Distribusi dan frekuensi karies distal pada gigi molar dua bawah akibat impaksi gigi molar tiga bawah (Di Rumah Sakit Khusus Gigi Dan Mulut Fakultas Kedokteran Gigi Universitas Indonesia Periode Tahun 2015 ? 2018) = Distribution and frequency of distal caries second molar due to impacted of third molar mandibular (in Dental Hospital, Faculty of Dentistry, Indonesia University, period 2015-2018)