Long-term Effects of Different Cleaning Methods on Vivera^® Retainers

Objectives: Clear retainers have increased in popularity due to their esthetic nature. However, few studies have focused on long-term maintenance of these retainers. This study evaluated the long-term effects of 7 different cleaning-methods on translucency, flexibility, and surface roughness of Vivera^® material.
Methods: Vivera^®-retainer (AlignTechnology) specimens (n=10,2x0.5x0.04in) were exposed to 7 different cleaning-methods(Table1) twice a week for 6months. As a negative control, specimens were brushed for 2minutes twice a week with a standardized toothbrushing machine. The specimens were in artificial saliva at 37°C when not exposed to the cleaning-methods. At 0,1,3, and 6months, translucency (% transmittance of light through specimen using spectrometer/integrating-sphere), flexibility (flexural modulus measured using 3-point-bend with Instron), and surface roughness (Surtronic3+ profilometer) of specimens were quantified. Qualitative assessment of random-specimens from each solution and control was performed at 6months using a scanning-electron-microscope (SEM). Mean comparisons were done using the independent Student t-test (P<0.05).
Results: A decrease in translucency of specimens was found with all cleaning-methods compared to baseline. Translucency comparable to brushing was found with vinegar after 1month and H₂O₂ at 3months. All other solutions exhibited significantly greater translucency values on specimens compared to brushing at every time-point. Listerine^®, vinegar, and brushing increased specimen roughness while NaOCl decreased specimen roughness at 1month compared to baseline. Furthermore, NaOCl-specimens showed decreased roughness compared to brushing-specimens after 1month. Specimens became less flexible with Listerine^®, vinegar, H₂O₂, and brushing compared to baseline. Cleaning-crystals and vinegar-specimens decreased in flexibility compared to brushing-specimens at 1month. For SEM analysis, no obvious qualitative differences were observed between specimens exposed to the various cleaning-methods and brushing-specimens.
Conclusions: The translucency of specimens decreased as early as 1-month after exposure to various cleaning-methods. Vinegar, H₂O₂, and brushing deteriorated the translucency of specimens more than the other cleaning-methods over time.