Higher temperatures can improve root canal cleaning to a point, but this benefit falls off if the temperature gets too high, according to researchers who used computational fluid dynamics to determine the effect of temperature on root canal cleaning efficiency.
Hailing from China and the United States, the researchers used a model of the conical-shaped root canal inside a tooth. This cavity usually is filled with pulp. When the pulp becomes inflamed or infected, and endodontist removes it and then cleans, shapes, and fills the canal. The apex is then sealed.
Irrigation, or rinsing, the root canal cavity with an antibacterial solution such as sodium hypochlorite is crucial to the procedure, the researchers said. Efficient cleaning and successful destruction of any bacteria or other microbes in the cavity depend on the penetration and cleaning ability of the irrigation fluid, they added.
The computational investigation used a structured mesh as a model of the conical root canal cavity. More than a million cells in the mesh completely and accurately described both the root canal and the side-vented needle through which the hypochlorite solution is injected. Fluid dynamics equations were used to model the flow of the hypochlorite solution.
The researchers varied the fluid velocity, temperature, and input power to determine the most efficient cleansing technique. As they expected, higher fluid velocities lead to better cleansing. Perhaps counterintuitively, they said, cleansing efficiently is higher on the wall behind the needle vent.
“The effective area on the root canal wall, in which the shear stress exceeds the critical value to clean the wall, is usually larger behind the needle outlet than in front of it,” said author Hanhui Jin, adding that the maximum shear stress also usually occurs on the wall behind the needle outlet.
The researchers also looked at the effect of temperature on cleansing. They considers four different temperatures: 22°C, which is room temperature; 37°C, which is body temperature; and 45°C and 60°C. Temperatures above 60°C are painful for the patient and tend to cause root canal damage.
Increasing the temperature to 45°C while holding the fluid velocity fixed improved the depth of cleansing and the cleansing span across the canal’s width, but further increases beyond 45°C decreased the cleansing efficiency.
The researchers considered the effect of power consumption by the irrigation device. If the power consumption is held at a fixed value, the effect of temperature on cleansing efficiency is much more pronounced.
“The fluid circulation within the canal is clearly enlarged when the temperature is increased,” said Jin.
Therefore, careful control of both power consumption and temperature leads to increased cleaning efficiency, the researchers said.
The study, “Effect of Inflow Temperature on Root Canal Irrigation: A Computational Fluid Dynamics Study,” was published by Physics of Fluids.
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