Tobacco smoking will probably end up staining your aligners, which can be unsightly since you need to keep them in for at least 22 hours a day. The stains can be impossible to remove.
If you remove your aligners prior to smoking, you need to ensure that you are keeping within the recommended number of hours required for aligner wear. Brushing your teeth after smoking can help to prevent tobacco stains from transferring to the aligner material.
Smoking will also stain the attachments or the joints around where the attachment meets the tooth surface.
Smoking increases your risk of serious gum disease (periodontitis), which can be aggravated by wearing aligners or braces, since these increase the amount of plaque accumulation around your teeth. Having meticulous oral hygiene is essential to ensure your gums remain healthy during orthodontic treatment.