The effect of topical fluoride agents on the physical and mechanical properties of NiTi and copper NiTi archwires. An in vivo study.

AIM

The aim of this in vivo study was to determine the effect of topical fluoride agents on the mechanical properties of NiTi and copper NiTi archwires.

METHODS

Thirty patients with fixed appliances were randomly divided into three groups: Group I (Control group) used no topical fluoride agents; Group II used a fluoride rinse; Group III applied a fluoride gel to the teeth. After 30 days, the archwires were retrieved and the moduli of elasticity and yield strengths measured. The groups were compared with the oneway ANOVA, and Tukey's HSD test was used to identify the significant groups. One wire was randomly selected from each group and the surface examined with a scanning electron microscope.

RESULTS

During unloading the modulus of elasticity of the NiTi archwire fell significantly in the gel group. The moduli of elasticity and yield strengths of the NiTi archwires during loading, and the copper NiTi archwires during loading and unloading, were not affected by either the gel or the rinse. Scanning electron microscopic analysis revealed that the copper NiTi archwires in the gel group had the most pitting.

CONCLUSIONS

Topical fluoride agents alter the mechanical properties of NiTi wires and, hence, may prolong orthodontic treatment.