Study Population N Horizontal plane Vertical plane
Apical to second
premolar
Between apices of
premolars
Other location
Fishel et al.
(1976)
Caucasian 1000 18.9 70.4 Apex first premolar: 3.3
Mesial to first premolar: 1.5
Between premolar/molar: 6.6
By the molar: 1
Superior to the level of the apices of the premolars
Wang et al.
(1986)
Chinese 100 59 21 Between premolars/molars: 19
By the molar: 1
Distance between superior border of the MF and
the bottom of the lower second premolar socket: 2.50 mm
Kekere-Ekun
(1989)
Nigerian 604 55.63 26.99 Mesial to first premolar: 0.17
Apex first premolar: 1.66
Between premolar/molars: 12.3
By the molar: 3.3
Not measured
Shankland
(1994)
Asian
Indians
138 75.4 5.8 Between premolar/molars: 14.5
By the molar: 4.3
Not measured
al Jasser and Nwoku
(1998)
Saudi 414 45.3 42.7 Not measured Not measured
Ngeow and Yuzawati
(2003)
Malay 169 69.2 19.6 Apex first premolar: 3.4
Between premolar/molar: 6.6
By the molar: 1
Not measured
Neiva et al.
(2004)
Caucasian 22 42 58 Not measured Distance between MF and CEJ of teeth: 15.52 ± 2.37 mm
Apinhasmit et al.
(2006)
Thai 106 56.9 28.7 Between premolar/molar: 10.2
Apex first premolar: 3
By the molar: 1.2
Not measured
Kim et al.
(2006)
Korean 72 64.3 26.8 Apex first premolar: 8.9 Distance between the cusp tip and the superior
border of the mental foramen: 23.42 mm
Fabian
(2007)
Tanzanian 100 45 12 Between premolar/molar: 35
By the molar: 8
Not measured
Haghanifar and Rokouei
(2009)
Iranian 400 46 47.2 Between premolar/molar: 5.3
By the molar: 1.5
Not measured