Neuropeptide Y regulation of dental pulp neurogenic inflammation provoked by tooth bleaching agents: a descriptive comparative clinical study

Objectives: This study aimed to assess the expression of neuropeptide Y (NPY) in human dental pulp after tooth bleaching with three in-office hydrogen peroxide (H₂O₂)-based systems. Methods: Forty pulps were collected from premolars scheduled for extraction and divided into four groups (n = 10): Control (no bleaching; basal NPY values); Pola Office (35% H₂O₂, 8 minutes); Opalescence Boost (40% H₂O₂, 20 minutes); and Zoom (25% H₂O₂ + cold blue light, 15 minutes). After extraction, pulps were fixed in 4% formaldehyde and processed. NPY levels were quantified using enzyme-linked immunosorbent assay. Data distribution was assessed with the Shapiro-Wilk test. One-way analysis of variance and Tukey post-hoc test with Bonferroni correction were applied (p < 0.05). Results: NPY expression differed significantly among groups (p = 0.0097). The control group showed the lowest mean expression (0.026 ± 0.002 pmol/mg of pulp tissue), followed by Zoom (0.031 ± 0.005 pmol/mg), Pola Office (0.040 ± 0.004 pmol/mg), and Opalescence Boost, which exhibited the highest NPY expression (0.044 ± 0.004 pmol/mg). Post-hoc analysis revealed a statistically significant difference between the control and Opalescence Boost groups (p = 0.0122). Conclusions: The increase in NPY expression—particularly with Opalescence Boost—indicates that in-office bleaching agents can elicit measurable neurobiological responses in pulp tissue after a single application. The significant difference between the control and Opalescence Boost groups suggests a possible H₂O₂ concentration-or formulation-dependent effect on pulpal neuropeptide activity, underscoring the need for further research on the biological impact of bleaching treatments.