Research Papers

Design of Laser Treatment Protocols for Bacterial Disinfection in Root Canals Using Theoretical Modeling and MicroCT Imaging

[+] Author and Article Information
Jennifer Gill, Dwayne Arola

Department of Mechanical Engineering,  University of Maryland Baltimore County, Baltimore, MD 21250

Ashraf F. Fouad

Department of Endodontics, Prosthodontics and Operative Dentistry,  University of Maryland, Baltimore, MD 21201

Liang Zhu1

Department of Mechanical Engineering,  University of Maryland Baltimore County, Baltimore, MD 21250zliang@umbc.edu


Corresponding author.

J. Thermal Sci. Eng. Appl. 4(3), 031011 (Jul 23, 2012) (9 pages) doi:10.1115/1.4006479 History: Received August 29, 2011; Revised March 19, 2012; Published July 23, 2012; Online July 23, 2012

Theoretical simulations of temperature elevations in root dentin are performed to evaluate, how heating protocols affect the efficacy of using erbium, chromium; yttrium, scandium, gallium, garnet (Er,Cr;YSGG) pulsed lasers for bacterial disinfection during root canal treatments. The theoretical models are generated based on microcomputer tomography (microCT) scans of extracted human teeth. Heat transfer simulations are performed using the Pennes bioheat equation to determine temperature distributions in tooth roots and surrounding tissue during 500 mW pulsed Er,Cr;YSGG laser irradiation on the root canal for eradicating bacteria. The study not only determines the heat penetration within the deep dentin but also assesses potential thermal damage to the surrounding tissues. Thermal damage is assumed to occur when the tissue is subject to a temperature above at least 47 °C for a minimum duration of 10 s. Treatment protocols are identified for three representative tooth root sizes that are capable of maintaining elevated temperatures in deep dentin necessary to eradicate bacteria, while minimizing potential for collateral thermal tissue damage at the outer root surfaces. We believe that the study not only provides realistic laser heating protocols for various tooth root geometries but also demonstrates utility of theoretical simulations for designing individualized treatments in the future.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

Seven longitudinal-sectional images of extracted human teeth from the microCT scans

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Figure 2

Root geometries of the largest, the middle, and the smallest tooth roots to be imported to the COMSOL® software package

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Figure 3

The two-dimensional axis-symmetric heat transfer model of the tooth, where the root of the tooth is embedded in a tissue block

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Figure 4

Simulated temperature contours in the dentin and surrounding tissue using the treatment protocol satisfying the two requirements for Tooth F. The white dashed lines represent the radial direction along which temperatures are plotted in Fig. 5. The black line gives the root–tissue interface.

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Figure 5

Radial temperature distributions along the white dashed lines shown in Fig. 4 at several segments. The black arrows represent the locations of the root–tissue interface. Note that 800 μm is the assumed bacterial penetration depth from the root canal surface.

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Figure 6

Schematic diagram of the tooth dentin and the five locations of the deep dentin (white stars) and the five locations of the root–tissue interface (black stars)

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Figure 7

Transient temperature elevations at the deep dentin location of segment 2 of Tooth F. The bars on top of the plot give the heating duration of individual segments. The two double arrows measure the total time at the deep dentin location of segment 2 when its temperature is above 47 °C.

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Figure 8

Transient temperature elevations at the five deep dentin locations of Tooth F

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Figure 9

Transient temperature elevations at the five locations along the root–tissue interface of Tooth F




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