Effect of Er: YAG laser etching on shear bond strength of orthodontic bracket

Abstract

Objectives: To evaluate and compare the shear bond strength (SBS) of Erbium laser etched enamel to acid etched and to detect morphological changes on laser etched enamel surface using scanning electron microscope (SEM). Moreover, Laser induced caries resistance is advantageous in Orthodontics.

Methods: This is an Ex vivo study between January 2016 and December 2017, which comprises a total of 50 human premolars, extracted for orthodontic purpose, were used in this study. The samples were randomly divided into 2 groups of 25 each. The first group was etched using 37% phosphoric for 30 seconds. As for the second group, enamel was treated by Er: YAG laser operating at wavelength 2.94µm, power 1.5W and repetition rate 15Hz. Five teeth from each group were selected for SEM evaluation and the study were continued on 20 teeth from each group.Teeth were subjected to shear bond strength test.

Results: It showed, no-significant difference between the mean of shear bond strength and of the etched groups (p=0.016).

Conclusion: It was concluded that, laser etched group (1.5W/15Hz) resulted in clinically accepted bond strength and could be an alternative to conventional acid etching.

Figure 1

Enamel surface roughness after conventional acid etching for 30 seconds (×750).

Figure 2

Enamel surface after conventional acid etching for 30 seconds (×1500). The enamel surface has the appearance of a characteristic regular honey comb (arrow), with areas of aprismatic enamel (star).

Figure 3

Enamel surface after Er:YAG laser irradiation (×750) showing surface roughness and crater formation (arrow).

Figure 4

Enamel surface roughness after Er: YAG laser irradiation (×1500). Resorption of the prism cores was observed when the peripheral boundaries were highly projected (arrows).