The assessment of different bleaching agents' efficiency on discoloured teeth using image-processing methods

Although triple antibiotic paste (TAP) has been successfully used as an intracanal medicament for regenerative endodontic treatments, TAP has also been shown to cause discolouration. The aim of this study is to investigate the efficacy of different bleaching agents to bleach teeth discoloured from TAP.

Two hundred extracted human maxillary incisors were evaluated with VITA Easyshade, and 120 teeth were prepared and discoloured by using TAP for three weeks. After colouration, 70 teeth were randomly divided into five groups: Group 1: Negative control, Group 2: Sodium perborate, Group 3: Opalescence Endo, Group 4: Endoperox, and Group 5: Biolase. The colour changes in the third and seventh days' standard images were obtained using stereomicroscopy, RGB and Lab color space transformations were applied to the images. The CIE Lab color system was used, and total color changes (ΔE) were calculated and compared among groups and over time, using analysis of variance testing.

At the third day, there was no difference between bleaching materials. At the seventh day, the Biolase group was superior to sodium perborate and there was no difference between other groups. A statistically significant difference was noted between the third and seventh-day measurements for all bleaching protocols. Bleaching effectiveness of all agents increased over time.

Teeth discoloured by using TAP may be bleached by means of the investigated protocols, and colour alteration can be increased over time. The CIE Lab colour system can be used as an alternative, in vitro test for evaluating the bleaching efficiency of bleaching agents.