An in vivo spectrophotometric evaluation of Vivera® and Essix® clear thermoplastic retainer discolouration

Abstract

Aim: To assess the in vivo colour alterations of two different clear thermoplastic retainers.

Methods: Thirty patients were randomly allocated into two Groups (N = 15) following the completion of active orthodontic treatment. Group 1 received Vivera® and Group 2 Essix® C+ thermoplastic retainers. Each patient was provided with two fabricated retainers (one for use and the other to serve as a control). The CIELAB parameters of the patients’ upper central incisors were measured with a SpectroShade™ spectrophotometer immediately after retainer placement (T0) and again after 15 days (T1), one month (T2) and three months (T3). The measurements were also performed on teeth without the retainer in place. ΔE differences were calculated.

Results: ΔE changes from T0 to T1, T2 or T3 showed no statistically significant differences between Groups 1 and 2 within any combination of measurements or teeth. ΔE(T3-T0) changes for used retainers were 1.55 times higher than control appliances (p = 0.002) and 1.44 times higher than for teeth-only (p = 0.004). For used retainers, changes between T3 and T0 were 1.56 times higher than between T1 and T0 and 1.47 higher than between T2 and T0 (p < 0.001). There were no statistically significant differences in ΔE between teeth 11 and 21.

Conclusions: Used retainers exhibited greater colour change than control appliances or teeth-only readings, and increased commensurate with the duration of use. Vivera® and Essix® retainers exhibited similar colour stability. All differences observed were considered clinically acceptable (ΔE < 3.7), although prolonged use could cause clinically significant colour changes.