Effect of BioMin F on tooth sensitivity after in-office bleaching.

All participants will undergo professional cleaning of the study teeth prior to whitening. The tooth surfaces will be cleaned using a non-abrasive, fluoride-free whitening powder and a brush attached to a microbrush to remove plaque and surface deposits. Participants in the intervention group will use BioMin F toothpaste, and participants in the control group will use a placebo paste, applied into customised trays at home. A thin, even layer of the assigned paste will be placed inside the tray in an amount sufficient to cover the study teeth without overflow. The tray will be worn once daily for 30 minutes for one week before the first in-office whitening session. Following this pre-treatment period, in-office whitening will be performed using 35% hydrogen peroxide gel applied to the study teeth (from the right first premolar to the left first premolar) for 40 minutes. Before application of the whitening gel, gingival isolation will be performed using a gingival barrier gel. All in-office whitening procedures will be performed by the treating dentist in the clinical setting. There will be two in-office whitening sessions separated by one week. After the first whitening session, the assigned paste (BioMin F or placebo) will be reapplied using the customised tray once daily for 30 minutes for another week, i.e. during the interval between the two whitening sessions. The tray-based paste application will be self-administered by the participants at home. Adherence will be monitored by asking participants to submit photographs showing the material placed inside the tray and the tray in situ during use. These photographs will be reviewed by the research team to confirm compliance with the study protocol.