Methods: The effect of acid reflux on enamel was mimiced by immersing extracted human molar in 10mM hydrochloric acid pH 2.5 for 10 minutes followed by rinsing with tap water or a sodium bicarbonate solution. The remineralization phase was carried out by 1 min application of NaF rinse (ACT) followed by one-hour immersion in artificial saliva containing calcium and phosphate or pooled human saliva (IRB #10-01122-XM). Enamel surface hardness (Vickers) was measured at baseline, softening, and remineralization stages. Percent hardness recovery was calculated and subjected to ANOVA followed by Student-Newman-Keuls post-hoc test (p=0.05). N=10.
Results: Vickers hardness and percent hardness recovery (mean±standard deviation) are shown in the table. Hardness significantly decreased after HCl immersion and significantly increased after remineralization in all groups (uppercase superscript letters). Sodium bicarbonate solution+ fluoride rinse significantly increased percent hardness recovery in comparison to water + fluoride rinse in both artificial saliva and human saliva (lowercase superscript letters).
|
water rinse + F-rinse / artificial saliva |
Sodium bicarbonate solution + F-rinse / artificial saliva |
water rinse + F-rinse / saliva |
Sodium bicarbonate solution + F-rinse / saliva |
Baseline hardness |
392 ± 11 A |
388 ± 15 A |
392 ± 13 A |
382 ± 14 A |
HCl/rinse hardness |
327 ± 21 B |
335 ± 18 B |
315 ± 22 B |
311 ± 21 B |
Remin hardness |
357 ± 11 C |
369 ± 13 C |
348 ± 11 C |
356 ± 13 C |
% hardness recovery |
44.9 ± 17.5 a |
67.9 ± 15.4 b |
40.5 ±14.9 a |
63.6 ±18.6 b |
Conclusions: The sodium bicarbonate solution and fluoride rinse improved the hardness recovery of enamel softened by hydrochloric acid.
Acknowledgement: Supported, in part, by a research grant from the University of Tennessee College of Dentistry Alumni Endowment Fund and the Tennessee Dental Association.