Effect of calcium hydroxide paste in combination with different vehicles on the pH of the root surface dentin

Calcium hydroxide paste has been used extensively in combination with different vehicles within the root canal. The aim of this study was to determine the pH changes in the root surface dentin after placement of two calcium hydroxide formulation into the root canal. To conduct this experimental study، 33 extracted human teeth with single-root were cleaned and shaped by standard step back technique. Three cavities with the depth of 0. 75 mm and diameter of 1. 5 mm were prepared in cervical، middle and apical area of the facial surface of the roots. The teeth were then divided into 3 groups randomly. The canals of the first group (A) were filled with creamy mixture of calcium hydroxide and normal saline، the second group (B) were filled with creamy mixture of calcium hydroxide and 2% chlorhexidine using lentulo spiral drills. In group (C) the canals were left empty as the negative control. The pH in different areas were measured at 1، 3، 7، 14 days. The results were analyzed with the repeated measured ANOVA test. Based on our findings، the pH value in normal saline group was significantly higher at all times compared to other groups (p<0. 001). The maximum average pH value (9. 9± 0. 5) was found to be in group (A) on the third day and in the apical area. In the group (B) the maximum average pH value on the third day in the apical area was 8. 7± 0. 3. Little changes of pH value at the root surface dentin، could be due to failure of hydroxyl ions to penetrate into the dentin tubules. Furthermore، to achieve a higher pH value at the dentinal surface، it is preferential to use normal saline as a vehicle for calcium hydroxide rather than materials with acidic pH