Concentration of hydrogen ions in several calcium hydroxide pastes over different periods of time

ABSTRACT

The purpose of this in vitro study was to measure the concentration of hydrogen ions (pH) of calcium hydroxide [(Ca(OH)2] pastes combined with different vehicles over 7 periods of time. The Ca(OH)2 was manipulated with the following vehicles i sterile water; ii iodoform plus sterile water; iii local anesthetics (Lydocaine 2 percent with 1 100,000 epinephrine); iv polyethyleneglycol; v glycerin; vi 2.0 percent chlorhexidine gel; vii camphorated paramonochlorophenol (CMCP); viii (CMCP) + glycerin; and ix polyethyleneglycol plus CMCP. The pastes were made on a glass plate to toothpaste consistency and the pH was measured at the following times 5 min, 1, 24, 48 h; 7, 14 and 28 days. The data were statistically analyzed (Kruskal-Wallis at p<0.05). At 5 min, 1 and 24 h, the pH of all tested pastes ranged from 13.05 to 11.16. At 48 h and 7 days the pH of all tested pastes ranged from 11.66 to 8.92. At 14 and 28 days almost all pastes had pH means lower than 10. In conclusion, the mean pH of all tested calcium hydroxide pastes decreased with the time. Pastes made with aqueous vehicles (especially with sterile water), followed by oily vehicles (especially with CMCP + glycerin), held the highest pH means over the periods of time tested.

RESUMO

O objetivo deste estudo in vitro foi mensurar a concentração de ions hidroxila (pH) de pastas de hidróxido de cálcio manipuladas com diversos veículos em 7 intervalos de tempo. As pastas foram manipuladas com os seguintes veículos (i) água destilada estéril; (ii) idodofórmio + água destilada estéril; (iii) anestésico local (Lidocaína a 2 por cento com 1100.000 epinefrina); (iv) polietilenoglicol (Calen); (v) glicerina; (vi) clorexidina gel 2 por cento; (vii) paramonoclorofenol canforado (PMCC); (viii) PMCC + glicerina; e (ix) PMCC + polietilenoglicol (Calen PMCC). As pastas foram manipuladas em consistência de pasta de dente e os pH mensurados 5 min; 1, 24, 48 h; 7, 14 e 28 dias após manipulação. Os resultados foram analisados estatisticamente através do teste Kruskal-Wallis (p<0,05). Aos 5 min, 1 e 2 h após manipulação o pH de todas as pastas ficou entre 13.05 e 11.16. Aos 48 h e 7 dias após a manipulação, o pH de todas as pastas testadas variou de 11.66 a 8.92. Aos 14 e 28 dias, quase todas as pastas mostraram pH menor que 10. Concluiu-se que o pH de todas as pastas hidróxido de cálcio decresceram de acordo com o tempo. Pastas feitas com veículos aquosos (especialmente com água destilada), seguida de veículos oleosos (especialmente com CMCP + glicerina) mantiveram as maiores médias de pH durante os períodos testados.