Tissue dissolution by sodium hypochlorite: effect of concentration, temperature, agitation, and surfactant.
OBJECTIVE
Sodium hypochlorite is the most commonly used endodontic irrigant because of its antimicrobial and tissue-dissolving activity. The aim of this study was to evaluate and compare the effects of concentration, temperature, and agitation on the tissue-dissolving ability of sodium hypochlorite. In addition, a hypochlorite product with added surface active agent was compared with conventional hypochlorite solutions.


METHODS
Three sodium hypochlorite solutions from two different manufacturers in concentrations of 1%, 2%, 4%, and 5.8% were tested at room temperature, 37 degrees C, and 45 degrees C with and without agitation by ultrasonic and sonic energy and pipetting. Distilled and sterilized tap water was used as controls. Pieces of bovine muscle tissue (68 +/- 3 mg) were placed in 10 mL of each solution for five minutes. In selected samples, agitation was performed for one, two, or four 15-second periods per each minute. The tissue specimens were weighed before and after treatment, and the percentage of weight loss was calculated. The contact angle on dentin of the three solutions at concentrations of 1% and 5.8% was measured.


RESULTS
Weight loss (dissolution) of the tissue increased almost linearly with the concentration of sodium hypochlorite. Higher temperatures and agitation considerably enhanced the efficacy of sodium hypochlorite. The effect of agitation on tissue dissolution was greater than that of temperature; continuous agitation resulted in the fastest tissue dissolution. Hypochlorite with added surface active agent had the lowest contact angle on dentin and was most effective in tissue dissolution in all experimental situations.


CONCLUSIONS
Optimizing the concentration, temperature, flow, and surface tension can improve the tissue-dissolving effectiveness of hypochlorite even 50-fold.
Stojicic
Sonja
S
Division of Endodontics, Department of Oral Biological & Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, Canada.
Zivkovic
Slavoljub
S
Qian
Wei
W
Zhang
Hui
H
Haapasalo
Markus
M
D000818:Animals; D002417:Cattle; D003804:Dentin / Q000187:drug effects*; D004202:Disinfectants / Q000737:chemistry / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D018482:Muscle, Skeletal / Q000187:drug effects; D012388:Root Canal Irrigants / Q000494:pharmacology*; D018915:Root Canal Preparation / Q000379:methods*; D012973:Sodium Hypochlorite / Q000494:pharmacology*; D013501:Surface-Active Agents / Q000494:pharmacology; D013696:Temperature; D007507:Therapeutic Irrigation
D004202:Disinfectants; D012388:Root Canal Irrigants; D013501:Surface-Active Agents; D012973:Sodium Hypochlorite