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Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC San Francisco Electronic Theses and Dissertations (2012)

Background and Objective: Excessive heat accumulation within the tooth, incomplete removal of composite, and variable damage to the enamel are shortcomings of using conventional burs to remove residual orthodontic composite after debonding fixed appliances. The objective of this study was to determine if composite could be selectively removed from the enamel surface using a rapidly scanned carbon dioxide laser controlled by spectral feedback.

Materials and Methods: A carbon dioxide laser operating at a wavelength of 9.3 µm with a pulse duration of 10-15 µs and a pulse repetition rate of ~ 200 Hz was used to selectively remove composite from the buccal surfaces of 21 extracted teeth. GrenGlooTM composite was used to better visualize residual composite and the amount of enamel lost was measured with optical microscopy. A spectral feedback system utilizing a miniature spectrometer was used to control the laser scanning system. Pulpal temperature measurements were performed during composite removal to determine if there was excessive heat accumulation.

Results: The amount of enamel lost averaged 22.7µm ± 8.9 and 25.3 µm ± 9.4 for removal at 3.8 and 4.2 J/cm2, respectively. An average maximum temperature rise of 1.9°C ± 1.5 was recorded, with no teeth approaching the critical value of 5.5°C. The average time of composite removal was 19.3 ± 4.1 seconds.

Conclusions: Residual orthodontic composite can be rapidly removed from the tooth surface using a rapidly scanned CO2 laser with spectral feedback, with minimal temperature rise within the pulp and with minimal damage to the underlying enamel surface.

    Cover page: Selective Removal of Residual Orthodontic Composite Using a Rapidly-Scanned CO2 Laser
    • Article
    • Peer Reviewed
    UC San Francisco Previously Published Works (2014)

    Objective

    Resin-based composites are used for many applications in dentistry. They are difficult to remove without damage to the underlying enamel since they adhere strongly and are color matched to the tooth. The objective of this study was to determine if an automated laser scanning system with spectral feedback could be used for selective removal of residual orthodontic composite from tooth surfaces with minimal damage to the underlying enamel.

    Materials and methods

    A CO2 laser operating at a wavelength of 9.3 μm with a pulse duration of 10-15 μs and a pulse repetition rate of ~200 Hz was used to selectively remove composite from the buccal surfaces of extracted teeth. A spectral feedback system utilizing a miniature spectrometer was used to control the laser scanning system. Pulpal temperature measurements were performed during composite removal to determine if there was excessive heat accumulation. Conventional and digital microscopes were used to assess the amount of enamel lost during removal.

    Results

    The amount of enamel lost averaged between 20 and 25 μm for irradiation intensities from 3.8 to 4.2 J/cm2, respectively. An average maximum temperature rise of 1.9±1.5°C was recorded, with no teeth approaching the critical value of 5.5°C. The average time for composite removal from an area of 5 mm2 was 19.3±4.1 s, fast enough for clinical feasibility.

    Conclusion

    Residual composite can be rapidly removed from tooth surfaces using a CO2 laser with spectral feedback, with minimal temperature rise within the pulp and with minimal loss of sound enamel.
      Cover page: Analysis of enamel surface damage after selective laser ablation of composite from tooth surfaces
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