Effect of Blue Covarine Toothpastes on Tooth Colour: A Randomised Crossover Study.

Objective: To measure the effect of toothpastes containing blue covarine on tooth whiteness and yellowness.

Methods: This was a randomised, double-blind, 4-period, crossover design study conducted at a Chinese clinical research facility. Sixty-six participants with 2 natural upper central incisors (UCIs) with Vita tooth shade in range 2M2 to 3M3, without visible damage, gum recession, restorations or extrinsic/intrinsic stain, were allocated to evaluate 4 test toothpastes in random order using Williams square approach. The toothpastes were (1) silica-based fluoride toothpaste containing clay, charcoal, blue covarine and green covarine (BC+GC), (2) silica-based fluoride toothpaste with blue covarine (BC1), (3) silica-based fluoride toothpaste with a higher level of blue covarine (BC2) and (4) silica-based fluoride toothpaste (control). Tooth colour was measured using a video-digital imaging system. At each test period, static images of UCIs were taken before and after a single brushing with allocated toothpaste. Tooth whiteness index (WIO; primary outcome) and tooth yellowness index (YIO) were calculated from Commission Internationale de l'Eclairage (CIE) XYZ colour values derived from the images. All variables were analysed using paired t-test for comparison within product and ANCOVA for comparison between products (P < .05).

Results: All toothpastes significantly increased tooth whiteness and reduced tooth yellowness immediately after brushing (P < .0001). BC + GC (n = 61), BC1 (n = 63) and BC2 (n = 63) showed significantly greater increases in WIO and reductions in YIO compared to control (n = 63) (p < .0001) with WIO mean differences ± SE of 5.51 ± 0.40, 3.79 ± 0.40 and 5.00 ± 0.39 and YIO mean differences of -4.37 ± 0.34, -3.20 ± 0.34 and -4.28 ± 0.34, respectively.

Conclusion: The toothpastes containing blue covarine effectively whiten teeth and reduce yellowness after a single brushing.

Clinical Significance: The toothpaste containing blue and green covarine plus clay and charcoal and two toothpastes containing blue covarine demonstrated tooth whitening and reduction in yellowness immediately after one brush.

Study Retrospectively Registered: NCT06800443 (Clinicaltrials.gov).