Detection of residual resin-based orthodontic adhesive based on light-induced fluorescence

Abstract

INTRODUCTION: This study evaluated the fluorescence of orthodontic adhesives using quantitative light-induced fluorescence-digital (QLF-D) images, and compared the fluorescence color difference between adhesive and the adjacent tooth with that under white-light illumination in specimens with various residual thicknesses.

METHODS: Transbond™ XT, Blugloo™, and Enlight were used to prepare (1) adhesive discs and (2) adhesive specimens attached to extracted human tooth, which was ground to thicknesses ranging from 800 to 20 μm. Fluorescence and white-light images of the two types of specimens were taken with a QLF-D system. The color parameters for the fluorescence from the discs and the color difference (ΔE) between residual adhesive and the adjacent tooth were quantified in images using the CIE L*a*b* system.

RESULTS: Fluorescence color values of the discs differed significantly among the three adhesive products (P < 0.05). The ΔE values in fluorescence (ΔEF) and white-light (ΔEW) images for all three adhesives decreased as the residual-adhesive thickness reduced, with the adhesive thickness being perceptible over ranges of 50-100 μm for fluorescence images and 400-800 μm for white-light images (ΔE > 3.3). ΔEF values were significantly larger than ΔEW for all residual-adhesives, Blugloo™ thickness higher than 100 μm, Transbond™ XT and Enlight thickness higher than 50 μm (P < 0.05).

CONCLUSIONS: The detection and analysis of fluorescence signals can be useful for improving the ability to detect residual adhesive on tooth as well as for providing thickness information.