Morphological effects of ArF excimer laser irradiation on enamel and dentin.

BACKGROUND AND OBJECTIVE: The aim of this investigation to determine the range of morphological and ablative effects that can be achieved on dental enamel and dentin using ArF excimer laser irradiation at a wavelength of 193nm. STUDY DESIGN/MATERIALS AND METHODS: Caries-free coronal enamel and dentin surfaces of 20 extracted human teeth were subjected to irradiation at 193nm using a Lamda-Physik model EMG 103 MSC and ArF fill. Morphology of cavity floors and walls were assessed by light microscopy and SEM. RESULTS: Morphological surface effects and ablation could be controlled effectively and reliably by choice of parameter combination, allowing the operator to achieve either a smooth, flat, or increasingly rough surface with differing degrees of selective ablation. No signs of thermal damage were apparent. CONCLUSION: Excimer laser irradiation at 193nm provided clinically useful cavity preparations and surface morphological effects.

Effect of ND:YAG laser irradiation and root planing on the root surface: structural and thermal effects.

Effects of ND:YAG laser irradiation on untreated and root planed tooth roots were investigated to determine whether a cleaning effect and/or removal of smear layer could be achieved without concomitant microstructural or thermal damage. Sixty (60) healthy extracted teeth were either untreated, irradiated only, root planed only, or irradiated and root planed. Intra-pulpal and surface temperatures were monitored during irradiation, then SEM was performed. Smear layer elimination was achieved without inducing hard tissue microstructural damage at 5W, using pulse durations and intervals of 0.1 s, a fluence of 0.77 J/cm2, and a total energy density of approximately 700 J/cm2. However, these results were not consistent in all samples. At these parameters, intra-pulpal temperature increases of 9 to 22 degrees C and surface temperature increases of 18 to 36 degrees C were recorded. Thus, despite their effectiveness for smear layer removal, these parameters may not be appropriate for clinical use as an adjunct to conventional periodontal therapy.

Incision properties and thermal effects of three CO2 lasers in soft tissue.

OBJECTIVES: It was the aim of this study to determine thermal and histologic events resulting from soft tissue incision with three CO2 lasers: one emitting light energy via a hollow waveguide at 9.3 microns; the others emitting light energy at 10.6 microns, one via a hollow waveguide, the other through an articulated arm delivery system. STUDY DESIGN: Thirty standardized incisions were made in the oral mucosa of pig's mandibles with three different lasers at actual power levels of 1, 4 and 12 W. Thermal events were recorded with thermocouples, and a histologic examination was performed to determine vertical and horizontal tissue damage as well as incision depth and width. RESULTS: Thermal and histologic results were related to parameters and beam characteristics rather than wavelength. CONCLUSION: In addition to wavelength, many variables can contribute to the surgical characteristics of a laser.

Root canal preparation using the second harmonic KTP:YAG laser: a thermographic and scanning electron microscopic study.

Thermal and microstructural events resulting from KTP laser use during root canal preparation were investigated in 30 extracted single-rooted human teeth. In the first section of this study, thermal events occurring on the root surfaces of 18 teeth during and after exposure of the root canal were measured using thermography. A variety of parameters were used to determine settings that would be effective without causing thermal damage to the periodontal ligament. In the second section of the study, root canals of 12 teeth exposed to KTP laser irradiation at parameters derived from section 1 were evaluated using Scanning electron microscopy. KTP laser application at a power setting of 3 W, an exposure time of 2 s, and a frequency of 5 Hz, applied five times, removed smear layer and debris from the root canal surface at temperatures below the thermal injury threshold for periodontal tissue.

Thermal effects of CO2 laser on the pulpal chamber and enamel of human primary teeth: an in vitro investigation.

BACKGROUND AND OBJECTIVE: Thermal effects of direct exposure of the pulp chamber to CO2 laser irradiation were evaluated and potentially safe parameters for its clinical application were determined. STUDY DESIGN/MATERIALS AND METHODS: Using conventional methods, the pulp chambers of freshly extracted primary cuspids were exposed and then subjected to CO2 laser irradiation at the following parameters: 2, 4, 6, 8, 10, 15, and 20 Watts power settings; 0.76 mm diameter spot size; total energy densities between 4-1,058 J/cm2; exposure time between .01-60 s. Exposures in the continuous wave mode were performed in some specimens. In others, single firings of a .01 s pulse duration and a 1 s pulse interval were conducted. Temperature measurements were conducted using a thermocouple and thermal camera. RESULTS: Significant statistical differences in maximum temperature rise on enamel were observed in groups that received total energy densities > or = 8 J/cm2 (P < or = 0.01); within the pulp chambers these were observed in groups that used > or = 44 J/cm2 (P < or = 0.01). CONCLUSION: Parameters appropriate for pulpotomy were observed at energy densities up to 176 J/cm2 in the continuous wave mode and 264 J/cm2 using single pulses, wherein temperature rises below 5.5 degrees C were recorded on tooth surface.

Comparative study of the thermal effects of four semiconductor lasers on the enamel and pulp chamber of a human tooth.

An in vitro thermometric study was conducted on various GaAlAs semiconductor lasers emitting at wavelengths between 750 nm and 905 nm, to verify whether these lasers produce significant heating during application to tooth structure. Measurements were conducted in vitro, using a thermal camera and a thermocouple during a 60, 120, and 180 s laser exposure at energy densities between 1.5 and 2,400 J/cm2. Mean temperature changes on surface enamel were statistically significant in all groups at P < or = .05 and P < or = .01. The higher the energy density applied to a surface area, the greater the temperature rise observed using the same spot size, operation mode, and wavelength. Intrapulpal temperature elevations measured > or = 3 degrees C. An in vivo study was also conducted to determine whether perceptible stimuli are experienced by patients during this time of laser treatment and to verify results of the in vitro study. The results did not conform well with the in vitro study because of uncontrollable variables. None of the patients who received irradiation treatment described any perceptible stimuli.