Efficacy, pH, and enamel effects of an over-the-counter non-hydrogen peroxide gel for at-home tooth bleaching

Objectives To evaluate the bleaching efficacy of an over-the-counter, non-hydrogen peroxide at-home gel based on phthalimidoperoxycaproic acid (PAP) combined with papain and bromelain, compared with a 10% carbamide peroxide (CP) gel and a negative control. Gel pH and enamel effects were also assessed. Methods Seventy enamel specimens from 35 sound human molars were randomly allocated to five groups (n = 14). The PAP gel (White Night) and 10% CP gel (Pola Night) were applied daily for 3 or 6 h over 28 days; an untreated group stored in artificial saliva served as control. Color coordinates (L*, a*, b*) were recorded using a spectrophotometer at baseline and after 7, 14, 21, and 28 days. The Whiteness Index (ΔWI D ), CIELab (ΔE ab ), and CIEDE2000 (ΔE 00 ) differences were calculated. Gel pH was measured hourly for 6 h using a calibrated microelectrode. Enamel micromorphology was examined by SEM. Data were analyzed using two-way repeated measures ANOVA (α = 0.05). Results The PAP gel showed higher ΔWI D values than the control from day 14 onward, with no additional increase thereafter. The CP gel produced higher ΔWI D values than both PAP and control from day 7, with progressive increases. No differences between the 3- and 6-hour protocols for either the PAP or CP groups were detected. PAP maintained an alkaline pH, whereas CP showed slightly acidic values. No relevant enamel alterations were observed. Conclusions The PAP gel produced a bleaching effect after 14 days, independent of application time, although less effective than 10% CP. Both gels showed no detectable enamel surface damage.