Effect of Low-level Laser Therapy on Post-bleaching Sensitivity and Color Change

Twenty-one volunteers were evaluated through the split-mouth model, so that the right and left maxillary/mandibular quadrants were randomized and allocated to one of two groups: GPLACEBO - the laser tip was positioned without the emission of light (placebo effect) + tooth bleaching with 35% hydrogen peroxide (HP); GLASER - treated with LLL + tooth bleaching with 35% HP. To assess tooth sensitivity, a modified visual analogue scale (VAS) was used after an evaporative stimulus (stimulated pain) and a daily pain questionnaire (unstimulated pain) was also applied. A spectrophotometer was used to measure the color. Three bleaching sessions were performed, with intervals of 7 days.

• Low-lever laser (Radiation), also known as Laserterapy: Received Low-lever laser therapy using the infrared spectrum, with a wavelength of 808 nm in its active medium AsGaAl (arsenic-gallium-aluminum), at two points: on the central of cervical and medial regions of incisors, canines and premolars in the corresponding hemi-arch. At each point, 60 J/cm2 was applied during 16 seconds with an irradiance of 3.75 W/cm² using the therapeutic visible infrared device.
• Tooth bleaching (Other): Three 15-minute applications of 35% hydrogen peroxide gel (Whiteness HP, FGM®, Joinville, SC, Brazil) were carried out, totaling 45 minutes in each of the four bleaching sessions, with an one-week interval between applications.
• Placebo (Other): The laser tip was positioned similarly to experimental group but without light irradiation

Primary outcomes

• Dental sensitivity induced by office bleaching [change in baseline sensitivity at the 3rd bleaching session]: Evaporative stimulus (stimulated pain) using air jet from a triple syringe and a daily pain questionnaire (unstimulated pain). Both methods were associated with a modified visual analogue scale was used: 0 (pain absent); 1 (mild pain); 2 (moderate pain) and 3 (severe pain).

Secondary outcomes

• Color change promoted by tooth bleaching [change in baseline color at the 3rd bleaching session]: Spectrophotometer was used to measure the color

Sex: All, ages: 18 Years to 30 Years, accepts healthy volunteers

Inclusion Criteria:

* Do not have previous dental sensitivity
* The canine had to be shade A2 or darker.

Exclusion Criteria:

* Enamel hypoplasia
* Gingival recession
* Dentin exposure
* Visible cracks on buccal enamel
* Pulpitis

• Cecy M Silva, Principal investigator, Federal University of Para