Influence of violet LED and fluoride-containing carbamide peroxide bleaching gels on early-stage eroded/abraded teeth

Abstract

PurposeThis study evaluated enamel with early-stage erosion/abrasion following bleaching with 20% and 45% carbamide peroxide (CP) gels containing fluoride (F) and irradiated with violet LED (LED). MethodsEnamel blocks were immersed in 1% citric acid (5 min) and artificial saliva (120 min) three times to produce early-stage enamel erosion. Simulated toothbrushing was performed only after the first saliva immersion, to provoke enamel abrasion. The erosive/abraded enamel samples were submitted to (n=10): LED/CP20, CP20, LED/CP20_F, CP20_F, LED/CP45, CP45, LED/CP45_F, CP45_F, LED, and control (without treatment). The pH of the gels was assessed, and color (ΔE00) and whiteness index (ΔWID) changes were calculated after cycling (T1), and 7 days from bleaching (T2). Enamel surface roughness average (Ra) and Knoop microhardness (kg/mm2, %SHR) were evaluated at baseline (T0) at T1 and T2. Scanning electron microscopy evaluated the enamel surface morphology at T2. ResultsThe gels’ pH was neutral and CP20 and CP45 exhibited no differences in ΔE00 and ΔWID (p>0.05) but LED increased these parameters for CP20_F and CP45. Erosion/abrasion significantly decreased mean kg/mm2, and the LED group was the only one not increasing microhardness after bleaching (p>0.05). None of the groups fully recovered the initial microhardness. All groups exhibited %SHR similar to the control (p>0.05) and the increase in Ra was detected only after erosion/abrasion. CP20_F groups exhibited a more preserved enamel morphology. ConclusionLight irradiation combined with low-concentrated CP gel promoted a bleaching effect comparable to the high-concentrated CP. The bleaching protocols did not adversely impact the surface of early-stage eroded/abraded enamel.