Er:YAG Laser for Metal and Ceramic Bracket Debonding: An In Vitro Study on Intrapulpal Temperature, SEM, and EDS Analysis

Abstract

Objective: To evaluate the effects of bracket removal using an erbium laser on the pulp temperature and enamel surface.

Background: Removal of orthodontic brackets with conventional debonding pliers may result in enamel cracks. To avoid damage to the enamel surface and effectively remove metal or ceramic brackets, different types of lasers, such as Nd:YAG, CO₂, TM:YAP, diode laser, or Er:YAG, have been introduced for debonding.

Materials and methods: A total of 55 brackets (n = 55; 20 metal and 35 ceramic ones) were bonded to 55 caries-free premolars extracted for orthodontic indications. Brackets were irradiated with Er:YAG laser (Morita, Irvine, CA) with a wavelength of 2940 nm at a power of 3.4 W, energy 170 mJ, frequency 20 Hz, pulse duration 300 μs, tip diameter 0.8 mm, air/fluid cooling 3 mL/s, and time of irradiation: 6 sec. Debonding was made by scanning (n = 15; 6 sec irradiation at distance of 2 mm from the bracket with an "S" shape movement) and circular (n = 15; 6 sec irradiation at distance of 1 mm from the bracket) motion technique in ceramic brackets or the circular motion technique in metal brackets (n = 15). The number of 10 nonirradiated teeth with ceramic (n = 5) or metal brackets (n = 5) was used as a control in SEM test and EDS analysis. The damage in tooth enamel surface and the calcium percentage were analyzed by means of scanning electron microscope (JEOL 6610LV, JEOL, Japan) and energy dispersive X-ray spectroscopy (EDS, Oxford, United Kingdom). Temperature changes in the pulp were measured by K-type thermocouple. Evaluation of the Adhesive Remnant Index (ARI) on the enamel surface of each tooth was examined after bracket debonding.

Results: The scanning method has caused significantly lower temperature increase (mean: 0.83°C) compared with circular motion technique around the ceramic brackets (mean: 1.78°C; p = 0.0001) or the metal brackets (mean: 1.29°C; p = 0.015). ARI score showed no differences between the study groups (p = 0.57). SEM analysis revealed no cracks on enamel surface after laser-assisted debonding in comparison with the control samples where cracks were found. EDS showed a higher mean percentage of the calcium (30.7-85.8%) for all test groups compared with control samples (mean: 7%; p = 0.0002). The amount of the calcium elements was higher for metal brackets in comparison with ceramic ones (p = 0.0002).

Conclusions: Er:YAG laser-assisted debonding causes a minor increase in the pulp temperature and reduced the risk of enamel damage compared with conventional bracket removal.

Keywords: EDS analysis; Er:YAG; SEM; enamel; laser; laser ablation; laser debonding; orthodontic treatment.