Preliminary report on the application of the CO2 laser scalpel for operations on the maxillo-facial bones

Acute and chronic effects of bone ablation with a pulsed holmium laser

A pulsed holmium laser transmitted through a quartz fiber was used to create osteotomies in the facial bones and sinuses of rabbits. The ablation process was quantified and residual thermal injury was assessed by light microscopy. Adjacent thermal damage was determined to vary between 130 and 220 microns and was independent of radiant exposure and pulse repetition rate. In other studies, large osteotomies were made to examine the biological response and to assess the technical feasibility of using fiber-delivered laser pulses in an operative setting. The animals tolerated the procedure without obvious problems and postoperative follow-up revealed a vigorous healing response. Because it can ablate both bone and soft tissue and can be transmitted through readily available, flexible quartz fibers, the holmium laser may prove to be a useful adjunct to endoscopic sinus surgical procedures.

Plasma-mediated excimer laser ablation of bone: a potential microsurgical tool

A pulsed ultraviolet excimer laser was used to ablate bone in vitro at 193, 248, 308, and 351 nm and in vivo at 193 nm. Ablation was dependent on sufficient fluence (energy delivered per unit area per pulse) for plasma formation at the target site at all wavelengths. Adjacent tissue damage at various fluences for each wavelength was examined using a light microscope. Damage was minimal at 193 nm (1 to 3 microns) and most extensive at 351 nm (60 to 75 microns). This is in sharp contrast to the 1 to 3 mm of adjacent thermal damage produced when carbon dioxide lasers are used to ablate bone. Differences in the degree and type of damage to adjacent tissues among the wavelengths studied indicated that other ablation mechanisms and tissue interactions are involved in addition to simple plasma vaporization of bone. Bleeding during and after ablation demonstrated that the use of this laser does not cause thermal damage, which would cauterize adjacent vessels. Pre- and post-mortem lesions made at identical power and pulse settings were of equal depth, indicating that bleeding does not affect the ablation rate. The excimer laser has potential as a microsurgical instrument for the precise removal of bone with minimal damage to adjacent structures.

Effects of exposure time and pulse parameters on CO2 laser osteotomies

Two sets of experimental linear osteotomies were performed on frozen cortical bone by means of a high-power industrial CO2 laser in the rapid superpulsed mode, varying the velocity of the operating table, the mean power of the laser beam, the pulsewidth, the pulse repetition rate, and the peak power. Both the depth and the width of the osteotomies were inversely related to the velocity and directly related to the mean power and to the pulsewidth, but they were not affected by changes in the repetition rate. The depth/width ratio, which describes the profile of the osteotomies, was affected by the mean power only. These data permit greater accuracy in the planning of laser osteotomies in cortical bone when using the rapid super-pulsed mode.

Changes in teeth and gingiva of dogs following laser surgery: a block surface light microscope study

The effect of laser surgery on tissues of the periodontal apparatus was studied histologically in dogs using block surface light microscopy, a novel microscopical method. With this approach, changes in the hard and soft tissue components were concomitantly demonstrated; the method enabled preservation of the in situ relationship between these components. Following laser surgery, healing in the gingiva was delayed as suggested by the presence of epithelial ulcerations and dense inflammatory infiltrate. In the enamel and cementum the application of laser resulted in crater-like defects that could be avoided only partially by insertion of a tinfoil shield into the gingival sulcus. In the vicinity of the cementoenamel junction these defects were filled with epithelium or periodontal ligament fibers; the close proximity of the hard and soft tissues at the defect sites suggested occurrence of new attachment. Enamel defects located coronal to the gingiva contained bacterial plaque. These histologic results do not demonstrate any substantial advantage of laser over conventional knife gingivectomy. Such advantage may be accomplished with the design of a special intraoral handpiece and further experiments.

Comparison of depth and profile of osteotomies performed by rapid superpulsed and continuous-wave CO2 laser beams at high power output

Osteotomies performed by continuous-wave (CW) and rapid superpulsed (RSP) CO2 lasers at high power outputs are compared. Both the RSP and CW modes were able to cut frozen cortical bone at a velocity of 2 mm/second. The RSP laser produced slightly more shallow cuts with profiles that were far superior, especially when lenses with longer focal lengths were employed. The RSP laser seems promising for use in osteotomies because it reduces paraincisional damage.