N. Hosoya et al., Calcium concentration and pH of the periapical environment after applying calcium hydroxide into root canals in vitro, J ENDODONT, 27(5), 2001, pp. 343-346
The purpose of the present study was to determine both calcium concentratio
n and pH in the periapical region after application of 1 of 4 different cal
cium hydroxide preparations into experimental root canals. Fifty root canal
models were divided into five groups: group 1- calcium hydroxide was mixed
with distilled water at a powder/water weight ratio of 38%; group 2- calci
um hydroxide was mixed with distilled water at 44%; group 3- calcium hydrox
ide was mixed with distilled water at 50%; group 1- calcium hydroxide powde
r only was used; and group 5 - the control group, in which nothing was appl
ied to the canals. All samples were immersed in distilled water maintained
at 37 degreesC. Calcium concentration and pH of the distilled water were me
asured after 3 days, 7 days, and then at weekly intervals up to 15 wk, duri
ng which time the storage medium was renewed after each measurement. Calciu
m concentration and the change in pH of the distilled water were statistica
lly quicker and greater in groups 1 to 3 (mixture groups) than group 4 (pow
der only) (p < 0.05). The highest calcium concentration (peak Ca2+ release)
was observed after 3 days for the mixture groups, whereas that for the pow
der only group was found at 7 days. Peak pH change was found after 14 days
for the mixture groups, whereas that for the powder only group was found at
49 days. After peaking, all groups showed a decline of the pH over time. T
hese results suggest that the time required for optimum intracanal activity
when using calcium hydroxide mixtures is at least 2 wk.