Resin infiltration and in-office dental bleaching on different substrates: hydrogen peroxide penetration, color change, and enamel morphology- an in vitro study.

OBJECTIVES

To evaluate the penetration of hydrogen peroxide into the pulp chamber, color change, and enamel morphology of human teeth with different substrates (sound and white spot), subjected to the application of a resin infiltration (RI) and in-office bleaching at different time intervals (immediately and 7 days after RI application).

MATERIALS AND METHODS

Fifty-four sound human premolars were randomly distributed into six groups (n = 9), all subdivided according to substrate (sound and white spot): bleaching with 35% hydrogen peroxide only (HP); RI followed by immediate bleaching (RI/HPi); and RI followed by bleaching after 7 days (RI/HP7d). The concentration of hydrogen peroxide (µg/mL) was measured by UV-Vis spectrophotometry, color change was evaluated using a digital spectrophotometer (ΔE and WI), and enamel surface morphology was analyzed by scanning electron microscopy (SEM) (α = 0.05).

RESULTS

In the groups without RI (HP), teeth with white spot lesions showed approximately 40% greater hydrogen peroxide penetration than sound teeth (p = 0.15). RI significantly reduced this penetration, regardless of the substrate or bleaching time (p > 0.02). According to WI values, the groups treated with RI (RI/HPi and RI/HP7d) achieved a final color similar to that of sound enamel treated with 35% HP. Enamel morphology was more homogeneous in the groups that received resin infiltration.

CONCLUSIONS

The application of RI prior to in-office bleaching significantly reduced hydrogen peroxide penetration into the pulp chamber without compromising bleaching efficacy. In teeth with white spot lesions, it led to a final shade comparable to that of sound teeth and resulted in a more uniform enamel morphology.

CLINICAL RELEVANCE

Resin infiltration is an effective, minimally invasive approach for treating white spot lesions, improving bleaching outcomes and limiting hydrogen peroxide penetration.