الفهرس 
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Abstract
Several factors interact to determine the longevity of the restorative materials, either intrinsic or extrinsic factors both affect the behavior of restoration in the oral environment. One property which can enhance longevity, insofar as it relates to recurrent caries, is fluoride released from restorative material. The present in vitro study was aimed at achieving three goals.
The first part of our study was designed to evaluate the effect of pH on the rate of fluoride release from fluoride releasing restorative materials. A total of 135 cylinders were divided into 3 groups each group were again divided into 3 subgroups of 15 cylinders each, as fluoride release were determined for the three materials (KetacTM Fil Plus, KetacTM Nano , and F 2000) in relation to a variable pH. Fluoride ions were measured with ion specific electrode, the electrode was previously calibrated. The mv readings were transformed into ppm. The fluoride release was evaluated after being stored in different media at various intervals after1st, 7th, 14th, and 21st days.
The second part of the study was designed to determine the amount of the fluoride absorption of the three groups after 21 day immersion in different pH media, NaF solution was used for fluoride recharge test for 3 minutes. The fluoride absorbing ability of the three materials was obtained by measuring the fluoride concentration in sodium fluoride solution before and after samples immersion.
The third part of the study was designed to measure the amount of fluoride re-release after fluoride absorption test, in relation to a variable pH. The fluoride re-release was evaluated after being stored in different pH media at various intervals after 1st, 2nd, 3rd days.
The data obtained from the fluoride release, absorption, and re-release test were recorded in ppm and statistically analyzed.
The need for use of restorative materials with the highest long-term fluoride release is preferable, especially in patients with moderate-to-high caries activity. Within the limitation of this study it can be concluded that:
1- Solution pH had a dramatic effect on the fluoride release of conventional glass ionomer cements (KetacTM Fil Plus), nano filled resin modified glass ionomer (KetacTM Nano 100), and polyacid modified composite resin (F 2000), with much more fluoride ions being released at strong acidic solution (pH 2) than at weak acidic solution (pH 5), while the least amount of fluoride was observed in neutral solution (pH7).
2- The pattern of fluoride release for KetacTM Fil Plus showed a significant highest fluoride release rate after first day (initial burst) then the rate significantly decreased after 7th, 14th, and 21st days.
3- The pattern of fluoride release for KetacTM Nano 100 (KN) showed the significant highest fluoride release rate after 7th, 14th, and 21st days, while after 1st day it showed a significant low initial burst.
4- The pattern of fluoride release for compomer (F 2000) showed the least fluoride release rate with significant difference through follow up period and its rate significantly increased.
5- The amount of weight loss observed after 21 day immersion showed that, cylinders immersed in strong acidic solution lost more weight than cylinders immersed in weak acidic solution and the least at neutral pH, and KetacTM Fil Plus showed more weight loss followed by F 2000 and the least weigh loss was for KetacTM Nano.
6- All tested materials exhibit the property of significant recharging through common neutral fluoride solutions. The increased recharge rate is related to decreasing pH. KetacTM Fil Plus showed a significant highest rate of fluoride absorption and re-release followed by KetacTM Nano, while F 2000 showed the least fluoride absorption.
7- High rate of fluoride re-released was observed in first and second day, while the rate was sharply deceased at the third day with significant difference for all tested materials after 1st,2nd, and 3rd days.
It goes without saying that conclusions from laboratory studies may not be comparable with studies in-vivo. In addition, it is important to take into consideration that different methodologies used in the studies, including specimen size, media used to measure fluoride release and uptake, quantity of media used to measure fluoride as well as different methods to measure fluoride release, are responsible for the numerous differences.