Application procedure:

• The tooth surface will be cleaned and saliva gently removed.
• The appropriate amount of varnish will be dispensed onto an application tray.
• The varnish will be applied with a cotton applicator, probe, or brush, forming a thin film.
• The patient will remain seated with lip retractors in place for 15 minutes.
• Patients will be instructed not to brush their teeth or chew hard foods for at least 4 hours post-application.

Application procedure:

• The tooth surface will be cleaned and dried; a lip retractor will be used.
• The varnish will be expressed fully into the dispensing chamber of the unit-dose package.
• Using the applicator brush, the varnish will be applied to fully cover the hypersensitive area.
• Patients will be instructed not to touch the teeth with the tongue or attempt to remove the varnish.
• After application, patients will remain with lip retractors in place for 15 minutes.

The tooth surface will be cleaned and dried with a lip retractor in place. The varnish will be dispensed into the unit-dose chamber and applied with a brush to fully cover the hypersensitive area. Patients will be instructed not to disturb the varnish and will remain with the lip retractors in place for 15 minutes.

Visual Analogue Scale (VAS) With the tooth isolated and dry, a curved dental probe will be gently passed in a mesiodistal direction across the lesion area. Pain perception will be assessed using a VAS, on which the patient indicates the perceived pain intensity, ranging from no pain (0) to the worst pain imaginable (100). The score, measured on a 0-100 mm scale, will be recorded for each lesion.

Air blast test (Schiff test)

An air stimulus will be applied for 4 seconds from a distance of 3-4 mm using a triple syringe with standardized air pressure (40-60 psi) at room temperature. In cases of cervical lesions on adjacent teeth, neighboring lesions will be isolated with cotton to ensure tooth-specific responses. Pain response will be assessed using the Schiff sensitivity scale:

• Score 0: No response to the air stimulus.
• Score 1: A response is perceived, but the subject does not request discontinuation of the stimulus and does not move away.
• Score 2: A response is perceived and the subject requests discontinuation of the stimulus or involuntarily moves away.
• Score 3: An intense pain response occurs, with immediate request to stop the stimulus or marked withdrawal from it.

This outcome will be measured using a validated translation to Spanish of the Oral Health Impact Profile (OHIP-14), evaluating the impact of dentin hypersensitivity on quality of life across seven domains: functional limitation, physical pain, psychological discomfort, physical disability, psychological disability, social disability, and handicap. Patients report how frequently they experienced dentin hypersensitivity-related problems using a 5-point Likert scale (0 = never to 4 = very often). Total scores range from 0-56, with higher scores indicating poorer oral health-related quality of life.