The influence of cigarette smoke on colour stability and friction property of aesthetic orthodontic wires-In vitro study.

OBJECTIVE: To evaluate the colour stability and friction property of aesthetic orthodontic wires when exposed to cigarette smoke. MATERIALS AND METHODS: Forty-eight samples of aesthetic orthodontic wires (0.019''x0.025'') were allocated to three experimental groups according to their brand (n=8): GAD (Aditek); GTP (TP Orthodontics); GRM (Rocky Mountain) and their respective control groups (GC) (n=8). Samples were exposed to 2 cycles of smoke in a hermetic chamber while GCs were stored in artificial saliva at 37 degrees C. Colour analysis (CIEL*a*b* colour space and NBS units) was performed on 5mm wire segments with the Vita Easyshade Compact spectrophotometer. The friction analysis was performed in a universal test machine, in segments of 5cm wires tied to ceramic brackets with maximum values recorded in N/cm. The comparison between groups was performed with the ANOVA/Tukey test (a=0.05) and the effect of the time evaluated with ANOVA-MR with Bonferroni correction (a=0.016). RESULTS: GTP and GRM did not show significant colour and friction property variations and did not differ from GC during the study (P>0.05). However, GAD was significantly sensitive to colour changes (T1-T0-L*: -4.09+/-1.06; a*: 2.25+/-0.39; b*: 1.70+/-0, (T2-T0-L* 0.66+/-0.92; a*: 2.76+/-0.35) and friction (T2-T0: 2.07+/-1.00N/cm) (P<0.016). CONCLUSION: Exposure to cigarette smoke may alter the mechanical and optical properties of aesthetic orthodontic wires.