Kartika, Dewi, and Rizky Agustin Putri. 2017. “The Root Length Of Mandibular Second Molar By Using Periapical Radiography On Batak Ethnics Aged 18-22 Years In Faculty Of Dentistry University Of Sumatera Utara”. IIUM Medical Journal Malaysia 16 (2). https://doi.org/10.31436/imjm.v16i2.1118.