The practical use of lasers in general practice.

The use of lasers in general dentistry is now an accepted--and to some extent, expected--treatment modality. Laser use can be either an adjunct to other procedures or the main form of treatment itself. For many procedures, lasers are now becoming the treatment of choice by both clinicians and patients, and in some cases, the standard of care. Though there are as many uses for lasers in general practice as the imagination can provide, this manuscript will address those indications for use that have received marketing clearance by the U.S. Food and Drug Administration (FDA).

Potential surface alteration effects of laser-assisted periodontal surgery on existing dental restorations.

OBJECTIVE: Laser-assisted gingivectomies are performed in proximity to teeth, existing restorations, and implants. In case of accidental exposures, a detrimental surface defect may cause failure. Surface interactions should be evaluated for safety margin determination of certain laser-material combinations. The purpose of this in vitro study was to assess the microscopic and visible effects of CO2, Nd:YAG, and 810-nm diode laser irradiations on various dental materials and tooth tissue. METHOD AND MATERIALS: Study samples were fabricated (10 x 7.5 mm irradiation surface area, 1 mm thickness) from eight material groups (amalgam, base metal, gold, palladium-silver, composite, ceramic, titanium, and extracted tooth slices). Laser irradiations were performed with CO2, Nd:YAG, and 810-nm diode lasers using the manufacturer's recommended settings for gingivectomy at a 45-degree angle for 30 seconds. Irradiated surfaces were evaluated under SEM at 200x and 1,000x magnifications. Standardized photographs were obtained using a camera mount system (10x high-definition macro lens). The SEM images and photographs were correlated to determine surface interactions. RESULTS: Nd:YAG detrimentally affected all metallic materials and tooth structures. CO2 altered amalgam, gold, and palladium-silver slightly, whereas composite, ceramic, and tooth surfaces were detrimentally altered. The 810-nm diode altered amalgam, gold, titanium, palladium-silver, and composite but only gold and palladium-silver surfaces were barely traceable. CONCLUSION: Within the limitations of this in vitro study, surface effects were all instant; therefore, even a short accidental exposure may be destructive in some laser-material combinations. During gingivectomies, CO2 near tooth-colored restorations and Nd:YAG near metallic restorations and implants should be used carefully. The 810-nm diode was found to be safer due to its reversible alterations in only some materials. Further in vivo studies are necessary to clinically apply the outcomes of this study.

Thermal safety of Er:YAG and Er,Cr:YSGG lasers in hard tissue removal.

OBJECTIVE: The aim of this study was to compare the thermal safety of Er:YAG and Er,Cr:YSGG lasers with conventional multi-use and single-use diamond burs. BACKGROUND DATA: Thermal effect of tooth preparation is mostly evaluated through the pulp chamber because it is difficult to measure the temperature of the preparation surface. A new in vitro method was introduced to simultaneously evaluate the heat increase of the preparation surface together with the pulp chamber. METHODS: Six laser and bur instrument groups were used to make standardized preparations on buccal surfaces of 60 intact third molars. The preparations removed an equal volume of hard tissue from each tooth (4 mm occluso-gingival x 8 mm mesial-distal x 1.6 mm bucco-lingual). The teeth also included tunnel preparations from the opposite (lingual) surface, exposing the pulpal axial wall (axial dentin wall in contact with the pulp chamber from the preparation surface site). An infrared thermal camera was positioned to capture the preparation surface in direct vision, while the pulpal axial wall was indirectly reflected to the thermal camera via a minimal-energy-loss mirror. Data from both surfaces were analyzed statistically using Nested Least Squares Analysis. RESULTS: The laser groups generated significantly lower heat compared to bur groups on the preparation surfaces. In contrast, both lasers generated greater pulpal heat increase, and the Er:YAG laser group showed significance (p < 0.0001). CONCLUSIONS: Lasers produced less heat on the preparation surface but more on the pulpal axial wall. However the temperature rise was less than the 5.5 degrees C threshold margin of safety.