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Scanning Electron Microscope Observations of CO2 Laser Effects on Dental Enamel

Department of Oral Sciences, Eastman Dental Center, 625 Elmwood Avenue, Rochester, New York, 14620

D. Fried

Department of Oral Sciences, Eastman Dental Center, 625 Elmwood Avenue, Rochester, New York, 14620

J.D.B. Featherstone

Department of Oral Sciences, Eastman Dental Center, 625 Elmwood Avenue, Rochester, New York, 14620

R.E. Glena

Department of Oral Sciences, Eastman Dental Center, 625 Elmwood Avenue, Rochester, New York, 14620

W. Seka

Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York, 14623

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 µm), 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 us. 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 µm, in contrast to no crystal fusion at 10.6 pm ( 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.

Key Words: CO2 laser • scanning electron microscopy • dental enamel

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Journal of Dental Research, Vol. 74, No. 10, 1702-1708 (1995)
DOI: 10.1177/00220345950740101201


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