The alkaline and antibacterial effect of seven Ca(OH)2 liners in vitro.

The alkaline effect of seven Ca(OH)2 liners was studied, using extractions with unbuffered 0.9% NaCl solutions and buffered bacterial growth media. The antibacterial effect was studied by cultivating Streptococcus mutans in the presence of liner specimens. All liners made the NaCl solutions strongly alkaline (pH greater than 10), although MPC and Reolite released much less Ca than did Dycal, Life, Procal, Renew, and Reocap-E. The weaker alkaline effect of MPC and Reolite was shown by the extractions with the growth media. Consequently, these two liners were not able to prevent the growth of Str. mutans. No growth was observed in the presence of the other five liners, and the media remained alkaline during the 12-h incubation period. Regrowth of the bacteria grown in the presence of these effective liners showed that only Dycal could be considered bactericidal, whereas the four other liners acted bacteriostatically.