In the context of health insurance, particularly dental coverage, Virginia Code § 38.2-3407.1 et seq. governs mandated benefits, though dental specifics often appear in policy riders or standalone plans. Orthodontics (option A) is the branch of dentistry focused on preventing and correcting irregularities of the teeth and jaws using mechanical devices like braces or aligners, precisely matching the question’s description. Endodontics (option B) deals with the tooth’s interior (e.g., root canals), not mechanical correction of alignment. Periodontics (option C) addresses gum diseases and supporting structures, not tooth positioning. Prosthodontics (option D) involves replacing missing teeth with prosthetics (e.g., dentures), not correcting irregularities mechanically. The study guide likely defines these terms in a health insurance section, emphasizing orthodontics’ role in alignment correction—both preventive (e.g., avoiding bite issues) and corrective—making A the clear answer. Examples like braces for malocclusion reinforce this distinction from other specialties.