The invention is generally a dental appliance that, in exemplary embodiments, includes a mouthpiece equipped with a tongue-securing mechanism. The dental appliance helps keep a user's airway unobstructed by securing a tip portion of the tongue slightly forward relative to the mouth so that the tongue is held from falling back into the throat. This invention helps alleviate problems including severe snoring and sleep apnea, which are typically caused by the tongue obstructing the airway at the throat, thus impeding respiration during sleep or when unconscious. In an exemplary embodiment, the dental appliance comprises a mouthpiece which is configured to circumscribe a tongue retaining mechanism, or tongue sleeve, that secures a user's tongue in place.