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. 2014 Feb 1;3(1):37-45.
doi: 10.1515/plm-2013-0052.

Analysis of enamel surface damage after selective laser ablation of composite from tooth surfaces

Kenneth H Chan  1 , Krista Hirasuna  2 , Daniel Fried  1
Affiliations

Analysis of enamel surface damage after selective laser ablation of composite from tooth surfaces

Kenneth H Chan et al. Photonics Lasers Med. .

Abstract

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.

Keywords: carbon dioxide laser; composite removal; laser ablation.

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Conflict of interest statement

Conflict of interest statement: This work was supported by NIH/NIDCR grant RO1-DE19631. None of the authors have any conflict of interest to disclose.

Figures

Figure 1
Figure 1
Flowchart describing the steps involved in selective ablation.
Figure 2
Figure 2
The experimental setup for selective ablation is shown with (A) XY galvanometers, (B) water spray, (C) microthermocouple, (D) CO2 laser beam, (E) composite on tooth buccal surface, (F) mounted tooth, (G) ZnSe f-theta scanning lens, and (H) imaging optics for spectrometer.
Figure 3
Figure 3
Mean depth±SD (n=3) for each scanned area for Grengloo™ composite (solid diamonds) and enamel (open circles) as a function of laser fluence. The enamel data is from [23].
Figure 4
Figure 4
Photographs of Grengloo™ composite on buccal surfaces before (A) and after composite placement (B), and after laser ablation (C) for two teeth at a fluence of 3.8 J/cm2 (Tooth#1 – Group #2a) and 4.2 J/cm2 (Tooth#2 – Group #2b).
Figure 5
Figure 5
Images of one of the Group #3 tooth surfaces before and after composite removal acquired with the VHX-1000 digital microscope at 175× magnification. Images (A) and (C) show depth composition and 3-D images of the region of interest before removal of the composite and images (B) and (D) are the corresponding images after irradiation by the laser. The surface roughness (RMS) was 12.5 μm for the enamel underlying the composite.
Figure 6
Figure 6
Images of the surface of another tooth from Group #3 before and after composite removal acquired with the VHX-1000 digital microscope at 175× magnification. Images (A) and (C) show depth composition and 3-D images of the region of interest before removal of the composite and images (B) and (D) are the corresponding images after irradiation by the laser. The surface roughness (RMS) was 19.6 μm for the enamel underlying the composite.
Figure 7
Figure 7
Digital depth composition and 3-D images of the underlying enamel surface at 1000× magnification for the two Group #3 samples shown in Figure 5 (A and C) and Figure 6 (B and D) after laser removal of the composite.
See this image and copyright information in PMC

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