Efektivitas Gel Ekstrak Etanol Kelopak Bunga Rosela (Hibiscus sabdariffa Linn.) sebagai Agen Antibakteri terhadap Bakteri Aggregatibacter actinomycetemcomitans secara In vitro = Efficacy of Roselle Calyx Ethanol Extract Gel (Hibiscus sabdariffa Linn.) as Antibacterial Agent on Aggregatibacter actinomycetemcomitans an In vitro Study