Author(s) Year Country/ethnic group Number of patients Age/mean values (years) Number of distomolars Remarks
Upper jaw: number or percent Lower jaw: number or percent Total (individuals) Percent
Stafne [39] 1932 USA 48550 40, not further specified 131 10 141 0.29 Micromorphous and conical in shape in maxilla, micromorphous or of equal size in mandible
Rajab and Hamdan [40] 2002 Jordan 152 10.1 +/- 1.9 0 0 0 0 One paramolar registered
Harris and Clark [43] 2008 North
Americans 		1700 12 - 18, not further specified 20 8 18 1.06 Significantly more black Americans affected, distomolar the most frequent site of supernumerary teeth in this group
Fernández Montenegro et al. [45] 2006 Spain 36057 17.11 +/- 10.53 n.d. n.d. 26 0.07 -
Fardi et al. [46] 2011 Greece 1239 33 +/- 15.71 n.d. n.d. 4 0.32 -
Martínez-González et al. [48] 2012 Spain 13557 14 - 70 (26.7) 63.6%a 15.6%a 137b 0.96 Three or more supernumerary molars in 6.1% of participants
Keil and Speth-Eschenbrenner [50] 1963 Germany 3400 n.d. 4 no 4 0.1 Male/female 1:1
Kara et al. [53] 2012 Turkey 104902 23.45 186 (53%) 35 (10%) 221 0.21 Two (0.7%) patients had three supernumerary molar teeth
Bereket et al. [54] 2015 Turkey 111293 22.71 222 24 204 0.21 Further six patients had 5th molars in a quadrant
Kaya et al. [55] 2015 Turkey 10111 > 18, not further specified 25 2 26 0.26 Two cases with bilateral supernumerary molars, one case with distomolars in both jaws
Amini et al. [56] 2013 Iran 3374 13.9 +/- 2.7 0 0 0 - Explicitly noted absence of distomolars

aPercentage relative to total number of supernumerary molars.
bTotal number of distomolars.
n.d. = not detailed.