Use of 10,600 nm carbon dioxide laser with silver diamine fluoride on caries prevention

Abstract

This PhD research investigated the use of 10,600 nm carbon dioxide (CO2) laser, which has been used in dentistry for over two decades. The 10,600 nm CO2 laser is a readily available dental laser on the market. Due to the advancement of technology, CO2 lasers with short pulse duration and high peak power are available. This research reviewed the effects of CO2 laser on prevention of dental caries. The review identified 22 publications that have shown CO2 laser could reduce carbonate content, induce recrystallization of mineral structure, increase the microhardness and decrease the mineral loss of enamel and dentin. Moreover, CO2 laser and fluoride treatment reduced mineral loss of dentin against acid challenge. In addition, this research reviewed the effects of CO2 laser on remineralizing caries and found the laser irradiation increased acid resistance, facilitated the fluoride uptake of caries lesions and reduced the growth of cariogenic bacteria. Further, this research also reviewed the parameters and irradiation techniques used for CO2 laser for dental caries prevention. For studies on enamel caries, the output power, pulse energy, frequency, spot area and fluence were respectively 0.1 to 2,800 W, 0.0025 to 2,000 mJ, 8.7×10-8 to 0.05 cm2, 1 to 226 Hz and 0.3 to 28.6 Jcm-2. The studies used either fixed spot or scanning motion and the time and irradiation distance ranged from 2 to 9 s and 1 to 370 mm, respectively. For dentin caries, the output i Abstract power, pulse energy, frequency, spot area and fluence ranged respectively from 0.17 to 480 W, 1.7 to 540 mJ, 0.008 to 0.05 cm2, 1 to 250 Hz and 0.05 to 715 Jcm-2. The studies used fixed spot or scanning motion. The time and irradiation distance range from 4 to 15 s and 5 to 198 mm, respectively. The review found considerable variations in the included articles’ parameters and irradiation techniques reported for CO2 laser for caries prevention. Some studies did not provide adequate information on the parameters and the irradiation technique. A few studies reported incorrect parameters or impractical irradiation distance for clinical practice. This research performed a laboratory study to investigate the caries prevention potential of CO2 laser irradiation followed by application of 38% silver diamine fluoride (SDF) solution to enamel. This research used 38% SDF solution because it contained 44,800 ppm fluoride, which is the highest concentration of fluoride among all topical fluoride agents. The results showed that using the CO2 laser or SDF separately enhanced the resistance of enamel to cariogenic challenge. Moreover, there was an additional effect of the combined use of the CO2 laser and SDF for preventing enamel demineralization. This research also performed a laboratory study to investigate the caries prevention effect of SDF with CO2 laser on dentin. The results showed that SDF can reduce dentin demineralization against cariogenic challenge, and the caries preventive effect of SDF is further enhanced through CO2 laser irradiation. Ultimately, a common laser parameter together with irradiation technique can be used by 10,600 nm CO2 lasers. (495 words)