Methods: Fifty bovine incisors were polished to produce a small flat enamel surface area for baseline Vickers hardness (VH) measurements. Each tooth was randomly assigned to one of five groups: (1) Control: no fluoride treatment, (2) 1 minute APF-gel treatment, (3) 4 minutes APF-gel treatment, (4) 1 minute APF-foam treatment, and (5) 4 minutes APF-foam treatment. After treatment, samples were submerged in saliva at 37°C for 30 minutes (IRB# 11-01367-XP), rinsed with deionized water, dried, and submerged in lactic acid gel pH 5.1 for three hours at 37°C. Post 3hr VH was measured and the difference in hardness was determined as an indication of demineralization. The hardness values were subjected to ANOVA/Student-Newman-Keuls (significance level 0.05).
Results: Baseline hardness was not significantly different among groups. Enamel hardness was reduced in all groups after the three-hour exposure to lactic acid gel. The reduction was significantly less in all APF-treatment groups compared to the control. Enamel hardness was not significantly different whether the tooth was exposed to APF gel or foam for 1 minute or 4 minutes.
|
Mean (SD) Vickers Hardness |
||
Treatment |
Baseline |
Post 3hr |
Difference |
Control |
364(8)a |
282(17)b |
82.8(17)b |
1-min Gel |
363(20)a |
311(17)a |
51.9(26)a |
4-min Gel |
366(15)a |
319(23)a |
47.5(29)a |
1-min Foam |
357(27)a |
320(26)a |
36.7(17)a |
4-min Foam |
363(16)a |
327(17)a |
35.5(25)a |
Same superscript letters indicate no significant difference between groups
Conclusions: APF gel and foam maintained a higher enamel hardness value (less demineralization) after acid exposure compared to the control that did not receive any treatment. One- or four-minute application time of APF gel or foam did not affect the degree of enamel demineralization.
Acknowledgement: Supported, in part, by UT College of Dentistry Alumni Student Research Training Program.