A laboratory study evaluating the release of hydroxyl ions from various calcium hydroxide products in narrow root canal-like tubes

Aim The aim of the present study was to describe pH changes in a variety of buffering solutions within a narrow test tube containing either a gutta-pe rcha point with incorporated calcium hydroxide, a commercial calcium hydrox ide paste (Calcicur(R)) or a freshly mixed paste of calcium hydroxide in di stilled water. Methodology The test material was placed centrally in a test tube of 2 mm i nner diameter. Saline (1%) was placed at one end. whilst the buffering solu tions were introduced at the other. The pH of the buffering solutions was m onitored using electrodes placed at each end of the test tube. Results It was found that the pH 4.01 buffer strongly resisted pH changes a t levels below 6.0, whilst saliva and bovine serum was buffered less and mo re evenly in the whole range up to pH 11.5. The calcium hydroxide containin g gutta-percha points caused the pH to increase quickly in the sodium chlor ide solution to levels above 11.5, However, in bovine serum, in saliva and in the pH 4.01 buffer the pH remained below 8,5, 8,0 and 6,0, respectively, 1 mm from the point. In contrast, the release of hydroxyl ions from the tw o calcium hydroxide pastes brought pH above pH 11.5 irrespective of the buf fering of the solutions 5 mm from the paste. Conclusion It is concluded that; Calcicur(R) and the calcium hydroxide-wate r mixture contained substantially more available calcium hydroxide than did the calcium hydroxide containing gutta-percha points. with the result that the release of hydroxyl ions from the points was limited in comparison to that from the pastes.