White spot lesions: Does etching really matter?

The clinical significance of acid etching prior to orthodontic bonding is controversial. In the present study, we evaluated the effect of 15 seconds of acid etching on enamel demineralization.

Twenty-seven human molars were sectioned and assigned to two groups. Under standardized conditions, the enamel surfaces were imaged using FluoreCam to obtain baseline data. Group 1 was etched using 37% phosphoric acid for 15 seconds, rinsed with water, and then imaged again; group 2 was only rinsed with water. Water rinse was collected for calcium chemical analysis using inductively-coupled plasma auger electron spectrometry. Both groups were subjected to 9 days of pH cycling, after which final FluoreCam images were obtained.

Group 1 showed a significant increase in lesion area (P=.012), decrease in light intensity (P=.009), and decrease in impact (P=.007) after acid etching. The amount of calcium that leached out over the 15 seconds was 14 ppm ±2.4 (0.35 mmol/L±0.06). Following pH cycling, there was no statistically-significant between-group difference in overall enamel demineralization.

Initial demineralization caused by 15 seconds of acid etching does not increase enamel susceptibility to further demineralization. This suggests that acid etching does not increase the risk of developing white spot lesions during orthodontics.