Pulsed carbon dioxide lasers operating at the highly absorbed 9.3 and 9.6-μm wavelengths with pulse durations in the microsecond range are ideally suited for dental hard tissue modification and removal. The purpose of these studies was to demonstrate that a low cost 9.3-μm CO 2 laser system utilizing low-energy laser pulses (1-5 mJ /pulse) delivered at a high repetition rate (400-Hz) is feasible for removing dental hard tissues. The laser beam was focused to a small spot size to achieve ablative fluence and an integrated/programmable optical scanner was used to scan the laser beam over the desired area for tissue removal. Pulse durations of 35, 60 and 75-μs were employed and the enamel and dentin ablation rate and ablation efficiency were measured. Laser irradiated human and bovine samples were assessed for peripheral thermal and mechanical damage using polarized light microscopy. The heat accumulation during rapid scanning ablation with water-cooling at 400-Hz was monitored using micro-thermocouples. The laser was able to ablate both enamel and dentin without excessive peripheral thermal damage or heat accumulation. These preliminary studies suggest that a low-cost RF excited CO 2 laser used in conjunction with an integrated scanner has considerable potential for application to dental hard tissues.
The propagation parameters of CO2 laser beams have been investigated using second moment and knifeedge width measurement techniques. The characteristics of two laser types have been measured: a low power stabilised single frequency instrument and a prototype 3 kW laser. The propagation parameters have been estimated by using two commercial beam analysing instruments: a rotating drum knife-edge device and a 2D array scanner.The propagation oferrors through the analysis procedures has been investigated. The experiments were designed to assess the viability of the draft ISO standard for the measurement of beam width and propagation characteristics of real laser beams. Uncertainties in the estimated beam parameters, resulting from the propagation of errors, are taken into account when assessing the relative merits of the width measurement procedures. It was found that, for the high quality laser beam investigated, there were some small but systematic variations in estimating the width ofwaists ofsubject laser beams. In the case ofthe lower quality, high power laser beam, both the knife-edge and second moment techniques produced estimates of the input beam waist properties that were within the experimental uncertainty limits but again some inconsistency was displayed. It is suggested that the source of the inconsistency is diffraction by hard-edge apertures in the beam path. Nevertheless, the ISO standard procedures are judged to be suitable for the measurement of important beam parameters with an accuracy that is sufficient for the majority ofindustrial applications.Keywords: Laser beam characterisation, ISO Standards, carbon dioxide laser, M squared, beam propagation factor, beam width measurement, knife edge, second moment, error propagation. 081941722X/95/$6.OO SPIE Vol. 2375 / 335 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/16/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.