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Clinical Studies | Convergent Dental


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

Badreddine AH and Kerbage C

ABSTRACT (Click here for full article)


In vitro studies were performed to investigate the effects of irradiating incisor enamel with a 9.3 µm CO2 laser in enhancement of whiting, stain resistance and surface hardness. 


A 9.3 µm CO2 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 mm2 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% H2O2 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. 


Both irradiated groups showed an enhanced whitening effect, with a delta E that was 1-2 higher than the H2 O2 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. 


Irradiation with a 9.3 µm CO2 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.

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