Color Characterization of Color-Changing Orthodontic Adhesives

Objectives: A popular product to facilitate removal of excess adhesive during bonding of orthodontic appliances is a color-changing adhesive. Before polymerization, these materials are a bright color but upon curing, manufacturers claim they become translucent. After debonding, there is often resin embedded within the enamel, so the appearance of these materials after polymerization can affect the esthetics of a patient’s dentition. The purpose of this study was to analyze the color characteristics of various orthodontic color-changing adhesives.
Methods: Grengloo and Blugloo (Ormco), BracePaste Color Change (American Orthodontics) and Transbond PLUS (3M Unitek) were evaluated. As a non-color-changing control, Transbond XT (3M Unitek) was analyzed. A Teflon mold was used to fabricate uniform discs of adhesives (n=10/adhesive). A spectrophotometer was used to analyze the color (L*a*b* values), color change (ΔEab) and translucency at various polymerization stages. The samples were analyzed at 20.6C and at 37.0C. Specimens were stored in Fusayama Meyer artificial saliva. Statistical analysis was completed with ANOVA, pairwise comparison analysis, t-test and response profile analysis.
Results: All materials demonstrated an increase in L* upon polymerization, but there was no trend in the changes noted with a* and b* values. There was a significant (p<0.05) difference in the color change between the materials during all stages of polymerization. Transbond Plus showed the largest color change during initial polymerization, and Grengloo had the smallest change. Upon a decrease in temperature, Transbond XT and BracePaste had minimal color change, and Blugloo and Grengloo had the largest change. Each color-changing adhesive had significantly (p < 0.05) less translucency when compared to Transbond XT.
Conclusions: All of the color-changing adhesives that were evaluated have significantly different color changing capabilities influenced by polymerization and temperature, but are still less translucent than the non-color-changing adhesive.