Evaluation and Comparison of CNA and TMA Wire Properties

Objectives:

The aim was to evaluate and compare the following properties: wire dimensions, edge bevel, composition, surface characteristics, frictional characteristics, ultimate tensile strength (UTS), modulus of elasticity (E), yield strength (YS), and load deflection characteristics of three wires used in orthodontics, namely, SS, TMA and CNA.

Materials & Methods: Thirty straight lengths of each arch wire brands with dimensions of 0.43 x 0.64 mm (0.017 x 0.025 inches) were divided into:

GroupI: Stainless Steel

GroupII: TMA

GroupIII: CNA.

The results were statistically analyzed using SPSS version 10. Kruskal-Wallis One-Way ANOVA and Mann-Whitney u-test was employed to identify P-value and the significant groups at 5% level. (P ≤ .05)

Results:

SS, CNA wires closely matched their manufacturers stated dimensions compared to TMA.Of the three wires, edge bevel was greatest for TMA and least for CNA. Composition of TMA and CNA varied little, with CNA having a lesser content of zirconium.The surface roughness of the wires studied through profilometry and SEM indicated that TMA had the roughest surface followed by CNA and SS. The frictional force levels showed an increased value for TMA compared to CNA with the least value for SS wire. The UTS and YS values were highest for SS followed by CNA and TMA.

Modulus of elasticity was highest for SS followed by TMA and CNA. SS had the highest stiffness followed by TMA and CNA, which was statistically significant.CNA wire had the largest springback of the wires tested followed by TMA and SS.

Conclusions:

CNA wire with increased UTS, YS and lowest E value shows that it would have a greater resistance to fracture, thereby overcoming one of the major disadvantages of TMA. The CNA wires exhibited greater springback, therefore would deliver gentler forces.