Effects of intraoral aging of arch-wires on frictional forces: An ex vivo study

Abstract

Introduction:Archwires act as gears to move teeth with light, continuous forces. However, the intraoral use of orthodontic archwires is liable to surface deposits which alter the mechanical properties of archwires, causing an increase in the friction coefficient.Objectives:To evaluate the surface changes of the stainless steel archwires after 6 weeks of intraoral use and its influence on frictional resistance during sliding mechanics.Materials and Methods:As-received rectangular 0.019” × 0.025” stainless steel orthodontic archwires (control) were compared with the archwires retrieved after the final phase of leveling and alignment stage of orthodontic treatment collected after 6 weeks of intraoral exposure (test samples) from 10 patients undergoing treatment. The control and test samples were used to evaluate surface debris using Scanning Electron Microscopy, surface roughness was assessed using Atomic Force Microscope and frictional forces were measured using Instron Universal Testing Machine in the buccal inter-bracket region that slides through the molar tube for space closure. Unpaired t-test and Pearson correlation tests were used for statistical analysis (P < 0.05 level of significance).Results:Significant increase was observed in the level of debris (P = 0.0001), surface roughness (P = 0.0001), and friction resistance (P = 0.001) of orthodontic archwires after their intraoral exposure. Significant positive correlations (P < 0.05) were also observed between these three variables.Conclusion:Stainless steel test archwires showed a significant increase in the degree of debris and surface roughness, increasing the frictional forces between the archwire-bracket interfaces which would considerably reduce the normal orthodontic forces. Thus, continuing the same archwire after levelling and alignment for space closure is not recommended.

A Comparative Evaluation of Frictional Resistance of Conventional, Teflon and Epoxy Coated Stainless Steel Archwires in Metal, Ceramic Brackets – An In vitro Study

“…Friction is a factor in sliding mechanics in orthodontics, when Arch wire must slide through bracket slots and tubes. [2,3] f During sliding mechanics in orthodontics, tissues response and tooth movement occur only when forces that are applied exceeds friction on bracket wire interface. High levels of frictional force will result in debonding of bracket, associated with either a small dental movement or no movement and possibly anchor loss.…”

“…Frictional forces in clinical orthodontics are considered as a primary concern since it resists regular tooth movements. During sliding movements of teeth, wire edges contact bracket angles, and a frictional force will develop that compete with normal tooth movements and decrease magnitude of applied orthodontic forces [2].…”

Comparison of frictional coefficient and surface roughness between three different active self-ligating brackets: An experimental in vitro study

“…The previous studies showed that the surface roughness of a material relates to its frictional coefficient. [17] Surface roughness of the brackets can be affected by its surface structures, such as material, coating, manufacture techniques, and the interaction between bracket and archwire. [18]…”

In Vivo Comparison of Ultimate Tensile Strength and Surface Topography of Three Different Nickel–Titanium Archwires

“…In vivo studies of orthodontic alloys have concluded that intraoral ageing of alloys affects their mechanical and surface properties. 13,14 The efficacy of heat-activated NiTi arch wires in relieving crowding, failure rates on use intra orally with unpredictable clinical responses occasionally and changes in material surface topography is minimal. [15][16][17] A study evaluating the efficacy of conventional NiTi and copper NiTi wires in alleviating crowding showed no significant differences in the use of either wire type.…”