Effects of different surface preparations of fluorotic enamel on the bonding strength of attachment in Clear aligners

Abstract Improving the bonding ability of the attachment on fluorotic enamel has great potential in clinical application and alternative orthodontic treatment for patients with dental fluorosis. To investigate the effects of different combination of Er: YAG laser and acid etching, 20 healthy teeth and 90 dental fluorosis were randomly allocated to different groups and separately handled. We evaluated shear bonding strength of each group. The changes of enamel structure and fracture mode of attachments were observed by Scanning Electron Microscope and stereo-microscope, respectively. The shear bonding strength of attachment group was higher than bracket group (P < 0.01). On the attachment, the combination of Er: YAG laser and acid etching improved bonding strength than only acid etching group (P < 0.01). The main fracture modes of attachment in the etching group were adhesive interface fracture and mixed fracture, while those in the combination group were mixed fracture and resin cohesion fracture (P < 0.05). In conclusion, the shear bonding strength of the attachment was higher than that of the bracket under the same conditions, and prolonging the etching time improved the bonding performance of the enamel. The excessive etching led to the dissolution of the enamel column structure and reduced the bonding performance. The combination of Er: YAG laser and acid etching improve the bonding ability of clear aligner attachment on the surface of dental fluorosis.