean initial forces/moments of -0.122 N/8.477 Nmm from the Light archwires compared to -0.300 N/11.486 Nmm for the Medium archwires.

SIGNIFICANCE

The measured forces and moments were suitable for initial orthodontic tooth movement in simulations #2 and #3, however inadequate in simulation #1. Reduced archwire dimensions (<0.016″) should be selected for initial leveling of vertical malocclusions.

Comparative Evaluation of Dimensional Accuracy, Surface Characteristics, and Load Deflection Attributes of 0.019" × 0.025" Stainless Steel Wires Sourced from Six Different Commercial Houses: An In Vitro Study

Aims & Objectives:

The aim of the study was to evaluate and compare dimensional accuracy, surface characteristics and load deflection attributes of SS wires sourced from six different commercial houses.

Materials & Methods:

0.019” x 0.025” SS wire samples were divided into 6 groups and evaluated and compared for the aforementioned properties. Dimensional accuracy, surface roughness, frictional resistance, load deflection rate and ultimate tensile strength were evaluated and compared.

Results:

Dimensional accuracy did not vary significantly. Surface Profilometry proved 3M Unitek (Group 1) to be the wire with least irregularities. According to SEM, Modern Orthodontics (Group 6) and 3M Unitek (Group 1) in terms of ‘Sa’ and ‘Sq’ respectively had the smoothest surface finish. SS wires sourced from G&H Orthodontics (Group 2) exhibited least frictional resistance. Load deflection rates varied for all the groups for all three parameters under the study. UTS was best for SS wires sourced from Rabbit Force Orthodontics (Group 5).

Conclusion:

No wire from a single commercial house excels in all the parameters that were evaluated, each one having its aces and minuses.