Nugroho, Juni J., and Wirna R. Hafsari. 2017. “The Effectiveness of Betel Leaf (piper Betle Linn) Extract Gel and Cocoa Bean (theobroma Cacao L) Extract Gel Application Against the Hardness of Enamel Surface in Vitro”. Journal of Dentomaxillofacial Science 2 (1):29-34. https://doi.org/10.15562/jdmfs.v2i1.450.