In vitro Acid Resistance of CO₂and Nd-YAG Laser-Treated Human Tooth Enamel

Abstract

The purposes of this study were to test the effectiveness of laser treatment (pulsed CO₂ and pulsed Nd-YAG) on in vitro acid resistance of human enamel. Thirty enamel surfaces were prepared from 10 extracted permanent premolars (3 surfaces per tooth). Two experimental surfaces on each tooth were irradiated with either CO₂ or Nd-YAG lasers. All specimens were demineralized in 10 ml lactate buffer for 24 or 72 h after laser treatment. After 24-hour acid treatment the mean concentration of calcium that dissolved into the lactate buffer in the CO₂ laser group was significantly less than in the control group, while the dissolved calcium concentration in the Nd-YAG laser group did not differ from the control group (p > 0.05). The erosion depth in the CO₂ laser group was significantly shallower than in the Nd-YAG laser group (p < 0.001). After 72-hour acid treatment, the acid resistances of neither group of laser-treated surfaces differed significantly from the controls. By scanning electron microscopy, the acid-eroded laser-treated enamel surfaces had type I and type II etching patterns, fissures, and disordered rough surfaces compared to control enamel, with a regular type II etching pattern. CO₂ laser-treated tooth enamel was more resistant to acid challenge than was Nd-YAG laser-treated enamel, given the same fluence, but neither type of laser increased acid resistance of subsurface enamel.

Effect of Nd:YAG Irradiation and Fluoride Application on Dentine Resistance to Erosionin Vitro

“…This cracked surface may be more susceptible to acid challenge. 24 Lan et al 26 showed that energy levels inducing crater formation by the Nd:YAG laser ranged from 100-150 mJ, which is much lower than the energy levels we used in the present study. Similarly to the results of the present study, Tsai et al 24 found no protective effect of Nd:YAG laser treatment on enamel demineralization in vitro.…”

“…24 Lan et al 26 showed that energy levels inducing crater formation by the Nd:YAG laser ranged from 100-150 mJ, which is much lower than the energy levels we used in the present study. Similarly to the results of the present study, Tsai et al 24 found no protective effect of Nd:YAG laser treatment on enamel demineralization in vitro. The pulsed Nd:YAG laser (83.33 J/cm 2 ) was unable to increase the enamel's resistance to acid challenge (lactate buffer solution, pH 4.5, for 24 and 72 h), as shown by calcium analysis and polarized light microscopy.…”

“…Several types of lasers, such as ruby, CO 2 , Nd:YAG, and argon, with different operational modes and energy outputs have been investigated. 24 Most of the studies of the effects of laser irradiation on dental hard tissue demineralization have been conducted in vitro using the Nd:YAG laser, due to its ease of application in the oral cavity. 24 However, microscopic analyses have been used in most studies that tested this laser, 12,25,26 and this method is unable to quantify the loss of dental hard tissue.…”

Structural Changes on Human Dental Enamel Treated with Er:YAG, CO2 Lasers and Remineralizing Solution: EDS Analysis

“…The caries-preventive effect produced on the enamel surface due to CO 2 laser irradiation was reported by Stern et al (Stern, et al, 1972). Subsequently, several studies, both in vitro Kantorowitz, et al, 1998;Hsu, et al, 2000;Tsai, et al, 2002) and in vivo (Kato, et al, 2003), have shown increases in enamel acid resistance.…”

Study on ceramic coating on the enamel surface using a carbon dioxide laser

“…Other researchers have reported that CO2-laser light application through a fluoride solution could be effective in the prevention of caries [18][19][20][21] . However, this treatment is insufficient where small defects are present in the enamel requiring some restorative treatment.…”