An in vitro and in vivo study on the relationship of temperature and sodium hypochlorite
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Sodium hypochlorite is the most widely used irrigant in endodontics. Its ability to dissolve pulp remnants and debris is just one of its important properties that facilitates cleaning and shaping of root canal systems. This tissue dissolving ability has been found to be affected by an increase in temperature. Studies were conducted to investigate this finding. An in vitro study was undertaken to compare the solvent ability of NaOCl at concentrations of 5%, 4%, 3%, 2% and 1% on human dural connective tissue when pre-warmed individually at constant temperatures of 60[degrees]C, 50[degrees]C, 40[degrees]C, 37[degrees]C and 23[degrees]C using a water bath. Each specimen 4mm in diameter was placed in a test tube containing 10 ml of the given NaOCI concentration and exposed to a constant temperature starting from 60[degrees]C. The rate it took for each specimen to completely dissolve in the pre-warmed NaOCl solution was monitored. In vivo studies which made use of thermocouples were undertaken to: (a) determine the temperature of a NaOCl solution when inside the root canal system and the rate it took for the solution to reach this temperature and (b) determine the rate it will take for a pre-warmed 60[degrees]C NaOCl solution to stabilize to the temperature within the root canal environment. Results of the in vitro study indicate that: a) Both concentrations and temperatures are inversely related to the solvent time of the NaOCI solution. b) There is no significant difference in the solvent time of 2% - 5% sodium hyphoclorite concentrations when used at temperatures of 37[degrees]C and above. c) There is a significant difference in the solvent time of 1% sodium hypochlorite solution when used below 60[degrees]C. Results of the in vivo studies indicate that: a) The final temperature of a sodium hypochlorite solution (whether it is prewarmed or used at room temperature) when irrigated into the root canal is approximately equal to the temperature of the tooth. b) The final temperature of a sodium hypochlorite solution inside the root canal is the result of a very complex thermodynamic system which involves the interaction of many factors namely: the temperature of the solution before it is irrigated into the root canal, the temperature of the tooth, the mass of the tooth and the solution, the size and surface area of the root canal, the length and thickness of the tooth, the ambient temperature of the air, the thermal properties (thermal conductivity, heat capacity, conduction, convection and evaporation) of the tooth and solution, and the position of the thermocouple in the canal. c) A solution of sodium hypochlorite when prewarmed or used at room temperature rapidly approaches thermal equilibrium with the tooth upon irrigation into the canal. d) In endodontic therapy, it does not appear useful to use a heated solution of sodium hypochlorite in order to enhance its solvent capacity because the sodium hypochlorite solution rapidly establishes thermal equilibrium with the tooth at 36[degrees]C [plus or minus] .1[degree]C. e) There is a significant difference between an in vivo and an in vitro study with regards to maintaining a prewarmed NaOCl solution at a constant temperature.
Thesis (M.Sc.D.)--Boston University, Henry M. Goldman School of Graduate Dentistry, 1988 (Endodontics)Bibliography: leaves 137-144.
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