Nugroho JJ, Hafsari WR. 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. J Dentomaxillofac Sci [Internet]. 2017 Apr. 1 [cited 2023 Dec. 5];2(1):29-34. Available from: https://jdmfs.org/index.php/jdmfs/article/view/450