The antibiotic of choice for a periapical abscess is

Penicillin V is the preferred antibiotic for treating a periapical abscess because it is effective against the bacteria commonly found in these types of abscesses, such as Streptococcus and Staphylococcus. Amoxicillin and Tetracycline may also be effective, but they have a broader spectrum of action and may lead to antibiotic resistance if used unnecessarily. Metronidazole is not commonly used for periapical abscesses and is more specific for anaerobic infections. Therefore, it is not the best choice for treating this type of abscess.