THE EFFECTS OF CO2-LASER AND ND-YAG WITH AND WITHOUT WATER AIR-SURFACE COOLING ON TOOTH ROOT STRUCTURE - CORRELATION BETWEEN FTIR SPECTROSCOPY AND HISTOLOGY

Morphologic and chemical characterization of root surfaces treated wit h either the CO2 laser, Nd:YAG, or Nd:YAG with water/air surface cooli ng (Nd:YAG-C) was completed using scanning electron microscopy (SEM) a nd FTIR photoacoustic spectroscopy (FTIR/PAS). Specimens for morpholog ic analysis consisted of 20 extracted single rooted teeth unaffected b y periodontal disease. The specimens were exposed at varying energy de nsities to a single pass of the laser. SEM examination revealed, for a ll lasers, a direct correlation between increasing energy densities an d depth of tissue ablation and width of tissue damage. The Nd:YAG-C re quired higher energy densities than either the CO2 or Nd:YAG lasers to achieve the same relative depth of tissue ablation. Regardless of ene rgy density, and in contrast with other laser types, areas treated wit h the Nd:YAG-C did not exhibit collateral zones of heat damage. Specim ens for spectroscopic examination consisted of 12 disks, 6x2 mm, cut f rom debrided root surfaces of extracted, unerupted human molars. The s pectral results indicate a substantial reduction in the absorption ban ds attributable to protein and an additional band at 2015 cm(-1) in sp ecimens exposed to the Nd:YAG without water. In the presence of water/ air coolant, the band at 2015 cm(-1) appears only at a substanially hi gher energy density. The spectra of the CO2 treated specimens, with th e char layer present, show a significant reduction in the protein band s and additional bands at 2015 and 2200 cm(-1), that are tentatively a ssigned to the cyanamide and cyanate ions, respectively. These results suggest a reaction of the organic matrix and mineral with laser expos ure.