الفهرس 
Aqueous Ca (OH)2 pasteOnly 14 pages are availabe for public view
 |  | from | 133 |  |  |
| | | from | 133 | | |
Abstract
The purpose of the this study was to evaluate and compare the calcium ions diffusion and pH changes in the external medium of radicular dentin following root canal dressing with different calcium hydroxide forms (paste, powder, and points).
Sixty human mature permanent maxillary canines were selected and their crowns were cut at the cement-enamel junction, and cleaning and shaping were done using k-type files in a crown down technique until # 60 master apical file was reached.
The sixty samples were divided into three equal groups according to the form of calcium hydroxide placed inside the canals, twenty samples were filled with calcium hydroxide in aqueous paste form, the other twenty samples were filled with calcium hydroxide powder mixed with normal saline, and furthermore the final twenty samples were filled with calcium hydroxide points.
Each group was divided into two sub-groups according to presence or absence of smear layer, the smear layer was removed with 18% EDTA gel, and each sub-group was divided into two sub-subgroups according to presence or absence of cementum
defects, these defects were created on the root external surface using carbide round bur # ½ ,six defects were done on each root, three buccal and three palatal at three levels (apical, middle, and coronal). Radiographic verification of complete filling of the canal was done.
After complete filling of the samples with the three forms of calcium hydroxide the coronal access of each canal was sealed with temporary filling material. Green sticky wax was used to cover the coronal temporary filling and to seal the apical foramen of each root. Samples were placed in separate vials containing 10ml saline and stored in an incubator at 370c for the assigned stored time period (1 hr, 24 hrs, 1 week, or 1 month). Changes in pH were measured using a pH-meter and Calcium ions concentration in the surrounding medium around each sample was measured using an atomic absorption spectrometer.
All data were collected, tabulated and subjected to statistical analysis using one way analysis of variance (ANOVA), and student t-test at level of significance of p≤ 0.05.
Results showed that the removal of smear layer and the presence of cementum defects resulted in an increase in the pH values for the three tested forms of calcium hydroxide with the highest values were for the samples dressed with calcium hydroxide powder followed by samples dressed with calcium hydroxide paste and the least values were for samples dressed with calcium hydroxide points.The highest pH values were observed after one week and then they were declined after one month for samples dressed with calcium hydroxide powder and paste but not for calcium hydroxide points.
Furthermore the removal of smear layer and the presence of cementum defects resulted in increase in the calcium ion concentration values for the three tested forms of calcium hydroxide with the highest values were for the samples dressed with calcium hydroxide paste followed by samples dressed with calcium hydroxide powder and the least values were for samples dressed with calcium hydroxide points. The values increased till after one month period for the three tested forms of calcium hydroxide.
Conclusions:
Under the conditions of the present study, the following conditions could be drawn:
1. Calcium hydroxide paste is the form of choice among other formulations.
2. Removal of smear layer with all formulations of calcium hydroxide improves its leaching.
3. All formulations of calcium hydroxide should be placed inside the root canal for extended time periods.