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A rough idea? An alternative method for describing early erosive surface change
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Dr James Field
Dr Paula Waterhouse
Dr Matthew German
Field J, Waterhouse P, German M
Journal of Applied Oral Science
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in vitro study aimed to investigate an alternative profilometric method for reporting early erosive surface changes on human and bovine enamel. Most dental studies report roughness average (Ra), but in isolation, this may misrepresent surface features. Enamel of human (n=4) and bovine (n=15) permanent lower incisor crowns was lapped to 1200 grit-size and a baseline profile taken using a stylus profilometer. Prepared teeth (n=20) were equally split between 4 experimental erosive conditions: 1% citric acid (pH 2.2) and 6% citric acid (pH 1.8) for 15s and 2min respectively. Immediately after each challenge, samples were rinsed with balanced salt solution and profiled. Ra was recorded, but also the
bearing area parameters, giving information about the proportions of peaks/troughs. One-way multivariate analysis was performed (SPSS, v17.0), investigating treatment differences on surface parameters. Although there were no significant differences in baseline Ra for human (x 0.12μm) and bovine samples (x 0.13μm) (p=0.576 CI 95%), a number of
bearing parameters were significantly different; human samples had higher proportions of peaks (Mr1 value 21.94% c.f. 7.13% for bovine) and bovine samples had higher proportions of troughs (MR2 value 92.89% c.f. 79.50% for human) (p<0.001 for both, CI 95%). Post-treatment, there was still no significant difference in Ra values between human and bovine enamel (p=0.129, CI 95%), yet significant differences in proportions of peaks and troughs (significantly affected by species, time and concentration of citric acid, p<0.001, CI 95%). In conclusion, reporting bearing area parameters may allow a more comprehensive description of surface changes, than Ra alone. The results suggest that care should be taken when using bovine enamel as a substitute in erosive studies. Further, it may be possible to use bearing parameters to predict longer-term effects of a range of other physical insults, such as hygiene regimes, dietary patterns and methods of micro-abrasion/polishing.
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