Time course of potassium nitrate penetration into the pulp cavity and the effect of penetration levels on tooth whitening efficacy

Objectives To establish time-course of potassium nitrate (PN) penetration into the pulp cavity, and determine whether PN pretreatment would affect whitening efficacy. Materials and Methods Extracted teeth (n = 100) were randomized into five groups of 20 specimens each. Relief ACP (Philips Oral Healthcare, Los Angeles, CA, USA) was applied for 0, 5, 15, 30, and 60 minutes for groups 15, respectively. A nitrate/nitrite assay kit was used for colorimetric detection of nitrate. Whitening was performed using a Zoom White Speed system (Philips Oral Healthcare) for 60 minutes. Tooth color was measured with a spectrophotometer at baseline (T₀), 1-day post PN application (T₁), 1-day post-whitening (T₂), and 1-month post-whitening (T₃). Kruskal-Wallis test was used to assess group differences in PN penetration and tooth color change. Results PN penetration differed among all groups except 2 and 3. There were no differences among groups for any baseline color parameters (p > 0.30). At T₂ there was no change relative to baseline for individual components L∗, a∗, and b∗. At T₃ and T₄ there was significant change relative to baseline for ΔL∗, Δb∗, and ΔE∗, for all groups. Conclusions PN penetration is time dependent and pretreatment with PN does not affect whitening efficacy. Clinical Significance Postassium nitrate penetration into the pulp cavity occurred as early as 5 minutes after application, and pretreatment with potassium nitrate containing desensitizers did not adversely affect tooth whitening efficacy.