Effect of calcium hydroxide form and placement on root dentine pH

Aim The aim of this study was to measure variations in dentinal pH followin g the placement of various forms of calcium hydroxide in either the root ca nal or the pulp chamber. Methodology Extracted single-rooted human teeth were prepared, and the root canals instrumented using a conventional technique. Three cavities were dr illed through the root dentine to within I mm. of the canal wall at the cer vical, middle and apical thirds. A total of 125 teeth were randomly divided into five groups; group 1: pure aqueous calcium hydroxide paste (calcium h ydroxide/distilled water solution) was placed in the root canal; group 2: t he same aqueous calcium hydroxide paste was placed in the pulp chamber; gro up 3: Hycal(R), a new form of calcium hydroxide paste, was placed in the pu lp chamber; group 4: calcium hydroxide gutta-percha points were placed in t he root canal; group 5: control group. wet canal (distilled water) without medication. The access cavities and apical ends were sealed, and the teeth were placed in individual vials containing phosphate-buffered saline, and s tored at 37 degreesC. The pH was measured in the dentinal cavities at 8 h a nd at 1, 2, 3, 7, 14, and 2 1 days using a calibrated microclectrode. Results At 8 h and 1, 2, and 3 days, the highest pH values were obtained wh en the aqueous calcium hydroxide paste was placed in the pulp chamber. At 7 days, the pH had increased in the Hycal(R) group without being significant ly different from the aqueous calcium hydroxide paste placed either in the root canal or in the pulp chamber. At 14 days, Hycal(k) had the highest pH values (pH 10.65); however, at 21 days no significant difference was noted amongst these first three groups. Control group values ranged from 7.88 to 8.60: the pH created by the calcium hydroxide gutta-percha points was lower than for the control group. Whatever the product or placement location, ce rvical pH was similar to middle pH, and greater than apical. However, there was no significant difference between the three when all groups were combi ned. Overall, aqueous calcium hydroxide paste placed in the pulp chamber pr ovided the highest pH values during the experiment, except at day 14. The a queous calcium hydroxide paste placed in the root canal or Hycal(R) had sim ilar values at days 7 and 2 1. Conclusions Under the conditions of this study, an aqueous calcium hydroxid e paste placed in the pulp chamber increased dentinal pH more than the othe r techniques. The pH of dentine is affected by the form of calcium hydroxid e used.