Assessment of Oxygen Expansion during Internal Bleaching with Enamel and Dentin: A Comparative In Vitro Study

Study of the Intra-Coronal Pressure Generated by Internal Bleaching Agents and Its Influence on Temporary Restoration

Intra-coronal bleaching is a treatment that whitens non-vital teeth from within the pulp chamber, a procedure by which oxygen and free radicals are released. This in vitro study analyzed and compares the oxygen expansion produced when different bleaching agents encounter dental tissues during this type of bleaching. Here, 120 lower incisors were included and prepared to achieve conditions as close as practicable to internal bleaching with the walking bleach technique. The access cavity of the lingual surface was prepared to seal glass tubes with oil inside them by adhesive restoration once the bleach was placed inside the pulp chamber. The following bleaching groups were used: hydrogen peroxide (HP) 30% (n = 30), sodium Perborate (SP) with distilled water (n = 30), a mixture of HP 30% with SP (n = 30) and a control group (n = 30). After 10 days, the oil displacement that took place through the tube due to oxygen release was measured daily. Displacement of the oil was observed in all groups except the control group. The final mean expansion at 10 days was 335.24 ± 76.85 mm for the HP 30% group, 8.40 ± 1.74 mm for the SP group and 183.07 ± 49.93 mm for the HP30% + SP mixture. Significant statistical differences were observed between the three groups using the Games–Howell post hoc test, where HP30% caused the greatest expansion and SP the least expansion. These results suggest that the higher the amount of HP in the sample, the more oxygen expansion is observed, so that temporary restoration must be performed more carefully to avoid displacement.