Laser irradiation of dental hard tissues

Dentists and patients alike desire an alternative to the dental drill that would eliminate or reduce the noxious stimuli of pain, vibration, and noise. Lasers have been explored for use in dentistry for over thirty years but success has been limited mostly to soft tissue applications. Problems previously encountered with laser mediated removal of hard tissue generally have led to excessive thermal damage at the surface and in the vital pulp chamber.; The effectiveness of a water cooling system designed for use during laser irradiation was investigated. Three infrared lasers were explored for their potential to remove hard dental tissues: Er:YAG ({dollar}lambda{dollar} = 2.94 {dollar}mu{dollar}m), Er:YSGG ({dollar}lambda{dollar} = 2.9 {dollar}mu{dollar}m), and CO{dollar}sb2{dollar} ({dollar}lambda{dollar} = 9.4 {dollar}mu{dollar}m). In vitro studies showed that a concurrent water stream directed at the irradiation site did not affect ablation rates significantly at higher fluences for Er:YAG and CO{dollar}sb2{dollar} lasers. Water cooling decreased ablation rates slightly at all fluences for the Er:YSGG laser. Er:YAG laser ablation rates of composite and amalgam restorative materials were also determined. During large area ablations of extracted teeth, water cooling limited the temperature rise in the pulp chamber to safe levels while irradiating with each of the three lasers.; The surface effects resulting from irradiation were viewed under a scanning electron microscope and used to corroborate proposed ablation mechanisms. The effect of Er:YAG laser irradiation on dentin surfaces was evaluated by adhering a composite restorative material and measuring the load required to shear the bond. Results were compared to control groups which were prepared with a dental drill followed by an optional acid treatment. The laser prepared surfaces yielded stronger bonds, indicating that acid etching could be eliminated with the use of lasers. Furthermore, the shear bond study showed that the irradiated surfaces were not compromised mechanically compared to traditional techniques.; Three lasers were investigated for their ability to prevent caries formation. The best results were produced with the Er:YSGG laser (60% inhibition), followed by the Er:YAG (44%) and Ho:YAG ({dollar}-{dollar}11%) lasers. Further study and optimization of the irradiation parameters may increase the success.