The objective of this present study was to compare percent of weight changing of enamel and calcium inos concentration in various solutions simulated oral conditions. Ninty six bovine enamel slabs were prepared and randomly divided into 4 groups of solutions: lactic acid (Group 1) artificial saliva (Group 2) lactic acid+artificial saliva (Group 3) and lactic acid+artificial saliva+hydroxyapatite crystal (Group 4). Each group was test in 5 hr, 24 hr, 72 hr, and 168 hr (n=6). At the end of each time, the sample solutions were diluted and analyzed for calcium ions concentration by inductively coupled plasma spectrometer. The specimens were cleaned and dried. The weight was measured and calculated to percent of weight changing. Statistically significant difference of percent of weight changing was found between groups in each time interval. Arrangement in order of percent weight loss was maximum in group 1, 3 and 4. Statistically significant difference in increasing weight of Group 2 was found in 168 hr. Calcium ions concentration were significant difference between groups in each time interval, except in 168 hr of Group 1 and 4 were no significant difference. Decreasingly in calcium ions concentration of Group 2 was significant difference in 168 hr. Increasingly in calcium ions concentration of Group 4 was no significant difference in all time intervals. The acidic condition caused weight loss of enamel. The degree of saturation in the solution reduced weight loss from acid demineralization.