Rapid and conservative ablation and modification of enamel, dentin, and alveolar bone using a high repetition rate transverse excited atmospheric pressure CO[sub 2] laser operating at λ=9.3 μm

Abstract

Transverse excited atmospheric pressure (TEA) CO(2) lasers tuned to the strong mineral absorption of hydroxyapatite near lambda=9 microm are well suited for the efficient ablation of dental hard tissues if the laser pulse is stretched to greater than 5 to 10 micros to avoid plasma shielding phenomena. Such CO(2) lasers are capable of operating at high repetition rates for the rapid removal of dental hard tissues. The purpose of this study was to test the hypothesis that stretched lambda=9.3-microA CO(2) laser pulses can produce lateral incisions in enamel, dentin, and alveolar bone for dental restorations and implants at repetition rates as high as 400 Hz without peripheral thermal damage. The single pulse ablation rates through enamel, dentin, and bone were determined for incident fluence ranging from (1 to 160 J/m(2)) for laser pulses from 5 to 18 mus in duration. Lateral incisions were produced in hard tissue samples using a computer-controlled scanning stage and water spray, and the crater morphology and chemical composition were measured using optical microscopy and high-resolution synchrotron radiation infrared spectromicroscopy. The residual energy remaining in tooth samples was measured to be 30 to 40% for enamel and 20 to 30% for dentin without water cooling, under optimum irradiation intensities, significantly lower than for longer CO(2) laser pulses. The transmission through 2-m length 300-, 500-, 750-, and 1000-microm silica hollow waveguides was measured and 80% transmission was achieved with 40 mJ per pulse. These results suggest that high repetition rate TEA CO(2) laser systems operating at lambda=9.3 microm with pulse durations of 10 to 20 micros are well suited for dental applications.

Non‐destructive assessment of inhibition of demineralization in dental enamel irradiated by a λ = 9.3‐µm CO2 laser at ablative irradiation intensities with PS‐OCT

“…An ablative fluence of 20 J/cm 2 was chosen for the l ¼ 9.3 mm CO 2 laser pulses of 15-mseconds duration since this fluence results in the most efficient ablation of dental enamel [5,33,34]. A water-spray was also used since it aids in producing a more desirable surface morphology and phase composition after laser irradiation.…”

A new sealed RF-excited CO2laser for enamel ablation operating at 9.4μm with pulse duration of 26 μs

“…This ablation rate exceeds ablation rates of previous CO 2 laser dental systems at 9.6-μm, 8-μs (~10-μm/pulse) and 9.3-μm, 18-μs (~20-μm/pulse). [14, 17] In addition, none of the samples exhibited any thermal damage (Fig. 4).…”

Influence of water layer thickness on hard tissue ablation with pulsed CO[sub 2] laser

“…For the short pulses (submicrosecond), the ablation rate and efficiency are much higher for 9.3 or 9.6 μm than for 10.6 μm. [29][30][31] However, when it is necessary to increase the ablation rate by using a pulse duration greater than 50 to 100 μs to avoid plasma shielding effects and excessive acoustic effects, the influence of wavelength tuning on the ablation of hard tissue would be less evident as the thermal diffusion length approaches 10 μm or greater for longer pulses. Scholz 32 reported for the laser pulse duration of 130 μs about a 70% higher ablation rate of compacta at the wavelength of 10.6 μm as compared to 9.6 mm.…”