In vivo evaluation of teeth color alterations following orthodontic treatment

OBJECTIVES: To prospectively assess color alterations of natural teeth following removal of fixed orthodontic appliances. MATERIAL AND METHODS: Debonding and cleaning procedures of 48 consecutive patients after orthodontic treatment were performed by two different carbide burs attached to a low-speed or a high-speed handpiece, respectively, using a split-mouth design. The reflectance spectrophotometer SpectroShade (MHT Optic Research AG, Zurich, Switzerland) was used for tooth color assessment in vivo. The spectrophotometric color data of teeth were recorded (a) after debonding, (b) three months later, prior to and following finishing with Soflex discs, and (c) after one year. The CIE color parameters (L*, a*, b*) were measured for each tooth and the corresponding color differences between the interval groups were calculated according to the equation ΔΕ = [(ΔL*)² + (Δa*)² + (Δb*)²]^1/2. RESULTS: Orthodontic debonding and cleaning procedures have statistically significant effects on the CIE color parameters of treated teeth, since the L* values decreased (p<0.001), whereas a* and b* values increased (p<0.001) during the first retention year. Conversely, finishing restored temporarily the enamel color appearance. Total color differences of all measured types of teeth ranged from 1.42 to 2.11 ΔΕ-units. The larger color changes exhibited during the first three months when the high-speed rotary instrument was used. According to the standard value of clinical detection (ΔΕ≤3.7), it was found that the 4.6% of the bonded teeth presented visible, clinically significant color differences, while 29.16% of patients presented at least one tooth with visible color change. CONCLUSIONS: Color of natural teeth following removal of fixed orthodontic appliances alters in a various extent. This outcome may be caused by the enamel surface texture alterations associated with debonding and finishing procedures, the discoloration of residual resin tags, and the low tolerance of color parameters to induced variations.