At-Home Bleaching equally effective for Upper and Lower Dental Arches, suggests study

A new study published in the Journal of Dentistry unveiled a curious phenomenon in cosmetic dentistry that teeth whitening treatments may be more effective on upper canines when compared to their lower counterparts. 

Teeth bleaching remains one of the most sought-after aesthetic dental procedures, designed to counter both external and internal tooth discoloration. Yet, dental professionals have long observed inconsistent results between upper and lower arches during treatment. This research assesses the role of sublingual salivary glands, which may increase saliva contamination of bleaching trays in the lower jaw which might accelerate the degradation of bleaching gel.

This prospective study included 32 participants with a standardized three-week at-home bleaching protocol using 16% carbamide peroxide gel. The research team monitored color changes weekly, employing objective color measurement systems: CIELAB, CIEDE2000, and the Whiteness Index for Dentistry (WID), through spectrophotometric analysis.

The results of this study found no statistically significant differences in whitening results between the upper and lower arches (p > 0.5) for incisors. However, disparities emerged when examining the canines, or eye teeth. By the second and third weeks of treatment, upper canines expressed significantly better bleaching results than their lower counterparts, with statistical significance confirmed using both the CIELAB and CIEDE2000 color difference formulas (p < 0.05).

Also, the WID formula for assessing tooth whiteness did not detect significant differences in any of the tooth groups studied, suggesting that while instrumental measurements show variations, these differences may not be easily noticeable in everyday interactions.

The average color difference (ΔE) values in upper canines increased more rapidly than those in lower canines during the second and third weeks, indicating more pronounced lightening. The largest gap was observed during week three, coinciding with the phase when bleaching trays tend to show diminished gel efficacy.

Despite the statistical variances, the study concludes that the slightly reduced bleaching effect in lower canines is not clinically visible, confirming that both arches benefit substantially from carbamide peroxide-based treatments. Overall, these findings may prompt dental professionals to tailor bleaching regimens more precisely and consider anatomical and physiological differences when planning treatments.

Source:

Pereira-Lores, P., Gancedo-Gancedo, T., Martín-Biedma, B., Varela-Aneiros, I., Dablanca-Blanco, A. B., Villasenín-Sánchez, C., Martín-González, J., Alonso de la Peña, V., & Castelo-Baz, P. (2025). Is at-home bleaching more effective on the upper arch than the lower arch? A prospective cohort study. Journal of Dentistry, 157(105729), 105729. https://doi.org/10.1016/j.jdent.2025.105729