Scanning Electron Microscope Observations of CO2 Laser Effects on Dental Enamel

Abstract

Studies of the effects of carbon dioxide (CO2) lasers on dental enamel have demonstrated that surface changes can be produced at low fluences (< 10 J/cm2) if wavelengths are used which are efficiently absorbed by the hard tissues. In this study, scanning electron microscopy (SEM) was used to characterize the wavelength dependence of surface changes in dental enamel after exposure to an extensive range of CO2 laser conditions. Bovine and human enamel were irradiated by a tunable, pulsed CO2 laser (9.3, 9.6, 10.3, 10.6 microns), with 5, 25, or 100 pulses, at absorbed fluences of 2, 5, 10, or 20 J/cm2, and pulse widths of 50, 100, 200, 500 microseconds. SEM micrographs revealed evidence of melting, crystal fusion, and exfoliation in a wavelength-dependent manner. Crystal fusion occurred at absorbed fluences as low as 5 J/cm2 per pulse at 9.3, 9.6, and 10.3 microns, in contrast to no crystal fusion at 10.6 microns (< or = 20 J/cm2). Longer pulses at constant fluence conditions decreased the extent of surface melting and crystal fusion. The total number of laser pulses delivered to the tissue did not significantly affect surface changes as long as a minimum of 5 to 10 pulses was used. Within the four easily accessible wavelengths of the CO2 laser, there are dramatic differences in the observed surface changes of dental hard tissue.

Morphological Alterations of the Surfaces of Enamel and Dentin of Deciduous Teeth Irradiated with Nd:YAG, C0(2)and Diode Lasers

“…With regard to the CO 2 laser action on the enamel surface of deciduous human teeth, our results showed the aspect of fusion and melting of the samples, similar to those related by McCormack et al (1995) and Kantorowitz et al (1996). Furthermore, we noticed the presence of extensive rugosities in all the area irradiated with laser, confirming the findings of Takahashi et al Around the rugosities, we noticed the formation of some cavities with variable sizes in the area of the enamel irradiated with the CO 2 laser, clearly showing fissures as had Ferreira et al (1989).…”

Near-IR imaging of erbium laser ablation with a water spray

“…Moreover, the normal highly ordered structure of dentin and enamel is conserved during the ablation process 12 . In contrast, the mechanism of ablation of dental hard tissue at the highly absorbed CO 2 wavelengths of 9.3 and 9.6 μm is apparently mineral mediated and SEM micrographs show that the tissue morphology is markedly changed after irradiation 13,14 . Although, it is advantageous to ablate enamel at lower surface temperatures to avoid heat deposition, it may also be useful to heat the tissue peripheral to the ablation site to temperatures exceeding 400 °C.…”

CO2 Laser: Evidence Based Applications in Dentistry

“…Literature suggests that 9.3 and 9.6um wavelength (pulse width <100usec) at a specified pulse rate has higher efficiency than 10.6um in heating dentin/enamel surface leading to desired crystallization and fusion of surface layer for sealing effect (McCormack, Fried, Featherstone, Glena, & Seka, 1995;Wigdor et al, 1995). A case report by Dederich, suggested to use 15W for 0.2sec duration to achieve dentinal sealing effect with CO2 laser without detrimental effect to pulpal tissue (Dederich, 1999).…”