Effect of fluoridated bleaching gels on the remineralization of predemineralized bovine enamel in vitro

Objectives

This study evaluated possible differences regarding the remineralization of predemineralized enamel after exposure to fluoridated or non-fluoridated bleaching gels.

Methods

120 enamel specimens were prepared from sixty bovine incisors; before and after demineralization (37 °C; pH 4.95; 10 d), one-quarter of each specimen's surface was covered with nail varnish (control sound/demineralized). Subsequently, the specimens were stored for 16 h daily in a remineralizing solution (pH 7.0; 14 d), while for the remaining time (8 h) various bleaching gels were applied: (1) no treatment (control), (2) Opalescence regular (O, Ultradent), (3) Opalescence PF (O-PF), (4) Nite White ACP (NW-ACP, Discus Dental) and (5) Nite White ACPF (NW-ACPF). Following, half of the bleached parts were nail-varnished and stored for another 3-weeks period in a remineralizing solution. Differences in mineral losses (ΔΔZ) and lesion depths (ΔLD) before and after treatment/remineralization period were evaluated from microradiographs. ΔΔZ_surface values (mineral loss of the outer 18 μm of the lesion) were calculated.

Results

After 2 and 5 weeks ΔΔZ/ΔLD values of the bleaching groups did not differ significantly from the controls. Treatment with NW-ACPF for 2 weeks resulted in significantly lower ΔΔZ values compared to NW-ACP (p = 0.032) and NW-ACPF in higher values than Opalescence regular (p = 0.006). Two weeks treatment with O and O-PF resulted in decreased ΔΔZ_surface values compared to control (p < 0.0005), whereas with NW-ACPF no significant differences could be observed (p = 0.062). Application of NW-ACP induced significantly increased ΔΔZ_surface values compared to control (p = 0.001).

Conclusions

No supporting influence of fluoride-containing bleaching gels on remineralization could be observed.