Long-Term Mechanical and Physical Effects of Various Cleaning Methods on Retainer Thermoplastics

Hypothesis: Essix-ACE® and Essix-C+® have no differences in long-term translucency, flexibility, or surface-roughness from 8 different cleaning methods. Objective: To evaluate if there are significant differences in initial translucency, flexibility, or surface-roughness between Essix-ACE® and Essix-C+®. To evaluate if there are significant differences in translucency, flexibility, or surface-roughness after long-term exposure to different cleaning methods in Essix-ACE® and Essix-C+®. Methods: For a 6-month period, 10 specimens (2x0.5x0.04in) of Essix-ACE® and Essix-C+® (Dentsply-Raintree-Essix) were exposed to 8 different cleaning methods (Invisalign® Cleaning Crystals, Retainer Brite®, Polident®, Listerine®, 2.5% vinegar, 0.5% NaOCl, 3% H2O2, and toothbrushing) twice a week. The specimens were stored in 37°C artificial saliva when not being cleaned. At baseline and 6-months, translucency, flexibility, and surface-roughness of the specimens were quantified. Qualitative evaluation of surface-roughness of specimens from each cleaning method was evaluated after 6-months using a scanning-electron-microscope. Student t-tests and ANOVA statistical analyses were used at a significance level of 0.05. Results: There were differences in translucency, flexibility, and surface-roughness between Essix-ACE® and Essix-C+® before exposure to different cleaning methods. Both Essix-ACE® and Essix-C+® demonstrated statistically significant less translucency between baseline and 6-month in all cleaning methods. Essix-ACE® showed statistically significant differences in flexibility in all cleaning methods except Invisalign® Cleaning Crystals and Retainer Brite®. Listerine® affected the translucency of Essix-ACE® significantly more than other methods except toothbrushing, while there was no difference in translucency among the methods in Essix-C+®. Qualitative study did not show any distinctive surface-roughness differences when compared to untreated materials. Conclusions: Over the 6-month period, the translucency of Essix-ACE® and Essix-C+® were significantly decreased between 6-months and baseline for all different cleaning methods. The results of flexibility and surface-roughness were varied. None of the cleaning methods were ideal for Essix ACE® or Essix C+®.