BASIC RESEARCH—TECHNOLOGY
Physical and Chemical Properties of Chlorhexidine and Calcium Hydroxide-Containing Medications

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This study was performed to evaluate the physicochemical properties (pH, contact angle, working time, radio-opacity, and viscosity) of chlorhexidine (CHX) and calcium hydroxide-containing medications in gel form in different concentrations. The pH value was assessed with a pH meter. The contact angle was measured with a goniometer. The radio-opacity and working time measurements were taken in accordance with the standards of the International Organization for Standardization. The viscosity was evaluated using a Brookfield RVDV viscometer. The results showed that CHX did not affect the pH, radio-opacity, and working time of the calcium hydroxide-containing medications (p < 0.05). However, adding CHX lowered the contact angle and increased the viscosity of calcium hydroxide significantly. This research showed that CHX in different concentrations and in combination with calcium hydroxide has satisfactory physicochemical properties to be used as an intracanal medication.

Section snippets

Medications

The physicochemical properties of CHX and calcium hydroxide-containing medications in different concentrations and combinations were evaluated. Medications were prepared by the following method. The required mass of methylcellulose (1 g/100 ml) (methylcellulose 4000 USP lot #PG15012N11; Medica Pharmaceutique, Montreal, Canada) was added to water and stirred until dissolution. Calcium hydroxide (USP lot #50K0121; Sigma Chemical Co., St. Louis, MO) at a concentration of 40 g/100 ml (to follow the

RESULTS

The means and SD of the pH, contact angle, and working time are shown in Table 1.

DISCUSSION

In this study, the physicochemical properties of different intra-canal medications were evaluated. There are no previous reports regarding the ideal physicochemical properties that an intracanal dressing should achieve. The different concentrations and modes of application of the medications likely affect the physical properties and subsequently the antibacterial activity of the CHX-calcium hydroxide–containing medications. No studies concerning this relationship have been reported. The

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      The pH values of the solutions with samples containing calcium hydroxide did not show considerable differences, whereas the pH of 2% chlorhexidine gel varied from 5.50 to 6.88, as expected and in accordance with values found in the literature.24 Despite the low pH values shown in group III (2% chlorhexidine gel), the pH of the mixture of chlorhexidine with calcium hydroxide in group II did not differ from the pH values of calcium hydroxide used with an aqueous vehicle (group I), which is corroborated by earlier studies.14,25 The calcium hydroxide pastes released calcium ions in all periods of the study.

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    This project was supported by grants from Dalhousie University, Halifax, Nova Scotia, Canada.

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