Influence of thermal or chemical degradation on the frictional force of an experimental coated NiTi wire

Abstract

Objective: To evaluate the friction force in sliding systems composed of coated NiTi archwires, coated NiTi subjected to thermal cycling, and coated NiTi subjected to acid solution immersion, and compare them to NiTi and polymeric wires. The null hypothesis is that there will be no difference among the wires as to friction force. Materials and Methods: Samples of NiTi (n 5 05), coated NiTi (n 5 15), and OPTIS (n 5 05) 0.016 inches in diameter and 50 mm long, in conjunction with Metafasix ligatures and saliva in InVu brackets, were submitted to friction testing. Among the 15 coated NiTi samples, 5 were submitted to thermal cycling for 3000 cycles; the other 5 samples were immersed in acid solution for 30 days. The results were statistically analyzed at P . .05 or P . .01. Microscopic analysis was performed in the coated NiTi wires before and after thermal cycling and acid solution immersion. Results: The mean (6 standard deviation) maximum friction force for NiTi, coated NiTi, and OPTIS was 105.20 6 (2.63); 99.65 6 (0.64); 59.76 6 (4.93) (P 5 .000), respectively. There was no significant difference in NiTi, coated NiTi, and acid-immersed coated NiTi (P . .05). Among the thermal-cycled or acid-immersed coated NiTi wires there was lower friction force in those undergoing thermal cycling (P 5 .001). The coated NiTi and the OPTIS presented homogeneous surfaces, whereas NiTi wires presented a heterogeneous surface. Fractures were observed in the coated NiTi wires that underwent thermal cycling.

Comparison of frictional forces between aesthetic orthodontic coated wires and self-ligation brackets

“…Recently, numerous studies have examined the physical properties of aesthetic materials, including the following: the corrosion and the fracture resistance of coated wires by Neumann et al3; the mechanical properties such as stiffness (evaluated through the three-point bending test), surface roughness, and resistance of the coating of coated wires by Elayyan et al4,5; and thermo-chemical degeneration of coated wires by Bandeira et al6 However, there are insufficient studies on the evaluation of frictional changes as a result of wire coating.…”

Color stability of esthetic coatings applied to nickel-titanium archwires

“…The esthetic demands of adult patients in relation to orthodontic appliances has prompted the industry not only to develop esthetic ligatures and other accessories, which have evolved greatly in terms of physical, mechanical and optical properties, but also to produce orthodontic archwires that mimic the natural color of teeth without jeopardizing clinical performance due to changes in their mechanical properties or induction of cytotoxic effects 6,[8][9][10]17 . In this context, the color stability of esthetic coatings applied to orthodontic archwires is also of great clinical relevance.…”

“…However, some disadvantages have also been pointed out, such as poor durability of the coating in the oral environment, color changing, cracking and pitting, increased surface roughness, and predisposition to a buildup of amorphous organic matter through the mechanical action of masticatory forces and tooth brushing as well as due to the effects of oral enzymes [7][8][9][10][11] . Therefore, further studies are needed to analyze the real applicability of esthetic archwires in clinical practice.…”

Relationship between friction force and orthodontic force at the leveling stage using a coated wire

“…In addition, the evaluation of wire properties, such as force and smoothness, would be valuable because the sliding of a wire with problematic surface properties, such as the durability of the coating material, may be inferior to that of an uncoated wire. Some reports have described the influence of wire sliding against a single piece of bracket with soaking solution 1 and the relationship between the cross-sectional dimensions of the wire and load deflection 21 .…”