Evaluation of calcium ion release and change in pH on combining calcium hydroxide with different vehicles

Intracanal medicaments have traditionally been used in endodontics to disinfect root canals between appointments. Calcium hydroxide is widely used as an intracanal medicament for disinfection and to promote periapical healing. It is stable for long periods, harmless to the body, and bactericidal in a limited area. The efficacy of calcium hydroxide as a disinfectant is dependent on the availability of the hydroxyl ions in the solution that depends on the vehicle in which the calcium hydroxide is carried. In general, three types of vehicles are used: Aqueous, viscous or oily. Some in vitro studies have shown that the type of vehicle has a direct relationship with the concentration and the velocity of ionic liberation as well as with the antibacterial action when the paste is carried into a contaminated area.

To evaluate the calcium ion release and measure the change in pH of the environment that occurred when calcium hydroxide was combined with different vehicles (distilled water, propylene glycol, calcium hydroxide containing gutta-percha points and chitosan) over different time periods.

Forty single rooted mandibular first premolar teeth were decoronated for this study. Working length was established and the root canals were enlarged and irrigation accomplished with 2 ml of NaOCl solution after every file. The teeth were then randomly divided into four groups. The canals were then packed with different preparations of calcium hydroxide using the following vehicles-distilled water, propylene glycol, gutta-percha points and chitosan. Calcium ion release in different groups was analyzed using an ultraviolet spectrophotometer at 220 nm. The change in pH of was determined using a pH meter. Results were statistically evaluated using one-way ANOVA test.

For calcium ion release, Group 2 showed cumulative drug release of 81.97% at the end of 15 days, whereas Group 1, 3 and 4 showed a release of 99.53, 17.98, 74.93% respectively with a significant difference among all groups. Group 1 reached the highest Ca(2+) level (39.79%) at the end of 1 day but showed almost complete release of calcium hydroxide at the end of 15 days. Group 3 showed least calcium ion release (17.98%) at 15 days. Group 4 showed a sustained release of Ca(+2) ions from 74% at 15 days to 95% at the end of 30 days. After the 1(st) h; Group 1 showed the highest pH level (11.8). However, pH reduced to 7.8 at the end of 30 days in this group. Group 2 showed the highest pH value (10.35), followed by Group 4 (10.32) after 30 days.

Chitosan can be used as a promising vehicle for calcium hydroxide to maintain an alkaline pH and to allow sustained release of calcium ions in the root canal system.