title: Comparison of different focusing fiber tips for improved oral diode laser surgery.
abstract: OBJECTIVE
  State of the art for use of the fiber guided diode laser in dental therapy is the application of bare fibers. A novel concept with delivery fiber and exchangeable fiber tips enables the use of tips with special and optimized geometries for various applications. The aim of this study is the comparison of different focusing fiber tips for enhanced cutting efficacy in oral surgery.
  
  
  METHODS
  For this purpose various designs of tip geometry were investigated and optimized by ray tracing simulations. Two applicators, one with a sphere, and another one with a taper, were realized and tested on porcine gingiva (diode laser, 940 nm, 5 W/cw; 7 W/modulated). The cutting depth and quality were determined by light microscope. Histological sections of the cuts were prepared by a cryo-microtome and microscopically analyzed to determine the cut depths and thermal damage zones.
  
  
  RESULTS
  The simulations show that, using a sphere as fiber tip, an intensity increase of up to a factor of 16.2 in air, and 13.2 in water compared to a bare 200 µm fiber can be achieved. Although offering high focusing factor in water, the cutting quality of the sphere was rather poor. This is probably caused by a derogation of the focusing quality due to contamination during cutting and light scattering. Much better results were achieved with conically shaped fiber tips. Compared to bare fibers they exhibit improved handling properties with no hooking, more regular and deeper cuts (5 W/cw: 2,393 ± 468 µm, compared to the cleaved bare fiber 5 W/cw: 711 ± 268 µm). The thermal damage zones of the cuts are comparable for the various tips and fibers.
  
  
  CONCLUSIONS
  In conclusion the results of our study show that cutting quality and efficiency of diode laser on soft tissue can be significantly improved using conically shaped fiber tips.
authors.affiliation: Institut für Lasertechnologien in der Medizin und Messtechnik an der Universität Ulm, 89081 Ulm, Germany. karl.stock@ilm.uni-ulm.de
authors.forename: Karl
authors.initials: K
authors.lastname: Stock
authors.forename: Thomas
authors.initials: T
authors.lastname: Stegmayer
authors.forename: Rainer
authors.initials: R
authors.lastname: Graser
authors.forename: Wolfram
authors.initials: W
authors.lastname: Förster
authors.forename: Raimund
authors.initials: R
authors.lastname: Hibst
mesh_terms: D000818:Animals; D003198:Computer Simulation; D005881:Gingiva / Q000528:radiation effects / Q000601:surgery*; D066298:In Vitro Techniques; D054023:Lasers, Semiconductor; D055100:Optical Fibers; D019647:Oral Surgical Procedures / Q000295:instrumentation*; D012984:Software; D013552:Swine