Method: Extracted caries free teeth were sectioned to produce a total of 720 highly polished enamel samples. Sections were immersed in CA, PA and HA (pH 3.2) at 0.3, 0.6 and 1% and for 5, 10, 15, 20 minutes together with abrasion. Each section was embedded in composite, with a window of exposed enamel (~1x3mm) and separated into 72 groups. Each group of 10 samples, underwent 5 cycles of erosion (1 cycle= immersion in acid à rinse with distilled water) at room temperature, in 80 mL of solution, with agitation (62.5 rpm) at each concentration and immersion time; and in addition for erosion/abrasion (1 cycle= erosion à abrasion on toothbrushing machine) with 120 linear strokes with Oral B P40 toothbrush, 290-295g force, in non-fluoridated toothpaste slurry. Samples were analysed with Non-contact laser profilometry and single/mean step height was calculated using 3 different surface analysis programs (Boddies, Image J and Mountains).
Result: There was excellent agreement between the surface analysis techniques (96.7%). The mean step height ± standard deviations (µm) for; erosion 0.3%/5 minutes with CA,PA,HA was 3.89 ±0.82, 1.62 ±0.64, 0.75 ±0.30; 1%/20 minutes with CA,PA,HA was 41.90 ±4.79, 40.49 ±4.95, 5.67 ±0.61; Erosion/abrasion 0.3%/5 minutes with CA,PA,HA was 7.77 ±1.66, 2.11 ±0.44, 0.35 ±0.26; 1%/20 minutes with CA,PA,HA was 37.30 ± 6.87, 44.74 ±3.16, 4.94 ±0.61 (p<0.01).
Conclusion: Within this laboratory model all acids showed that an increase in time and concentration produced higher mean step heights for erosion and erosion/abrasion. CA and PA were more erosive than HA suggesting that chelation and calcium binding play a large role in erosion and low buffering capacity after pH adjustment affected the erosive potential of HA.