B

GEM 21S (PDGF-BB + β-TCP), Periochip (2.5 mg chlorhexidine chip) and Atridox (10 % doxycycline hyclate gel) have all received U.S. FDA clearance for periodontal use [Khehra 2024 PMID 39619169; Killoy 1998 PMID 9839852; Johnson 1999 PMID 11908360].  
Elyzol is a 25 % metronidazole dental gel that is marketed in Europe and other regions but has never been cleared by the U.S. FDA, remaining only “licensed” abroad [Drug Ther Bull 1994 PMID 7635031]. Therefore, Elyzol is the only option listed that is not FDA-approved.