What additional antibiotic coverage, if any, would you give to a patient with penicillin-susceptible Strep viridans prosthetic valve endocarditis on ceftriaxone who needs to undergo a dental procedure?

I'm a little baffled by the phraseology of "therapeutic endocarditis" because this implies to me the patient is on therapy for endocarditis and therefore is therapeutic on the ceftriaxone therapy. Additionally, the patient could be switched to penicillin as either is recommended as therapy in the 20...