Investigation into the optimum beam shape and fluence for selective ablation of dental calculus at λ = 400 nm

Authors

  • Joshua E. Schoenly BSc,

    Corresponding author
    1. Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623-1299
    2. The Institute of Optics, University of Rochester, Rochester, New York 14627
    • Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, NY 14623-1299.
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  • Wolf Seka PhD,

    1. Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623-1299
    2. The Institute of Optics, University of Rochester, Rochester, New York 14627
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  • Peter Rechmann DDS, PhD

    1. Department of Preventive and Restorative Dental Sciences, School of Dentistry, University of California at San Francisco, San Francisco, California 94143
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Errata

This article is corrected by:

  1. Errata: Erratum: Investigation into the optimum beam shape and fluence for selective ablation of dental calculus at λ = 400 nm Volume 42, Issue 5, 442, Article first published online: 25 June 2010

Abstract

Background and Objectives

A frequency-doubled Ti:sapphire laser is shown to selectively ablate dental calculus. The optimal transverse shape of the laser beam, including its variability under water-cooling, is determined for selective ablation of dental calculus.

Study Design/Materials and Methods

Intensity profiles under various water-cooling conditions were optically observed. The 400-nm laser was coupled into a multimode optical fiber using an f = 2.5-cm lens and light-shaping diffuser. Water-cooling was supplied coaxially around the fiber. Five human tooth samples (four with calculus and one pristine) were irradiated perpendicular to the tooth surface while the tooth was moved back and forth at 0.3 mm/second, varying between 20 and 180 iterations. The teeth were imaged before and after irradiation using light microscopy with a flashing blue light-emitting diode (LED). An environmental scanning electron microscope imaged each tooth after irradiation.

Results

High-order super-Gaussian intensity profiles are observed at the output of a fiber coiled around a 4-in. diameter drum. Super-Gaussian beams have a more-homogenous fluence distribution than Gaussian beams and have a higher energy efficiency for selective ablation. Coaxial water-cooling does not noticeably distort the intensity distribution within 1 mm from the optical fiber. In contrast, lasers focused to a Gaussian cross section (≤50-µm diameter) without fiber propagation and cooled by a water spray are heavily distorted and may lead to variable ablation. Calculus is preferentially ablated at high fluences (≥2 J/cm2); below this fluence, stalling occurs because of photo-bleaching of the calculus. Healthy dental hard tissue is not removed at fluences ≤3 J/cm2.

Conclusion

Supplying laser light to a tooth using an optical fiber with coaxial water-cooling is determined to be the most appropriate method when selectively removing calculus with a frequency-doubled Ti:sapphire laser. Fluences over 2 J/cm2 are required to remove calculus efficiently since photo-bleaching stalls calculus removal below that value. Lasers Surg. Med. 42:51–61, 2010. © 2010 Wiley-Liss, Inc.

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