The study investigates the effect of toothbrushing with a toothpaste containing blue covarine compared to a control toothpaste without blue covarine on tooth color. Participants brush their teeth once with either the blue covarine containing toothpaste or a control toothpaste for two minutes. Before and after brushing, tooth color is assessed with a spectrophotometer. Moreover, satisfaction of the participants with their tooth color is assessed using a numeric analogue scale before and after treatment.

The null hypotheses are that neither brushing with the toothpaste containing blue covarine nor brushing with the control toothpaste change a) the tooth color and b) the satisfaction of the participants with their tooth color.

Participants are recruited by advertizing in several public areas in Aarhus, Denmark.

Written and oral information on the study is provided, eligibility criteria are checked, and informed consent is given by the participants.

The upper front teeth of the participants are cleaned with pumice and a rubber cup by operator A.

Participants look at the color of their upper front teeth with a mirror, in a room with controlled lighting conditions.

Thereafter, participants rate their satisfaction with the color of their teeth using an 11-point aesthetic numeric analogue scale.

Tooth color is assessed by operator B using a spectrophotometer (VITA Easyshade Advance) and a positioning device to standardize measurements. Measurements are performed in a room with controlled lighting conditions. VITA SYSTEM 3D-MASTER color, L*, a* and b* are recorded.

Participants are then randomly assigned to either the blue covarine toothpaste group or the control toothpaste group.

They are given a short video introduction to the Bass toothbrushing technique by operator C (caregiver).

Operator C provides a toothbrush and 1 g of either blue covarine toothpaste or control toothpaste, according to the randomization scheme.

Participants brush their teeth for two min, starting with the upper front teeth, and then rinse their mouth with tap water.

Thereafter, participants look again at the color of their upper front teeth with a mirror, in the same room as before treatment.

They rate their satisfaction with the color of their teeth using the 11-point aesthetic numeric analogue scale.

Moreover, they rate the color difference before and after treatment on an 11-point aesthetic numeric analogue scale.

Again, tooth color is assessed by operator B using a spectrophotometer (VITA Easyshade Advance) and a positioning device to standardize measurements. Measurements are performed in the room with controlled lighting conditions. Again VITA SYSTEM 3D-MASTER color, L*, a* and b* are recorded.

The null hypotheses of the study are that neither brushing with the toothpaste containing blue covarine nor brushing with the control toothpaste change a) the tooth color and b) the satisfaction of the participants with their tooth color.

Inclusion Criteria:

• Healthy volunteers

Exclusion Criteria:

• Dental caries in the upper front teeth
• Intrinsic stain of the upper front teeth, including tetracyclin stains, fluorosis, and staining due to pulpitis or pulp necrosis
• Dental restorations in the upper front teeth, including fillings, veneers, crowns, and root canal fillings
• Dental anomalies of the upper front teeth, including molar incisor hypomineralisation, amelogenesis imperfecta, and dentinogenesis imperfecta

Due to general data protection regulations, individual participant data will not be made available publicly. Summary data will be made available upon publication of the results.

Participants are randomly assigned to one of the two arms and perform the treatment without knowing whether they use the blue covarine toothpaste or the control toothpaste. Treatment outcomes are assessed by a) a blinded operator and b) the blinded participants in a different room. Allocation of treatment groups will be revealed to the principal investigator after all data have been collected.