Two novel lasers and their adjunctive use with silver diamine fluoride on caries management

Abstract

Carbon dioxide lasers and diode lasers are most commonly used lasers. Carbon dioxide lasers at 9,300 nm and 445 nm diode lasers are novel lasers which have just entered the market. This thesis begins with a literature review to provide an overview of the use of the novel 9,300 nm carbon dioxide laser in dentistry. The high absorption affinity of the 9,300 nm carbon dioxide laser for hydroxyapatite can make a shallow depth of heat absorption in enamel and dentine. Therefore, a 9,300 nm carbon dioxide laser reduces the risk of thermo-damage to the dentine–pulp complex. It can effectively alter the chemical structure and surface morphology of the teeth. It can also be used for caries removal. It can enhance the success of restoration through increasing the bond strength of dental adhesives to the dentine and enamel. Besides, it has a preventive effect on dental caries. A 9,300 nm carbon dioxide laser can also be applied with topical fluoride for enhancing the preventive effect of fluoride on dental caries. Therefore, we conducted a systematic review and meta-analysis on the effect of treatment combining 9,300 nm carbon dioxide lasers and fluoride on preventing enamel caries. Through the meta-analysis, we found the combined use of 9,300 nm carbon dioxide laser and fluoride was better compared to the single use of the laser and fluoride in preventing enamel demineralisation. Further, we performed a laboratory study to investigate the effect of 9,300 nm carbon dioxide laser irradiation followed by topical application of silver diamine fluoride on preventing enamel caries. The study results confirmed that irradiation with a 9,300 nm carbon dioxide laser can prevent the demineralisation of enamel. Besides, we found the 9,300 nm carbon dioxide laser can reduce the adhesion of cariogenic bacteria on the enamel surface. Moreover, the combined use of a 9,300 nm carbon dioxide laser and silver diamine fluoride can significantly enhance the caries-preventive effect and antibacterial ability compared to single use of the laser or the fluoride. Recent studies found evidence on the effect of the newly developed 445 nm diode laser on preventing enamel demineralization. We conducted another systematic review and meta-analysis on the effect of treatment combining diode lasers and fluoride on preventing enamel caries. The results of the meta-analysis demonstrated that diode lasers can enhance fluoride’s effect on remineralising but not on preventing enamel caries. We evaluated the power output of two common diode laser devices before we carried out a study to investigate the treatment combining a novel diode laser at 445 nm and topical fluoride. We found that the actual power was not necessarily lower but it could be higher compared to the displayed power output. We calibrated the 445 nm diode laser device and studied the effects of treatment combining 445 nm diode laser and silver diamine fluoride on preventing enamel demineralisation and inhibiting cariogenic bacteria. The result showed there was an interaction effect between the 445 nm diode laser and silver diamine fluoride on inhibiting enamel demineralisation and cariogenic biofilm formation.