Enhanced Enamel Whitening, Surface Hardness and Stain Resistance by 9.3-μm CO2 Laser Irradiation: An In-Vitro Pilot Study

Objectives: In vitro studies were performed to investigate the effects of irradiating incisor enamel with a 9.3 μm CO 2 laser in enhancement of whitening, stain resistance and surface hardness. Methods: A 9.3 μm CO 2 laser beam was used to irradiate the labial surface of incisors with 0.8 J/cm2 pulse fluence at 333 Hz automatically scanning a 5.8 mm 2 area for 0.381 seconds repeated to cover the whole teeth surface. The teeth were divided into three groups of n=10 each: a control group that received 40% H2 O 2 gel for 20-minutes application time, an irradiated group followed with two 10-minute gel applications, and another irradiated group followed with two 20-minute gel applications. A spectroscopy device was used to analyze the overall color change (delta E) and degree of whitening. A 24-hour tea stain protocol was used to investigate the uptake of stain after the treatment procedure. Additionally, a small flat polished area on each sample was used to investigate microhardness before and after an acid challenge with pH 3.6 citric acid buffer. Result: Both irradiated groups showed an enhanced whitening effect, with a delta E that was 1-2 higher than the H2 O 2 gel control group. The 10-minute application time was sufficient to reach the full benefit from irradiation. The irradiated groups showed increased resistance to acid solubility and reduced the absorption of tea stain. Conclusion: Irradiation with a 9.3 μm CO 2 laser before application of whitening gel on incisor enamel increased the effect of whitening in half the time. It also provided an increased resistance to acid attack and staining