Effect of toothpaste containing d-limonene on natural extrinsic smoking stain: a 4-week clinical trial

To determine whether natural smoking stain could be removed/inhibited effectively by a toothpaste containing 5% d-limonene. For comparison and contrast, the effects of d-limonene on tea stain were also assessed.

The design was a randomized controlled double-blind trial with parallel groups. Toothpastes were: A: positive control with perlite whitening formulation; B: A+5% d-limonene; C: D + 5% d-limonene; D: negative control. The extrinsic stains were measured using Lobene Stain Index. Following baseline examination, all subjects were randomly assigned to one of the four toothpaste groups and instructed to brush with the assigned products twice daily. Subjects returned to the clinic after 4-week brushing for stain removal assessment, then all extrinsic stains, plaque and supragingival calculus were removed and use of assigned products was continued for another 4 weeks, and the stain scores were repeated for inhibition assessment.

A total of 408 subjects, 201 with smoking stains and 207 with tea stains, participated in the trial. 5% d-limonene combined with Perlite whitening formulation significantly reduced stain scores both for smoking stain removal and inhibition (P < 0.05). Furthermore, 5% d-limonene alone (in negative formulation) exhibited an additional advantage for smoking stain inhibition (P < 0.05), but the advantage was not found for long-standing smoking stain removal (P > 0.05). The additional advantage of 5% d-limonene was shown neither for removal nor for inhibition in the tea stain study (P > 0.05). All test products were well tolerated over the study period.